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How to improve nitrogen (N) efficiency and reduce environmental pollution caused by N loss has attracted much attention. However, limited research has lacked a comprehensive exploration of the effects of applying UAN under the micro sprinkling fertigation on reactive N (Nr), fertilizer efficiency and net benefits including environmental costs, plus associated responses of the microbial metagenome. The aim of this study was to assess the impact of N management practices on maize yield, Nr losses, and soil microbial community composition and function. Urea and urea ammonium nitrate solution (UAN) were used as N sources, and three N application rates (210, 168 and 0 kg N ha−1) and two fertilization methods (micro sprinkling fertigation and traditional fertilization) were set as the three key components. The results showed that micro sprinkling fertigation treatments reduced Nr losses, increased yield and N efficiency. Compared with urea, the total NH 3 volatilization and N 2 O emissions of UAN under micro sprinkling fertigation were decreased by 14.8% and 30.6%, respectively. Furthermore, the N reduction (FU1) treatment promoted plant N uptake, was saved 20% of N by affecting soil NH 4 +- N and NO 3 --N content, compared to that of urea, and it regulated the microbial abundance of N cycle function related to denitrification and N respiration, reduced global warming potential and greenhouse gas emission intensity. N application method, N source and N rate affected the diversity and composition of soil bacterial community, and altered Nr emissions by changing the abundance of functional microorganisms related to N cycle. Overall, improved N management practice was more conducive to increasing maize yield and net income, saving N resources, and reducing the risk of environmental damage. Our results contribute to a comprehensive understanding of the impact of N management on summer maize production, providing an effective N management practice that is conducive to "green agricultural development". [Display omitted] • A field trial was conducted in Huang-Huai-Hai Plain of China to clarify N losses and net income. • The soil bacterial community was changed by fertilization methods and N sources. • Applying UAN under micro sprinkling fertigation improved maize yield and saved N resources. [ABSTRACT FROM AUTHOR]

The application of nitrogenous fertilizer synergist to coordinate nitrogen transformation process in soil may be an efficient strategy to increase nitrogen use efficiency and decrease environmental pollution. However, there are few reports on the application effects of UAN synergistic nitrification and urease inhibitors under the integration of water and fertilizer. This study aimed to explore effects of urea ammonium nitrate solution (UAN) combined with urease and nitrification inhibitors on yield and nitrogen efficiency of summer maize and its ecological effects under the fertigation, and to provide scientific basis for the efficient utilization of UAN. The experimental treatments were as follows: no inhibitor treatment (U), nitrification inhibitor treatment (U-D), urease inhibitor treatment (U-N), and the combination of nitrification and urease inhibitors treatment (U-D+N). Results showed that UAN combined with urease or nitrification inhibitors could significantly reduce the cumulative emission of N 2 O, and then significantly decreased the N 2 O warming potential (GWP N2O) and N 2 O greenhouse gas intensity (GHGI N2O). Compared with U treatment, the cumulative N 2 O emissions of U-D+N, U-N, and U-D treatments was reduced by 45.7 %, 25.3 % and 35.8 %, respectively. The GWP N2O of U-D+N, U-N and U-D treatments decreased by 45.7 %, 25.3 % and 35.7 %, while GHGI N2O decreased by 50.9 %, 30.3 % and 38.9 % on average, respectively, compared to those of U treatment. Application of urease inhibitors significantly reduced NH 3 volatilization. The cumulative NH 3 volatilization of U-N and U-D+N treatments was reduced by 30.7 % and 23.4 %, while U-D treament was significantly increased by 12.3 %, respectively, compared to that of the U treatment. In addition, UAN combined with urease or nitrification inhibitor could significantly increase the contents of NO 3 --N and NH 4 --N in the 0–20 cm soil layer, and significantly reduced the leaching of NO 3 --N to the deep soil. The total nitrogen accumulation, grain nitrogen content, nitrogen transport efficiency and post-anthesis assimilation of summer maize were significantly increased, which were beneficial to the improvement of grain yield and economic benefits. under the fertigation, the synergistic application of UAN with urease and nitrification inhibitors were beneficial to reduce greenhouse gas emissions and ammonia volatilization, improved the nitrogen use efficiency, and then improved the yield and economic benefits of summer maize. Under the fertigation, UAN combined with urease and nitrification inhibitors were beneficial to emission reduction, high yield, and high efficiency. [Display omitted] • The combination of DCD and NBPT reduced N 2 O and NH 3 emission under fertigation. • The combination of UAN with DCD and NBPT improved N use efficiency under fertigation. • The combination of UAN with DCD and NBPT increased maize yield under fertigation. [ABSTRACT FROM AUTHOR]

