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This 2-year field study analyzed plastic film mulching (PFM) effects on nitrogen use efficiency (NUE), and soil N pools under rainfed dryland conditions. Compared to no-mulching (NM, control), maize yields under PFM were increased by 36.3% (2515.7 kg ha−1) and 23.9% (1656.1 kg ha−1) in the 2020 and 2021 growing seasons, respectively. The PFM improved (p < 0.01) the water use efficiency (WUE) of maize by 39.6% and 33.8% in the 2020 and 2021 growing seasons, respectively. The 2-year average NUE of maize under the PFM was 40.1, which was 30.1% greater than the NM. The average soil total N, particulate organic N, and microbial biomass N contents under the PFM soil profile were increased by 22.3%, 51.9%, and 35%, respectively, over the two growing seasons. The residual 15N content (%TN) in soil total N pool was significantly higher (p < 0.05) under the PFM treatment. Our results suggest that PFM could increase maize productivity and sustainability of rainfed dryland faming systems by improving WUE, NUE, and soil N pools. [ABSTRACT FROM AUTHOR]

The intensive winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping systems in the North China Plain (NCP) rely on the heavy use of mineral nitrogen (N) fertilizers. As the fertigated area of wheat and maize in the NCP has grown rapidly during recent years, developing N management strategies is required for sustainable wheat and maize production. Field experiments were conducted in Hebei Province during three consecutive growth seasons in 2012–2015 to assess the influence of different N fertigation rates on N uptake, yield, and nitrogen use efficiency [NUE: recovery efficiency (REN) and agronomic efficiency (AEN)]. Five levels of N application, 0 (FN0), 40 (FN40%), 70 (FN70%), 100 (FN100%), and 130% (FN130%) of the farmer practice rate (FP: 250 kg N ha−1 and 205.5 kg N ha−1 for wheat and maize, respectively), corresponding to 0, 182.2, 318.9, 455.5, and 592.2 kg N ha−1 y−1, respectively, were tested. Nitrogen in the form of urea was dissolved in irrigation water and split into six and four applications for wheat and maize, respectively. In addition, the treatment "drip irrigation + 100% N conventional broadcasting" (DN100%) was also conducted. All treatments were arranged in a randomized complete block design with three replications. The results revealed the significant influence of both N fertigation rate and N application method on grain yield and NUE. Compared to DN100%, FN100% significantly increased the 3‐year averaged N recovery efficiency (REN) by 0.09 kg kg−1 and 0.04 kg kg−1, and the 3‐year averaged N agronomic efficiency (AEN) by 2.43 kg kg−1 and 1.62 kg kg−1 for wheat and maize, respectively. Among N fertigation rates, there was no significant increase in grain yield in response to N applied at a greater rate than 70% of FP due to excess N accumulation in vegetative tissues. Compared to FN70%, FN100%, and FN130%, FN40% increased the REN by 0.17–0.57 kg kg−1 and 0.03–0.34 kg kg−1and the AEN by 4.60–27.56 kg kg−1 and 2.40–10.62 kg kg−1 for wheat and maize, respectively. Based on a linear‐response relationship between the N fertigation rate and grain yield over three rotational periods it can be concluded that recommended N rates under drip fertigation with optimum split applications can be reduced to 46% (114.6 kg N ha−1) and 58% (116.6 kg N ha−1) of FP for wheat and maize, respectively, without negatively affecting grain yield, thereby increasing NUE. [ABSTRACT FROM AUTHOR]

