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Straw return can improve crop yield as well as soil organic carbon (SOC) but may raise the possibility of N 2 O and CH 4 emissions. However, few studies have compared the effects of straw return on the yield, SOC, and N 2 O emissions of various crops. Which management strategies are the best for balancing yield, SOC, and emission reduction for various crops needs to be clarified. A meta-analysis containing 2269 datasets collected from 369 studies was conducted to investigate the influence of agricultural management strategies on yield increase, soil carbon sequestration, and emission reduction in various crops after the straw return. Analytical results indicated that, on average, straw return increased the yield of rice, wheat, and maize by 5.04%, 8.09%, and 8.71%, respectively. Straw return increased maize N 2 O emissions by 14.69% but did not significantly affect wheat N 2 O emissions. Interestingly, straw return reduced the rice N 2 O emissions by 11.43% but increased the CH 4 emissions by 72.01%. The recommended nitrogen application amounts for balancing yield, SOC, and emission reduction varied among the three crops, while the recommended straw return amounts were more than 9000 kg/ha. The optimal tillage and straw return strategies for rice, wheat, and maize were plow tillage combined with incorporation, rotary tillage combined with incorporation, and no-tillage combined with mulching, respectively. A straw return duration of 5–10 years for rice and maize and ≤5 years for wheat was recommended. These findings provide optimal agricultural management strategies after straw return to balance the crop yield, SOC, and emission reduction for China's three major grain crops. [Display omitted] • The yield, SOC, and N 2 O of three crops (rice, wheat, and maize) respond differently to straw return. • Straw return amounts greater than 9000 kg/ha balance three-grain crops' yield, SOC, and emissions. • We recommend straw incorporation for rice and wheat, and mulching for maize. • The optimal nitrogen rate and tillage method are dependent on the crops. • We recommend a return duration of 5–10 years for rice and maize and ≤5 years for wheat. [ABSTRACT FROM AUTHOR]

At present, excessive nutrient inputs caused by human activities have resulted in environmental problems such as agricultural non-point source pollution and water eutrophication. The Net Anthropogenic Nitrogen Inputs (NANI) model can be used to estimate the nitrogen (N) inputs to a region that are related to human activities. To explore the net nitrogen input of human activities in the main grain-producing areas of Northwestern China, the county-level statistical data for the Ningxia province and NANI model parameters were collected, the spatio-temporal distribution characteristics of NANI were analyzed and the uncertainty and sensitivity of the parameters for each component of NANI were quantitatively studied. The results showed that: (1) The average value of NANI in Ningxia from 1991 to 2019 was 7752 kg N km−2 yr−1. Over the study period, the inputs first showed an overall increase, followed by a decrease, and then tended to stabilize. Fertilizer N application was the main contributing factor, accounting for 55.6%. The high value of NANI in Ningxia was mainly concentrated in the Yellow River Diversion Irrigation Area. (2) The 95% confidence interval of NANI obtained by the Monte Carlo approach was compared with the results from common parameters in existing literature. The simulation results varied from −6.4% to 27.4% under the influence of the changing parameters. Net food and animal feed imports were the most uncertain input components affected by parameters, the variation range was −20.7%–77%. (3) The parameters of inputs that accounted for higher proportions of the NANI were more sensitive than the inputs with lower contributions. The sensitivity indexes of the parameters contained in the fertilizer N applications were higher than those of net food and animal feed imports and agricultural N-fixation. This study quantified the uncertainty and sensitivity of parameters in the process of NANI simulation and provides a reference for global peers in the application and selection of parameters to obtain more accurate simulation results. MAX and MIN are the upper and lower limits of the confidence interval, respectively, AVE is the Monte Carlo simulation average value, OPT is the calculation result using common parameters from the existing literature. [Display omitted] • Spatio-temporal change NANI of Ningxia in China from 1991 to 2019 was analyzed. • Fertilizer N application was a primary source of NANI in the studied region. • The Monte Carlo method for uncertainty of the NANI model parameter was integrated. • The most sensitive parameter was in the chemical fertilizer application component. [ABSTRACT FROM AUTHOR]

Excess inputs of nitrogen (N) and phosphorus (P) are the main contributors of aquatic environmental deterioration. Due to the agricultural and industrial activities in the rapidly urbanized basin, the anthropogenic N and P cycle are significantly different from other regions. In this study, we took the Pearl River Delta as an example and introduced the budget list of N and P in the five survey years, including the net anthropogenic N inputs (NANI) and net anthropogenic P inputs (NAPI). The results revealed that the intensities of NANI and NAPI in this area increased from 2008 to 2010 and then decreased after 2010. The peak values were 21001 kg N km−2yr−1 and 4515 kg P km−2yr−1 for the intensities of NNAI and NAPI, respectively, while the lowest values decreased to 19186 kg N km−2yr−1 and 4103 kg P km−2yr−1 in 2016. The most important contribution of NANI and NAPI sources in this area were net N and P inputs for human food and animal feed with an average contribution of 61.41% and 76.83%, which indicated that large amounts of N and P were introduced into the environment through the food system. This study expanded the knowledge on regional environmental management from human dietary consumption, human life consumption, animal consumption and fertilizer consumption. Its reuse will be put into practice by understanding the driving factors of N and P inputs in each region of the basin, combining the urbanization characteristics. • The mean intensities of NANI and NAPI in the Pearl River Delta basin were higher than that of the mean level in China. • Human food and animal feed inputs comprised more than 60% for NANI, and 70% for NAPI in PRD. • Site-specific management strategies for N and P were needed in the PRD. [ABSTRACT FROM AUTHOR]