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Excessive nitrogen (N) application in wheat-maize cropping systems was adjusted towards more sustainable practices to reduce hydrological N losses while maintaining crop yield. In comprehensive quantification of N management effects on crop yield, N use efficiency (NUE), hydrological N losses, and soil nitrate residual across eight seasons, we have added to growing evidence of strategies beneficial for sustainable crop production with lower hydrological N losses. The results show that adjusted N practices enhanced crop yield and NUE, as compared to farmer's practices, but benefits varied with N rates and types. Optimized N treatment (OPT, 180 kg N ha-1 in both maize and wheat seasons) with or without straw returning produced the most crop yield. They increased maize yield by 5.5% and 7.3% and wheat yield by 6.2% and 3.2% on average, as compared to farmer's practice with huge N application (FP, 345 kg N ha-1 and 240 kg N ha-1 in maize and wheat). Regulation of N release through amendment with controlled release urea at a rate of 144 kg N ha-1 crop-1 (CRU treatment) obtained 4.4% greater maize yield than FP, and sustained a similar wheat yield with less N input, resulting in the highest crop NUE. Additionally, CRU was most effective in mitigating hydrological N loss, with 39.5% and 45.5% less leachate N and 31.9% and 35.9% less runoff N loss than FP in maize and wheat seasons. Synthetic N input correlated significantly and positively with runoff and leachate N losses, indicating it was one of the dominant factors driving hydrological N losses. Moreover, compared to OPT, additional straw returning (STR) or substituting 20% of the nutrients by duck manure (DMS) further reduced runoff N discharges due to the fact that organic matter incorporation increased resilience to rainfall. N over-application in FP caused considerable nitrate accumulation in the 0-90-cm soil profile, while the adjusted N practices, i.e., OPT, STR, CRU, and DMS treatments effectively controlled it to a range of 79.6-92.9 kg N h-1. This study suggests that efforts using optimized N treatment integrated with CRU or straw returning should be encouraged for sustainable crop production in this region. [ABSTRACT FROM AUTHOR]

Nitrogen loss from paddy fields contributes to most of the nitrogen pollution load in the Ningxia Yellow River irrigation area, threatening the water quality of the Yellow River. Consequently, optimizing the nitrogen management practices in this area is essential, which can maintain paddy grain productivity and reduce nitrogen loss simultaneously. Five treatments with different nitrogen application rates and nitrogen fertilizer types were set in this study, including conventional urea application with zero nitrogen application rate (CK, 0 kg hm-2), nitrogen expert-based fertilization application strategy (NE, 210 kg hm-2), optimized nitrogen fertilizer application strategy recommended by local government (OPT, 240 kg hm-2), and farmer’s experience-based nitrogen fertilizer application strategy (FP, 300 kg hm-2), and controlled-release urea application (CRU, 180 kg hm-2). The data from one growth season field experiment in 2021 revealed the dynamics of nitrogen concentration, paddy yield and its nitrogen uptake characteristic, and nitrogen balance in the paddy field under different nitrogen application practices. Most nitrogen leaching was observed during the seedling and tillering stages in the form of nitrate nitrogen (NO3 –N). Compared with the FP, the CRU and OPT significantly reduced the nitrogen concentrations of total nitrogen (TN), ammonium nitrogen (NH4 +N in the surface and soil water and reduced the nitrogen leaching at 100 cm soil depth. Meanwhile, the paddy grain yield in CRU (7737 kg hm3 –N in the surface and soil water and reduced the nitrogen leaching at 100 cm soil depth. Meanwhile, the paddy grain yield in CRU (7737 kg hm-2) and OPT (7379 kg hm-2) was not significantly decreased compared with FP (7918 kg hm-2), even though the nitrogen uptake by grain and straw was higher in FP (135 kg hm-2) than in other treatments (52.10~126.40 kg hm-2). However, the grain yield in NE (6972 kg hm-2) was decreased compared with the FP. The differences in grain yield among these treatments were mainly attributed to the ear number and grain number changes. Also, the highest nitrogen use efficiency (40.14%), apparent nitrogen efficiency (19.53 kg kg-1), and nitrogen partial productivity (43.98 kg kg-1) were identified in CRU than in other treatments. Considering increased grain yield and reducing nitrogen loss in the paddy field simultaneously, the treatments of CRU (i.e., 180 kg hm-2 nitrogen application rate with controlled-release urea) and OPT (i.e., 240 kg hm-2 nitrogen application rate with conventional urea) were recommended for nitrogen fertilizer application in the study area. [ABSTRACT FROM AUTHOR]

