Search

Introduction: Long-term application of excessive nitrogen (N) not only leads to low N use efficiency (NUE) but also exacerbates the risk of environmental pollution due to N losses. Substituting partial chemical N with organic fertilizer (SP) is an environmentally friendly and sustainable fertilization practice. However, the appropriate rate of SP in rainfed maize cropping systems in semi-arid regions of China is unknown. Methods: Therefore, we conducted a field experiment between 2021 and 2022 in a semi-arid region of Northern China to investigate the effects of SP on maize growth, carbon and N metabolism (C/NM), and NUE. The following treatments were used in the experiment: no N application (CK), 100% chemical N (SP0, 210 kg N ha-1), and SP substituting 15% (SP1), 30% (SP2), 45% (SP3), and 60% (SP4) of the chemical N. The relationship between these indicators and grain yield (GY) was explored using the Mantel test and structural equation modeling (SEM). Results and discussion: The results found that the SP1 and SP2 treatments improved the assimilates production capacity of the canopy by increasing the leaf area index, total chlorophyll content, and net photosynthetic rate, improving dry matter accumulation (DMA) by 6.2%-10.6%, compared to the SP0 treatment. SP1 and SP2 treatments increased total soluble sugars, starch, free amino acids, and soluble protein contents in ear leaves via increasing the enzymatic reactions related to C/NM in ear leaves during the reproductive growth stage compared with SP0 treatment. The highest plant nitrogen uptake (PNU) and nitrogen recovery efficiency were obtained under the SP2 treatment, and the GY and nitrogen agronomic efficiency were higher than the SP0 treatment by 9.2% and 27.8%. However, SP3 and SP4 treatments reduced DMA and GY by inhibiting C/NM in ear leaves compared to SP0 treatment. Mantel test and SEM results revealed that SP treatments indirectly increased GY and PNU by directly positively regulating C/NM in maize ear leaves. Therefore, in the semi-arid regions, substituting 30% of the chemical N with SP could be considered. This fertilizer regime may avoid GY reduction and improve NUE. This study provides new insights into sustainable cultivation pathways for maize in semi-arid regions. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) fertilizer nitrogen (N) recovery efficiency (FNRE) shows regional differences in China, and is more strongly affected by soil properties than by climate. However, how soil factors regulate maize FNRE is poorly understood. Herein, 15N tracer pot experiments combined with absolute microbial quantification sequencing were conducted using eight soils covering the main maize cropping systems from northern to southern China. The aim was to elucidate which soil factors affect maize FNRE and identify their optimal range for maximizing FNRE while minimizing N loss. Our results show that soil pH, soil organic matter (SOM), and clay and sand contents were the key factors affecting maize biomass and FNRE across the eight tested soils. Maize biomass and FNRE had parabolic relationships with soil pH, SOM, clay, and sand contents, whereas N loss displayed the opposite trend. The highest maize biomass and FNRE and lowest fertilizer N loss were in the soils with pH of 6.50–6.62, SOM level of 35.25–46.90 g kg−1, clay content of 41.12 %–44.42 %, and sand content of 17.71 %–23.41 %. Under these soil conditions, maize growth and soil N retention capabilities exhibited a high degree of coordination. Bacterial communities differed significantly among the soils, sharing the same soil drivers as maize biomass and FNRE. The abundance of N cycling genes (nasA, narI, narJ, nrfA, and nrfB) involved in dissimilatory nitrate reduction to ammonium (DNRA) was positively correlated with FNRE and negatively correlated with fertilizer N loss, suggesting that DNRA may contribute to soil N retention and enhance FNRE by affecting substrates for nitrification and denitrification. Our study demonstrates that soil pH, SOM, and texture are three key factors driving FNRE variation in maize cropping systems across China, and high microbial-driven DNRA may account for maximum maize FNRE. These findings highlight the importance of tailored FNRE enhancement strategies based on soil characteristics.

Introduction: Drought is known as the most important factor limiting corn production in the world. Depending on the growth stage and severity of drought stress, it can decrease corn yield by 76%. In addition, the increase in drought stress can decrease the efficiency of elements such as nitrogen in this crop. Therefore, many ways have been studied to decrease the effects of drought stress on crops. The results show that the use of cover crops can be an important approach for agriculture to protect crops against climate changes. These crops improve crop yields and soil nutrients by reducing runoff and soil erosion. The use of legumes as cover crops can decrease the need for chemical nitrogen fertilizer by biological N fixation in these crops. Materials and methods: In 2019, a pot experiment was conducted in the greenhouse of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran. The experimental treatments were faba bean cultivation (cultivated, non-cultivated), the different rates of nitrogen based on urea (0, 50, 100% of the recommended amount) and water deficit stress (40, 60, 80, 100% FC). In this experiment, 72 pots of 10 kg were used. First, the field capacity of the soil was determined, then the pots were filled with the air-dried soil. Ten grains of faba bean were planted in each pot, 5 of which were removed after germination. Shoots of faba bean were cut at the 50% flowering stage and mixed with the soil to the depth of 10 cm. Four corn grains were planted in each pot, two of which were removed after germination. In this experiment, the variety Shadan of faba bean and the corn hybrid 201 (single cross) were used. Different levels of nitrogen were applied at the V5 stage of corn, drought stress was applied ten days later and continued until the harvest stage of corn. Pots were weighed regularly for the application of drought stress. Corn was harvested at the pasty stage. Experimental characteristics included grain and shoot fresh and dry weights, grain and shoot protein content, nitrogen agronomic efficiency, nitrogen productivity, nitrogen recovery efficiency, and shoot and grain partial factor productivity. Statistical analysis of data was performed using SPSS software (version 26), and significant differences between treatment means were tested using Duncan's Multiple Range Test at P < 0.05. Results and discussion: Our results showed that all traits were influenced by interactions between faba bean cultivation × N fertilizer × water deficit stress. The highest grain yield was obtained of treatment the faba bean cultivation+100% of the recommended nitrogen rate+no application of water deficit stress, while no grains were observed in the treatment of non-cultivation of faba bean+100% of the recommended rate of nitrogen+application of severe water deficit stress, non-cultivation of faba bean+no nitrogen application+application of moderate water deficit stress and non-cultivation of faba bean+no nitrogen application+application of severe water deficit stress. The higher rate of nitrogen in the soil under severe water deficit stress can be considered as the limiting factor for crop growth, and therefore we observed lower yields in these treatments. Addition, our results showed that faba bean cultivation as cover crop increased some traits such as fresh and dry weight of shoot, agronomic efficiency and nitrogen recovery of nitrogen compared to non-cultivation of faba bean. The highest fresh dry shoot weight was obtained from the treatments of faba bean cultivation+100% of the recommended nitrogen rate+no application of water deficit stress and non-cultivation of faba bean cultivation+100% of the recommended nitrogen rate+no application of water deficit stress. Also, the highest shoot and grain agronomic efficiency was observed from the faba bean cultivation+100% of the recommended nitrogen rate+ no nitrogen application+application of moderate water deficit stress. Conclusion: Overall, our results showed that the use of faba bean as cover crop can decrease the effects of water deficit stress and improve the growth status of corn, although the increase at higher water deficit stress level is lower than the other levels. Based on the results, it can be concluded that the use of faba bean as cover crop and and 50% of the recommended rate of nitrogen can be recommended under the same conditions (under water deficit stress). [ABSTRACT FROM AUTHOR]

