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The Haihe Plain in China is situated in the world's largest groundwater funnel area, with per capita water resources far below the internationally recognized "extremely water-scarce" standard. To address the issue of water shortage in summer maize-planting areas of the Haihe Plain, we conducted research on the variation of summer maize evapotranspiration using a medium-sized lysimeter. This study aims to provide technical support for water-saving irrigation in summer maize fields. Through path analysis, direct and indirect influencing factors affecting the evapotranspiration of summer maize fields were determined. The results showed that the cumulative evapotranspiration of bare ground and farmland during the entire growth period of summer maize was 173.57 mm and 382.97 mm, respectively, with evapotranspiration intensities of 1.52 mm/d and 3.36 mm/d, respectively. Evapotranspiration during the maturity stage of summer maize was the least, accounting for only 1.82% of total evapotranspiration during the entire growth period. The period from the jointing to milk-ripening stage is when evapotranspiration in maize fields is at its highest. During this period, evapotranspiration in maize fields amounted to 265.58 mm, accounting for 69.35% of total evapotranspiration. The evapotranspiration intensity was 3.59 mm/day, which is 1.34 times higher than that of bare soil. The evapotranspiration intensities during each growth stage were ranked as jointing stage > tasseling-silking stage > seedling stage > milk maturity stage > maturity stage. The daily evapotranspiration of summer maize fields showed a "unimodal" curve with low values in the morning and evening, and high values at noon. Path analysis indicated that daily radiation and maximum daily temperature had the greatest impact on the evapotranspiration of maize fields, with the direct effect of maximum daily temperature being restrictive and the indirect effect being promotive, resulting in an overall promotive effect. [ABSTRACT FROM AUTHOR]

Purpose: Cover cropping during the summer fallow is a feasible practice for soil residual nitrogen (N) absorption and subsequent N supply in greenhouse vegetables. However, the change in these effects with a progression in the cultivation years of greenhouse vegetables remains unknown. This study aimed to evaluate the effects of different cover crops on the uptake of residual N in soil and N mineralization as affected by the planting years of greenhouse vegetables. Methods: Five soil samples were collected from fields that had been cultivated with greenhouse vegetables for different number of years (0, 5, 10, 15, and 20 years); upper layers (0–30 cm) of the soil were sampled from a major vegetable production area in Xinxiang City, Henan Province, China. Three cover crop treatments were included for each soil sample: no cover crop planted during summer fallow with no straw return (CK), summer maize (Zea mays L.) planted and straw return (SM), and alfalfa (Medicago sativa L.) planted and straw return (A). Pot and incubation experiments were conducted to determine the amounts of N absorbed by cover crops during the fallow and soil N mineralization after cover crop straw return. Results: The effects of cover crops on soil residual N absorption and subsequent N mineralization changed with cover crop types and greenhouse vegetable planting years. SM performed better as a cover crop than A in crop biomass development (on average 6.67 times larger), soil residual N absorption (4.46 times larger), and loss (3.61 times smaller) control, regardless of the greenhouse vegetable planting years. In terms of soil net N mineralization and straw-induced N mineralization, SM was inferior to A (1.15 and 2.12 times smaller). With the increase of planting years, total biomass yield and N uptake by the SM increased, whereas these parameters decreased for treatment A due to the plants' different tolerance to soil available N and pH (pondus hydrogenii). For all cover crop treatments, with the increase of greenhouse vegetable planting years, net N mineralization of the soil increased due to the positive contribution of soil organic matter, whereas straw-induced N mineralization decreased due to the negative regulation of accumulated soil nitrate nitrogen. Conclusions: Non-legumes, as represented by SM, were a good choice for cover cropping regardless of the greenhouse vegetable cultivation years. However, attention should be paid to N supplementation at an early stage of subsequent crop cultivation, especially in newly built greenhouse vegetables. [ABSTRACT FROM AUTHOR]

To improve the yield and water-nitrogen (N) use efficiency of summer maize, a two-year field experiment with four irrigation soil layers (0–10, 0–20, 0–30, and 0–40 cm, denoted as W10, W20, W30, and W40, respectively) and three N applications (180, 240, and 300 kg ha–1, denoted as N180, N240, and N300, respectively) was performed using micro-sprinkling irrigation system in 2018 and 2019. The interaction between water and N application significantly affects dry matter accumulation (DM). Under the same N application, the grain yield of W10 was significantly lower than that of W40. The irrigation amount and evapotranspiration for W20N180 and W20N240 significantly decreased by 47.18%–52.31% and 12.32%–12.68%, respectively, over that of W40N300, and water-use-efficiency (WUE) significantly increased by 7.75%–12.47%. Compared with N180, the N partial factor productivity of N240 and N300 decreased by 21.02%~22.04% and 37.12%~38.24%, respectively; with no significant difference in yield. Grain yield was significantly positively correlated with leaf area index at tasseling, grains per ear, DM at maturity, and evapotranspiration. Overall, suitable irrigation (W20) and N application (180–240 kg ha–1) can achieve higher grain yield and WUE for summer maize in the Huang-Huai-Hai Plain of China. [ABSTRACT FROM AUTHOR]

To investigate the impact of brackish water irrigation on the multidimensional root distribution and root-shoot characteristics of summer maize under different salt-tolerance-training modes, a micro-plot experiment was conducted from June to October in 2022 at the experimental station in Hohai University, China. Freshwater irrigation was used as the control (CK), and different concentrations of brackish water (S0: 0.08 g·L−1, S1: 2.0 g·L−1, S2: 4.0 g·L−1, S3: 6.0 g·L−1) were irrigated at six-leaf stage, ten-leaf stage, and tasseling stage, constituting different salt tolerance training modes, referred to as S0-2-3, S0-3-3, S1-2-3, S1-3-3, S2-2-3, and S2-3-3. The results showed that although their fine root length density (FRLD) increased, the S0-2-3 and S0-3-3 treatments reduced the limit of root extension in the horizontal direction, causing the roots to be mainly distributed near the plants. This resulted in decreased leaf area and biomass accumulation, ultimately leading to significant yield reduction. Additionally, the S2-2-3 and S2-3-3 treatments stimulated the adaptive mechanism of maize roots, resulting in boosted fine root growth to increase the FRLD and develop into deeper soil layers. However, due to the prolonged exposure to a high level of salinity, their roots below 30 cm depth senesced prematurely, leading to an inhibition in shoot growth and also resulting in yield reduction of 10.99% and 11.75%, compared to CK, respectively. Furthermore, the S1-2-3 and S1-3-3 treatments produced more reasonable distributions of FRLD, which did not boost fine root growth but established fewer weak areas (FLRD < 0.66 cm−3) in their root systems. Moreover, the S1-2-3 treatment contributed to increasing leaf development and biomass accumulation, compared to CK, whereas it allowed for minimizing yield reduction. Therefore, our study proposed the S1-2-3 treatment as the recommended training mode for summer maize while utilizing brackish water resources. [ABSTRACT FROM AUTHOR]

Simulation has been intensively implemented on the effect of water supply on the grain-filling process of crops. However, there are few reports on the fitting analysis of summer maize with the various types of nitrogen fertilizer synergists under different irrigation amounts. This study aims to reveal the effect of water supply and nitrogen fertilizer synergists on the summer maize at the grain filling. The maize variety Zhendan 958 was selected in a field experiment in Guanzhong area, Shaanxi Province, China. The experiment contained eight treatments, where two levels of water supply (i.e., low water W1, 40 mm; high water W2, 60 mm), and three types of nitrogen-based synergists were added into the single urea (U) application (urease inhibitor NBPT, nitrification inhibitor DCD, double-acting inhibitor NBPT+DCD). The grain filling model was also established and verified under the water supply and nitrogen fertilizer synergists using Richards’ equation. A systematic analysis was carried out to determine the filling characteristic parameters, including the initial growth potential, grain filling active days, occurrence time of the maximum grain-filling rate (Tmax), the maximum grain-filling rate, and mean grain-filling rate. An investigation was then made to explore the effects of water supply and nitrogen fertilizer synergists on the grain-filling duration days and rates at various stages, dry matter transfer quantity and rate, and yield. The results showed that the Richards model better simulated the dynamic process of grain filling in summer maize, with the determination coefficients of above 0.99 for the grain filling fitting equation in each treatment. Specifically, the nitrogen fertilizer synergist DCD increased the seed initial growth potential under water supply level W2; NBPT+DCD extended the period of grain filling active days, retarded Tmax and possessed higher Vmax and mean grain-filling rate. W2 significantly retarded Tmax to prolong the total grain-filling duration days, where the improved mean grain-filling rate at grain-filling slowly increased the period, compared with the W1. DCD and NBPT+DCD were significantly improved average filling rate during grin-filling fast increase period, but slowly increased period. Significant interactions were found in the water supply and nitrogen fertilizer synergist on grain-filling duration days and mean grain-filling rate. DCD significantly extended the grain-filling duration days to 47.10 d under the W2. Meanwhile, there was the optimal proportion of the three grain-filling stages with a relatively higher average filling rate of 0.828 g/d. There were higher transfer quantities and contribution rates to grain stored in stems and sheaths. The W2 possessed a 3.63% lower contribution rate of stem and sheath to grain, compared with the W1. NBPT+DCD obtained the highest contribution rates of stems and sheath to grain, followed by NBPT, DCD and U, in terms of the nitrogen fertilizer synergists. Plants possessed a 7.21% higher yield under the W2 than those under the W1. The NBPT, DCD, and NBPT+DCD significantly improved the summer maize yield by 6.16%, 13.43% and 11.06%, respectively, compared with the U. Among them, the yield obtained by DCD and NBPT+DCD was higher than that of NBPT. Overall, both increasing water supply and nitrogen synergists can be expected to improve the summer maize yield, whereas, the higher water supply can improve the maize yield via the prolonged duration days of grain filling. W2+DCD was recommended as the optimized combination of water supply and nitrogen fertilizer synergist in this experiment, as it extended the total grain-filling period of summer maize for the highyield formation. These findings can also provide a strong reference to optimize the water and nitrogen fertilizer synergist in the production of summer maize. [ABSTRACT FROM AUTHOR]