The application of nitrogen (N) fertilizer combined with nitrification inhibitor is considered to be one of the effective strategies to improve N efficiency and reduce N loss. While the chemical and physical properties of nitrapyrin (CP) in fertilizers have been evaluated to increase N efficiency, a lack of comprehensive evaluation of the effects of adding CP on summer maize yield, environmental benefits and economic income under different fertilization methods. In this study, two fertilization methods were used: split-N application and one-time basal N fertilizer before sowing. The comprehensive effects of N fertilizer with CP on N loss (NH2 volatilization, NO2- leaching, and N2O emissions), N efficiency, yield and profit under two N application methods were explored. Results showed that under the two N application methods, N fertilizer with CP treatment increased the N efficiency and yield (+3.4%~+5.7%), significantly reduced the soil NO2--N content and N2O emissions, while increased NH3 volatilization. Especially, the increase amplitude of NH3 was much less than the decrease amplitude of N2O induced by adding CP. Although split-N application could achieve higher yield and N efficiency, N2O emissions and NH3 volatilization also increased. However, the T1 + N (one-time basal N fertilizer before sowing mixed with CP) achieved the same yield level as T2 treatment (split-N application). Taking agronomic, economic and environmental benefits into consideration, onetime basal N fertilizer before sowing mixed with CP could ensure the target yield, increase economic benefits, maintain soil N content, and reduce N losses. Therefore, optimizing N management is essential to the sustainable development of agriculture. [ABSTRACT FROM AUTHOR]

Soil deterioration, low nitrogen use efficiency (NUE), and environmental risks caused by excessive chemical N fertilizer use are key factors restricting sustainable agriculture. It is extremely critical to develop effective N management strategies that consider both environmental and agronomic benefits. From 2017 to 2019, a field experiment was conducted to assess the effects of combinations of organic fertilizers (OF, provided at 30, 50, and 70% of the total applied N) and controlled-release urea (CU) on the NUE, N leaching and wheat yield compared with the effects of urea and CU. The results suggested that OF released N slowly in the early stage and showed a significant residual effect, while CU released N quickly in the first 2 months. The OF substitutes with 30–50% CU increased wheat yield by 4.2–9.2%, while the 70%OF+30%CU treatment showed no significant difference relative to the urea treatment. The average maximum apparent NUE recovery (50.4%) was achieved under the 50%OF+50%CU treatment, but the partial factor productivity was not affected by the N type. As the OF application rate increased, the total carbon content increased, and the total N value decreased. The NO 3 − -N and NH 4 + -N concentrations in the OF+CU treatments were lower before the jointing stage but higher from the grain-filling to mature stages than those in the urea treatment. NO 3 − -N and NH 4 + -N were mainly concentrated in the 0–60-cm layer soil by OF substitution, and N leaching to the 60–100-cm soil layer was significantly reduced. Hence, the results suggest that the combination of 30–50% OF with CU synchronizes absorption with availability due to a period of increased N availability in soils and proved to be the best strategy for simultaneously increasing wheat production and reducing N leaching. [ABSTRACT FROM AUTHOR]

Soil deterioration, low nitrogen use efficiency (NUE), and environmental risks caused by excessive chemical N fertilizer use are key factors restricting sustainable agriculture. It is extremely critical to develop effective N management strategies that consider both environmental and agronomic benefits. From 2017 to 2019, a field experiment was conducted to assess the effects of combinations of organic fertilizers (OF, provided at 30, 50, and 70% of the total applied N) and controlled-release urea (CU) on the NUE, N leaching and wheat yield compared with the effects of urea and CU. The results suggested that OF released N slowly in the early stage and showed a significant residual effect, while CU released N quickly in the first 2 months. The OF substitutes with 30–50% CU increased wheat yield by 4.2–9.2%, while the 70%OF+30%CU treatment showed no significant difference relative to the urea treatment. The average maximum apparent NUE recovery (50.4%) was achieved under the 50%OF+50%CU treatment, but the partial factor productivity was not affected by the N type. As the OF application rate increased, the total carbon content increased, and the total N value decreased. The NO3−-N and NH4+-N concentrations in the OF+CU treatments were lower before the jointing stage but higher from the grain-filling to mature stages than those in the urea treatment. NO3−-N and NH4+-N were mainly concentrated in the 0–60-cm layer soil by OF substitution, and N leaching to the 60–100-cm soil layer was significantly reduced. Hence, the results suggest that the combination of 30–50% OF with CU synchronizes absorption with availability due to a period of increased N availability in soils and proved to be the best strategy for simultaneously increasing wheat production and reducing N leaching.

Excessive nitrogen (N) application in wheat-maize cropping systems was adjusted towards more sustainable practices to reduce hydrological N losses while maintaining crop yield. In comprehensive quantification of N management effects on crop yield, N use efficiency (NUE), hydrological N losses, and soil nitrate residual across eight seasons, we have added to growing evidence of strategies beneficial for sustainable crop production with lower hydrological N losses. The results show that adjusted N practices enhanced crop yield and NUE, as compared to farmer's practices, but benefits varied with N rates and types. Optimized N treatment (OPT, 180 kg N ha -1 in both maize and wheat seasons) with or without straw returning produced the most crop yield. They increased maize yield by 5.5% and 7.3% and wheat yield by 6.2% and 3.2% on average, as compared to farmer's practice with huge N application (FP, 345 kg N ha -1 and 240 kg N ha -1 in maize and wheat). Regulation of N release through amendment with controlled release urea at a rate of 144 kg N ha -1 crop -1 (CRU treatment) obtained 4.4% greater maize yield than FP, and sustained a similar wheat yield with less N input, resulting in the highest crop NUE. Additionally, CRU was most effective in mitigating hydrological N loss, with 39.5% and 45.5% less leachate N and 31.9% and 35.9% less runoff N loss than FP in maize and wheat seasons. Synthetic N input correlated significantly and positively with runoff and leachate N losses, indicating it was one of the dominant factors driving hydrological N losses. Moreover, compared to OPT, additional straw returning (STR) or substituting 20% of the nutrients by duck manure (DMS) further reduced runoff N discharges due to the fact that organic matter incorporation increased resilience to rainfall. N over-application in FP caused considerable nitrate accumulation in the 0-90-cm soil profile, while the adjusted N practices, i.e., OPT, STR, CRU, and DMS treatments effectively controlled it to a range of 79.6-92.9 kg N ha -1 . This study suggests that efforts using optimized N treatment integrated with CRU or straw returning should be encouraged for sustainable crop production in this region., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wang, Ma, Li, Geilfus, Wei, Zheng, Liu and Tan.)

