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Excessive nitrogen (N) fertilizer application severely degrades soil and contaminates the atmosphere and water. A 2-year field experiment was conducted to investigate the effects of different N fertilizer strategies on wheat-summer corn rotation systems in yellow-brown soil areas. The experiment consisted of seven treatments: no N fertilization (CK), conventional fertilization (FP), optimized fertilization (CF), reduced N rates of 10% (90% FP), 20% (80% FP), 30% (70% FP), and a combination of controlled release with conventional urea at 7:3 ratio (CRU). The results indicate that under the condition of 80% FP, both CF and CRU treatments can increase the yield of wheat and corn for two consecutive years. Compared with FP treatment, the wheat yield of CF and CRU treatments increased by 3.62–2.57% and maize yield by 3.53–1.85% with N fertilizer recovery rate (NRE) of crops by 46.2–37.8%. The agronomic N use efficiency (aNUE) under CF treatment increased by 35.4–37.7%, followed by CRU, which increased by 30.5–33.9%. Moreover, compared with FP treatment, both CF and CRU treatment increased the content of organic matter (OM), total N (TN), and hydrolyzed N (HN) in the topsoil layer, and 70% FP treatment significantly reduced the HN content. Both CF and CRU treatments significantly increased the NO3 concentrations in the 0–20 cm soil depth during the wheat and maize season at maturity stages and decreased the residual inorganic N below the plow layer (40–60 cm). During the corn season, the CF and CRU treatments significantly reduced the NO3 concentration in the 40–60 cm soil layer from seedling to jointing. Considering various factors, CRU treatment under 80% FP conditions would be the best fertilization measure for wheat-corn rotation in yellow-brown soil areas.

Ever-increasing nitrogen fertilizers have posed extreme pressure on the environment for the winter wheat-summer maize rotation system in the North China Plain. Controlled-release fertilizer can be expected to serve as the nutrient-efficient and environment-friendly approach. The available nutrients are applied at controlled rates or concentration levels required for the crop growth in the soil while maintaining the nutrients for a longer period. The controlled-release fertilizers can be considered as an effective measure to improve crop yield and nitrogen use efficiency. This study aims to explore the impacts of one-time fertilization of controlled-release blended fertilizer on the crop yield, greenhouse gas emissions (GHGs) and nitrate residues in the winter wheat-summer maize rotation system. A field experiment was conducted with the summer maize cultivar of Zhengdan 958 and the winter wheat cultivar of Jimai 22. Five treatments were performed on both winter wheat and summer maize, including no nitrogen control (CK), farmers' conventional nitrogen application (FFP), optimized nitrogen application (OPT), CRU1 (the blending ratios of coated urea and traditional urea on winter wheat and summer maize were 5:5 and 3:7, respectively), and CRU2 (the blending ratios of coated urea and traditional urea on winter wheat and summer maize were 7:3 and 5:5, respectively). A comparison was then made on the yield, GHGs, and soil nitrate nitrogen residues among different treatments. The results showed that the nitrogen application significantly improved the single-season and annual crop yield in the wheat-maize rotation system (P<0.05). CRU1 and CRU2 treatments increased the summer maize, winter wheat, and annual yields by 1.4%-3.0%, 1.9%-3.4%, and 1.6%-3.1%, respectively (P>0.05), compared with FFP. Nitrogen application also significantly increased the annual emissions of soil N2O and CO2 in the wheat-maize rotation system (P<0.05). The annual accumulation of N2O emissions from soil treated with CRBF1 and CRBF2 was significantly reduced by 27.7%-34.6%, compared with FFP treatment (P<0.05). The nitrogen also increased the annual global warming potential (GWP) of the wheatmaize rotation system (P<0.05). The annual GWP of CRBF1 and CRBF2 treatments decreased by 4.2% and 5.7%, respectively, compared with FFP treatment. There was a significant difference in the CRBF2 treatment (P<0.05). The application of nitrogen reduced the annual greenhouse gas emission intensity (GHGI) of the wheat-maize rotation system. The annual GHGI of CRBF1and CRBF2 treatments decreased by 5.6% to 8.6%, respectively, compared with FFP treatments (P>0.05). CRBF1 and CRBF2 treatments were also reduced by 30.6%-34.3% (P<0.05) for the nitrate nitrogen residues in the 100-200 cm soil layer, indicating the lower risk of nitrate nitrogen leaching. In summary, the controlled-release blended fertilizer can be expected to reduce the GHGs and soil nitrate nitrogen residues for the high crop yield. The finding can provide the data and theoretical support for the highly efficient application of nitrogen fertilizer in the winter wheat-summer maize rotation system. [ABSTRACT FROM AUTHOR]