As an important food crop, summer maize is widely planted all over the world. Monitoring its growth and output is of great significance for world food security. With the trend of global warming and deterioration, the frequency of high temperature and heat damage affecting summer corn has been increasing in the past ten years. Therefore, there is an increasing demand for monitoring the high temperature and heat damage of summer maize. At present, there are nearly a hundred indices or methods for research on high temperature and heat damage. However, research based on the vegetation index cannot fully describe the damage caused by high-temperature thermal damage, and there is an obvious asynchrony effect. Research based on hyperspectral remote sensing has many inconveniences in data acquisition and complex physical model construction. Therefore, this study uses remote sensing data, including MODIS surface reflection data, MODIS land surface temperature products, as well as ground observation data and statistical data, combined with multiple remote sensing indices and land surface temperature, to construct a remote sensing index, LSHDI (land surface heat damage index). The LSHDI first searches for a location with the worst vegetation growth conditions in the three-dimensional feature space based on the LST (land surface temperature), the normalized difference vegetation index (NDVI), and the land surface water index (LSWI). Then, it calculates the distance between each point and this location to measure the degree of vegetation affected by high temperature and heat damage. Finally, because there is no reliable disaster verification dataset that has been published at present, this study uses soil moisture as a reference to explain the performance and stability of the LSHDI. The results showed that their coefficient of determination was above 0.5 and reached a significance level of 0.01. The LSHDI can well-reflect the high temperature and heat damage of land surface vegetation and can provide important data support and references for agricultural management departments. [ABSTRACT FROM AUTHOR]

High temperatures during flowering stage affects the seed setting in maize and thereby result in significant yield penalties in recent changing climate era. Based on the daily maximum temperature data of the maize growing season from 1971 to 2019 at the surface meteorological observatory in Henan Province of China and maize observation data at the agricultural meteorological observatory, an early warning grade of high temperatures during the summer maize flowering stage was constructed. The daily maximum temperature of the summer maize flowering stage was ≥ 32 °C as the critical threshold of high temperature disaster, and ≥ 35 °C as the threshold of high temperature disaster. The number of high temperature days (HD) ≥ 32 °C and ≥ 35 °C during 10 days of the summer maize flowering stage were counted. The sequence of high temperature days of summer maize flowering stage was constructed and its normal distribution characteristics were verified. The quartile value of the normal distribution sequence was selected as the threshold value of high temperature in different grades, and the high temperature heat damage in the summer maize flowering stage was divided into three early warning meteorological grades. The index verification of the early warning meteorological grade was carried out by using the observation data of kernel number per ear in the agricultural meteorological station for maize. The results showed that the three grade indexes corresponding to the number of high temperature days with daily maximum temperature ≥ 32 °C were: 3 ≤ HD < 5 (Grade I), 5 ≤ HD < 7 (Grade II), and HD ≥ 7 (Grade III) and the three grade indexes corresponding to high temperature days ≥ 35 °C were: 2 ≤ HD < 3 (Grade I), 3 ≤ HD < 5 (Grade II), HD ≥ 5 (Grade III). The constructed indexes were verified as follows, the number of high temperature days ≥ 32 °C at about 90% stations was significantly negatively correlated with the number of maize grains per ear, and 74% stations which the number of high temperature days ≥ 35 °C was significantly negatively correlated with the number of maize grains per ear. Applying this index to evaluate the high temperature risk in the flowering period, we can indicate that the high temperature risk had trend of increasing gradually from north to south. In conclusion, the constructed high temperature warning meteorological grade index during the flowering stage could accurately reflect the damage grade of maize during the flowering stage. [ABSTRACT FROM AUTHOR]

Co-application of organic-chemical fertilizer (CAOFCF) has attracted wide attention in China in recent years. However, its short-term effect on topsoil quality and maize yield in a medium-productivity meadow-cinnamon soil is not clear. In order to address this problem, a 3-year (2019–2021) field trial was established by arranging the following five treatments: (1) CF, applying chemical fertilizer alone; (2) OFCF1, 15% organic fertilizer + 85% chemical fertilizer; (3) OFCF2, 30% organic fertilizer + 70% chemical fertilizer; (4) OFCF3, 45% organic fertilizer + 55% chemical fertilizer; (5) OFCF4, 60% organic fertilizer + 40% chemical fertilizer. The results showed that short-term CAOFCF treatments were beneficial to the topsoil aggregate stability by increasing the percentage and mean weight diameter of macro-aggregate in topsoil. In addition, lower soil bulk density and higher soil organic carbon sequestration in topsoil were observed under the CAOFCF treatments. There was no difference in rhizosphere microbial diversity among all treatments. Compared to CF, OFCF1 and OFCF2 improved the activities of some key enzymes, including sucrase, urease, and acid phosphatase. Moreover, higher relative abundance of Actinobacteria and Chloroflexi were observed under the CAOFCF treatments. The root-shoot dry matter and maize grain yield were obviously higher in OFCF1 and OFCF2 than in CF; however, no significant difference was found in the OFCF3 and OFCF4 treatments compared to CF. The analysis of correlation suggested that there were no direct correlations between maize yield and various soil indexes measured. Nevertheless, root dry weight and root-shoot ratio were positively correlated with the activities of urease and sucrase. Meanwhile, the relationships between root dry weight, root-shoot ratio, shoot dry weight, and grain yield were all significant. In conclusion, short-term co-application of organic and chemical fertilizer (i.e., replacing 15–30% chemical fertilizer with organic fertilizer with an equal N rate) was beneficial to soil properties and maize grain yield in a medium-productivity meadow-cinnamon soil. The higher grain yield was associated with a strong maize root system, which was driven by the improved rhizosphere urease and sucrase activities. [ABSTRACT FROM AUTHOR]

Spring wheat–summer maize (SWSM) annual crop systems were formed to satisfy the maize grain mechanized harvest thermal requirement in the thermal–resource–limited region of the North China Plain. However, the nitrogen (N) application rate effect on SWSM annual yield formation, N accumulation and utilization were barely evaluated. Two–year field experiments were conducted to evaluate the effects of the N application rate on the annual yield of SWSM, observe N accumulation and utilization, and identify the optimized N application. The experiments were conducted under 5 N levels of 0 (N0), 180 (N180), 240 (N240), 300 (N300), and 360 (N360) kg ha−1. The results showed that spring wheat, summer maize and annual cereal yield under the N240 and N480 treatments obtained the highest grain yield (GY) of 5038, 1282 and 16,320 kg ha−1, respectively, and the optimal N application rate was estimated using a linear–plateau model to be 231–307, 222–337 and 463–571 kg ha−1 with maximum GY of 4654–5317, 11,727–12,003 and 16,349–16,658 kg ha−1, respectively. With the increase in the N application rate, the dry matter accumulation (DM) were significantly increased by 16.9–173.5% for spring wheat and 11.1≈–76.8% for summer maize, respectively; and the annual cereal DM was 15.1–179.7% greater than that with N0 treatment, respectively. Spring wheat, summer maize and the annual cereal total N accumulation (TN) under N360 and N720 treatments were significantly increased by 5.4–19.1%, 16.6–32.3% and 11.5–26.2%, respectively, compared to the other treatments; however, N use efficiency for biomass and grain production (NUEbms and NUEg) were decreased significantly by 10.9–13.6% and 8.9–20.7%, 6.8–13.8% and 12.2–15.6%, and 5.5–11.7% and 10.0–16.0%, respectively. Meanwhile, the N partial factor productivity (PFPN), N agronomy use efficiency (ANUE), N recovery efficiency (NRE) and N uptake efficiency (NEupk) under the N240 treatment for spring wheat and summer maize obtained high levels of 20.99 and 47.01 kg−1, 9.27 and 16.35 kg−1, 32.53% and 32.44%, and 0.85 and 0.72 kg−1, respectively. Correlation analysis showed that the N application rate, TN and NEupk played significantly positive roles on GY, spring wheat spilke grain number, summer maize ear grain number and 1000–grain weight, DM LAImax and SPADmax, while NUEbms, NUEg, PFPN and ANUE always played negative effects. These results demonstrate that spring wheat, summer maize and annual cereal obtained the highest GY being 4654–5317, 11,727–12,003 and 16,349–16,658 kg ha−1 with the optimal N application rate 231–307, 222–337 and 463–571 kg ha−1, respectively, which provide N application guidance to farmer for spring wheat–summer maize crop systems to achieve annual mechanical harvesting in the thermal–resource–limited region of the North China Plain. [ABSTRACT FROM AUTHOR]

Leaf area index and dry matter mass are important indicators for crop growth and yields. In order to solve the problem of predicting the summer maize growth index and yield under different soil quality and field management conditions, this study proposes a prediction model based on the supervised machine learning regression algorithm. Firstly, the data pool was constructed by collecting the measured data for maize in the main planting area. The total water input (rainfall plus irrigation water), fertilization, soil quality, and planting density were selected as the training set. Then, the maximum leaf area index (LAImax), maximum dry material mass (Dmax), and summer maize yields (Y) in the data pool were trained by using Gaussian regression (rational quadratic kernel function and Matern kernel function), support vector machine (SVM) and linear regression models. The training models were verified with the data-set not included in the data pool, and the water and fertilizer coupling functions were developed. The prediction results showed that compared to the support vector machine models and the linear regression models, the Gaussian regression prediction models comprising the rational quadratic and Matern kernel functions had good prediction accuracy. The coefficients of determination (R2) of the prediction results were 0.91, 0.89 and 0.88; the root-mean-square errors (RMSEs) were 0.3, 1138.6 and 666.16 kg/hm2; and the relative root-mean-square errors (rRMSEs) were 6.3%, 5.94% and 6.53% for LAImax, Dmax and Y, respectively. The optimal total water inputs and nitrogen applications indicated by the prediction results and the water and fertilizer coupling functions were consistent with the measured range from the field tests. The supervised machine learning regression algorithm provides a simple method to predict the yield of maize and optimize the total water inputs and nitrogen applications using only the soil quality and planting density. [ABSTRACT FROM AUTHOR]