The crop nitrogen (N) use efficiency has been recognized as a useful indicator to measure the overall progress of the country towards achieving the sustainable development goal. Moreover, national level N use efficiency indicators are essential for improved estimate of global N budget and environmental impact assessment. We made an attempt to calculate the indicators of N use efficiency for rice at national and regional level in India. We utilized the data from research papers (23 no) published in reputed scientific journals and theses (83 no) submitted to different state agricultural universities over a period of 46 years (between 1972 and 2018). The partial factor productivity of N for rice in India ranged from 39.8 to 68.0 kg kg−1 with a national average value of 52.8 kg kg−1. The national average agronomic N use efficiency and nitrogen recovery efficiency (REN) were 18 kg kg−1 and 42.6%, respectively. Conducive agro-climatic condition coupled with improved crop management resulted in higher REN (>50%) in northern zone states of India. Whereas, rain-fed eastern and central zone states have REN<40%. The partial N balance (PNB) in rice ranged from 0.72–1.42 in India. The states with lower PNB need to reconcile their N addition with crop N uptake by adopting N responsive varieties and advanced fertilizer management to prevent environment degradation and economic loss. The findings of this study have significant implications for N budget estimation and policy decisions on hunger, food security and environment at national and global level. [ABSTRACT FROM AUTHOR]

The objectives were to i) assess the effect of enhanced-efficiency nitrogen (N) fertilizers (EENF) [maleic itaconic acid copolymer (NSN) or 3,4-dimethylpyrazole phosphate (DMPP)] and urea on potato (Solanum tuberosum L.) tuber yield, N agronomic efficiency (NAE), N recovery efficiency in tuber (NREtuber) and plant (NREplant), N physiological efficiency, residual inorganic N in soil at harvest (Nresidual) and N losses (Nlosses) and ii) determine the impact of the amount of drainage water on NAE and Nlosses. On-farm experiments were conducted in seven sites with two fertilizers (EENF and urea) and two N rates (0 and 100 kg N ha−1). A N mass balance was used to calculate Nlosses. At two sites (one with NSN and one with DMPP), tuber yield response to N was greater with EENF than urea (avg. 5.0 Mg ha−1). NAE, NREtuber and NREplant were 17%, 31% and 25% higher with EENF than urea, respectively. These efficiencies decreased as drainage water increased. The estimated Nlosses were 12% lower with EENF, being the reduction particularly relevant with increasing drainage water. Therefore, using EENF in combination with irrigation management that ensures low drainage water amounts is essential for maximizing the fertilizer use efficiency and minimizing Nlosses in potato production systems. [ABSTRACT FROM AUTHOR]

Management of nitrogen (N) fertilizer and irrigation can play a critical role to increase nitrogen use efficiency (NUE). However, the impacts of N application at the root zone via urea briquette deep placement (UDP) and water-saving irrigation alternate wetting and drying (AWD) on N2O emissions are not well-understood. A greenhouse study was conducted to investigate the impacts of UDP on N2O emissions, NUE, and grain yields of rice and wheat compared with broadcast prilled urea (PU). For rice, the effect of UDP was evaluated under continuous flooding (CF) and AWD, while the control (no N) and PU were tested only under CF. In rice, UDP under CF irrigation produced similar emissions to PU-CF, but UDP under AWD irrigation increased emissions by 4.5-fold compared with UDP under CF. UDP under CF irrigation increased (p < 0.05) rice grain yields and N recovery efficiency (RE) by 26% and 124% compared with PU-CF, respectively. In wheat, UDP had no effects (p > 0.05) on emissions compared with PU. However, it produced higher wheat grain yields (9%) and RE (35%) over PU. In conclusion, UDP under CF irrigation increases the RE and grain yields of rice without increasing N2O emissions, but the yield may reduce and N2O emissions may increase under AWD. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of the transformation, migration and loss pathways of nitrogen (N) fertilizer was pivotal for optimum nutrient management. Three different cultivation practices (conventional cultivation, plastic film mulching and straw retention) and N rates (0, 144 and 180 kg N ha−1) were assigned as the main plots and split plots separately in a split-plot design during 2017–2020. Moreover 15N-labeled urea was used in each microplot to trace the fertilizer N fate. The results showed that the N recovery efficiencies with plastic film mulching, straw retention and conventional cultivation were 44–46%, 34–37% and 43–44% in the first season. However, it sharply decreased in the next two seasons. The N residual rates in straw retention and plastic film mulching were 21–26% and 20–27% after three wheat seasons, which were higher than that in conventional cultivation. Furthermore, residual nitrate nitrogen was detected in the deep profiles in plastic film mulching and straw retention at the third season. The ammonia volatilization sourced from fertilizer was 3–5 kg ha−1 in the first season and accounted for 2–3% of the total applied N. Overall, plastic film mulching treatment increased fertilizer N utilization by plants and residual fertilizer N in soil, and reduced unidentified fertilizer N. Although, straw retention depressed fertilizer N uptake by plants, it improved the N budget and had the potential to reduce N input. Accordingly, plastic film mulching and straw retention are recommended in dryland wheat cropping systems. However, we should pay attention to the residual plastic pollution in the practice. [ABSTRACT FROM AUTHOR]

In this study, the nitrogen conversion efficiency in the integrated catfish farming system was estimated based on the sludge and wastewater treatment processes. The nitrogen sources were recovered using the composting process (organic fertilizer). The wastewater treatment process was recovered using the aquatic plant uptake (water hyacinths). The sludge waste was mixed with cow dung and water hyacinth biomass at a ratio of 8:1:1. The compost improved the nutrient content of the poor soil, as well as providing additional nitrogen for the plant and limiting the loss of nitrogen sources in the environment. The nitrogen dynamics were estimated using the nutrient biomass flow equality method. The results show that nitrogen was successfully recovered through the composting process and via accumulation in the biomass of the water hyacinths. The nitrogen removal efficiency by using water hyacinth reached 60% after 25–30 days; nitrogen recovery efficiency was found to be 66.94%; and total nitrogen concentration in the soil increased by 53.5% after applying organic fertilizer. The system could be used to recover and reuse nitrogen within the integrated catfish farming circle, under the context of circular economy concept. [Display omitted] [ABSTRACT FROM AUTHOR]

Applying fertilizer nitrogen (N) only when a crop response is predicted may enhance use efficiency and profitability while protecting the environment. The crop response index at harvest (RI-harvest, the ratio of the maximum grain yield and that of the plot in question) indicates the actual crop response to applied fertilizer N, although it is calculated after harvest. The objective of this study was to predict RI-harvest of wheat using normalized difference vegetation index (NDVI) response index (RI-NDVI, defined as the ratio of the NDVI in an N-sufficient plot and that in the field in question) captured at Feekes 6 stage. Field experiments were carried out across seven site-years (2017/18 to 2020/21) on wheat. In the first three seasons, the relationships between RI-harvest and RI-NDVI were established by applying a range of fertilizer N levels (0–320 kg N ha− 1), whereas the fourth season was used for validation. The results indicated that RI-NDVI could explain 79% of the variation in RI-harvest using the linear relationship: RI-harvest = 7.077 × RI-NDVI – 6.4885. This model was satisfactorly validated in the fourth season using an independent data set in which a range of fertilizer N doses was applied before the Feekes 6 growth stage. Validation was also carried out by applying a fertilizer N dose corresponding to the predicted RI-harvest. In comparison to the general recommendation, the application of appropriate prescriptive fertilizer N dose along with a fertilizer N dose based on the predicted RI-harvest resulted in an 11% increase in fertilizer N recovery efficiency. It suggests that estimation of in-season RI-NDVI is a viable method for identifying fields that are likely to respond to additional fertilizer N. [ABSTRACT FROM AUTHOR]

Foxtail millet [Setaria italica (L.) P. Beauv.], as a rich source of folates, has been cultivated on arid infertile lands, for which N deficiency is one of the major issues. Growing environments might have a significant influence on cereal folate levels. However, little is known whether N deficiency modulates cereal folate levels. In order to obtain enriched folate foxtail millet production in nutrient-poor soil, we conducted a study investigating the content of folate derivatives of 29 diverse foxtail millet cultivars under two N regimes (0 and 150 kg N ha−1) for 2 years to explore folate potential grown under low N. The contents of total folate and most derivatives were reduced by N deficiency. The effect on total folate content caused by N was stronger than cultivar genotype did. Folate content of enriched folate cultivars was prone to be reduced by N deficiency. Structural equation models (SEMs) revealed that N fertilization had a positive indirect effect on grain folate content through influencing plant N and K accumulation. Collectively, the results indicate much more attention should be paid to N management when foxtail millet is cultivated in infertile soil, to improve foxtail millet folate contents.

