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Supplying adequate nitrogen (N) to meet crop demand is critical for enhancing agricultural sustainability. Not only fertilizer N, but also N from other available sources should be considered in N supply capacity. We conducted a 10-year farming experiment using a split-plot design with two different main fertilizer management approaches and three N application strategies as add-on sub-treatments. Based on the experiment, we estimated the total N supply (TNsupply) for the summer maize cropping system, through considering environmental, soil, crop residue, and fertilizer N sources. An appropriate TNsupply was established by correlating TNsupply with the relative yield (RY), N input and output, and N use efficiency (NUE). The results revealed a wide variation in TNsupply (from 88 to 755 kg ha−1). The RY, N input, and N output fitted well to TNsupply using linear-plateau, linear, and linear-plateau models, respectively. The lower limits of TNsupply for achieving the maximum RY and N output were 361 and 358 kg ha−1, respectively. The relationship between N input and N output was described as linear-plateau. We determined the slope of the linear curve (55.4%) as the lower limit of NUE, beyond which the upper limit of TNsupply was determined to be less than 497 kg ha−1. Thus, appropriate TNsupply values ranged from 325 to 497 kg ha−1 for summer maize production, which could ensure enough N supply for higher yields and avoid excessive N input for higher NUE and lower environmental N loss. Our findings highlight that TNsupply can be an alternative indicator for evaluating N management.

Excessive synthetic nitrogen (N) applications, high mineral N accumulation and low N use efficiency (NUE) are current issues in intensively cultivated winter wheat production system impeding the sustainable development of agriculture in China. To solve these problems, soil accumulated N in the top 1 m of the soil profile before sowing (Nsoil), returned straw-N from the previous maize crop (Nstraw) and fertilizer N application (Nfertilizer) should be comprehensively considered N supply sources in N management. As such, the objective of this research was to determine the optimal total N supply (TNsupply) level needed to meet crop requirements while minimizing environmental impacts. A 9-year on-farm experiment was conducted in accordance with a split-plot design involving two different fertilizer management systems (main treatments) and three N application strategies (sub treatments). Extensive TNsupply levels (ranging from 61 kg ha−1 to 813 kg ha−1) were detected, and relative yield (RY), N input and N output in response to the TNsupply were measured. The relationships between TNsupply and RY, N input, and N output strongly fit linear-plateau, linear, and linear-plateau models, respectively. The minimum TNsupply levels needed to achieve the maximum RY and N output were 325 and 392 kg ha−1, respectively. On the basis of N supply capacity, the TNsupply was removed from the growing system by 61% (N input). As the N input increased past 209 kg ha−1, the NUE declined, at which point the TNsupply reached 433 kg ha−1. Therefore, the suitable TNsupply should range from 325 kg ha−1 (ensuring a total N supply for high yield and N uptake) to 433 kg ha−1 (obtaining a relatively higher NUE and less N loss to the environment). The TNsupply was highlighted to be an indicator for use in N management recommendations. Considering the average high N accumulation in winter wheat production systems, N management should essentially take into account the consumption of Nsoil, the levels of Nstraw and the minimum application of Nfertilizer to obtain high yields while minimizing environmental impacts under suitable TNsupply levels.

Decision-making related to nitrogen (N) fertilization is a crucial step in agronomic practices because of its direct interactions with agronomic productivity and environmental risk. Here, we hypothesized that soil apparent N balance could be used as an indicator to determine the thresholds of N input through analyzing the responses of the yield and N loss to N balance. Based on the observations from 951 field experiments conducted in rice (Oryza sativa L.) cropping systems of China, we established the relationships between N balance and ammonia (NH3) volatilization, yield increase ratio, and N application rate, respectively. Dramatical increase of NH3 volatilizations and stagnant increase of the rice yields were observed when the N surplus exceeded certain levels. Using a piecewise regression method, the seasonal upper limits of N surplus were determined as 44.3 and 90.9 kg N ha−1 under straw-return and straw-removal scenarios, respectively, derived from the responses of NH3 volatilization, and were determined as 53.0–74.9 and 97.9–112.0 kg N ha−1 under straw-return and straw-removal scenarios, respectively, derived from the maximum-yield consideration. Based on the upper limits of N surplus, the thresholds of N application rate suggested to be applied in single, middle-MLYR, middle-SW, early, and late rice types ranged 179.0–214.9 kg N ha−1 in order to restrict the NH3 volatilization, and ranged 193.3–249.8 kg N ha−1 in order to achieve the maximum yields. If rice straw was returned to fields, on average, the thresholds of N application rate could be theoretically decreased by 17.5 kg N ha−1. This study provides a robust reference for restricting the N surplus and the synthetic fertilizer N input in rice fields, which will guide yield goals and environmental protection.