To improve the grain yield (GY) and water–nitrogen (N) use efficiency of summer maize, a 2–year field experiment was conducted using micro–sprinkling irrigation water–fertilizer integration. Surface irrigation and N application methods were applied in the control (CK, irrigation at sowing; 300 kg N ha−1). Under water–fertilizer integration, N was applied at five rates (0, 120, 180, 240, and 300 kg N ha−1, N applied at sowing, jointing, and tasseling and ratio of 1:1:1; designated WN0, WN120, WN180, WN240, and WN300, respectively). The leaf area index and dry matter accumulation increased with increasing N application rate, with a slower rate of increase when N application rate ≥180 kg N ha−1. Compared with CK, the GY of WN300, WN240, WN180, and WN120 was not significantly different,but WN120 significantly decreased by 7.16% and 5.47% than WN240 and WN300.The evapotranspiration,irrigation amount,and N application rate in WN180 were 9.86%–16.40%, 47.11%–52.23%, and 40% lower,respectively,than in CK,while the water use efficiency and N partial factor productivity was 3.38%–15.14% and 32.04%–60.43% higher.Thus,application of 180 kg N ha−1 with water–fertilizer integration can achieve high GY and improve resource–use efficiency. [ABSTRACT FROM AUTHOR]

Zhengdan 958 (ZD958) is the summer maize variety with the widest planting area in Huang-Huai-Hai plain in the past 20 years. Understanding the agronomic characteristics of maize and its adaptability to climatic factors is of great significance for breeding maize varieties with high yield and stability. In this study, the experimental data of 33 experimental stations from 2005 to 2015 were analyzed to clarify the effects of different agronomic traits on yield and the correlation between agronomic traits, and to understand the effects of different climatic factors on summer maize yield and agronomic traits. The results showed that the average yield of ZD958 was 9.20 t ha-1, and the yield variation coefficient was 13.41%. There was a certainly negative correlation between high yield and high stability. Plant heights, ear heights, double ear rate, ear length, ear rows, line grain number, grain number per ear, ear diameter, cob diameter, and 1000 grainsweight were significantly positive correlation with maize yield. Solar radiation before and after silking were significantly positive correlation with maize yield. Path analysis showed that changes in agronomic traits accounted for 54% of the yield variation, and changes in climate factors accounted for 26% of the yield variation. Our study showed that higher plant height, ear height, grain number per ear and 1000-grain weight, lower lodging rate, pour the discount rate and shorter bald tip long were themain reasons for high yield. Among the climatic factors, solar radiation and the lowest temperature have significant effects on the yield. [ABSTRACT FROM AUTHOR]

The growing degree days (GDD) is an important factor for crop growth because it affects dry matter formation and crop yield. In this study, the universal logistic models were established employing GDD and the relative GDD (RGDD) as the main parameters to characterize summer maize growth indices such as plant height (H), leaf area index (LAI), and dry matter accumulation (DMA). The relationships were analyzed between the growth indices, harvest index (HI), water consumption, and yield in maize. By considering China as an example, the results showed that the logistic model performed well at simulating the changes in the summer maize growth indices in different regions and the universal model parameters were within specific ranges. Furthermore, the logistic model with RGDD as the independent variable was more suitable for modeling summer maize growth in large areas than GDD. The relationship between the maximum LAI and HI was described by a quadratic polynomial function. HI was optimal (0.53) when the maximum LAI was about 5.13. The maximum LAI, maximum H, and maximum DMA could be described by a quadratic polynomial function of water consumption during the growing season. The summer maize yield could be predicted with a binary quadratic equation using the maximum GDD and water consumption. This study confirmed that a logistic model can be used to establish a universal growth model for summer maize in large areas. Reasonable ranges of parameters were recommended for the logistic model, as well as the reasonable water consumption and each growth index value for summer maize. These results will be helpful for predicting the growth and yield of summer maize. [ABSTRACT FROM AUTHOR]

Mulches combined with drip irrigation techniques have been widely applied in China for higher yield and water use efficiency (WUE). To develop an efficient strategy that can improve maize yield and save water in the North China Plain (NCP), we conducted a two-year field experiment, using transparent plastic film mulching (T), black plastic film mulching (B), and straw mulching (S) and non-mulching (N) for spring maize in 2019 and summer maize in 2020, and high drip irrigation amount (H) and low drip irrigation amount (L) were also considered in 2019. We mainly studied the effects of mulches on soil water content, soil temperature, crop growth rate, grain yield, and water use efficiency (WUE). The results indicated that T and B treatment increased soil water content (SWC) and topsoil temperature. The T treatment promoted the growth rate significantly more than N treatment, by 27.7–43.4% at the early stage in two years. The grain yield under TH treatment was significantly (p < 0.05) higher than that of other treatments, by 9.8–17.4% for spring maize in 2019, and significantly (p < 0.05) higher under both TH and BH than under NH, by 8.9% and 4.7% for summer maize in 2020. There was a significant quadratic parabola relationship between ET and grain yield in 2019, and the correlation between SEAT of 0–10 cm soil depth with grain yield or with biomass was positive. These results indicate that the transparent plastic film with high drip irrigation amount treatment (TH) can be recommended for spring maize, and both transparent and black film mulch treatments (TH and BH) can be recommended for summer maize in the NCP. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Waterlogging (W-B) is a major abiotic stress during the growth cycle of maize production in Huang-huai-hai plain of China, threatening food security. A wide range of studies suggests that the application of 6-benzyladenine (6-BA) can mitigate the W-B effects on crops. However, the mechanisms underlying this process remain unclear. In this study, the application of 6-BA that effectively increased the yield of summer maize was confirmed to be related to the hormone and sugar metabolism. At the florets differentiation stage, application of 6-BA increased the content of trans-zeatin (TZ, + 59.3%) and salicylic acid (SA, + 285.5%) of ears to induce the activity of invertase, thus establishing sink strength. During the phase of sexual organ formation, the TZ content of ear leaves, spike nodes, and ears was increased by 24.2, 64.2, and 46.1%, respectively, in W-B treatment, compared with that of W. Accordingly, the sugar metabolism of summer maize was also improved. Therefore, the structure of the spike node was improved, promoting the translocation of carbon assimilations toward the ears and the development of ears and filaments. Thus the number of fertilized florets, grain number, and yield were increased by the application of 6-BA. [ABSTRACT FROM AUTHOR]

Summer maize crop development, yield, and water use characteristics under water deficit conditions at different growth stages were investigated in this study using different irrigation regime treatments at the seedling (S), jointing (J), tasseling (T), and grain filling stages (F) in 2018 and 2019 in China. Ten different irrigation treatments were set, including three-irrigation application intervals (JTFi, STFi, SJFi, SJTi), two-irrigation applications (STi, JTi, JFi), and single-irrigation applications (Ti, Ji). These were compared to the control treatment (CK), which had sufficient irrigation provided at four intervals (SJTFi). The results showed that compared to CK, a water deficit at the seedling and jointing stages had a greater effect on plant height, whereas a water deficit at the tasseling and filling stages had a greater effect on the leaf area index, and a continuous water deficit had an effect on the stem diameter of summer maize. Limitations in terms of the growth and development of summer maize increased with less frequent irrigation. As irrigation decreased, the grain yield decreased, and the water use efficiency increased, and a water deficit at the tasseling stage had the greatest effect on the yield and water use efficiency. The JTFi treatment was the optimal irrigation regime with a yield decline, and its water consumption was reduced by 16.9% (p < 0.05) on average. However, compared to CK, the water use efficiency of the JTFi treatment increased by 17.3% (p < 0.05). Moreover, the JTFi treatment had the smallest maize yield response factor value (Ky) of 0.16, and its comprehensive score was the second highest after CK. [ABSTRACT FROM AUTHOR]

Accurately simulating maize (Zea mays L.) yield at the regional scale is of paramount importance for making informed policy adjustments and for ensuring food security. Sobol sensitivity analysis was used in this study to screen sensitive parameters of a process-based crop model (Chinese Agricultural Meteorological Model, CAMM). An upscaling approach was utilized to reduce the intra-pixel heterogeneity error of MODIS LAI. Then upscaled MODIS LAI data were assimilated into the CAMM model through a 4DVar assimilation algorithm to optimize pixel-level sensitive parameters, thereby improving the simulation accuracy of the summer maize growth process and yield. Specific leaf area (SLATB&#95;0, SLATB&#95;1) during the period from emergence to tasseling of summer maize exhibited the strongest impact on summer maize yield. Additionally, the average LAI value within the 85-95 % range of ordered LAI values for small pixels within large pixels effectively reduced the intra-pixel heterogeneity error of MODIS LAI, and pixel-based parameterization of SLATB&#95;0 and SLATB&#95;1 at a larger pixel scale (0.0625°) was achieved. Based on yields recorded at agrometeorological stations from 2015 to 2020, assimilated yields in both data assimilation scheme 1 (DA1, optimization of only the sensitive parameter SLATB&#95;0) and scheme 2 (DA2, simultaneous optimization of sensitive parameters SLATB&#95;0 and SLATB&#95;1) exhibited higher accuracy than schemes without data assimilation (with r values of 0.41-0.72 and NRMSE values of 19-30 %). Furthermore, DA2 showed greater simulation accuracy (r: 0.64-0.93, NRMSE: 9-21 %) than DA1 (r: 0.61-0.91, NRMSE: 12-23 %). Upscaling remotely sensed LAI products can significantly reduce the uncertainties of LAI data at a larger pixel scale, and assimilating these LAI data into crop models can effectively increase the simulation accuracy of crop growth and development processes at the regional scale., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is very important to master the rainfall utilization efficiency and spatial-temporal distribution characteristics in order to improve the agricultural water resource utilization efficiency. In this study, an adaptability index (AI) was constructed to reflect the relationship between rainfall and crop water demand. Spatial analysis and clustering analysis were used to study the spatial distribution characteristics and evolution rules of the adaptability between water demand and rainfall in the growing period of summer maize in Henan Province of China. The results showed that there were significant spatial differences in the adaptability of different regions, and such differences change with time, indicating that AI has certain uncertainties in the region and growth season. In general, the AI of the whole growth period of summer maize is mainly determined by the AI of tasseling period–milky period, while the multi-year change rate of AI is mainly determined by the emergence period–jointing period, tasseling period–milky period, and milky period–maturity period The adaptability of summer maize to rainfall in the study area can be divided into three categories, among which the one with increased adaptability occupies the main part, and the one with sharply decreased adaptability were also distributed in the study area. The above studies indicate that it is important to pay attention to the adaptability of rainfall to agricultural water management. The complexity division of crop water demand by rainfall adaptability index can guide the establishment of reasonable and accurate irrigation system. [ABSTRACT FROM AUTHOR]