To improve crop nitrogen recovery efficiency (NRE), plants must be supplied with their preferred form of nitrogen (N). However, whether pH affects crop N-form preference remains unclear. Here, we aimed to explore how maize (Zea mays L.) preference for NH4+ and NO3− is affected by pH and to determine the critical pH controlling this preference. Maize plants were grown with NH4+ or NO3− in different soils (pH 4.32–8.14) and nutrient solutions (pH 4.00–8.00). After harvest, plant dry weights, N content, N uptake, NRE, soil pH, and exchangeable aluminum (Al) were measured. Compared with the effect of NO3−, NH4+ decreased maize dry weight, N uptake, and NRE by 28–94% at soil pHs of 4.32 and 4.36 and a solution pH of 4.00, whereas it increased these parameters by 10–88% at soil pHs of 6.52–8.02 and solution pHs of 7.00 and 8.00. NO3− increased soil pH and decreased soil exchangeable Al content at soil pHs of 4.32–6.68. Critical soil and solution pHs for changing plant growth and N uptake preference for NH4+ vs. NO3− ranged from 5.08 to 5.40 and from 5.50 to 6.59, respectively. In conclusion, the preference of maize seedling growth and N uptake for NH4+ vs. NO3− mainly depends on the pH of the growth medium, and maize seedlings generally prefer NO3− in strongly acid soils but NH4+ in neutral to alkaline soils. [ABSTRACT FROM AUTHOR]

Growth duration is an important agronomic trait that determines the season and area of crop growth. Previous experiments showed that overexpression of nitrate transporter OsNRT2.3b significantly increased rice yield, nitrogen use efficiency, and growth duration. Through screening, we obtained four ethyl methanesulfonate (EMS)-mutagenized mutants with shorter growth duration compared with O8 of OsNRT2.3b overexpression line. The nitrogen translocation efficiency and physiological nitrogen use efficiency of the mutants were not significantly different from O8, which were increased by 24.4% and 14.2%, respectively compared with WT, but the growth duration of the mutant was significantly lower than O8. Analysis of O8 and mutants showed that the growth duration positively correlated with grain weight per panicle, grain yield, and nitrogen recovery efficiency. In conclusion, our results provide a new idea for balancing rice yield and growth duration. [ABSTRACT FROM AUTHOR]

In continuously-flooded paddies, the small, fast-growing aquatic plant duckweed (Lemna minor L.) considered to compete with rice for nitrogen, thereby having a negative impact on early rice growth. While duckweed overpopulation was known can be effectively overcome through field water management, the influence of such management on the N fate and its use efficiency in rice-duckweed systems is poorly documented. Accordingly, a three-year (2020–2022) field experiment was conducted to examine the combined impact on rice yield, as well as N loss and utilization, of two water management approaches (flood irrigation, FI vs. alternate wetting and drying irrigation, AWD), factorially combined with two rice production systems (rice-duckweed, +D, vs. duckweed-free rice, -D). In AWD+D fields, the density of duckweed generally remained below 250 g m−2 (about 85 % coverage), whereas in FI+D fields it reached 100 % coverage (300 g m−2) within 5 days after transplanting, with individual duckweeds overlapping one another. Following AWD irrigation, duckweed performed as a nitrogen "cache," akin to a split fertilizer application, with the first of several splits occurring at the rice crop's early tillering stage. Within the first 2 days of a specific wet-dry cycle, duckweed can store 0.5–1.5 g N m−2, and then, within a further 3 days, release 0.3–1.0 g N m−2. In contrast, in FI+D paddies, this caching function occurred once under mid-season drainage, with further N being stored in the duckweeds during the remaining rice production season. As a result, at harvest the 0–0.10 m soil layer's N level increased significantly (p <0.05) in both FI+D (8.5–16.8 %) and AWD+D (14.9–20.8 %) compared to FI-D and AWD-D, respectively. Due to the coverage and storage-release function of duckweed, apparent N loss decreased in rice-duckweed system by 1.4–12.5 % in the FI field and 22.1–31.3 % in the AWD field compared to their respective duckweed-free systems. In FI fields, except for a 10 % relative reduction in nitrogen recovery efficiency (NRE) in 2020, duckweed didn't significantly affect rice yield or NRE. The yield reduction (3.5–6.7 %) and the NRE increase (0.8–7.4 %) under AWD-D (vs. FI-D) was, in the presence of duckweed, compensated for and overrun, resulting in a greater yield (5.3–6.7 %) and NRE (5.4–28.9 %) in the AWD+D vs. AWD-D field. When duckweed was present, AWD irrigation improved the by-path nitrogen cycling through duckweed, making the AWD+D system more beneficial for rice cultivation and the agroecosystem's environment health. The AWD+D system offers a promising measure for building an efficient and sustainable rice-duckweed agroecosystem. [Display omitted] • Duckweed performed as a N cache due to its rapidly N storage-release in rice season. • AWD avoid over reproduction of duckweed and N competition with rice plant. • Multiple wet-dry cycles resulted in multi-splits low dosage return of duckweed N. • Duckweed enhanced rice N recovery utilization especially under AWD irrigation. • Rice-duckweed with AWD is a promising solution for sustainable rice cultivation. [ABSTRACT FROM AUTHOR]

Black soldier fly frass fertilizer (BSFFF) is increasingly gaining momentum worldwide as organic fertilizer. However, research on its performance on crop production remains largely unknown. Here, we evaluate the comparative performance of BSFFF and commercial organic fertilizer (SAFI) on maize (H513) production. Both fertilizers were applied at the rates of 0, 2.5, 5, and 7.5 t ha-1, and 0, 30, 60, and 100 kg nitrogen (N) ha-1. Mineral fertilizer (urea) was also applied at 0, 30, 60 and 100 kg N ha-1 to establish the N fertilizer equivalence (NFE) of the organic fertilizers. Maize grown in plots treated with BSFFF had the tallest plants and highest chlorophyll concentrations. Plots treated with 7.5 t ha-1 of BSFFF had 14% higher grain yields than plots treated with a similar rate of SAFI. There was a 27% and 7% increase in grain yields in plots treated with 100 kg N ha-1 of BSFFF compared to those treated with equivalent rates of SAFI and urea fertilizers, respectively. Application of BSFFF at 7.5 t ha-1 significantly increased N uptake by up to 23% compared to the equivalent rate of SAFI. Likewise, application of BSFFF at 100 kg N ha-1 increased maize N uptake by 76% and 29% compared to SAFI and urea, respectively. Maize treated with BSFFF at 2.5 t ha-1 and 30 kg N ha-1 had higher nitrogen recovery efficiencies compared to equivalent rates of SAFI. The agronomic N use efficiency (AEN) of maize treated with 2.5 t ha-1 of BSFFF was 2.4 times higher than the value achieved using an equivalent rate of SAFI. Also, the AEN of maize grown using 30 kg N ha-1 was 27% and 116% higher than the values obtained using equivalent rates of SAFI and urea fertilizers, respectively. The NFE of BSFFF (108%) was 2.5 times higher than that of SAFI. Application rates of 2.5 t ha-1 and 30 kg N ha-1 of BSFFF were found to be effective in improving maize yield, while double rates of SAFI were required. Our findings demonstrate that BSFFF is a promising and sustainable alternative to commercial fertilizers for increased maize production.