Tremendous amounts of nitrogen (N) fertilizer have been added to arable lands, often resulting in substantial effects on terrestrial ecosystems, including soil acidification, altered enzyme activities and changes in microbial community composition. Soil microbes are the major drivers of soil carbon (C) and N cycling; therefore, understanding the response of microbial communities to elevated N inputs is of significant importance. This study was carried out to investigate the influences of different N fertilization rates (0, 182, and 225 kg ha-1 representing control, low, and high N supply for each crop season for summer maize and winter wheat) on soil biochemical attributes, extracellular enzyme activities, and the microbial community composition in a winter wheat-summer maize rotation cropping system in north-central China. The results showed that N addition significantly decreased the soil pH in both the wheat and maize seasons. Microbial biomass N (MBN) decreased following N fertilization in the wheat season, while the opposite trend in MBN was observed in the maize season. Response ratio analysis showed that the activities of enzymes involved in C, N, and phosphorus cycling were significantly enhanced under N enrichment in both the wheat and maize seasons, and higher enzyme activities were noted in the high N addition treatment than in the low N addition treatment. A linear increase in fungal abundance with the N addition gradient was observed in the wheat season, whereas the fungal abundance increased and then decreased in the maize season. The bacterial abundance showed an increased and then decreased trend in response to the N addition gradient in both the wheat and maize crop seasons. Moreover, the partial least squares path model (PLS-PM) analysis showed that soil pH and soil organic carbon (SOC) were the most important soil variables, causing shifts in the soil bacteria. Furthermore, compared with the N-cycling enzymes, the C-cycling enzymes were significantly affected by the soil pH and SOC. Taken together, these results suggest that the effect of N addition on enzyme activities was consistent in both crop seasons, while the effects on MBN and microbial community composition to N addition were highly variable in the two crop seasons. Moreover, N fertilization-induced changes in the soil chemical properties such as soil acidity and SOC played a substantial role in shaping the microbial community.

As the traditional Chinese herbal formula, Xiaoyaosan and its modified formula have been described in many previous studies with definite anti-depressive effects, but its underlying mechanism remains mystery. Previous work in our lab has demonstrated that depression induced by chronic stress could generate brain blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signals disorder, accompanied by the impairment of hippocampal neuronal plasticity, decrease of brain-derived neurotrophic factor, and reduction of the number and complexity of adult neurons in the dentate gyrus. We hypothesized that herbal formula based on Xiaoyaosan could exert anti-depressive effects through restoring these neurobiological dysfunctions and rectifying BOLD-fMRI signals. To test this hypothesis, we examined the effect of modified Xiaoyaosan (MXYS) on depressive-like behaviors, as well as hippocampal neurogenesis and BOLD signals in a mice model of chronic unpredictable mild stress (CUMS)-induced depression. MXYS exerted anti-depressant effects on CUMS-induced depression that were similar to the effects of classical antidepressants drug (fluoxetine hydrochloride), with a significant alleviation of depressive-like behaviors, an improvement of hippocampal neurogenesis, and a reversal of activation of BOLD in the limbic system, particularly in the hippocampus. These results suggested that MXYS attenuated CUMS-induced depressive behaviors by rectifying the BOLD signals in the mice hippocampus. These novel results demonstrated that MXYS had anti-depressive effects accompanied by improving BOLD signals and hippocampal neurogenesis, which suggested that BOLD-fMRI signals in brain regions could be a key component for the evaluation of novel antidepressant drugs.

Excessive fertilizer consumption, poor management, and intense pollution currently restrict sustainable agriculture in China. To address these problems, two 9-year experiments involving typical maize production systems in Northcentral China (summer maize) and Northeast China (spring maize) were conducted to evaluate the effectiveness of Nutrient Expert (NE) management, a Nutrient Decision Support System which combines 4 R nutrient management with improved varieties and optimized plant density, on reducing carbon (C) and nitrogen (N) footprints. The mean grain yields under NE were 7.4 and 11.5 tons ha−1, which were 3.9% and 6.9% higher than those of local farmers’ practices (FP) in the summer and spring maize systems, respectively; the N-derived (affected by N fertilization) yield accounted for 21.7% and 73.5% of the total yield under NE, respectively. Compared with FP, NE achieved 21.8% and 16.0% lower reactive nitrogen (Nr) losses, 18.4% and 20.9% lower greenhouse gas (GHG) emissions, 24.8% and 21.4% smaller N footprints (9.1 and 2.3 kg N ton−1 grain), and 21.5% and 26.0% smaller C footprints (436 and 206 kg CO2 eq ton−1 grain) in summer and spring maize, respectively. NE reduced the N-derived N and C footprints by 30.3% and 27.2% in summer maize and 22.9% and 28.0% in spring maize, respectively, as a result of greater yields and optimal N management. Moreover, compared with summer maize, spring maize showed significantly smaller N-derived N (12.6-fold) and C (7.2-fold) footprints. The results demonstrated the ability of long-term NE management to sustain maize yields, reduce Nr losses and GHG emissions, and cut C and N footprints, indicating its potential suitability as an alternative management for sustainable agriculture. Moreover, the summer maize system still had considerable potential for environmental footprints reduction even when current NE management practices were adopted.