The stability of maize production is essential to global food security. Climate factors, such as temperature, precipitation, and solar radiation, directly affect the development of maize plants and hence the final grain yield. In this study, we investigated the spatial distributions and temporal trends of agro-climatic indices and severe weather indicators during the actual growing season for summer maize in Huanghuaihai region of China. The results showed that during the growing season, accumulated effective thermal time had significantly increased. From R3 to R6, accumulated effective thermal time, effective precipitation, and photosynthesis active radiation all showed an increasing trend, with the rate of 20.3 °C day, 1.1 mm, and 7.3 MJ m−2 per decade, respectively. From VE to R3, most of the study years showed a > 50% ratio of high-temperature days to subtotal days and > 7 consecutive days without available precipitation. During most of the study years, there were at least 0.5 thunderstorm events from V6 to VT stage in the locations of study; days with strong winds accounted for more than half the subtotal days during the V6-VT stage. And potential risk of lodging may be reduced by the decrease in days with strong wind. The results of this study could be used in optimizing agricultural management in summer maize production in order to take advantage of beneficial climatic elements while combating adverse climatic elements. [ABSTRACT FROM AUTHOR]

Crop phenology is a significant factor that affects the precision of crop area extraction by using the multi-temporal vegetation indices (VIs) approach. Considering the phenological differences of maize among the different regions, the summer maize cultivated area was estimated by using enhanced vegetation index (EVI) time series images from the Moderate Resolution Imaging Spectroradiometer (MODIS) over the Huanghuaihai Plain in China. By analyzing the temporal shift in summer maize calendars, linear regression equations for simulating the summer maize phenology were obtained. The simulated maize phenology was used to correct the MODIS EVI time series curve of summer maize. Combining the mean absolute distance (MAD) and p-tile algorithm, the cultivated areas of summer maize were distinguished over the Hunaghuaihai Plain. The accuracy of the extraction results in each province was above 85%. Comparing the maize area of two groups from MODIS-estimated and statistical data, the validation results showed that the R2 reached 0.81 at the city level and 0.69 at the county level. It demonstrated that the approach in this study has the ability to effectively map the summer maize area over a large scale and provides a novel idea for estimating the planting area of other crops. [ABSTRACT FROM AUTHOR]

• Straw mulching (SM) increased summer maize yield in this region. • SM increased LAI, photosynthetic capacity and apparent quantum efficiency. • The liner regressions between A max and N mass were affected by SM treatment. • Higher leaf N use efficiency of SM were first found in field experiment. • The lower leakiness of the bundle-sheath cells to CO 2 (L) were found of SM. Better understanding on the photosynthetic regulation of yield will be useful to improve agricultural water use efficiency under straw mulching. The yield, photosynthetic parameters and related leaf traits were measured and compared between straw mulching (SM) and non-mulching (NM) treatments in a maize field of North China Plain in 2013–2015. Total aboveground biomass of the SM treatment increased by 7.1%, 11.2% and 14.7%, and grain yield increased by 11.5%, 6.8% and 12.1%, respectively for the three years, comparing to those of the NM treatment. Such increases were related to higher leaf area index (LAI) and leaf area duration, photosynthetic capacity per unit of area (A max) and the apparent quantum efficiency (α) for the SM treatment. Maximum LAI of the SM treatment were 17.2%, 19.2% and 20% higher than those of the NM treatment, respectively, for the three years. A max and α of the SM treatment were 7.9%–36.8% and 7.7%–16.7% higher than those of the NM treatment during different growth stages in the three years. A max and α were linearly correlated to leaf nitrogen content on mass basis (N mass). Liner regressions between A max and N mass , and between α and N mass were affected by straw mulching treatment, under which the slopes were similar but the intercepts were higher. With no significant increase of N mass in most measurements, the results suggested that the SM treatment improved N-use efficiency, which may be due to lower leakiness of the bundle-sheath cells to CO 2 (L) under the SM treatment. Collectively, the results help understanding the physiological basis of positive effect of the straw mulching on yield and quantified the photosynthetic parameters of summer maize in this area. [ABSTRACT FROM AUTHOR]

Evaluating climatic suitability of crop cultivation lays a foundation for agriculture coping with climate change scientifically. Herein, we analyse changes in the climatically suitable distribution of summer maize cultivation in China at 1.5 °C (GW1.5) and 2.0 °C (GW2.0) global warming in the future according to the temperature control targets set by the Paris Agreement. Compared with the reference period (1971–2000), the summer maize cultivation climatically suitable region (CSR) in China mainly shifts eastwards, and its acreage significantly decreases at both GW1.5 and GW2.0. Despite no dramatic changes in the CSR spatial pattern, there are considerable decreases in the acreages of optimum and suitable regions (the core of the main producing region), indicating that half-a-degree more global warming is unfavourable for summer maize production in China's main producing region. When the global warming threshold increases from GW1.5 to GW2.0, the centres-of-gravity of optimum areas shift northeastward under RCP4.5 and RCP8.5, the centres-of-gravity of both suitable and less suitable areas shift northwestward, though the northward trend is more prominent for the less suitable areas, and the centre-of-gravity of unsuitable areas shifts southeastward. Generally, half-a-degree more global warming drives the cultivable areas of summer maize to shift northward in China, while the west region shows a certain potential for expansion of summer maize cultivation. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we analyzed the effects of different maize varieties with nitrogen utilization efficiency, fertilizer type, and rate on the ammonia volatilization emission of farmland. Aimed to seek the best matching method to improve grain yield and fertilizer utilization efficiency of summer maize simultaneously. Materials and methods: In field experiments, we choose two maize varieties with different nitrogen utilization efficiency (Zhengdan958, Z and Lainong14, L) as material. Set four different fertilizer treatments (200 kg N hm−2 inorganic fertilizer (U1), 100 kg N hm−2 inorganic fertilizer (U2), 200 kg N hm−2 organic fertilizer (M1), and 100 kg N hm−2 organic fertilizer (M2) to study their effect on NH3 emission and loss, maize grain yield, and nitrogen accumulation. Results and discussion: Ammonia volatilization accounted for 8.61–21.68% of applied N. Under the same variety, ammonia volatilization accumulation after fertilization was as follows: U1 > U2 > M1 > M2. Ammonia volatilization rates increased first and then gradually decreased after the fertilization. The ammonia volatilization loss and cumulative loss increased due to increased nitrogen fertilizer application rate. The average nitrogen accumulation and harvest index of 200 kg N hm−2 N treatments were higher than 100 kg N hm−2 N treatments, and the difference between the inorganic fertilizer and organic fertilizer was not significant. In 2016 and 2017, the average yield of Zhengdan958 was 11,758.79 kg hm−2, which was 15.78% higher than that of Lainong14, and the difference between the two fertilizer types was not significant. The average yield of 200 kg N hm−2 N treatment was 11,959.42 kg hm−2, which was 20.13% higher than those of 100 kg N hm−2 N treatment. Conclusions: By changing the type of fertilizer, replacing chemical fertilizers with organic fertilizer can reduce the loss of ammonia volatilization and promote the synergistic improvement to yield and resource utilization efficiency. Among them, using nitrogen-efficient varieties and using organic fertilizer instead of chemical fertilizer was beneficial to reduce the loss of ammonia volatilization, increase the accumulation of nitrogen, and promote the growth of maize to obtain high yield. [ABSTRACT FROM AUTHOR]

Biomass is one of the important growth indicators of summer maize (Zea mays). Timely and accurate acquisition of field summer maize biomass data and its dynamic changes is conducive to county agricultural management departments to rationally adjust field production management measures, which is of great significance for increasing maize yield based on the establishment of a simulation model of summer maize biomass process.In this paper, we analyzed above ground biomass and its variation characteristics of summer maize at different growth stages and discussed the feasibility of adjusting parameters of biomass simulation modelusing measured leaf area index and biomass datain Dafengdistrict ofYanchengcity, Jiangsu province, along the east coast of China. The simulation model of biomass process of summer maize could estimate the dynamic changes of aboveground biomass of summer maize at different growth stages from emergence to grain filling.Firstly, the simulation model can predict above ground biomass effectively because of biomass accumulation mainly coming from leaf formation from seedling emergence to pre-jointing growth stage, the root mean square difference (RMSE) of which was 18.31 kg/hm2. During the growth stage from jointing to tasseling stage, the biomass accumulation accelerate due to the elongation of stem nodes and the increase of number of nodes, and the difference between the predicted and measured values waslarge and RMSE was825.92 kg/hm2. For example, the predicted value of biomass at early jointing stage was 535.5 kg/hm2, and the measured value was 480 kg/hm2, with a difference of 10.36%. Another example, the predicted value of biomass beforetasseling stage was 7036.46 kg/hm2, and the measured value was 5794 kg hm-2, the difference was 17.66%. Then, adjusting the parameters of the model, the predicted biomasswas6014 kg/hm2, which was close to the measured biomasswithRMSE 219.43 kg/hm2.Finally, by using the simulation model adjusted by the parameters, we predictedbiomass during the growth period from tasseling to grain filling that predicted values were in good agreement with the measured values, and the determinant coefficient between them was 0.978 and RMSE was 182.95 kg/hm2. For example, the predicted biomass at grain filling stage before parameter adjustment was12 492 kg/hm2, the measured biomass was 10 785 kg/hm2, the relative error was15.83%, and the predicted biomass after parameter adjustment was 11 156 kg/hm2with the relative error of 3.44%.This study provided an effective informatics method for forecasting the aboveground biomass and its dynamic changes of summer maize at different growth stages, and could assist the county agricultural management departments to adjust production measurestimely. Combining remote sensing data with crop process simulation model to estimate regional crop biomass or yield was a hot topic in the remote sensing application in agriculture. In this paper, crop process simulation model was used to analyze the trend of biomass change at three growth stages of summer maize, namely, emergence to jointing, jointing to tasseling, tasseling to filling, and to clarify the law of biomass accumulation and nutrient uptake characteristics at corresponding growth stages. In the follow-up study, LAI and biomass inversion using remote sensing data will be further considered, and assimilation and application of remote sensing data and crop process simulation model will be studied to enhance the universality and effectiveness of maize biomass process simulation model in maize planting areas along the East coast in China. [ABSTRACT FROM AUTHOR]