Cytokinin is known to be involved in the regulation of plant responses to counteract the adverse effects of stress conditions. This work investigated the effects of exogenous spraying of 6-benzyladenine (6-BA) after water logging for 6 days at the third leaf stage (V-3WL + BA) and the sixth leaf stage (V-6WL + BA) on grain yield and growth of summer maize hybrids DengHai605 (DH605) and ZhengDan958 (ZD958), which are planted most popularly in China. Waterlogging under field conditions delayed the growth process, decreased leaf area index, chlorophyll content and dry matter accumulation, resulted in a significant reduction of grain yield with a decrease of 30.30% and 18.78% under V-3WL (water logging for 6 days at the third leaf stage) and V-6WL (waterlogging for 6 days at the sixth leaf stage) of DH605, 30.39% and 21.38% under V-3WL and V-6WL of ZD958, respectively, compared to the control (CK). By contrast, exogenous application of 6-BA effectively alleviated the adverse effects of waterlogging on summer maize by delaying leaf senescence, increasing chlorophyll content and improving photosynthetic performance. At tasseling stage, the P n of V-3WL + BA and V-6WL + BA in DH605 increased by 9.57% and 8.38%, respectively, compared to that of V-3WL and V-6WL, while the corresponding values for ZD958 increased by 2.96% and 4.05%, respectively. Those responses are conducive to the accumulation of photosynthetic products, increasing grain filling rate, and improving ear character, and then leading to increase grain yield of summer maize. Grain yield of DH605 under V-3WL + BA and V-6WL + BA increased by 15.57% and 12.39%, respectively, compared to that of V-3WL and V-6WL, while the corresponding values for ZD958 increased by 20.05% and 15.32%, respectively. Clearly, spraying exogenous 6-BA could effectively improve grain-filling characteristics and photosynthesis of waterlogged summer maize, resulting in a significant increase of grain yield, compared to water logging treatments. [ABSTRACT FROM AUTHOR]

• A moderate nitrogen rate ensures appropriate nitrogen content in leaves. • An appropriate nitrogen content in leaves affects grain yield formation by adjusting spike differentiation. • The leaf-N status influences spike differentiation through N accumulation and transport. Spike differentiation plays a pivotal role in maize (Zea mays L.) yield formation. However, it is unclear if leaf-N status affects yield formation by modifying spike differentiation. To understand how the spike differentiation is affected by leaf N content, as affected by the N rate, a field experiment was conducted. The experiment consisted of four N rates: N0 (0 kg N ha–1), N1 (129 kg N ha1), N2 (184.5 kg N ha−1), and N3 (300 kg N ha−1). At zero (N0) or low (N1) N rate, N stress significantly reduced the leaf N content of summer maize, which in turn reduced the N accumulation and N transfer from leaves to spike during spike differentiation, compared to the moderate N rate (N2), especially at the tassel-floret and ear-spikelet differentiation stage (FT-SE). So the reproductive growth was delayed by 2–4 days under N0 and N1, abortive florets of the ear were increased by 28.2–166.2 %, and the anthesis-silking interval was lengthened by 2–4 days, compared with N2, which reduced the kernel set and subsequently the silk and grain number per ear. Appropriate N rate (N2) could increase N metabolism-related enzymatic activities and increase the content of glutamine (Gln) and asparagine (Asn) in leaves, which in turn increased N transfer to spike to promote spike differentiation and decrease abortive florets. Finally, the silk and kernel set under N2 were increased, which resulted in an increased in grain number per ear and yield by 3.5–27.4 % and 13.1–41.8 %, respectively, compared with N0 or N1. However, the excessive N rate (N3) demonstrated a threshold, which no longer promoted spike differentiation. Moreover, leaves had an N-absorption peak at the FT-SE, and the N content positively correlated with the total numbers of silks and florets per ear. The efficient absorption of N at the FT-SE was beneficial to increase floret fertility. Collectively, a moderate N fertilizer rate (around 185 kg N ha−1) assured appropriate N accumulation in leaves and N transfer to spike, improved spike development and increased floret fertility, grain number and yield. [ABSTRACT FROM AUTHOR]