‘One film for 2 years’ (PM2) has been proposed as a practice to control the residual film pollution; however, its effects on grain-yield, water-use-efficiency and cost-benefit balance in dryland spring maize production have still not been systematically explored. In this study, we compared the performance of PM2 with the annual film replacement treatment (PM1) and no mulch treatment (CK) on the Loess Plateau in 2015-2016. Our results indicated the following: (1) PM2 was effective at improving the topsoil moisture (0-20 cm) at sowing time and at seedling stage, but there was no significant influence on soil water storage, seasonal average soil moisture or evapotranspiration; (2) PM2 induced significantly higher cumulative soil temperatures compared to CK, and there was no significant difference between PM2 and PM1; (3) no significant differences were identified in grain-yield and water-use-efficiency between PM1 and PM2, and compared to CK, they improved by 16.3% and 15.5%, respectively; (4) because of lower cost of plastic film, tillage, film laying and remove in PM2, economic profits improved by 21% and 70% compared to PM1 and CK. This research suggested that PM2 was effective at alleviating the spring drought and was beneficial in reducing poverty traps in dryland. [ABSTRACT FROM AUTHOR]

• The SW m , PT m , and DK m models were developed in a rainfed spring maize cropland. • The three modified models could reasonably reproduce the ET and its components. • The PT m model was finally recommended for rainfed spring maize. Accurately estimated evapotranspiration (ET) and its components in the growing season of cropland are required to optimize agricultural practices and improve water use efficiency. In this study, we developed a modified Shuttleworth–Wallace (SW m) model, a modified Priestley-Taylor (PT m) model, and a modified dual crop coefficient (DK m) model based on the characteristics of a rainfed spring maize cropland on the Loess Plateau. The estimated ET and its components by the three models were compared with the measured ET and its components using an eddy covariance system and microlysimeters. The results indicated that the three models performed well in estimating the 30 min ET and daily ET and its components during the growing seasons of the rainfed spring maize field in 2015 and 2016. The diurnal course of the measured 30 min ET was closest to that of the estimated 30 min ET from the DK m model, and this model performed best to estimate 30 min ET with a regression coefficient (b 0) of 1.01 (R2 = 0.89) in 2015 and 0.97 (R2 = 0.88) in 2016. According to statistical analysis, the PT m model outperformed the other two modified models on estimating daily ET with b 0 of 0.97 (R2 = 0.89) and 0.94 (R2 = 0.89) and daily plant transpiration (T p) with b 0 of 1.07 (R2 = 0.93) and 1.11 (R2 = 0.93) during the both growing seasons. The performance of the three modified models on daily soil evaporation (E s) was not as good as that of daily ET and T p , and the DK m model performed best to reproduce daily E s with a b 0 of 0.91 (R2 = 0.37) and 0.88 (R2 = 0.54) in 2015 and 2016, respectively. As the PT m model required the fewest input variables among the three modified models, this model was finally recommended for rainfed spring maize on the Loess Plateau, China. [ABSTRACT FROM AUTHOR]

An understanding of the dynamics of soil organic carbon (SOC) as affected by farming practices is imperative for maintaining soil productivity and mitigating global warming. The objectives of this study were to investigate the effects of long-term fertilization on SOC and SOC fractions for the whole soil profile (0–100 cm) in northwest China. The study was initiated in 1979 in Gansu, China and included six treatments: unfertilized control (CK), nitrogen fertilizer (N), nitrogen and phosphorus (P) fertilizers (NP), straw plus N and P fertilizers (NP+S), farmyard manure (FYM), and farmyard manure plus N and P fertilizers (NP+FYM). Results showed that SOC concentration in the 0–20 cm soil layer increased with time except in the CK and N treatments. Long-term fertilization significantly influenced SOC concentrations and storage to 60 cm depth. Below 60 cm, SOC concentrations and storages were statistically not significant between all treatments. The concentration of SOC at different depths in 0–60 cm soil profile was higher under NP+FYM follow by under NP+S, compared to under CK. The SOC storage in 0–60 cm in NP+FYM, NP+S, FYM and NP treatments were increased by 41.3%, 32.9%, 28.1% and 17.9%, respectively, as compared to the CK treatment. Organic manure plus inorganic fertilizer application also increased labile soil organic carbon pools in 0–60 cm depth. The average concentration of particulate organic carbon (POC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) in organic manure plus inorganic fertilizer treatments (NP+S and NP+FYM) in 0–60 cm depth were increased by 64.9–91.9%, 42.5–56.9%, and 74.7–99.4%, respectively, over the CK treatment. The POC, MBC and DOC concentrations increased linearly with increasing SOC content. These results indicate that long-term additions of organic manure have the most beneficial effects in building carbon pools among the investigated types of fertilization. [ABSTRACT FROM AUTHOR]