Emissions of nitrous oxide (N2O), a potent greenhouse gas, from farmland have been recognized to be affected by soil pH and nitrogen (N) fertilizer application. However, the interactive effects of soil pH and N fertilizer type on N2O emissions and their influencing mechanism are poorly understood. A field experiment was conducted to elucidate the impacts of synthetic fertilizer and manure on soil properties and N2O fluxes along a soil acidity gradient (soil pH = 6.8, 6.1, 5.2, and 4.2) in the Huai River Basin, and a lab incubation experiment was performed to understand the underlying mechanisms of changed N2O flux. Low soil pH inhibited the ammonia-oxidizing bacteria abundance and thereby reduced the N2O production by nitrification under both synthetic fertilizer and manure application. The N2O production by denitrification was also reduced with declining soil pH, likely due to the decreased nirS and nirK abundances, and lower NO3−. However, low soil pH reduced the nosZ abundance and increased (nirS + nirK)/nosZ ratio, resulting in the increased N2O/(N2O + N2) ratio. Finally, with the decreased nitrification and denitrification, soil N2O emission was significantly reduced with declining soil pH regardless of fertilizer types. Compared with synthetic fertilizer, manure application increased soil nutrients (total N, dissolved organic C, and NO3−), nirK abundance, and (nirS + nirK)/nosZ ratio in the soils with pH of 5.2 and 4.2, thereby promoting N2O production by denitrification and N2O/(N2O + N2) product ratio in acidic soils. Consequently, soil N2O emission was increased with manure application in acidic soils. This study provides novel insight and improves our understanding of how soil pH regulates nitrification, denitrification, and N2O emissions from soils amended with chemical fertilizer and manure, which gives guidance on developing N management strategies for sustainable production and N2O mitigation in acid soils. [ABSTRACT FROM AUTHOR]

The one-time application of blended urea (BU), combining controlled-release urea (CRU) and uncoated urea, has proven to be a promising nitrogen (N) management strategy. However, the long-term sustainability of blending urea remains largely unexplored. To assess whether a single application of blended urea could effectively replace split uncoated urea applications, a long-term field experiment was conducted in the North China Plain (NCP). The results indicated that, when compared to common urea (CU) at the optimal N rate (180 kg N ha−1), BU achieved comparable grain yields, N uptake and NUE (61% vs. 62). BU exhibited a 12% higher 0–20 cm soil organic nitrogen stock and a 9% higher soil organic carbon (C) stock. Additionally, BU reduced life–cycle reactive N (Nr) losses and the N footprint by 10%, and lowered greenhouse gas (GHG) emissions and the C footprint by 7%. From an economic analysis perspective, BU demonstrated comparable private profitability and a 3% greater ecosystem economic benefit. Therefore, BU under the optimal N rate has the potential to substitute split applications of common urea in the long–term and can be regarded as a sustainable N management strategy for wheat and maize production in the NCP. [ABSTRACT FROM AUTHOR]

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]

High temperature is known to reduce crop yield, while increased nitrogen (N) application will increase crop grain and protein yields to a certain extent. However, there are few studies on the effects of different N application treatments on crop yield and protein under climate warming in different wheat-maize rotation cultivation sites. Therefore, by utilizing the APSIM model, we investigated crop yield, yield components, grain N contents, and biomass N content across 71 key sites of wheat-maize rotation cultivation systems in China. Four N treatments of 0, 90, 180 and 270 kg N ha–1 (N0, N90, N180 and N270) were applied before sowing in both wheat and maize seasons. The APSIM model was calibrated and validated using data of yield and grain N content. We predicted regional differences in crop yield and grain N content under a warming 2°C scenario. There were regional differences in the effects of increased N application treatments and warming 2°C on wheat and maize yields, yield components and grain N contents. Increased N application improved maize 1000-grain weight and wheat grain number, and consequently affected crop yield and grain N content but reduced N translocation from plants to grains (NHI), especially in areas with more precipitation in wheat season and higher temperature in maize season. Warming shortened the duration of the reproductive growth period in maize by 6.2–9.5 d but lengthened it in wheat by 9.1–16.5 d. Furthermore, warming reduced maize yield mainly by decreasing maize 1000-grain weight and improved wheat yield mainly by increasing 1000-grain weight. Warming improved wheat grain N content and NHI under different N application treatments, especially in Shandong, Guanzhong, and Henan regions (0.86–1.98 kg ha–1 and 0.01–0.27, respectively). However, warming reduced maize yield, grain N content and NHI by 4.1 %–10.9 %, 1.5 %–6.8 % and 0.7 %–6.1 %, respectively, under different N application treatments except in Guanzhong. Additionally, increasing N application rate could alleviate the negative effects of warming on maize yield and grain protein production. In 2050–2067 maintaining historical plantation area, the regional total maize protein supply population was projected to reduce by 962.17 and 388.95 million people under N application of N180 and N270 kg N ha–1, respectively, compared with 2000–2017. The findings would provide scientific basis for N management strategies in wheat-maize rotation planting areas of China under climate warming. [Display omitted] • The impact of warming on wheat and maize yields and protein production was analyzed. • Increased nitrogen rates improved crop protein, but reduced nitrogen transport. • Warming increased yield and protein in wheat, but maize had opposite results. • Increased nitrogen rates will help mitigate the impacts of warming on the protein. [ABSTRACT FROM AUTHOR]