The NO3- transporter plays an important role in rice nitrogen acquisition and nitrogen-use efficiency. Our previous studies have shown that the high affinity systems for nitrate uptake in rice is mediated by a two-component NRT2/NAR2 transport system. In this study, transgenic plants were successful developed by overexpression of OsNAR2.1 alone, OsNRT2.3a alone and co-overexpression of OsNAR2.1 and OsNRT2.3a. Our field experiments indicated that transgenic lines expressing p35S:OsNAR2.1 or p35S:OsNAR2.1-p35S:OsNRT2.3a constructs exhibited increased grain yields of approximately 14.1% and 24.6% compared with wild-type (cv. Wuyunjing 7, WT) plants, and the agricultural nitrogen use efficiency increased by 15.8% and 28.6%, respectively. Compared with WT, the 15N influx in roots of p35S:OsNAR2.1 and p35S: OsNAR2.1-p35S:OsNRT2.3a lines increased 18.9%‑27.8% in response to 0.2 mM, 2.5 mM 15NO3–, and 1.25 mM 15NH415NO3, while there was no significant difference between p35S:OsNAR2.1 and p35S:OsNAR2.1-p35S:OsNRT2.3a lines; only the 15N distribution ratio of shoot to root for p35S:OsNAR2.1-p35S:OsNRT2.3a lines increased significantly. However, there were no significant differences in nitrogen use efficiency, 15N influx in roots and the yield between the p35S:NRT2.3a transgenic lines and WT. This study indicated that co-overexpression of OsNAR2.1 and OsNRT2.3a could increase rice yield and nitrogen use efficiency.

Growth duration is an important agronomic trait that determines the season and area of crop growth. Previous experiments showed that overexpression of nitrate transporter OsNRT2.3b significantly increased rice yield, nitrogen use efficiency, and growth duration. Through screening, we obtained four ethyl methanesulfonate (EMS)-mutagenized mutants with shorter growth duration compared with O8 of OsNRT2.3b overexpression line. The nitrogen translocation efficiency and physiological nitrogen use efficiency of the mutants were not significantly different from O8, which were increased by 24.4% and 14.2%, respectively compared with WT, but the growth duration of the mutant was significantly lower than O8. Analysis of O8 and mutants showed that the growth duration positively correlated with grain weight per panicle, grain yield, and nitrogen recovery efficiency. In conclusion, our results provide a new idea for balancing rice yield and growth duration.

Deep placement of nitrogen (N) fertilizer has become one of the effective management practices for increasing crop yield and improving N recovery efficiency (NRE). However, it is unclear how different N fertilization depths affect grain yield, nitrogen use efficiency, and root characteristics in direct-seeded rice (DSR) in South China. Here, we conducted stainless steel-box experiment to evaluate the effects of different N fertilization depths at four fertilization depths (0, 4, 8, and 12 cm, written as D0, D4, D8, and D12, respectively) with a conventional ammonium bicarbonate fertilizer (TN = 17.7%) (150 kg N ha−1) and a control (no N fertilizer applied, CK) on grain yield, NRE, and root characteristics of DSR. The results indicated that both D8 and D12 significantly increased grain yields by 72.91 and 81.84%, respectively, compared with CK. The highest nitrogen agronomic efficiency (NAE) and NRE were found under D12 treatment, which were increased by 165.42 and 129.45% compared to D0, respectively. We also found that deep placement of N fertilizer (both D8 and D12) could also promote rice root growth such as larger root length, root superficial area, and thicker root diameter. Furthermore, nitrate reductase (NR), glutamine synthetase (GOGAT), and glutamine synthetase (GS) activities of flag leaves at the heading stage were also increased. The result shows that both 8 and 12 cm are relatively reasonable fertilization depths depended on adopted rice varieties when ammonia bicarbonate fertilizer is used in DSR production. [ABSTRACT FROM AUTHOR]

Black soldier fly frass fertilizer (BSFFF) is increasingly gaining momentum worldwide as organic fertilizer. However, research on its performance on crop production remains largely unknown. Here, we evaluate the comparative performance of BSFFF and commercial organic fertilizer (SAFI) on maize (H513) production. Both fertilizers were applied at the rates of 0, 2.5, 5, and 7.5 t ha-1, and 0, 30, 60, and 100 kg nitrogen (N) ha-1. Mineral fertilizer (urea) was also applied at 0, 30, 60 and 100 kg N ha-1 to establish the N fertilizer equivalence (NFE) of the organic fertilizers. Maize grown in plots treated with BSFFF had the tallest plants and highest chlorophyll concentrations. Plots treated with 7.5 t ha-1 of BSFFF had 14% higher grain yields than plots treated with a similar rate of SAFI. There was a 27% and 7% increase in grain yields in plots treated with 100 kg N ha-1 of BSFFF compared to those treated with equivalent rates of SAFI and urea fertilizers, respectively. Application of BSFFF at 7.5 t ha-1 significantly increased N uptake by up to 23% compared to the equivalent rate of SAFI. Likewise, application of BSFFF at 100 kg N ha-1 increased maize N uptake by 76% and 29% compared to SAFI and urea, respectively. Maize treated with BSFFF at 2.5 t ha-1 and 30 kg N ha-1 had higher nitrogen recovery efficiencies compared to equivalent rates of SAFI. The agronomic N use efficiency (AEN) of maize treated with 2.5 t ha-1 of BSFFF was 2.4 times higher than the value achieved using an equivalent rate of SAFI. Also, the AEN of maize grown using 30 kg N ha-1 was 27% and 116% higher than the values obtained using equivalent rates of SAFI and urea fertilizers, respectively. The NFE of BSFFF (108%) was 2.5 times higher than that of SAFI. Application rates of 2.5 t ha-1 and 30 kg N ha-1 of BSFFF were found to be effective in improving maize yield, while double rates of SAFI were required. Our findings demonstrate that BSFFF is a promising and sustainable alternative to commercial fertilizers for increased maize production. [ABSTRACT FROM AUTHOR]

This long-term study used a lysimeter platform to monitor the NH3 and N2O emissions of summer maize resulting from various fertilization treatments in the Huanghuaihai area, with the goal to assess the efficiency of fertilization measures aimed at reducing NH3 and N2O losses during the production of summer maize; the results provide a theoretical basis for synergistically improving maize yield and fertilizer utilization efficiency. A 2-year field trial was conducted. The trial included a no-N-fertilizer treatment as a control to study the following three fertilizer treatments: the exclusive application of urea, the exclusive application of cattle manure, and the combined application of organic and inorganic fertilizers. The results show that during the two maize growth seasons included in the trial, the average N2O losses associated with exclusively applying urea, exclusively applying cattle manure, and the combined application of organic and inorganic fertilizers were 273%, 542%, and 376% higher than those associated with the control treatment, respectively. During the same period, the average accumulative ammonia volatilization losses were 311%, 542% and 376% higher than those for the control treatment, respectively. The average nitrogen accumulation resulting from the combined application of organic and inorganic fertilizers was 82% higher than that for the control treatment, 12% higher than that for the exclusive application of cattle manure, and 6% higher than that for the exclusive application of urea. The average grain yield for the combined application of organic and inorganic fertilizers, the exclusive application of urea and the exclusive application of cattle manure were 76%, 68% and 61% higher than that for the control treatment, respectively. Overall, the combined application of organic and inorganic fertilizers showed a lower ammonia volatilization loss than the exclusive application of urea, which resulted in a higher ammonium nitrogen and nitrate nitrogen content in the soil, an increased nitrogen uptake, an increased dry matter accumulation of maize, and a high grain yield and nitrogen recovery efficiency. [ABSTRACT FROM AUTHOR]