Abstract: Estimation of global solar radiation (R s ) from the daily range of air temperature (ΔT) offers an important alternative in the absence of measured R s or sunshine duration because of the wide availability of air temperature data. In this paper, we assessed 16 R s models including modified versions of the Bristow and Campbell (B–C) and the Hargreaves (Harg) models across a wide range of agro-ecological conditions in China. Using long-term data from 15 sites in Northeast, North China Plain and Northwest China, we explored the main factors affecting model parameters and the predictive accuracy and proposed empirical equations to estimate these parameters. Two schemes in calculating ΔT were employed: ΔT 1 (based on single day T min) used in the Harg and ΔT 2 (based on 2-day average of T min) used in the B–C model. Results showed that the original B–C model performed similarly to the best performing modified Harg model, but significantly outperformed the original Harg model with a 4–7% higher accuracy. The common practice of fixing some parameters in the B–C model caused the most significant effect and resulted in a 3–9% lower accuracy than that of the original model. In contrast, modifications had the smallest effect and yielded little improvement and are thus unnecessary. The ΔT scheme had a moderate effect, with ΔT 1 generally resulting in a higher accuracy especially in high altitude areas. This indicates that the effect of cold or warm air advection is negligible in the B–C model even in a temperate climate. The accuracy of the temperature-based models was affected mainly by the magnitude of ΔT, with larger ΔT resulting in higher accuracy. Parameters of the B–C model correlated significantly with many commonly used geographical and meteorological factors, meaning that they are more easily obtainable without the need for calibration and consequently R s measurement. The parameter of the original Harg model correlated insignificantly with all the examined factors, meaning that it has to be calibrated. Main findings in this study are valuable in clarifying the relative impact of different approaches in applications on model accuracy, in demonstrating the advection effect, in identifying the dominant factors of model parameters and thus in increasing their availability. [Copyright &y& Elsevier]

Abstract: Accurate estimation of the reference crop evapotranspiration (ET 0) is investigated due to its critical role in affecting calculation of crop water use and efficiency in agricultural ecosystems. The main emphasis in this paper is to clarify the possible uncertainty in the estimation of ET 0 associated with using un-calibrated Ångström–Prescott (A–P) coefficients. We first calibrated the coefficients using long-term data records from 34 sites in the Yellow River basin in China, and then applied these coefficients to estimate short wave irradiance (R s ) and ET 0 at 16 sites to evaluate the difference in ET 0 between the FAO recommended and the locally calibrated. We found that the direct use of the FAO recommended coefficients significantly affected the estimation of ET 0 at most sites, which differed from −3% to 15% at daily scale and from −4% to 16% at monthly scale from the locally calibrated ones. These differences are comparable with or larger than those caused by some alternatives of the FAO recommended algorithms for net irradiance or vapor pressure, which further highlights the importance of using the locally calibrated coefficients. The degree of difference in ET 0 showed a significant threshold relation with altitude and longitude in such a way that relatively small impact lies around 2233m and 98°E, and away from these, the effect begins to increase. Given the large overestimation in water use as a consequence of the significant overestimation in ET 0 associated with the direct use of the FAO coefficients, especially in those high yield production areas with altitude <1200m, we developed several relationships between the A–P coefficient a, b, (a + b) and other easily obtainable factors (altitude, longitude and air temperature). A three-step procedure was recommended in applying these relations, which was (1) determine if calibration is needed or not for a given location; (2) estimate one of the A–P coefficients, either a or b if calibration is needed; (3) estimate the remaining coefficient using relations of (a + b) due to its higher coefficient of determination. In summary, we have revealed the errors and areas that are most affected when using the un-calibrated coefficients, and discussed the consequence of such error on agricultural production, and proposed practical solutions to avoid large errors. These results are intended to make the research community aware of such errors so that more appropriate choice of these coefficients is made. We hope that similar assessment will be done in other climates, contributing to managing water resources efficiently in water basins. [Copyright &y& Elsevier]