The one-time application of blended urea (BU), combining controlled-release urea (CRU) and uncoated urea, has proven to be a promising nitrogen (N) management strategy. However, the long-term sustainability of blending urea remains largely unexplored. To assess whether a single application of blended urea could effectively replace split uncoated urea applications, a long-term field experiment was conducted in the North China Plain (NCP). The results indicated that, when compared to common urea (CU) at the optimal N rate (180 kg N ha−1), BU achieved comparable grain yields, N uptake and NUE (61% vs. 62). BU exhibited a 12% higher 0–20 cm soil organic nitrogen stock and a 9% higher soil organic carbon (C) stock. Additionally, BU reduced life–cycle reactive N (Nr) losses and the N footprint by 10%, and lowered greenhouse gas (GHG) emissions and the C footprint by 7%. From an economic analysis perspective, BU demonstrated comparable private profitability and a 3% greater ecosystem economic benefit. Therefore, BU under the optimal N rate has the potential to substitute split applications of common urea in the long–term and can be regarded as a sustainable N management strategy for wheat and maize production in the NCP.

The increasing use of nitrogen fertilizers exerts extreme pressure on the environment (e.g., greenhouse gas emissions, GHGs) for winter wheat-summer maize rotation systems in the North China Plain. The application of controlled-release fertilizers is considered as an effective measure to improve crop yield and nitrogen fertilizer utilization efficiency. To explore the impact of one-time fertilization of controlled-release blended fertilizer on crop yield and GHGs of a wheat-maize rotation system, field experiments were carried out in Dezhou Modern Agricultural Science and Technology Park from 2020 to 2022. Five treatments were established for both winter wheat and summer maize, including no nitrogen control (CK), farmers' conventional nitrogen application (FFP), optimized nitrogen application (OPT), CRU1 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 5:5 and 3:7, respectively), and CRU2 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 7:3 and 5:5, respectively). The differences in yield, nitrogen fertilizer utilization efficiency, fertilization economic benefits, and GHGs among different treatments were compared and analyzed. The results showed that nitrogen application significantly increased the single season and annual crop yields of the wheat-maize rotation system ( P &lt; 0.05). Compared with those of FFP, the CRU1 and CRU2 treatments increased the yields of summer maize by 0.4% to 5.6%, winter wheat by -5.4% to 4.1%, and annual yields by -1.1% to 3.9% ( P &gt; 0.05). N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (NPFP) were increased by -8.6%-43.4%, 2.05-6.24 kg·kg -1 , and 4.24-10.13 kg·kg -1 , respectively. Annual net income increased by 0.2% to 6.3%. Nitrogen application significantly increased the annual emissions of soil N 2 O and CO 2 in the rotation system ( P &lt; 0.05) but had no effect on the annual emissions of CH 4 (except for in the FFP treatment in the first year). The annual total N 2 O emissions under the CRU1 and CRU2 treatments were significantly reduced by 23.4% to 30.2% compared to those under the FFP treatment ( P &lt; 0.05). Additionally, nitrogen application significantly increased the annual global warming potential (GWP) of the rotation system ( P &lt; 0.05), but the intensity of greenhouse gas emissions was reduced due to the increase in crop yields. Compared with that under FFP, the annual GWP under the CRU1 and CRU2 treatments decreased by 9.6% to 11.5% ( P &lt; 0.05), and the annual GHGs decreased by 11.2% to 13.8% ( P &gt; 0.05). In summary, the one-time application of controlled-release blended fertilizer had a positive role in improving crop yield and economic benefits, reducing nitrogen fertilizer input and labor costs, and GHGs, which is an effective nitrogen fertilizer management measure to promote cleaner production of food crops in the North China Plain.