To illustrate the agronomic and economic effects of precision automatic fertilization and micro-spray irrigation technology on the winter wheat and summer maize, 3 field experiments were conducted in Beimeng village(38°14′24.87′′N, 114°46′56.41′′E), Fengshang village(38 13′ 21.6′′N, 114 46′48′′E) and Wangxia village(38°2′44.17′′N, 115°25′32.98′′E) in Xinji City Gaocheng District from October 2016 to June 2018. Each experiments including 2 treatments of CK and precision automatic fertilization and micro-spray irrigation treatment, the plot area is 6.67 hm2 for each treatment with 3 replication at random arrangement. The study areas belongs to the typical winter wheat and summer maize rotation in the northern North China Plain, and belongs to the semi-humid climate in warm temperate zone. The average annual temperature is 12.4-12.6 ºC, the accumulated temperature is 4 181-4 863 ºC, the annual precipitation is 488.2-498 mm, and the frost-free period is 190-209 days. The winter wheat sown in mid-October, and harvested in next mid-June, the maize sown in mid-June and harvested from the end of September to the beginning of October. Totally 2 winter wheat-summer maize rotation seasons were included in this experiments. For CK treatment, the fertilization rates and allocation budgets were based on farmers’ survey in the experiments areas. The winter wheat fertilization rates was N 216, 231 and 268.5 kg/hm2, P2O5 112.5, 120 and 105 kg/hm2, and K2O 37.5, 75 and 112.5 kg/hm2 respectively for each teat sites. All the P and K fertilizer applied before sowing, 52%-61% N as basal fertilizer applied before sowing and 39%-48% applied at shooting stage as topdressing. The summer maize fertilization rates were N 306, 318 and 294 kg/hm2, P2O5 36, 48 and 60 kg/hm2, K2O 36, 24 and 48 kg/hm2 respectively for each teat sites, all the P and K fertilizers applied as basal fertilizer, 53%-57% N as basal fertilizer applied before sowing and 43%-47% applied at 10 leaf stage as topdressing. The irrigation strategy for CK treatment was flooding irrigation. For precision automatic fertilization and micro-spray irrigation, fertilization rates and allocation budgets were based on agriculture experts knowledge. The winter wheat fertilization rates were N 157,180 and 180 kg/hm2, P2O5 90, 90 and101.5 kg/hm2, K2O 52.5, 75 and 75 kg/hm2 for each teat site. The allocation proportion for N as basal fertilizer, jointing stage topdressing and booting stage topdressing was 42.5%, 42.5% and 15%, respectively. P2O5 was 65%, 5%, 30%, respectively. K2O was 60%, 20%, 20%, respectively. The summer maize fertilization rates were N 210, 240 and 270 kg/hm2, P2O5 37.5, 43.5 and 45 kg/hm2, K2O 52.5, 60 and 67.5 kg/hm2 for each teat sites. The allocation proportion for N as basal fertilizer, 10 leaf stage topdressing and flowering stage topdressing was 50%, 45% and 5% respectively, P2O5 was 60%, 20% and 20% respectively, K2O was 50%, 30% and 20% respectively. For this treatment, the precision automatic fertilization and micro-spray irrigation was used in the whole growth seasons, fertilizers were accompanied with the irrigation water through the automatic irrigation channel system. The results showed that large scale the precision automatic fertilization and micro-spray irrigation technology used on winter wheat and summer maize could increase the crop yield, decrease the N, P fertilizer application and irrigation water amount, improve the net benefit. Compared with CK, the precision automatic fertilization and micro-spray irrigation technology significantly increased winter wheat yield by 10.6%, increased net income by 43. 77%, significantly reduced the production cost by 26.17%, reduced the amount of nitrogen and phosphorus by 24.20%, decreased the irrigation water by 57.45%. Correspondingly, precision automatic fertilization and micro-spray irrigation technology significantly increased summer maize yield by 13.73%, maize net benefits increased by 13.73%, reduced the production cost by17.09%, reduced the amount of nitrogen and phosphorus by 20.34%, decreased the irrigation water by 36.94% than the CK treatment. For the whole winter wheat and summer maize rotation season, the precision automatic fertilization and micro-spray irrigation technology significantly increased the crop yield by 12.26%, increased the net benefits by 37.39%, reduced the production cost by 21.85%, reduced the amount of nitrogen and phosphorus by 22.26%, reduced the irrigation water by 46.51%. This study confirmed the effect of precision automatic fertilization and micro-spray irrigation technology on winter wheat and summer maize, which can provides reference basis for the promotion of this new technology, thus promoting productivity and agricultural sustainable development. [ABSTRACT FROM AUTHOR]

• VWI is proposed by normalizing NDWI for daily drought monitoring of summer maize. • Double logistic fitting function is the optimal function form for fitting VWI with the highest R2. • The daily dynamic thresholds of different drought grades for summer maize are determined based on the actual disaster records. • The actual drought samples are used for validation of VWI with a high overall accuracy of 96.90%. • VWI shows a higher robustness and utility in temporal and spatial evolution of typical drought processes than CWDI. Effective daily drought monitoring for summer maize (Zea mays L.) is critical to prevent crop yield reduction. Most of the vegetation indicators used for drought identification have been based on changes in canopy greenness that may not change immediately under drought stress, and have relatively long-time intervals (e.g., eight or 16 days) that are limited by available remote sensing products. Moreover, drought thresholds, may be potentially different during different crop growth stages, rather than constant during the entire growing season, as has been widely used in most existing drought indicators. We used the orthorectified reflectance in the short-wave infrared (SWIR) band, extracted from MODIS MCD43A4 because of its high sensitivity to variations in vegetation water content due to this waveband's liquid water absorption characteristics. The Vegetation Water Index (VWI), calculated with the Normalized Difference Water Index (NDWI), was proposed for daily drought monitoring of summer maize in order to minimize the effects of geographical location, soil conditions, and ecological systems in different areas. Additionally, daily dynamic thresholds for drought-free, mild drought, moderate drought, and severe drought were determined with double logistic fitting functions having the highest R2 (0.79), based on the observed drought disaster and phenophase records of summer maize in the Huang-Huai-Hai region (HHH). Drought samples constructed from regional drought records and the Yearbook of Meteorological Disasters in China were used for drought validations. The results exhibited high accuracy (78.04% of total drought samples correctly showing complete correspondence with historical records regarding drought grades, and 96.90% of drought samples being within one drought grade level). Additionally, compared with the Crop Water Deficit Index (CWDI), the temporal and spatial evolution of typical drought processes were more accurately characterized by VWI. The results of this study provide a scientific basis and achieve quantitative monitoring for daily drought assessment of summer maize in HHH, and also provide a new perspective in dynamic and quantitative monitoring of agricultural disasters over large regions based on actual disaster records and remotely sensed images. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accurate diagnosis of nitrogen (N) fertilizer required for crop growth can serve as a guide for N management by improving N use efficiency and grain yields. The critical N concentration (N c ), the minimum N required for maximal crop growth has been widely used to determine crop N status. N c dilution curves have been determined in several crops including summer maize on plant dry matter (DM) basis, yet no attempt has been made to determine the N c dilution curve on the basis of leaf dry matter (LDM) in summer maize. The present study aimed to determine a N c dilution curve based on LDM for in-season assessment of crop N status in summer maize. Six field experiments were performed with four summer maize cultivars using varied N fertilizer rates ranging from 0 to 320 kg N ha −1 . The leaf N c curve was described by the equation: N c = 3.45LDM −0.22 , when LDM ranged from 1.18 to 3.45 t ha −1 . For LDM <1.18 t ha −1 , the constant N c = 3.33% was used. The newly developed curve effectively distinguishes N-limiting from non-N-limiting treatments under different environmental conditions. In the present study, the N nutrition index (NNI) ranged from 0.49 to 1.16 under different N rate treatments. The correlation between NNI and relative yield (RY) was a significantly positive, while the correlation between NNI and the agronomic N use efficiency (AE) was significantly negative. The newly developed leaf N c dilution curve not only determines the crop N status, but also elucidates the yield and AE changes in response to different N rate treatments in summer maize. The projected results of the study will provide accurate N status diagnosis at critical growth stages and guidance for precision N management in summer maize, thus contributes towards the sustainability of intensive maize cropping systems in China. [ABSTRACT FROM AUTHOR]

North China Plain is a main grain producing area in China. It is very important for China to find a simple and low carbon method for grain production. To better understand the potential for increasing grain yield and carbon absorption, treatment effects of straw mulching on grain yield, carbon absorption in crop growth period, and soil CO2 emission characteristics in 2012-2014 summer maize growing seasons were quantified. The experiment involved summer maize with two straw mulching rates, i.e., 0 and 0.6 kg m-2. The result showed that soil respiration rate in straw mulching (M) was significantly lower than that in non-mulching (N). The carbon absorption and grain yield in M was significantly higher than that in N. In the three growing seasons, ear number, kernels per row, 1000-kernel weight, and grain yield in M were higher than that in N by 4.07%, 4.03%, 10.93%, and 20.54%, respectively. The result indicates that straw mulching has the effect of yield increasing and soil carbon sequestration in summer maize crop in North China. [ABSTRACT FROM AUTHOR]