Abstract: The Ångström–Prescott (A–P) equation relating in its current form the incident top-of-atmosphere solar radiation to the solar radiation received at the surface, is one of the most accurate and widely used sunshine-based methods estimating global solar radiation (R s). The key in its application is the calibration of the locally specific coefficients. Although the coefficients have been extensively studied and calibrated in many places over the world, their relations with time scale are much less investigated. This paper addressed the variation in these coefficients caused by time scale and how this variation results on the accuracy of R s predictions. This was done using long-term data at 31 sites from the Yellow River basin in China by parallel calibration at three time scales: daily, monthly mean daily and yearly mean daily. We found that the A–P coefficients obtained using monthly data generally had higher a and lower b and larger variations over those using daily data. At yearly time scale, the sunshine–radiation relationship can no longer be described by the linear A–P formula. The difference in coefficients between daily and monthly calibration was rather large accounting for 71% of the differences in a and 61% in b that in turn were greater than 0.03, corresponding to 81% for a and 49% for b being greater than 10%. Time scale had a larger effect on a than on b, and it caused a maximum variation of 82% in a and 43% in b in the basin, equaling half of the variation caused by geographical location. However, the large effect of time scales on a and b produced no significant impact on the estimation accuracy of R s because of the conservative response of the sum a + b to time scale. In this sense, the coefficients calibrated at daily scale are interchangeable with those calibrated at monthly scale, indicating the high flexibility of the A–P formula. Nevertheless, calibration made at daily scale has two important advantages over monthly scale in that it requires fewer years’ data to obtain stabilized coefficients, and that it is easily predicted more accurately with common site information. Our findings have two implications. Firstly, they provide an additional guidance on the explanation of the large variability of the coefficients found in the literature for the same geographical location. Secondly, they facilitate the choice of the coefficients in practical applications by proving their interchangeability in the estimation of R s. [Copyright &y& Elsevier]

Crop simulation models play an essential role in evaluating irrigation management strategies for improving agricultural water use in crop production. In this study, the AquaCrop model was used to calibrate and validate the grain yield and biomass of 11 cultivars (9 winter wheat and 2 summer maize) under full and water-saving irrigation practices. The model results were verified with the available data from the published literature. Under the full irrigation practice, widely used by farmers in the region for winter wheat, the Normalized Root Mean Square Error (NRMSE) was found to be between 2.00–9.90% for grain yield, 2.40–10.85% for biomass, and 0.42–19.61% for water productivity. Under water-saving irrigation for winter wheat, the NRMSE range was found to be between 5.80–16.00% for grain yield, 3.70–17.30% for biomass, and 3.80–13.79% for water productivity. For summer maize, the NRMSE was 5.95%, 6.08%, and 16.41% under full irrigation, and 9.51%, 8.41%, and 3.60% under water-saving irrigation for grain yield, biomass, and water productivity, respectively. For winter wheat and summer maize, the simulation accuracy of grain yield was high under full irrigation, with percent deviations under ± 11.00%. In this study, the simulation accuracy for winter wheat was low under water-saving irrigation, while the model simulated the yield and biomass for summer maize to acceptable accuracy. The model can be reliably used as a tool to simulate grain yield and biomass across the NCP region for winter wheat and summer maize. However, the limitations of the model must be considered when simulating winter wheat under water-stressed conditions. • AquaCrop is a crop growth model to simulate yield response to water. • The model simulation accuracy was high under full irrigation for wheat and maize. • For water-saving irrigation, model accuracy was high for maize compared to wheat. • The model can be reliably used as a tool to simulate yield and biomass across NCP. [ABSTRACT FROM AUTHOR]