Nitrogen loss from paddy fields contributes to most of the nitrogen pollution load in the Ningxia Yellow River irrigation area, threatening the water quality of the Yellow River. Consequently, optimizing the nitrogen management practices in this area is essential, which can maintain paddy grain productivity and reduce nitrogen loss simultaneously. Five treatments with different nitrogen application rates and nitrogen fertilizer types were set in this study, including conventional urea application with zero nitrogen application rate (CK, 0 kg hm -2 ), nitrogen expert-based fertilization application strategy (NE, 210 kg hm -2 ), optimized nitrogen fertilizer application strategy recommended by local government (OPT, 240 kg hm -2 ), and farmer's experience-based nitrogen fertilizer application strategy (FP, 300 kg hm -2 ), and controlled-release urea application (CRU, 180 kg hm -2 ). The data from one growth season field experiment in 2021 revealed the dynamics of nitrogen concentration, paddy yield and its nitrogen uptake characteristic, and nitrogen balance in the paddy field under different nitrogen application practices. Most nitrogen leaching was observed during the seedling and tillering stages in the form of nitrate nitrogen (NO 3 - N). Compared with the FP, the CRU and OPT significantly reduced the nitrogen concentrations of total nitrogen (TN), ammonium nitrogen (NH 4 N in the surface and soil water and reduced the nitrogen leaching at 100 cm soil depth. Meanwhile, the paddy grain yield in CRU (7737 kg hm + -N), and NO 3 - N in the surface and soil water and reduced the nitrogen leaching at 100 cm soil depth. Meanwhile, the paddy grain yield in CRU (7737 kg hm -2 ) and OPT (7379 kg hm -2 ) was not significantly decreased compared with FP (7918 kg hm -2 ), even though the nitrogen uptake by grain and straw was higher in FP (135 kg hm -2 ) than in other treatments (52.10~126.40 kg hm -2 ). However, the grain yield in NE (6972 kg hm -2 ) was decreased compared with the FP. The differences in grain yield among these treatments were mainly attributed to the ear number and grain number changes. Also, the highest nitrogen use efficiency (40.14%), apparent nitrogen efficiency (19.53 kg kg -1 ), and nitrogen partial productivity (43.98 kg kg -1 ) were identified in CRU than in other treatments. Considering increased grain yield and reducing nitrogen loss in the paddy field simultaneously, the treatments of CRU (i.e., 180 kg hm -2 nitrogen application rate with controlled-release urea) and OPT (i.e., 240 kg hm -2 nitrogen application rate with conventional urea) were recommended for nitrogen fertilizer application in the study area., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Liu, Wang, Hong, Wang, Mao and Yi.)

The application of nitrogen (N) fertilizer combined with nitrification inhibitor is considered to be one of the effective strategies to improve N efficiency and reduce N loss. While the chemical and physical properties of nitrapyrin (CP) in fertilizers have been evaluated to increase N efficiency, a lack of comprehensive evaluation of the effects of adding CP on summer maize yield, environmental benefits and economic income under different fertilization methods. In this study, two fertilization methods were used: split-N application and one-time basal N fertilizer before sowing. The comprehensive effects of N fertilizer with CP on N loss (NH 3 volatilization, NO 3 - leaching, and N 2 O emissions), N efficiency, yield and profit under two N application methods were explored. Results showed that under the two N application methods, N fertilizer with CP treatment increased the N efficiency and yield (+3.4%∼+5.7%), significantly reduced the soil NO 3 - -N content and N 2 O emissions, while increased NH 3 volatilization. Especially, the increase amplitude of NH 3 was much less than the decrease amplitude of N 2 O induced by adding CP. Although split-N application could achieve higher yield and N efficiency, N 2 O emissions and NH 3 volatilization also increased. However, the T1 + N (one-time basal N fertilizer before sowing mixed with CP) achieved the same yield level as T2 treatment (split-N application). Taking agronomic, economic and environmental benefits into consideration, one-time basal N fertilizer before sowing mixed with CP could ensure the target yield, increase economic benefits, maintain soil N content, and reduce N losses. Therefore, optimizing N management is essential to the sustainable development of agriculture., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ren, Ma, Zhao, Liu and Zhang.)