A quantitative description of the change in the cultivation distribution of summer maize under climate change can provide a scientific basis for optimizing the distribution of maize production in China and making countermeasures to cope with climate change. In this paper, we studied the relationship between the cultivation distribution of summer maize and climate in China and investigated the decadal change of cultivation distribution of summer maize and the change in climatic suitability from 1961 to 2010. The results indicate that there has been significant decadal change in the cultivation distribution and climatic suitability of summer maize in China. The most climate-suitable planting area for summer maize exhibited an obvious trend of eastward expansion, reaching its maximum area (3.4 × 10 7 hm 2 ) in the 1990s; the climate-suitable planting area exhibited a trend of southward expansion, the magnitude of which was relatively large in the last 20 years, approaching about 1.6 × 10 8 hm 2 in the last 10 years. The least climate-suitable planting area was the largest and generally exhibited a fluctuating change with a decrease-increase-decrease-increase pattern, with the largest magnitude of fluctuation reaching 2.9 × 10 7 hm 2 ; the climate-unsuitable area generally exhibited a downward trend, except for a slight increase in the 1970s. In the past 50 years, the arable area of summer maize clearly moved northward. Before the 1990s, expansion in a northwestern direction dominated; since the 1990s, expansion was mainly to the northeast. It indicated that there remains a very large potential of yield increase for summer maize in China against the background of climate change, which primarily concentrates in Northern China. [ABSTRACT FROM AUTHOR]

Cytokinin is known to be involved in the regulation of plant responses to counteract the adverse effects of stress conditions. This work investigated the effects of exogenous spraying of 6-benzyladenine (6-BA) after water logging for 6 days at the third leaf stage (V-3WL + BA) and the sixth leaf stage (V-6WL + BA) on grain yield and growth of summer maize hybrids DengHai605 (DH605) and ZhengDan958 (ZD958), which are planted most popularly in China. Waterlogging under field conditions delayed the growth process, decreased leaf area index, chlorophyll content and dry matter accumulation, resulted in a significant reduction of grain yield with a decrease of 30.30% and 18.78% under V-3WL (water logging for 6 days at the third leaf stage) and V-6WL (waterlogging for 6 days at the sixth leaf stage) of DH605, 30.39% and 21.38% under V-3WL and V-6WL of ZD958, respectively, compared to the control (CK). By contrast, exogenous application of 6-BA effectively alleviated the adverse effects of waterlogging on summer maize by delaying leaf senescence, increasing chlorophyll content and improving photosynthetic performance. At tasseling stage, the P n of V-3WL + BA and V-6WL + BA in DH605 increased by 9.57% and 8.38%, respectively, compared to that of V-3WL and V-6WL, while the corresponding values for ZD958 increased by 2.96% and 4.05%, respectively. Those responses are conducive to the accumulation of photosynthetic products, increasing grain filling rate, and improving ear character, and then leading to increase grain yield of summer maize. Grain yield of DH605 under V-3WL + BA and V-6WL + BA increased by 15.57% and 12.39%, respectively, compared to that of V-3WL and V-6WL, while the corresponding values for ZD958 increased by 20.05% and 15.32%, respectively. Clearly, spraying exogenous 6-BA could effectively improve grain-filling characteristics and photosynthesis of waterlogged summer maize, resulting in a significant increase of grain yield, compared to water logging treatments. [ABSTRACT FROM AUTHOR]

By understanding the relation between maize ( Zea mays L.) grain yield and phosphorus (P) uptake requirements it is possible to reduce both cost and environmental impact of maize production. The goal of this study was to determine P uptake requirements and patterns of P accumulation, pre- and post-silking, at different maize grain yield levels. A database comprising measurements in 955 plots in 44 on-farm and research station experiments during the period 2000–2012 on the North China Plain was used for the analyses. The P requirement (P req. , the P content Mg −1 grain yield on the basis of 155 g kg −1 moisture content) increased significantly from 2.84 kg in the P < Opt. treatment to 3.44 kg in the P > Opt. treatment. In the Optimal P treatment, average P req. values were 3.41, 3.15, 3.09, and 2.94 kg for grain yields ranging from <8.0, 8–10, 10–12, and >12.0 Mg ha −1 , respectively. The decrease in P req. values with increasing grain yield was mainly attributable to the increase in the harvest index from 0.47 to 0.53 and the decrease in grain P concentrations from 2.73 to 2.42 g kg −1 . A larger proportion of the P was accumulated post-silking when grain yields were higher than 10 Mg ha −1 (48%) and 8–10 Mg ha −1 (44%) than when yields were less than 8 Mg ha −1 (35%). Using this knowledge of P uptake requirements should improve assessments of global P balance, and help optimize P management, especially in high-yielding maize system. [ABSTRACT FROM AUTHOR]

Optimizing yields while reducing soil CO 2 emissions in cropping systems has become the focus of agricultural study. To explore effective ways to achieve the balance, short-term field experiments (2018–2020) were conducted in North China Plain. Three replications of three-factor combinations of two tillage systems (i.e., no-tillage and conventional tillage), two straw management (i.e., no straw and straw mulch), and two nitrogen fertilization levels (i.e., medium nitrogen of 180 kg N ha 1 and high nitrogen of 210 kg N ha 1) were arranged in a randomized complete block design. It was discovered that soil CO 2 emissions were mainly dominated by soil temperature. No-tillage decreased soil CO 2 emissions by 7.3% than conventional tillage, straw mulch promoted soil CO 2 emissions than no straw, and high fertilization increased CO 2 emissions by 21.8% compared to medium fertilization. However, maize yields were not significantly affected by above treatments. The combinations of agricultural practices that achieved the highest maize yields were medium nitrogen in combination with straw mulch under no-tillage and conventional tillage. The combination of no-tillage, straw mulch, and medium nitrogen decreased soil CO 2 emissions intensity by 11.5%. It was concluded that the combination of no-tillage, straw mulch amendment, and medium nitrogen achieved a balanced yields and soil CO 2 emissions, which should be recommended for local farmers in North China Plain. Sustainable agriculture: no-tillage, straw mulch, and medium nitrogen rate [Display omitted] • No-tillage and MN significantly decreased soil CO 2 emissions by 7.30% and 17.89%, respectively. • Straw mulch significantly increased soil CO 2 emissions by 105.17%. • No-tillage, straw mulch, and MN improved the grain yields by 3.69%, 18.68%, and 6.69%, respectively. • CO 2 emissions were suppressed by no-tillage combined with straw mulch. • No-tillage combined with straw mulch amendment and MN are recommended for intensive maize farming. [ABSTRACT FROM AUTHOR]

[Objective] The aim was to explore scientific application of N fertilizer for summer maize species. [Method] A test was designed to research effects of N quantities on Zhengdan No.958, Xundan No.20, Nonghua No.101 and Xianyu No. 335 in terms of yield, economic benefits, accumulated nitrogen and use efficiency of N fertilizer. [Result] The increase of N fertilizer improved yields of summer maize dramatically. Specifically, with low N quantity, yield and net revenue of Zhengdan No.958 reached 18.19% and 3 158 yuan/hm², respectively, and yields and net revenues of Jundan No.20, Nonghua No.101 and Xianyu No.335 were 17.31% and 2 642 yuan/hm², 25.03% and 3 726 yuan/hm², 17.41% and 3 182 yuan/hm², accordingly. With N quantity increased, agricultural efficiency of Zhengdan No.958 reduced significantly and the agricultural efficiencies showed little differences among Xundan No.20, Nonghua No.101 and Xianyu No.335. [Conclusion] In practice, Zhengdan No.958 is suitable to be applied with N at low quantity, and Xundan No.20, Nonghua No.101 and Xianyu No.335 are suitable to be applied with N at high quantity. [ABSTRACT FROM AUTHOR]

Haihe plain is an important food production area in China, facing an increasing water shortage. The water used for agriculture accounts for about 70% of total water resources. Thus, it is critical to optimize the irrigation scheduling for saving water and increasing crop water productivity (CWP). This study first simulated crop yield and CWP for winter wheat and summer maize in historical scenario during 1961-2005 for Haihe plain using previously well-established Soil and Water Assessment Tool model. Then, scenarios under historical irrigation (scenario 1) and sufficient irrigation (scenario 2) were, respectively, simulated both with sufficient fertilizer. The crop yield in scenario 2 was considered as the potential crop yield. The optimal irrigation scheduling with sufficient fertilizer (scenario 3) was explored by iteratively adjusting irrigation scheduling based on the scenario 1 and previous studies related to water stress on crop growth. Results showed that net irrigation amount was, respectively, reduced 23.1% and 18.8% in scenario 3 for winter wheat and summer maize when compared with scenario 1. The CWP was 12.1% and 8.2% higher with very slight change of crop yield. Using optimal irrigation scheduling could save 8.8 × 108 m3 irrigation water and reduce about 16.3% groundwater over-exploitation in winter wheat growth period. The corresponding yield was 18.5% and 12.9% less than potential yield for winter wheat and summer maize but using less irrigation water. Therefore, it could be considered that the optimal irrigation was reasonable, which provided beneficial suggestions for increasing efficiency of agricultural water use with sustainable crop yield in Haihe plain. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Although straw mulching and nitrogen applications are extensively practiced in the agriculture sector, large uncertainties remain about their impacts on crop yields and especially the environment. The responses of summer maize yields, fertilizer use efficiency, and greenhouse gas (GHG) emissions including carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) in the North China Plain (NCP) to two straw management practices (S0: no straw and S1: straw mulching) and two nitrogen application rates (N1: 180 and N2: 210 kg N ha -1 ) were investigated in field tests in 2018, 2019, and 2020. The highest yields and partial factor productivity (PFP) were obtained by S1N1, followed by S1N2, S0N1, and S0N2. S1N2 had the highest CO 2 emissions and greatest CH 4 uptake, S0N1 had the lowest CO 2 emissions, and S0N2 had the smallest CH 4 uptake. The highest and lowest N 2 O emissions were found in S0N1 and S1N1, respectively. The S1N2 treatment, an extensively applied practice, had the greatest global warming potential (GWP), which was 70.3 % larger than S1N1 and two times more than S0N1 and S0N2. The largest GHG emission intensity (GHGI) of 19.4 was found in the S1N2 treatment, while the other three treatments, S0N1, S0N2, and S1N1, had a GHGI of 10.1, 10.7, and 10.7, respectively according to three tested results. In conclusion, S1N1 treatment achieved a better trade-off between crop yields and GHG emissions of summer maize in NCP., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. This manuscript has not been published or presented elsewhere in part or in entirety and is not under consideration by another journal. We have read and understood your journal's policies, and we believe that neither the manuscript nor the study violates any of these. There are no conflicts of interest to declare., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Climate change has and will continue to exert significant effects on social economy, natural environment, and human life. Research on the climatic suitability of crops is critical for mitigating and adapting to the negative impacts of climate change on crop production. In the study, we developed the climate suitability model of maize and investigated the climate suitability of summer maize during the base period (1981–2010) and two future periods of 2031–2060 (2040s) and 2071–2100 (2080s) in the North China Plain (NCP) based on BCC-CSM2-MR model (BCC) from the Coupled Model Comparison Program (CMIP6) under two Shared Socioeconomic Pathways (SSP) 245 and SSP585. The phenological shift of maize under future climate scenarios was simulated by the Agricultural Production Systems Simulator (APSIM). The results showed that the root mean square errors (RMSE) between observations and projections for sunshine suitability (SS), temperature suitability (ST), precipitation suitability (SP), and integrated climate suitability (SZ) during the whole growth period were 0.069, 0.072, 0.057, and 0.040, respectively. Overall, the BCC projections for climate suitability were in suitable consistency with the observations in the NCP. During 1981–2010, the SP, ST, and SZ were high in the north of the NCP and low in the south. The SP, ST, and SZ showed a downward trend under all the future climate scenarios in most areas of NCP while the SS increased. Therein, the change range of SP and SS was 0–0.1 under all the future climate scenarios. The ST declined by 0.1–0.2 in the future except for the decrease of more than 0.3 under the SSP585 scenario in the 2080s. The decrease in SZ in the 2040s and 2080s under both SSP scenarios varied from 0 to 0.2. Moreover, the optimum area decreases greatly under future scenarios while the suitable area increases significantly. Adjusting sowing data (SD) would have essential impacts on climate suitability. To some extent, delaying SD was beneficial to improve the climate suitability of summer maize in the NCP, especially under the SSP585 scenario in the 2080s. Our findings can not only provide data support for summer maize production to adapt to climate change but also help to propose agricultural management measures to cope with future climate change. [ABSTRACT FROM AUTHOR]