Improving irrigation and fertilization management for greater productivity is critical to address water scarcity. Drip fertigation can synchronize the water and nitrogen (N) supply with crop demand, offering the potential for enhanced water productivity (WP) and nitrogen use efficiency (NUE). To quantitatively assess the efficacy of drip fertigation and identify the main affecting factors, we used a meta-analysis to evaluate the effects of drip fertigation on the yield, WP and NUE under different conditions and to quantify the irrigation water saving potential (WSP) and N saving potential (NSP) of drip fertigation. Our results showed that, overall, drip fertigation led to significantly higher yields (12.0%), WP (26.4%) and NUE (34.3%), while significantly decreased crop evapotranspiration (ET) by 11.3%, compared to farmers' practices referring to traditional irrigation by furrow or flood and fertilization by broadcasting N fertilizer (broadcasting N fertilizer without irrigation in rainfed farming). However, the extent of improvement highly depended on crop types and was subject to edaphic, climatic and managerial factors. Among crop types, potato showed the highest increase in yield (40.3%) and WP (100.3%), and fruit showed the highest increase in NUE (68.2%). At a regional scale, drip fertigation performed best in semiarid regions. In addition, irrigation water inputs had large effects (P < 0.05) on the magnitude of yield, ET, and WP response, while N inputs had significant effects (P < 0.05) on yield and NUE but not on WP and ET. The results of WSP and NSP indicated that water input under drip fertigation for maize, wheat, potato, tomato and cotton could be further decreased by 14% (41 mm), 22% (87 mm), 20% (42 mm), 20% (59 mm) and 13% (50 mm), and N input could be further decreased by 23% (68 kg N ha−1), 26% (88 kg N ha−1), 33% (60 kg N ha−1), 21% (117 kg N ha−1) and 23% (66 kg N ha−1), respectively, without crop yield reduction. • Meta-analysis concluded drip fertigation significantly increased yield, WP and NUE. • Drip fertigation performance depended on crops, environmental and management factors. • Water and N saving potentials of different crops under drip fertigation were estimated. [ABSTRACT FROM AUTHOR]

Abstract: A field experiment was conducted to investigate the effect of long-term (30-year) fertilizer and organic manure treatments on grain yield, soil chemical properties and some microbiological properties of arable soils in Pingliang, Gansu, China. Six treatments were chosen for this work: unfertilized control (CK), nitrogen fertilizer annually (N), nitrogen and phosphorus (P) fertilizers annually (NP), straw plus N added annually and P fertilizer added every second year (NP+S), farmyard manure added annually (FYM), and farmyard manure plus N and P fertilizers added annually (NP+FYM). Mean winter wheat yields for the 20years ranged from 1.60Mgha−1 for the CK treatment to 4.62Mgha−1 for the NP+FYM treatment. Maize yields for the 8years averaged 3.40 and 7.66Mgha−1 in the same treatments. The results showed that there was no interaction between farmyard manure and NP fertilizers. Compared with the CK treatment, the average soil organic carbon (SOC) and total nitrogen (TN) content were 2.0 and 3.1%, 1.9 and 13.3%, 32.7 and 24.5%, 23.0 and 19.4%, and 39.9 and 27.6% larger, respectively, for N, NP, FYM, NP+S and NP+FYM. The N only resulted in not only lowering of pH but also deficient of both P and K in the soil. Soil available K declined rapidly without straw or manure additions. The microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents increased with the application of nitrogen and phosphorus inorganic fertilizers. However, there was greater increase of these parameters when organic manure was applied along with inorganic fertilizers. Organic manure application also increased soil dehydrogenase, alkaline phosphatases, β-glucosidasen and urease activity significantly. The results indicated that long-term additions of organic manure have the most beneficial effects on grain yield and soil quality among the investigated types of fertilization. [ABSTRACT FROM AUTHOR]