Wheat is an important staple crop in arid and semi-arid areas of the Tigray region of Ethiopia. However, the yield and quality of the crop is markedly constrained by low soil fertility, inappropriate rate and timing of nitrogen application. Therefore, an experiment was conducted to elucidate the effect of different rates and timing of nitrogen fertilizer application on the yield, quality, and nitrogen use efficiency of bread wheat varieties during 2013 and 2014 main cropping seasons. The treatments consisted of four rates of nitrogen (23, 46, 69, and 92 kg N ha-1), three timing of N application (½ at sowing + ½ at tillering, ¼ at sowing + ½ at tillering + ¼ at anthesis, and 1/3rd at sowing + 1/3 rd at tillering + 1/3rd at anthesis) and two bread wheat varieties (Picaflor and Mekelle I) and 0 kg N ha-1 (control). The experiment was laid out as a randomized complete block design in a factorial arrangement with three replications. During both cropping years, increasing the rate of nitrogen application up to 69 kg N ha-1 significantly (P< 0.01) increased the total aboveground biomass and grain yields of the crop and decreased with further increase of applied N fertilizer. The highest aboveground biomass (6871 kg ha-1) and grain yields (2775 kg ha-1) of the crop were obtained in response to the application of 69 kg N ha-1, in 2013. The equivalent value for total aboveground biomass and grain yields during 2014 cropping season were (8815 kg ha-1and 3695 kg ha-1), respectively . The highest apparent recovery efficiency of 75% was obtained in response to the rate of 69 kg N ha-1applied in three splits of 1/4 at planting, ½ at tillering, and 1/4 at anthesis. The equivalent values for the highest apparent recovery was 81% in the 2014 cropping season. The highest agronomic efficiency of 25 kg kg-1 and utilization efficiency of 55 kg kg-1 were recorded at the rate of 46 kg N ha-1 in three splits of 1/4 at planting, ½ at tillering and ¼ at anthesis. The equivalent values in 2014 were 34 kg kg-1 and 78 kg kg-1, respectively. Grain protein concentration increased from 10.57% to 11.82% in 2013 and from 8.97% to 9.84% in 2014 cropping season as the rate increased from 23 kg N ha-1 to 69 kg N ha-1. The acceptable marginal rate of return (1618%) and highest net benefit (34141ETB ha-1) was obtained from 69 kg N ha-1 for the variety Picaflor. In conclusion, applying 69 kg N ha-1 in three splits of ¼ at planting, 1/2 at tillering and ¼ at anthesis resulted in optimum grain yield, protein concentration and economic return of the crop.

Aims: Matching a crop's nitrogen (N) preference with the specific form of N is critical to enhance N recovery efficiency (NRE). Many studies show that maize (Zea mays L.) has a preference for NH4+ uptake over NO3−, but the contribution of this preference to NRE is unclear. This study evaluated the utilization of ammonium (NH4+) and nitrate (NO3−) by maize and its relationship with NRE. Methods: Maize (cv. 'Zhengdan 958') seedlings were grown in a soil culture experiment with 15NH4+ or 15NO3− applied to sterilized or non-sterilized soils, and in a hydroponic experiment supplied with NH4+ or NO3−. We recorded maize root and shoot growth and N uptake, and the distribution of 15N-labeled N in the soil–plant system. Results: Ammonium application enhanced maize root and shoot growth and N uptake compared with those of NO3−-treated plants in both culture systems. This enhancement by NH4+ was further promoted in sterilized soil. More applied N remained in soil supplied with NO3− than with NH4+ after seedling harvest. The NRE of NH4+ in maize was significantly higher than that of NO3−, while a similar proportion of applied N was lost with NH4+ or NO3−supply. Conclusions: Ammonium supply enhances maize growth and NRE compared with NO3− under the present experimental condition, which may be attributable to the superior capability of maize to utilize NH4+. [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]

The study aimed to understand the effects of nitrogen (N) and soil types on maize (Zea mays L.). Grain yield (GY) is essential for identifying optimal N fertilizer management practices and agricultural policies. In this study, we report results from an on-farm experiment carried out from 2009 to 2012 with five N levels and three soil types in Northeast China. Results revealed that the GY was affected significantly by soil types, with loam soil having an average GY of 10225 kg ha–1, followed by clay soil (9218 kg ha–1) and sandy soil (6434 kg ha–1). The optimal N rates required to achieve maximum GY were on average 182, 173, and 160 kg ha−1, and the corresponding maximum GYs were 10872, 9999, and 7266 kg ha−1 for loam, clay, and sandy soils, respectively. The optimum N treatment (168 kg N ha-1) reduced residual nitrate N content and N losses by 97 and 451 kg N ha–1, respectively, and improved N recovery efficiency (REN) by 17%. In conclusion, within-field soil management zones based on soil textural classes could be used to guide soil sampling and establish soil-specific N fertilizer recommendations to achieve high GY with high REN in Northeast China. [ABSTRACT FROM AUTHOR]

Long-term experiments are an important tool to investigate the effects of crop rotation and fertilization measures under climate change conditions. However, there are few studies on nitrogen use efficiency (NUE) of crops in long-term cropping systems in Europe, but no consolidate studies in Germany. We analyzed a long-term experiment established in 1982 to observe the role of legumes on total nitrogen uptake, NUE, agronomic efficiency, nitrogen response index and N recovery efficiency compared to fallow land and cereals in a crop rotation over the long-term. The experiment included five different precrops (fallow land, maize, oat, field bean and clover mulch) in combination with four levels of fertilization (control, PK, PK+N with reduced dosage, and PK+N with full dosage followed by three years of cereal cultivation (winter wheat, winter rye, summer barley) in all treatments. The field trial was conducted as a fully factorial split plot design, with spatially randomized field repetitions in four blocks. Long-term mineral NPK fertilization improved the N uptake of winter wheat (185.7 kg N ha−1), winter rye (152.2 kg N ha−1) and summer barley (92.2 kg N ha−1) when the higher level of fertilization (NPK 100%) was implemented. A year-round application of clover mulch as green manure in the rotational system resulted in higher NUE (up to 37%) compared to fallow land after 40 years. Crop rotation with oat and maize (100% cereals) led to lower NUE (up to 30%) compared to fallow land. Clover mulch (198%), field bean (155%), fallow land (148%) and maize (119%) significantly increased the N uptake of wheat compared to oat in 2015. Over time, the agronomic efficiency was increased. This increase was 4 or 5 times higher in the 9th and 10th crop rotation compared to the beginning of the experiment (in 1983). Nitrogen response index of clover mulch was approximately 33–37% lower than fallow land at the beginning of the experiment in 1983 and 45–50% lower over the 40 years. N recovery efficiency values of winter wheat (94%), winter rye (66%) and summer barley (46%) increased within the 10th crop rotation compared to the beginning of the long-term experiment. Combining clover mulch as a green manure with mineral fertilizer has greater potential to improve NUE and crop productivity by increasing soil N availability. Our study highlights the importance of evaluating agronomic management practices in long-term field experiments to understand their sustainable effects. • Soil nutrition is regulated by the quality & quantity of plant residues incorporated into the soil. • Long-term application of green mulch and mineral fertilizer improves NUE and crop productivity. • After 40 years, agronomic efficiency was about 4 or 5 times higher than at the beginning of the experiment in 1983. • Nitrogen response index of clover mulch was about 33–37% lower than fallow at onset of the experiment. [ABSTRACT FROM AUTHOR]

The excessive nitrogen (N) fertilizer input coupled with flood irrigation might result in higher N leaching and lower nitrogen recovery efficiency (NRE). Under an intensive rice system in the Ningxia irrigation region, China, environmental friendly N management practices are heavily needed to balance the amount of N input for optimum crop production while minimize the nitrogen loss. The objective of this study was to determine the influences of side-dressing (SD) technique in mechanical transplanting systems on the NRE, N leaching losses and rice yield in anthropogenic-alluvial soil during two rice growing seasons (2010–2011). Four fertilizer N treatments were established, including conventional urea rate (CU, 300 kg ha−1 yr−1); higher SD of controlled-release N fertilizer rate (SD1, 176 kg ha−1 yr−1); lower SD of controlled-release N fertilizer rate (SD2, 125 kg ha−1 yr−1); and control (CK, no N fertilizer). Field lysimeters were used to quantify drainage from undisturbed soil during six rice growing stages. Meanwhile, the temporal variations of total nitrigen (TN), NO3−-N, and NH4+-N concentrations in percolation water were examined. The results showed that SD1 substantially improved NRE and reduced N leaching losses while maintaining rice yields. Across two years, the averaged NRE under SD1 treatment increased by 25.5% as relative to CU, but yet the rice yield was similar between two treatments. On average, the nitrogen loss defined as TN, NH4+-N, and NO3−-N under the SD1 treatment reduced by 27.4, 37.2 and 24.1%, respectively, when compared with CU during the study periods. Although the SD2 treatment could further reduce N leaching loss to some extent, this technique would sharply decline rice yield, with the magnitude of as high as 21.0% relative to CU treatment. Additionally, the average NRE under SD2 was 11.2% lower than that under SD1 treatment. Overall, the present study concluded that the SD technique is an effective strategy to reduce N leaching and increase NRE, thus potentially mitigate local environmental threat. We propose SD1 as a novel alternative fertilizer technique under an irrigated rice-based system in Ningxia irrigation region when higher yields are under consideration.