With the extensive promotion of controlled-release urea (CRU), its N-release pattern has been shown to match the crop's N-demand period and improve crop yield by reducing N losses. Nevertheless, the impacts of CRU on summer maize yield, especially on greenhouse gas emissions, have rarely been reported during its long-term use. It is necessary through long-term positioning field experiment with CRU application to investigate the regulatory mechanisms of maize yield formation, nitrogen use efficiency (NUE), ammonia volatilization and greenhouse gas emissions. The long-term fertilizer positioning experiment for ten years, four treatments were performed: polymeric-coated controlled-release urea (CRF, 42% N, 3-months controlled-release period), sulfur-coated controlled-release urea (SCF, 35% N, 3-months controlled-release period), common urea (CCF, 46% N) and no nitrogen fertilizer (CK). Results showed that the two coated controlled-release fertilizers significantly increased NUE and dry matter accumulation in summer maize, and ultimately improved grain yield. Compared to CCF, CRF and SCF treatments increased post-silking dry matter accumulation by 16.3% and 13.3%; NUE by 42.3% and 28.9%. The 2-year mean grain yield of CRF and SCF treatment increased 9.0% and 12.4% compared to CCF treatment. CRF treatment significantly increased the NO 3 --N content in 0–60 cm soil layer; while CRF and SCF treatments showed a significantly higher NH 4 +-N concentration in the 0–20 cm soil layer than CCF treatment. Compared to CCF treatment, the CRF and SCF treatments significantly reduced peak ammonia volatilization, and the average cumulative emissions of ammonia volatilization of two years were reduced by 80.8% and 53.2%, respectively. CRF treatment had lower peak of N 2 O emissions but longer N 2 O emission duration than other N application treatments. The two-year average cumulative N 2 O emissions from CRF treatment increased by 49.6%, and SCF treatment increased by 61.1% compared to CCF treatment. Compared to CK treatment, total cumulative CH 4 uptake was 36.1% lower in CRF treatment, 60.9% in SCF and 78.9% in CCF treatment. The higher cumulative N 2 O emissions from CRF and SCF treatment resulted in a significantly higher global warming potential (GWP) than CCF treatment. The two-year mean increase in greenhouse gas intensity (GHGI) was 36.2% for CRF treatment and 44.7% for SCF treatment compared to CCF treatment. Long-term application of coated controlled-release fertilizers could achieve high yields and nitrogen use efficiency. However, there is a risk of increased N 2 O emissions, causing elevated GHGI. In the future, it is necessary to strengthen the research on the comprehensive effects of long-term reduced application of CRU on crop yield and greenhouse gas emissions, in order to promote the wide application of environmentally friendly CRU in the field. [Display omitted] • Long-term application of CRU could achieve sustainable crop yield improvement. • Long-term application of CRU significantly reduced ammonia volatilization and CH 4 emissions. • Long-term application of CRU carried the risk of increased N 2 O emissions, leading to higher GHGI. [ABSTRACT FROM AUTHOR]

The experiment is to explore the efficient and comprehensive utilization of maize straw resources to achieve the sustainability of the soil fertility under double cropping of winter wheat and summer maize. Summer maize hybrid Denghai 605 (DH605) and winter wheat variety Tainong 18 (TN18) were used as experimental materials. Based on all winter wheat straw returned to the field, the treatment of all summer maize straw (SR) and half of summer maize straw (1/2SR) and summer maize straw not returned to the field (CK) 3 experimental treatments were tested for 8 consecutive years. Under the condition of normal nitrogen application of 210 kg ha−1, two split areas were set to reduce the amount of nitrogen fertilizer by 15% and 30% (SR-15%、SR-30%、1/2SR-15%、1/2SR-30%、CK-15%、CK-30%) at the beginning of the 2016 wheat season. In the first two years of reduced nitrogen application, the yields of SR and 1/2SR treatments were significantly higher than that of CK under the same nitrogen application conditions, while the yields of SR, 1/2SR, SR-15%, and 1/2SR-15% were not significantly different. In the third year of the process of reducing nitrogen fertilizer, compared with SR, 1/2SR, and SR-15% treatments, the yield of 1/2SR-15% were significantly reduced by 9% under winter wheat season. During winter wheat and summer maize season, the nitrogen use efficiency, and nitrogen absorption efficiency of SR and 1/2SR were significantly increased compared with CK treatment under the same nitrogen rate, of which SR-15% treatment was not significantly different from SR and 1/2SR. The pre-anthesis nitrogen transfer rate and nitrogen harvest index of summer maize treated with SR, 1/2SR, SR-15% and 1/2SR-15% were also significantly increased, compared with CK and CK-15% treatments. The win-win situation of ecological and crop yield can be achieved by return half of the straw to the field or reducing the nitrogen fertilizer application by 15% under the condition of straw returned to the field. • Returning the full amount of summer corn to the field can stably replace 15% of the nitrogen fertilizer application. • The yield stability and NUE of SR-15% treatment are not significantly different between with SR and 1/2 SR treatments. • The 1/2SR treatment can achieve a synergistic increase in crop yield and nitrogen utilization under NCP in China. [ABSTRACT FROM AUTHOR]