• Root morphology is crucial in optimizing crop production in the rainfed area. • Soil monolith excavation method was used to determine root parameters. • Grain yield was positively correlated with root biomass mainly in 0−30 cm vertically and 0−15 cm horizontally. • Full plastic mulching performed better synchronization of seasonal soil water transport and root water uptake for increasing maize yield. Knowledge of root systems and soil water status across the root-zone is crucial in developing effective cropping technologies. Mulching improves soil water status and root water transport for increasing grain yield. Therefore, a field experiment with five treatments: (1) plastic film mulching ridge and non-mulching furrow (RF), (2) full plastic mulching with conventional flat cultivation (FPM), (3) straw mulching with conventional flat cultivation (SM), (4) partial plastic mulching with conventional flat cultivation (PPM) and (5) non-mulch with conventional flat cultivation (CK) was conducted during 2018 and 2019 in the eastern Loess Plateau of China. The total root biomass and the grain yield of all treatments were lower in 2019 than that of 2018 because of lower rainfall. However, all the mulching treatments improved root growth in both growing seasons mainly on the top 30 cm soil depth, which led to a distinct effect on grain yield as compared with CK. FPM produced the highest total root parameters in 2018 and at 45 DAS in 2019 due to the highest soil moisture content mainly in 0−30 cm soil depth. However, root biomass of FPM in 30−100 cm soil depth was lower than that of PPM, RF and SM because assimilate at reproductive stage was mostly for plant and seed growth than root growth, thus, there was negative correlation between grain yield and root biomass below 30 cm soil depth especially at grain filling stage. Over two growing seasons, soil moisture content (SMC) under FPM was 8.4 %, 0.6 %, 8.8 % and 11.1 % more than that of RF, SM, PPM and CK. FPM reduced soil evaporation, improved SMC, root distribution and transpiration rate, consequently, increased grain yield and net profit. Therefore FPM is an effective cropping system for improving the synchronization of soil water transport and root water uptake for maize production in rain-fed farming. [ABSTRACT FROM AUTHOR]

In the dryland regions of North China, water is the limiting factor for rainfed crop production. Conservation agriculture (featuring reduced or zero tillage, mulching, crop rotations and cover crops) has been proposed to improve soil and water conservation and enhance yields in these areas. Conservation agriculture systems typically result in increased crop water availability and agro-ecosystem productivity, and reduced soil erosion. To evaluate the potential of conservation agriculture to improve soil water balance and agricultural productivity, the DSSAT crop model was calibrated using the data of a field experiment in Shouyang County in the semi-arid northeastern part of the Yellow River Basin. The average annual precipitation at the site is 472 mm, 75% of which falls during the growing season. The site had a maize-fallow-maize rotation. data from two crop seasons (2005 and 2006) and four treatments for calibration and analysis were used. The treatments were: conventional tillage (CT), no-till with straw mulching (NTSM), all-straw incorporated (ASRT) and one-third residue left on the surface with no-till (RRT). The calibration results gave satisfactory agreement between field observed and model predicted values for crop yield for all treatments except RRT treatment, and for soil water content of different layers in the 150 cm soil profile for all treatments. The difference between observed and predicted values was in the range of 3%-25% for maize yield and RMSE was in the range of 0.03-0.06 cm3/cm3 for soil water content measured periodically each cropping season. While these results are encouraging, more rigorous calibration and independent model evaluation are warranted prior to making recommendations based on model simulations. Medium-term simulations (1995-2004) were conducted for three of the treatments using the calibrated model. The NTSM and ASRT treatments had similar or higher yields (by up to 36%), higher crop water productivity by up to 28% and reduced runoff of up to 93% or 43 mm compared to CT treatment. [ABSTRACT FROM AUTHOR]