The irrigated areas in the northern region of China are important food production areas. Therefore, studies on the variability of the carbon balance in these agro-ecosystems are fundamental for the management of carbon sequestration. This paper simulated the long-term variability of the carbon balance in a typical irrigated area along the lower Yellow River from 1984 to 2006, using a process-based ecosystem model called the Simple Biosphere Model, version 2. The mean annual gross primary production (GPP), mean annual net assimilation rate (NAR), mean annual soil respiration ( R), and mean annual net ecosystem exchange (NEE) were 1733, 1642, 1304, and −338 g C m a, respectively. A significant increasing trend in the seasonal total NAR during the wheat growing season, and a significant decreasing trend in the seasonal total NAR during the maize growing season were detected. However, no significant trend was found in the annual NAR, R, and NEE. The average carbon sequestration was 1.93 Tg C a when the grain harvest was not taken into account, and the carbon sequestration amount during the maize season was higher than that during the wheat season. However, the agro-ecosystem was a weak carbon source with a value of 0.23 Tg C a, when the carbon in the grain was assumed emitted into the atmosphere. [ABSTRACT FROM AUTHOR]

Here, we investigated the effects of straw returning combined with biochar application on summer maize yield and soil nitrous oxide (N 2 O) emissions, based on a field location trial in the Guanzhong Plain from 2019 to 2020. The soil N 2 O emission rates were monitored using the static chamber-chromatography method. A comprehensive analysis of summer maize yields, soil N 2 O emissions, and soil labile nitrogen components was conducted to clarify the effects of straw returning combined with biochar application on improving soil fertility, increasing summer maize yield, and reducing greenhouse gas emissions. The three treatments were no straw returning (S 0 ), straw returning (S), and straw returning combined with biochar application (SB). The results showed that the peak of N 2 O emissions from each treatment occurred 10 d after the straw return, and the rate of soil N 2 O emissions remained at a low level after 30 d of straw return. The rate of soil N 2 O emissions showed highly significant positive correlations ( P <0.05) with ammonium nitrogen (NH 4 -N), inorganic nitrogen (SIN), microbial nitrogen (MBN), and dissolved organic nitrogen (DON) contents. S significantly increased summer maize yield, cumulative N + -N), inorganic nitrogen (SIN), microbial nitrogen (MBN), and dissolved organic nitrogen (DON) contents. S significantly increased summer maize yield, cumulative N 2 O emissions, yield-scaled N 2 . Although the trend for SB to increase summer maize yield (2.5%-3.3%) compared to that in S was not significant ( 0 . Although the trend for SB to increase summer maize yield (2.5%-3.3%) compared to that in S was not significant ( P >0.05), SB significantly reduced cumulative N 2 O emissions and yield-scaled N 2 O intensity by 24.0%-27.3% and 26.4%-29.2%, respectively, compared to that in S. SB significantly reduced the rate of soil N 2 O emissions by 45.1%-69.6% at the peak of N 2 O emissions induced by straw return and had a peak-shaving effect. SB significantly increased soil total N by 9.1%-12.2% compared to that in S. Combining summer maize yield, soil N 2 O emissions, and TN content, SB not only improved soil fertility and summer maize yield but also reduced yield-scaled N 2 O emissions, and TN content, SB not only improved soil fertility and summer maize yield but also reduced yield-scaled N 2 O intensity, making it a suitable management practice that can be replicated to balance crop yield and environmental friendliness.

Abstract: Excessive nitrogen (N) fertilizer application, outdated fertilization techniques, and non-optimal planting patterns are current cultivation problems with summer maize (Zea mays L.) among smallholders in North China. To try to solve those problems, this study examined four integrated agronomic management treatments-MT (FP: traditional farming practices; OPT-1: an optimized combination of cropping systems and fertilizer treatment; HY: treatment based on high-yield studies; and OPT-2: further optimized combination of cropping systems and fertilizer treatment) and four N application rate treatments-NT (0, 129.0, 184.5, and 300.0kgha−1). Maize grain yield and N efficiency were determined under each treatment. Grain yield, yield components, individual/population dry matter weight, N partial factor productivity (PFPN), N use efficiency (NUE), and agronomic efficiency of N (AEN) were measured. Results from the NT revealed no significant increase in grain yield in response to N applied above 184.5kgha−1 and increased yield was achieved by the MT. In MT, the change in sowing method from relay intercropping to direct seeding was effective in avoiding maize rough dwarf virus and in encouraging mechanized production; individual and population dry matter accumulation from the tasseling stage (VT) to physiological maturity stage (R6) increased in response to delayed sowing date and harvesting time; grain yield increased significantly from more ears per hectare due to increased planting density; and high N efficiency was achieved after optimizing fertilization patterns. In this study, OPT-2 obtained 67.0%, 104.0%, and 53.5% higher grain yield, PFPN, and NUE, respectively, compared to FP, achieving high yield and high N efficiency. Furthermore, the low AEN value suggests that further reduction in the N application rate of OPT-2 may be possible. [Copyright &y& Elsevier]

Abstract: In the rain-fed areas of northern China, maize (Zea mays L.) is a main field crop, as it is well adapted to high temperatures and bright sunshine. However, low and variable rainfall and high evapotranspiration rates are common in water-limited environments during the growing season, and often mismatched rainfall events with the critical growth stages, making yield unstable. In this study, the performance of a furrow-planting and straw-mulching system was compared with the conventional flat-planting system in a double-crop culture of winter wheat (Triticum aestivum L.) and summer maize for two consecutive years (2005–2006 and 2006–2007). The four tested treatments were: conventional flat planting (F), furrow planting between ridges (B), flat planting with wheat straw-mulching (FS), and furrow planting between ridges with wheat-straw mulch (BS). Soil water content and leaf area index (LAI) were measured throughout the growing season each year, and grain yield and precipitation-use efficiency (PUEY) were determined. On average, ridge tillage combined with furrow planting increased maize yield by 430kgha−1 (7.3%) and PUEY by 10.7% (1.5kgha−1 mm−1), compared with the conventional flat planting; furrow planting coupled with straw mulching increased yield by an additional 16.9% and PUEY by 19.4%, respectively. From jointing to maturity, LAI values of BS were significantly higher than those of F-system (55.6% vs. 26.1% in 2006 and 81.4% vs. 21.7% in 2007). Our data suggest that maize production adopted by furrow planting with straw-covered ridges performed best under seasonal average rainfall below 480mm, which was associated with better synchronization of seasonal soil water supply and crop needs, leading to improved maize yield and PUEY. [Copyright &y& Elsevier]

Abstract: Fresh water shortages are severally restricting sustainable agriculture development in the North China Plain. The scarcity of fresh water has forced farmers to use brackish water from shallow underground sources, which helps to overcome drought and increase crop yields but also increases the risk of soil salinization. To identify safe and effective ways of using brackish water in this region, field experiments were conducted to evaluate the effect of brackish water irrigation and straw mulching on soil salinity and crop yield in a winter wheat–summer maize double cropping system. The experiment was in a split-plot design. Six rates of straw mulching (0, 4.5, 6.0, 7.5, 15.0 and 30.0Mg/ha) were assigned to the main plots and two irrigation water qualities (i.e. brackish water with salt content of 3.0–5.0g/L and fresh water with only 1.27g salt/L) were applied to subplots. The brackish water irrigation significantly increased the salt content at different soil depths in the upper 1m soil layer during the two growing seasons. Straw mulching affected the vertical distribution of salt in the brackish water irrigation plots and the average salt content of straw mulch treatments (4.5, 6.0, 7.5, 15.0 and 30.0Mg/ha) within the 0–20, 20–40 and 0–100cm soil depths was 10.2, 14.0 and 1.8% lower than that without straw mulch (A0). No salt accumulation occurred to a depth of 1m in the brackish water irrigation plots and there was no correlation between the value of SAS (salt accumulated in 1m of soil) and straw mulch rate. In 2000 and 2001, the salt content within the 0–40cm soil layer in brackish water irrigation plots increased due to high evaporation rates during April–June, and then decreased up to September as salts were leached by rain. For the fresh water irrigation plots, the salt content remained relatively stable. Straw mulching affected the salt content in the 0–40cm soil layer in brackish water irrigation plots in different periods of 2000 and 2001, but no correlation between salt content and straw mulch rates was observed except in September of 2000. Unlike for wheat, the yield of maize increased as the straw mulch rate increased according to the equation, y =0.1589x +5.3432 (R 2 =0.6506). Our results would be helpful in adopting brackish water irrigation and straw mulching in ways that enhance crop yields and reduce the risk of soil salinization. However, long-term effects of brackish water irrigation and straw mulching on soil salinity and crop yield need to be further evaluated for sustainability of the system. [Copyright &y& Elsevier]