In order to improve the grain yield of food crops, which is necessary to ensure food security, it is crucial to narrow existing yield gaps. Quantitative analyses of crop yield gaps can provide theoretical support for ascertaining the primary cause of these yield gaps, and then it can be used to increase the grain yield. We evaluated the size and characteristics of the summer maize yield gap in the North China Plain by combining crop models, farmer surveys, and farm experiments. We simulated the summer maize population of farmers' yield level, attainable yield level and potential yield level by establishing three cultivation modes: traditional farming practices (FP), established high-yield and high-efficiency practices (HH) and super-high-yield practices (SH), and introduce the cultivation relying solely on the basic soil fertility (BSF) to reveal the impact of environmental and management factors on yield gap. We explored the driving factors causing observed variations of yield gaps through a quantitative analysis of several additional parameters that are commonly used to characterize the efficiency of the maize production process, including the contribution rates of dry matter and harvest index to grain yield, the radiation interception rate and the radiation conversion efficiency. Our results show that the total yield gap based on farmer surveys and crop models was 4.9 t ha-1, accounting for 37% of the potential yield, of which 46% was exploitable. The total yield gap based on the farm experiments was 3.9 t ha-1, accounting for 30% of the potential yield, of which 69% was exploitable. The grain yield of FP significantly positively correlated with the grain yield of BSF, HH and SH. The contribution rates of dry matter and harvest index to grain yield of FP treatment were 45.7% and 54.3%, respectively. With the increase of yield level, the contribution rate of dry matter increased and the contribution rate of harvest index decreased. In summary, we found a sizeable total yield gap in summer maize in the North China Plain, and a considerable part is exploitable. Optimizing integrated agronomic management has a great potential for closing the exploitable yield gap. Narrowing the yield gap requires a synergistic increase in the contribution rate of dry matter and harvest index to grain yield, but a substantial increase in dry matter is more important. At present, narrowing the exploitable yield gap requires synergistic improvement of radiation interception rate and radiation conversion efficiency to increase the dry matter of maize population. In the future, the regulation measures aiming at narrowing the unexploitable yield gap should further focus on improving the radiation conversion efficiency. • Quantification of the exploitable and unexploitable yield gaps for maize in the NCP. • Dry matter and harvest index contributions to maize grain formation depend on the yield level. • Suggestions for improving the productivity of established maize farming practices. [ABSTRACT FROM AUTHOR]

Root growth demonstrates a high degree of plasticity in response to spatial variations in the availability of vital nutrients, and P fertilizer placement depth affects the development and distribution of plant roots. Optimizing the spatial matching between soil nutrients and the roots of maize plants in order to improve their N and P uptake and utilization capacity is a potential measure for improving the grain yield from summer maize. The spatial distribution profile of N, P and roots in the soil, as well as the roots' absorption and utilization characteristics with respect to N and P and how these relate to the dry matter accumulation and grain yield formation were evaluated under four different placement depths of 5, 10, 15 and 20 cm (labeled P 5 , P 10 , P 15 , and P 20 , respectively). Compared with the P 5 treatment, the P 15 treatment induced a larger root length density, as well as a larger rooting depth. That happened because a higher number of root cortical aerenchyma, combined with a larger cortical cell size, reduces the metabolic cost required to establish them, which drives regulation processes that result in the allocation of more biomass to root proliferation. It also helped plants to maintain a higher level of biomass and N and P accumulation during the later growth period, which in turn increased the N and P assimilation of grain and enhanced the grain yield by 22%, the P recovery efficiency by 74%, the P agronomic efficiency by 150%, and both the partial factor productivity of P and the partial factor productivity of N by 21%. In conclusion, this study demonstrates that placing P fertilizer at a depth of 15 cm promotes root growth by reducing the metabolic cost of having a higher number of root cortical aerenchyma and a larger cortical cell size, and also that it improves the N and P absorption and utilization of roots and synergistically increases the grain yield and nutrient utilization efficiency of the whole plant. • Moderate deep P fertilization improved the matching degree of root and nutrient. • The optimization of root anatomical structure reduced its metabolic cost. • Grain yield and nutrient use efficiency were both improved by deep P fertilization. [ABSTRACT FROM AUTHOR]