Nitrogen fertilizer management can impact soil organic C (SOC) stocks in cereal-based cropping systems by regulating crop residue inputs and decomposition rates. However, the impact of long-term N fertilizer management, and associated changes in SOC quantity and quality, on the fate of N fertilizer inputs is uncertain. Using two 15-year N fertilizer rate experiments on continuous maize ( Zea mays L.) in Iowa, which have generated gradients of SOC, we evaluated the legacy effects of N fertilizer inputs on the fate of added N. Across the historical N fertilizer rates, which ranged from 0 to 269 kg N ha −1  yr −1 , we applied isotopically-labeled N fertilizer at the empirically-determined site-specific agronomic optimum rate (202 kg N ha −1 at the central location and 269 kg N ha −1 at the southern location) and measured fertilizer recovery in crop and soil pools, and, by difference, environmental losses. Crop fertilizer N recovery efficiency (NRE crop ) at physiological maturity averaged 44% and 14% of applied N in central Iowa and southern Iowa, respectively (88 kg N ha −1 and 37 kg N ha −1 , respectively). Despite these large differences in NRE crop , the response to historical N rate was remarkably similar across both locations: NRE crop was greatest at low and high historical N rates, and least at the intermediate rates. Decreasing NRE crop from low to intermediate historical N rates corresponded to a decline in early-season fertilizer N recovery in the relatively slow turnover topsoil mineral-associated organic matter pool (0–15 cm), while increasing NRE crop from intermediate to high historical N rates corresponded to an increase in early-season fertilizer N recovery in the relatively fast turnover topsoil particulate organic matter pool and an increase in crop yield potential. Despite the variation in NRE crop along the historical N rate gradient, we did not detect an effect of historical N rate on environmental losses during the growing season, which averaged 34% and 69% of fertilizer N inputs at the central and southern locations, respectively (69 kg N ha −1 and 185 kg N ha −1 , respectively). Our results suggest that, while beneficial for SOC storage over the long term, fertilizing at the agronomic optimum N rate can lead to significant environmental N losses. [ABSTRACT FROM AUTHOR]

Few studies have assessed the common, yet unproven, hypothesis that an increase of plant nitrogen (N) uptake and/or recovery efficiency (NRE) will reduce nitrous oxide (N2O) emission during crop production. Understanding the relationships between N2O emissions and crop N uptake and use efficiency parameters can help inform crop N management recommendations for both efficiency and environmental goals. Analyses were conducted to determine which of several commonly used crop N uptake-derived parameters related most strongly to growing season N2O emissions under varying N management practices in North American maize systems. Nitrogen uptake-derived variables included total aboveground N uptake (TNU), grain N uptake (GNU), N recovery efficiency (NRE), net N balance (NNB) in relation to GNU [NNB(GNU)] and TNU [NNB(TNU)], and surplus N (SN). The relationship between N2O and N application rate was sigmoidal with relatively small emissions for N rates

A long-term field experiment was carried out (since 2008) for evaluating the effects of different substitution rates of inorganic nitrogen (N) fertilizer by green manure (GM) on yield stability and N balance under double rice cropping system. Treatments included, (1) N0 (no N fertilizer and no green manure); (2) N100 (recommended rate of N fertilizer and no green manure); (3) N100-M (recommended rate of N fertilizer and green manure); (4) N80-M (80% of recommended N fertilizer and green manure); (5) N60-M (60% of recommended N fertilizer and green manure); and (6) M (green manure without N fertilization). Results showed that, among all treatments, annual crop yield under N80-M treatment was highest. Crop yield did not show significant differences between N100-M and N80-M treatments. Substitution of different N fertilizer rates by GM reduced the yield variability index. Compared to the N0 treatment, yield variability index of early rice under N100-M, N80-M, and N60-M treatments was decreased by 11%, 26%, and 36%, respectively. Compared to the N0 treatment, yield variability index of late rice was decreased by 12%, 38%, 49%, 47%, and 24% under the N100, N100-M, N80-M, N60-M, and M treatments, respectively. During period of 2009−2013 and 2014−2018, nitrogen recovery efficiency (NRE) was highest under N80-M treatment and N balance was highest under N100 treatment. NRE of all treatments with GM was increased over the time from 2009−2013 to 2014−2018. All treatments with GM showed increasing trend of SOC over the years. Substitution of N fertilizer by GM also increased C inputs and soil C:N ratio compared to the N100 and N0 treatments. Boosted regression model indicated that C input, N uptake and AN were most influencing factors of crop yield. Thus, we concluded that N fertilization rates should be reduced by 20% under GM rotation to attain high yield stability of double rice cropping system through increasing NRE and C inputs.

Few studies have assessed the common, yet unproven, hypothesis that an increase of plant nitrogen (N) uptake and/or recovery efficiency (NRE) will reduce nitrous oxide (N2O) emission during crop production. Understanding the relationships between N2O emissions and crop N uptake and use efficiency parameters can help inform crop N management recommendations for both efficiency and environmental goals. Analyses were conducted to determine which of several commonly used crop N uptake-derived parameters related most strongly to growing season N2O emissions under varying N management practices in North American maize systems. Nitrogen uptake-derived variables included total aboveground N uptake (TNU), grain N uptake (GNU), N recovery efficiency (NRE), net N balance (NNB) in relation to GNU [NNB(GNU)] and TNU [NNB(TNU)], and surplus N (SN). The relationship between N2O and N application rate was sigmoidal with relatively small emissions for N rates <130 kg ha-1, and a sharp increase for N rates from 130 to 220 kg ha-1; on average, N2O increased linearly by about 5 g N per kg of N applied for rates up to 220 kg ha-1. Fairly strong and significant negative relationships existed between N2O and NRE when management focused on N application rate (2 = 0.52) or rate and timing combinations (r2 = 0.65). For every percentage point increase, N2O decreased by 13 g N ha-1 in response to N rates, and by 20 g N ha-1 for NRE changes in response to rate-by-timing treatments. However, more consistent positive relationships (R2 = 0.73-0.77) existed between N2O and NNB(TNU), NNB(GNU), and SN, regardless of rate and timing of N application; on average N2O emission increased by about 5, 7, and 8 g N, respectively, per kg increase of NNB(GNU), NNB(TNU), and SN. Neither N source nor placement influenced the relationship between N2O and NRE. Overall, our analysis indicated that a careful selection of appropriate N rate applied at the right time can both increase NRE and reduce N2O. However, N2O reduction benefits of optimum N rate-by-timing practices were achieved most consistently with management systems that reduced NNB through an increase of grain N removal or total plant N uptake relative to the total fertilizer N applied to maize. Future research assessing crop or N management effects on N2O should include N uptake parametermeasurements to better understand N2O emission relationships to plant NRE and N uptake. [ABSTRACT FROM AUTHOR]