Modelling of the carbon dynamics in arable soils is complex and the accuracy of the predictions is unknown before the model is applied to each specific site. Objectives were (i) to test the accuracy of predictions of the carbon dynamics using the Rothamsted Carbon (RothC) Model in a field trial in Quzhou, North China Plain, using different methods for initialization and estimation of carbon input into the soil and (ii) to test the applicability of the RothC model for plots with either conventional tillage (CT) or no-tillage (NT) systems. A field trial was conducted with applications of differing amounts of N (0, 112 or 187 kg N ha−1 year−1), P (0, 75 or 150 kg P2O5 ha−1 year−1) and wheat straw (0, 2.25 or 4.5 t DM ha−1 year−1) in differing combinations with either CT or NT for 18 years. CT and NT affected stocks of soil organic carbon (SOC) similarly. Carbon inputs from crops were either estimated from published regression functions that relate C inputs to crop yield including rhizodeposition (models 1 and 2) or published root:aboveground biomass ratios (model 3). Model 1, which was not calibrated to the site conditions, was successful in predicting the carbon dynamics in seven out of nine treatments (model efficiencies EF ranged from 0.28 to 0.87), whereas for two treatments, EF (−0.35 and−2.3) indicated an unsuccessful prediction. The prediction of the C dynamics in NT experiments using model 1 was generally successful, but this may have been due to the fact that NT did not have a specific effect on SOC stocks for this trial. Model 2, which was the same as model 1 except for an optimization of the stock of inert organic matter using one treatment, predicted SOC stocks in the remaining eight treatments overall better than model 1. Model 3 was less successful than models 1 and 2 in all treatments (−19 ≤ EF ≤ 0.56). The results indicate that the RothC model may successfully predict C dynamics—for the site studied even without prior calibration as in model 1—, but care should be taken in choosing an appropriate approach for estimating C inputs into the soil. [ABSTRACT FROM AUTHOR]

Abstract: Using the eddy covariance technique, three years (October 2005–September 2008) of water and energy flux measurements were obtained for a winter wheat/summer maize rotation cropland in the North China Plain. This region is critical for food production in China, and is prone to significant water shortages and drought. Seasonal and interannual variability in evapotranspiration (ET) were examined in terms of relevant controlling factors. The annual ET was 595 and 609mm in the periods of 2005–2006 and 2006–2007, respectively. The average seasonal ET in the wheat and maize field was 401 and 212mm, respectively. Seasonal variability in ET was primarily explained by the variations in equilibrium evaporation (ET eq) and canopy conductance (G s). Daily evapotranspiration ranged from 1.0 to 7.8mmday−1 during the wheat season and reached up to 5.1mmday−1 during the maize season. The maximum midday average G s was 32mms−1 for wheat and 17mms−1 for maize. During the rapid growth stages, the average midday LE/R n (LE is latent heat flux, R n is net radiation) was 83% for wheat and 57% for maize, indicating a higher water consumption for wheat than for maize. On an annual basis, latent heat flux accounted for about 59% of the net radiation, suggesting that more energy is partitioned into evapotranspiration in this agroecosystem site. Regional irrigation promoted sensible heat advection from the surrounding drier surface during the wheat seasons. Monthly ET totals enhanced by sensible heat advection accounted for 27% of the ET eq during the rapid growing season of wheat. [Copyright &y& Elsevier]

Summary: The eddy covariance technique and the cuvette method were used to investigate water use efficiency in an irrigated winter wheat (Triticum asetivum L.)/summer maize (Zea mays L.) rotation system in the North China Plain. The results show that ecosystem water use efficiency (WUEe) changed diurnally and seasonally. Daily maximal WUEe appeared in the morning. WUEe generally peaked in late April in wheat field and in late July/early August in maize field. From 2003 to 2006, seasonal mean WUEe was 6.7–7.4mg CO2 g−1 H2O for wheat and 8.4–12.1mg CO2 g−1 H2O for maize. WUEe was much lower than canopy water use efficiency (WUEc) under small leaf area index (LAI) but very close to WUEc under large LAI. With the increase in LAI, WUEe enlarged rapidly under low LAI but slowly when LAI was higher than one. WUEe was greater on the cloudy days than on the sunny days. Under the same solar radiation, WUEe was higher in the morning than in the afternoon. The ratio of internal to ambient CO2 partial pressure (C i/C a) decreased significantly with the increase in photosynthetically active radiation (PAR) when PAR was lower than the critical values (around 500 and 1000μmolm−2 s−1 for wheat and maize, respectively). Beyond critical PAR, C i/C a was approximately constant at 0.69 for wheat and 0.42 for maize. Therefore, when LAI and solar radiation was large enough, WUEe has negative correlation with vapor pressure deficit in both of irrigated wheat and maize fields. [Copyright &y& Elsevier]

Best nitrogen (N) management and N-efficient cultivars were two main strategies used to add N capture from soil, environment and fertilizer N sources, and increase grain yield and N use efficiency (NUE). This study aimed to evaluate the interaction between genotypic difference and nitrogen management strategy and to determine optimal N management strategy for summer maize hybrids ( Zea mays L.) in China. Two on-farm experiments with six N levels and two maize hybrids (NE and ND) were conducted in HM County of the North China plain (NCP) in 2005 and 2006. The maize hybrid of NE has proved to have higher grain yield potential with lower N applications, compared to ND of the major commercial hybrid in the NCP. Calculated maximum grain yield of NE reached 9.3 and 7.7 t ha−1 using grain response curve, compared to 6.4 and 6.4 t ha−1 for ND in 2005 and 2006, respectively. No N fertilizer and only 79 kg N ha−1 for NE were required to achieve the maximum grain yield of ND, which required 150 and 116 kg N ha−1 in 2005 and 2006, respectively. Compared with those of ND, high N stress tolerance, low N demand with low straw N concentration and high growing capacity after ten-leaf stage were main reasons to achieve higher grain yield with lower N fertilizer application for NE. Although calculated optimal N rates for NE by grain yield response curve were significantly higher than these for ND, no differences were observed before the ten-leaf stage. Therefore, we conclude that more N fertilizer should be applied after ten-leaf stage for higher grain yield potential hybrid of NE in comparison to common hybrid of ND. [ABSTRACT FROM AUTHOR]

The intensive use of groundwater and nitrogen fertilizer has led to serious negative impacts on the environment of the North China Plain (NCP). Water footprint is an emerging approach to assess the consumptive water use and the environmental impacts on winter wheat-summer maize systems. A seven-year rotation experiment was conducted to collect data on wheat and maize growth response to nitrogen rates and irrigation schedules and to explore how the water footprint was affected, using DSSAT 4.6 Wheat and Maize crop models. Results showed that the increase in farm inputs contributed greatly to the increase in water footprint, primarily through the grey water footprint. The water footprints of maize and wheat were more sensitive to the nitrogen rate and irrigation, respectively. An irrigation of 160 mm produced a minimum total water footprint and higher yield for wheat. The grey water footprint of maize increased linearly when the nitrogen rate applied to maize exceeded 60 kg ha−1. Water-saving irrigation with 300 kg ha−1 of nitrogen can maintain a higher grain yield and have little impact on the environment. The approach used and the results can help to develop management strategies to maintain high yields while minimizing the water footprint in NCP. [ABSTRACT FROM AUTHOR]

In order to explore the optimal cultivar × sowing date × plant density for summer maize (Zea mays L.) in the Northern Huang–Huai–Hai (HHH) Plain of China, field experiments were conducted over two consecutive years (2018–2019) on a loam soil in the Northern HHH Plain. A split–split plot design was employed in this study, and the main plots included three cultivars (HM1: early-maturing cultivar; ZD958: medium-maturing cultivar; DH605: late-maturing cultivar); subplots consisted of three sowing dates (SD1: June 10; SD2: June 17; SD3: June 24); sub-sub plots include two plant densities (PD1: 6.75 × 104 plants ha−1; PD2: 8.25 × 104 plants ha−1). The results showed that the effects of cultivar and plant density on grain yield of summer maize were not significant, and the sowing date was the major factor affecting the grain yield. Delayed sowing significantly decreased the grain yield of summer maize, this was due mainly to the reduced kernel weight, which is associated with the lower post-anthesis dry matter accumulation. Moreover, radiation use efficiency (RUE), temperature use efficiency (TUE), and water use efficiency (WUE) were significantly affected by cultivar, sowing date, and plant density. Selecting early- and medium-maturing cultivars was beneficial to the improvements in RUE and TUE, and plants grown at earlier sowing with higher plant density increased the RUE and TUE. The interactive analysis of cultivar × sowing date × plant density showed that the optimum grain yields of all tested cultivars were observed at SD1-PD2, and the optimum RUE and TUE for HM1, ZD958, and DH605 were observed at SD1-PD2, SD2-PD2, and SD2-PD2, respectively. The differences in the optimum grain yield, RUE, and TUE among the tested cultivars were not significant. These results suggested that plants grown at earlier sowing with reasonable dense planting had benefits of grain yield and resource use efficiency. In order to adapt to mechanized grain harvesting, early-maturing cultivar with lower grain moisture at harvest would be the better choice. Therefore, adopting early-maturing cultivars grown with earlier sowing with reasonably higher plant density would be the optimal planting pattern for summer maize production in the Northern HHH Plain of China in future. [ABSTRACT FROM AUTHOR]