Soil mulching technologies are effective practices which alleviate non-point source pollution and carbon emissions, while ensuring grain production security and increasing water productivity. However, the lack of comprehensive understanding of the impacts of mulching technologies on rice fields has hindered progress in global implementation due to the varying environments and application conditions under which they are implemented. This study conducted a meta-analysis based on 2412 groups of field experiment data from 313 studies to evaluate the effects of soil mulching methods on rice production, greenhouse gas (GHG) emissions and water use efficiency. The results show that plastic mulching, straw mulching and no mulching (PM, SM and NM) have reduced CH 4 emissions (68.8 %, 61.4 % and 57.2 %), increased N 2 O emissions (84.8 %, 89.1 % and 96.6 %), reduced global warming potentials (50.7 %, 47.5 % and 46.8 %) and improved water use efficiency (50.2 %, 40.9 % and 34.0 %) compared with continuous flooding irrigation. However, PM increased rice yield (1.6 %), while SM and NM decreased yield (4.3 % and 9.2 %). Furthermore, analysis using random forest models revealed that rice yield, GHG emissions and WUE response to soil mulching were related to climate, soil properties, fertilizer and rice varieties. Our findings can guide the implementation of plastic mulching technology in priority areas, contribute to agricultural carbon neutrality and support the development of practical guidelines for farmers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

The impact of chemical to organic fertilizer substitution on soil labile organic and stabilized N pools under intensive farming systems is unclear. Therefore, we analyzed the distribution of soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), dissolved organic N (DON), and mineral N (NO 3 - ) levels down to 100 cm profile under wheat-maize rotation system in northern China. The experiment was established with four 270 kg ha 4 + ) levels down to 100 cm profile under wheat-maize rotation system in northern China. The experiment was established with four 270 kg ha -1 N equivalent fertilizer treatments: Organic manure (OM); Organic manure with nitrogen fertilizer (OM + NF); Nitrogen fertilizer (NF); and Control (CK). Results found that the OM and OM + NF treatments had significantly higher STN, PON, MBN, DON, and NO 3 - contents in 0-20 cm topsoil depths. Conversely, the NF treatment resulted in the highest ( p < 0.01) DON and NO 3 - depositions in 40-100 cm subsoil depths. The NH 4 + contents in selected profile depths were significantly highest ( p < 0.01) under OM treatment. The correlations between STN and its fractions were positively significant at 0-10 and 10-20 cm topsoil depths. Our results suggest that partial substitution of chemical fertilizer with organic manure could be a sustainable option for soil N management of intensive farming systems.

We estimated ecosystem respiration (Re) and its components in a rainfed spring maize field in the Loess Plateau, China, during the growing seasons of 2012, 2013, and 2014 using measurements of eddy covariance and soil respiration (Rs). The multi-factor equation, which included photosynthetic active radiation, 5-cm soil temperature, 10-cm soil water content, and green leaf area index (GLAI), had goodness-of-fit values of between 0.81 and 0.94 for Re, autotrophic respiration (Ra), and above-ground autotrophic respiration (Raa), and goodness-of-fit values of between 0.50 and 0.67 for Rs, below-ground autotrophic respiration (Rab), and heterotrophic respiration (Rh). The highly significant linear correlations between gross primary production (GPP) and Re and its components indicate that GPP had a strong influence on Re and its components. The growing season Re was dominated by Ra (64-71%), which in turn was dominated by Raa (63-73%). Although Rs was mainly made up of Rh (56-61%), Rs resembled Rab more closely than Rh. The relationships between GLAI and Ra/Re and between GLAI and Rab/Rs were described by logarithmic equations with goodness-of-fit values of between 0.88 and 0.89 and between 0.77 and 0.84, respectively, indicating that GLAI controlled Ra/Re and Rab/Rs.