Sustainable crop production systems can be attained by using inputs efficiently and nitrogen use efficiency (NUE) parameters are indirect measurements of sustainability of production systems. The objective of this study was to investigate the effect of selected nitrogen (N) management treatments on wheat yields, grain and straw N concentration, and NUE parameters, under conservation agriculture (CA). The present study was conducted at the International Maize and Wheat Improvement Center (CIMMYT), in northwest, Mexico. Seventeen treatments were tested which included urea sources, timing, and methods of fertilizer application. Orthogonal contrasts were used to compare groups of treatments and correlation and regression analyses were used to look at the relationships between wheat yields and NUE parameters. Contrasts run to compare wheat yields or agronomic efficiency of N (AEN) performed similarly. Sources of urea or timing of fertilizer application had a significant effect on yields or AEN (p > 0.050). However, methods of application resulted in a highly significant (p < 0.0001) difference on wheat yields and agronomic efficiency of N. NUE parameters recorded in this study were average but the productivity associated to NUE levels was high. Results in this study indicate that wheat grew under non-critically limiting N supply levels, suggesting that N mineralization and reduced N losses from the soil under CA contributed to this favorable nutritional condition, thus minimizing the importance of N management practices under stable, mature CA systems.

Knowledge of the dynamics of plant nitrogen (N) uptake at varying irrigation water levels is critical for strategizing increased N recovery efficiency (NRE), water use efficiency (WUE), and maize yield. The N dynamics were studied under various irrigation regimes to evaluate NRE, WUE, and maize yield. A pot experiment was conducted using three irrigation water regimes (50, 75, and 100% field capacity (FC)) and four N fertilizer rates (0, 1.6, 3.2, and 4.8 g pot) applied with two fertilizer application methods including foliar and soil applications. The highest plant growth and grain yields were achieved by application of 4.8 g N pot with 100% FC. Contrarily, the maximum WUE (7.0 g L) was observed by the lowest irrigation water (50% FC) with the highest N fertilizer rates (4.8 g pot). Nitrogen concentration in the stem and grain was linearly increased by increasing N fertilizer rates with irrigation water. However, in the root, N concentration was decreased when the crop was supplied with 100% FC. In plant, maximum N uptake (6.5 mg g) was observed when 4.8 g N pot was applied with 100% FC. Nitrogen recovery efficiency was increased by increasing N rate up to 3.2 g pot with 100% FC. Therefore, for achieving maximum WUE and NRE, the highest water and N applications, respectively, are not necessary. [ABSTRACT FROM AUTHOR]

We aimed to quantitatively investigate the effects of rate and timing of nitrogen (N) application on fate of N-labelled urea in an alkaline calcareous soil during a winter wheat (WW) and summer maize (SM) seasons. The treatments consisted of conventional N application (i.e., WN300-2T or MN240-2T, 300 or 240 kg N ha with two N splits to WW or SM), reduced N application (i.e., WN210-2T or MN168-2T, 210 or 168 kg N ha with two N splits to WW or SM), recommended N application (i.e., WN210-3T or MN168-3T, 210 or 168 kg N ha with three N splits to WW or SM), and control (N0). The result showed that the fate of N fertilizer was significantly influenced by rate and timing of the applied N. Compared with the conventional N treatment, crop N recovery in the recommended N treatment increased significantly by 16.7 % for WW and 17.2 % for SM, but total N losses reduced significantly by 12.3 and 13.5 %, respectively. Residual N in 100-200 cm soil layer was the lowest in recommended N treatment, preventing leaching of much NO -N to deeper soil layers. Our results indicated that the recommended N treatment at rate of 210 or 168 kg N ha with three N splits to WW or SM would maintain crop yields but significantly increase N recovery efficiency and reduce the risk of environmental pollution caused by N losses. [ABSTRACT FROM AUTHOR]

Pot experiment were conducted from 2013 to 2014 to provide solutions for poor water–nitrogen (N) use efficiency with zeolite (Z) in near-surface soil. This article aims to study the influences of different levels of Z (Z1, Z2, Z3, 0, 7500, and 15,000 kg hm−2) and N (N1, N2, N3, 0, 78.75, and 157.5 kg hm−2) on rice grain yield, soil total N (STN), water productivity (WP), and N recovery efficiency (NRE). Results showed that higher dry matter weight, grain yield, water consumption, N accumulation, and WP were obtained with increasing N rates. There were no significant influences on dry matter weight of stem and leaf, water consumption, and WP with the application of Z. However, Z input could obtain a higher spike and root weight, grain yield, 1000-grain weight, N accumulation, STN, and NRE. Z might alleviate the water used in jointing-booting stage, heading-flowering stage, and milky ripen stage. Overuse of Z and N led to a decrease in NRE. N3Z2 increased rice grain yield by 10.4%, WP by 7.3%, and NRE by 63% compared with conventional fertilization (N3Z1). The way of N3Z2 is recommended to improve rice yield, WP, NRE, and STN comprehensively in coastal region of Northeast China. [ABSTRACT FROM AUTHOR]

Recovery efficiency of nitrogen fertilizer(REN) is an important index for the increasing crop yield and reducing environmental benefits of nitrogen fertilizer. But the determination and calculation methods of REN have some problems to study. They are lower rate and higher variability of the rate than it should be. The long-term nitrogen fertilizer location test had been taken since 2007 to analyze the nitrogen uptake rate of wheat year after year and the REN rate was calculated annually. A reasonable measurement specification of REN determination method was put forward. The REN measurement specification was:(1)The wheat nitrogen uptake of CK kept relatively stable after a few years; (2)The wheat nitrogen uptake ratio of fetilized treatment retained stable; (3)REN must be used the average of 3 years of steady period value. With this measurement specification of REN determination method, REN rate was in the range of 69.2%~76.2%(Wheat) when applied nitrogen fertilizer in range of 120~180 kg N·hm-2. REN determination method should follow this specification. In this case the correct and reasonable REN parameter can be measured. The reasonable REN can be applied in scientific research and production. [ABSTRACT FROM AUTHOR]

Ammonium (NH 4 +) has been reported as the preferred mineral N source (a preference for NH 4 + uptake over NO 3 -) for rice (Oryza sativa L.), the predominant supply of NH 4 + has been hypothesized as a means of increasing the N recovery efficiency (NRE). However, the contribution of NH 4 + preference to NRE is unclear under different irrigation regimes. To evaluate the NRE of rice as affected by varied N supply forms, rice (cv. 'Suijing 18') was grown in a pot experiment with 15N-NH 4 + or 15N-NO 3 - applied to flooded and water-saving irrigation regimes. At harvest, plant biomass, N accumulation, and the fate of 15N-labeled N in the plant-soil system were assessed. Ammonium-N application enhanced rice shoot growth compared with nitrate-N under both irrigation regimes. This enhancement by NH 4 + was further promoted under water-saving irrigation. In contrast, nitrate-N enhanced rice root growth, more fertilizer-derived N residues in the soil compared with those of NH 4 + treated, regardless of the irrigation regimes. Ammonium enhanced the NRE of rice compared with NO 3 - treated under flooded irrigation. However, the so-called 'preference' for NH 4 + by rice did not always turn into high N recovery efficiency, and there was no difference in NRE of rice between varied N supply forms under water-saving irrigation. Even if NH 4 + is ' preferred ' by the rice, the N cycle in the paddy soil is complex and dynamic, especially under water-saving irrigation which resulted in a rapid conversion of the applied 15NH 4 + to NO 3 -, and hence less opportunities for rice to take up the applied 15NH 4 +. Therefore, the nitrogen preference of plants is not the only critical factor in selecting a proper nitrogen fertilizer source for rice, it is better to take the match of plant N preference, N fertilizer type, and irrigation regime into consideration to optimize irrigation and fertilization management and increase the NRE of plants. • The NRE of rice under water-saving irrigation was higher than under flooded irrigation regardless of NH 4 + or NO 3 - supply. • No significant difference in NRE of rice was observed between NH 4 + and NO 3 - under water-saving irrigation. • 'Preferential' ammonium uptake by rice does not always turn into higher NRE. • The match between crop N preference, N fertilizer type and irrigation regime is critical for improving crop NRE. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon sources with lower number of C atoms were more available for DNRA bacteria. • DNRA bacteria had high NH 4 +-N transformation efficiency at COD/N ratio 7.7. • Ethanol systems showed abundant fermenting bacteria. • Potential carbon metabolism pathway in DNRA process was estimated firstly. The dissimilatory nitrate reduction to ammonium (DNRA) process was known as a short circuit in nitrogen cycle, a key step in recovering nitrogen from nitrate wastewater, and has attracted people's attention for a long time. Here, three organic substances supported DNRA systems, sodium succinate, glucose, and ethanol, were constructed in membrane bioreactor at three different COD/N ratios (6.5, 7.7, and 10) for nitrogen recovering from nitrate wastewater. The experiment results indicated that the maximum ammonium nitrogen transformation efficiency of 71.49%, 66.92%, and 92.05% were achieved at a COD/N ratio of 7.7 in sodium succinate, glucose, and ethanol supported DNRA systems. The high-throughput sequencing, which targeted nrfA gene, showed a greater diversity of DNRA microbiota at a COD/N ratio of 7.7. The quantitative PCR and 15N isotope tracing experiment showed that the ethanol-supported DNRA system had the highest nrfA gene abundance and DNRA potential rate. Meanwhile, ethanol-supported DNRA systems were found to contain a large number of fermenting bacteria (such as Acetoanerobium , Lentimicrobium , and Fusibacter), suggesting that anaerobic digestion may accompany the DNRA system. The potential metabolic pathways of three carbon sources were further predicted. Glucose and succinate may enter pyruvate metabolism via glycolysis and the citrate cycle. The high abundance of genes encoding phosphate acetyltransferase in ethanol system suggested that ethanol was most likely to be degraded via acetyl-CoA pathway and ensured electron supply to nitrate-reducing bacteria. This study is expected to provide new ideas for efficient recovery of nitrogen resources. [ABSTRACT FROM AUTHOR]

field micro-plot experiment for winter wheat was conducted in an irrigated winter wheat ( Triticum aestivum)-summer maize ( Zea mays L.) rotation system in Mazhuang, Xinji of Hebei province in the North China Plain, using the N isotope method to determine the effects of N application (rates and timing), and irrigation frequency on urea-N fate, residual-N and N recovery efficiency (NRE) of wheat. The experiment was conducted under two irrigation treatments (I2 and I3, representing for two and three irrigations, respectively), at three N rates (150, 210, and 270, kg ha), divided between two N-labeled applications of basal-N (90 kg ha) and topdress-N (60, 120, and 180, kg N ha, respectively). The total N uptake by wheat (ranging from 186 to 238 kg ha) and the fertilizer-derived N (Ndff, about 34-55%) were measured. The Ndff from labeled basal-N and from labeled topdress-N were about 15-22% and 16-40%, respectively. The NRE (measured either as recovery in grain or as the total N recovery in the plant) was higher with I3 (39-41 or 47-49%) than with I2 (35-40 or 42-47%), showing maximum NRE in grain of about 40% both at N210 with I2 and at N150 with I3 treatment. The NRE by the first wheat crop (in grain or the total N recovery in plant) was higher with labeled topdress-N (39-48 or 45-56%) as compared to that with labeled basal-N (30-37 or 36-45%), while the unaccounted N losses were lower with labeled basal-N (14-22%) relative to labeled topdress-N (14-35%). Higher residual N in soils was found with labeled basal-N (41-51%), as compared to labeled topdress-N (18-35%). Residual N in the 0- to 150-cm soil depth ranged from 26 to 44% while the unaccounted N losses ranged from 14 to 30%. Recovery of residual N by the 2nd and 3rd crops in the rotation was 5-10% in the maize crop and a further 1.7-3.5% in the subsequent wheat crop. The accumulated N recovery and the unaccounted N losses in continuous wheat-maize-wheat rotations derived from labeled topdress-N were 54-64% and 16-37%, respectively while they were 47-53% and 16-28%, respectively from labeled basal-N. This study also suggested that an N rate of 210 kg ha (with a ratio of basal-N to topdress-N of 1:1.3) with two irrigation applications could optimize wheat grain yields and NRE, under the water limited conditions in North China Plain. [ABSTRACT FROM AUTHOR]

field micro-plot experiment for summer maize was conducted in an irrigated winter wheat ( Triticum aestivum)-summer maize ( Zea mays L.) rotation system in Mazhuang, Xinji of Hebei province in the North China Plain, using the N isotope method to determine the effects of N application (rates and timing) on urea-N fate, residual N effects and N recovery efficiency (NRE) by maize. The experiment included three N rates (90, 180, and 270 kg ha), divided by two N-labeled groups of basal-N (30, 60, and 90 kg ha, respectively) and topdress-N (60, 120, and 180 kg N ha, respectively). All of the treatments were irrigated two times, once at seeding time and once at topdressing time. The absorbed N in the maize plant derived from basal-N (6.8-13%) and topdress-N (17-30%) was identified. The residual N in the 0-150-cm soil depth ranged from 45 to 60% at the first maize harvest, mainly retained in the top 20-cm layers. Both NRE in grain and total N recovery in plant in the first maize crop were higher from topdress-N (26-31 or 41-51%, respectively) than from basal-N (18-23 or 34-43%, respectively). The residual N in the 0-150-cm soil layer was lower from topdress-N (45-47%) than from basal-N (55-60%) after the first maize harvest. Residual N recovery was 6-11% in the second and 1.5-3.5% in the third crop. Cumulative N recovery in the maize-wheat-maize rotations was higher from the topdress-N (49-59%) than from basal-N and (45-55%). The unaccounted N loss was 14-24% from the basal-N and 20-33% from the topdress-N, with a double dose of basal-N application. An N rate of approximately 180 kg ha appears to be an effective application rate to optimum maize yield and NRE on North China Plain, depending on the residual N and the crop yield potential. [ABSTRACT FROM AUTHOR]

Abstract: Northeast Thailand is one of the representative rainfed rice culture areas in Asia, where rice productivity is limited not only by unstable rainfall but also by poor soil. The objective of this study was to improve rainfed rice yield at degraded fields in upper toposequence by incorporation of sediment soil accumulated at the lowest toposequence in mini-watersheds. We collected sediment soil from the pond when it was dry in the dry season in 2001 and placed it uniformly on the experimental field at a thickness of 5cm, and incorporated it into the plow layer by double plowings and puddling. The clay content, soil organic carbon (SOC) content and cation exchange capacity (CEC) of the pond sediment soil were 0.42kgkg−1, 12.9gkg−1 and 13.8cmolkg−1, respectively, those of the field soil before the incorporation were 0.08, 4.6 and 5.0, respectively, and those after the incorporation were 0.19, 5.7 and 7.1, respectively. Rice cultivar KDML105 was grown under rainfed condition, incorporated with and without the pond sediment soil, each with and without fertilization (four treatments in total) for the seasons from 2001 to 2003. Incorporation of the pond sediments increased rice yield in the fertilized plot by 28% on the average over three seasons, but not in the unfertilized plots. The yield increase in the fertilized plot was associated with increased fertilizer-N recovery efficiency. Since incorporation of the pond sediment did not significantly improve field water holding capacity and mineralizable N in soil, its effect on the fertilizer-N recovery efficiency and rice yield could be ascribed to the increased CEC. As much clay sediments rich in SOC and clay are accumulated in the lower toposequence such as the bottom of ponds, the present study suggests that incorporation of pond sediment soil into fields is an effective technology to improve rainfed rice yield at upper toposequence in mini-watersheds in Northeast Thailand. [Copyright &y& Elsevier]