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Balancing the use of maize (Zea mays L.) residues for soil amendment and forage is an important strategy for agricultural sustainability. Therefore, the study assessed the impacts of four proportions of maize residues to soil retention (S) and forage (F) on soil total organic carbon (TOC); total nitrogen (TN); carbon/nitrogen ratio (C/N); grain yield, economic benefits and nutritional contents of removed residues. The concentrations of TOC and TN increased when more residue returned, while the C/N ratios were S100 + F0 > S34 + F66 > S66 + F34. Also, crude protein, crude fat, and crude starch in the removed residues were F34 > F66 > F100, while the crude fiber and ash contents exhibited the opposite trend. The crop yield improved with residue retention increased, but there were no differences on the economic benefits of the four residue-use systems. The S34 + F66 system maintained a TOC ranging from 11.51 to 13.37 g/kg, a TN from 1.12 to 1.16 g/kg, 92.93% of the annual yields of the S100 + F0 system, and 6.2 t/ha/year of forage. Therefore, the S34 + F66 system can balance the use of maize residues for soil amendments and forage to sustainably develop a household crop-livestock system.

BACKGROUND The carbon sequestration potential is affected by cropping system and management practices, but soil organic carbon ( SOC) sequestration potential under fertilizations remains unclear in north China. This study examined SOC change, total C input to soil and, via integration of these estimates over years, carbon sequestration efficiency ( CSE, the ratio of SOC change over C input) under no fertilization (control), chemical nitrogen fertilizer alone (N) or combined with phosphorus and potassium fertilizers ( NP, NK, PK and NPK), or chemical fertilizers combined with low or high (1.5×) manure input ( NPKM and 1. 5NPKM). RESULTS Results showed that, as compared with the initial condition, SOC content increased by 0.03, 0.06, 0.05, 0.09, 0.16, 0.26, 0.47 and 0.68 Mg C ha−1 year−1 under control, N, NK, PK, NP, NPK, NPKM and 1. 5NPKM treatments respectively. Correspondingly, the C inputs of wheat and maize were 1.24, 1.34, 1.55, 1.33, 2.72, 2.96, 2.97 and 3.15 Mg ha−1 year−1 respectively. The long-term fertilization-induced CSE showed that about 11% of the gross C input was transformed into SOC pool. CONCLUSION Overall, this study demonstrated that decade-long manure input combined with chemical fertilizers can maintain high crop yield and lead to SOC sequestration in north China. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Knowledge about the impacts of the application of organic amendments such as straw and biochar to dryland agricultural soils with respect to soil properties, crop production, soil carbon sequestration and greenhouse gases emissions is limited. The objective of this study was to compare the effects of straw and straw-derived biochar amendments on soil properties, net global warming potential (NGWP) and net greenhouse gas intensity (NGHGI). A field experiment extending over two years was conducted involving simultaneous measurement of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) emissions and soil organic carbon (SOC) content in a wheat–maize crop rotation on the Loess Plateau of China. There were five treatments: control with no amendment (CK); conventional chemical fertilizer only (F); 8 t ha −1 wheat straw plus fertilizer (FS); 8 t ha −1 straw−derived biochar plus fertilizer (FBlow); and 16 t ha −1 straw−derived biochar plus fertilizer (FBhigh). SOC, C:N ratio and high active organic carbon (HAC) increased by 26.4%, 30.8% and 17.1%, respectively in the FBhigh treatment relative to the FS treatment. As compared to the F treatment, addition of straw significantly increased the total soil organic carbon sequestration rate (TSOCSR) in the soil depth of 0–100 cm and CO 2 emissions, but had no significant effect on soil N 2 O and CH 4 emissions or crop yield. However, straw–derived biochar amendment significantly decreased N 2 O emissions while significantly increasing (p < 0.05) crop yield and TSOCSR, but there was no effect on soil CO 2 emissions. Over all, our result showed an overall reduction in NGWP of 37.8% and 31.5% and in NGHGI of 28.1% and 21.2% under straw−derived biochar amendment at 8 t ha −1 and 16 t ha −1 , respectively as compared to the straw amendment. Thus, amending the soil with straw–derived biochar could provide a mechanism to lower the greenhouse gas intensity while increasing the productivity of wheat and maize cropping system in the Loess Plateau of China. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Controlled-release urea (CRU) has been shown to improve nitrogen use efficiencies (NUEs) and yields in wheat and maize crops, although high cost has limited its use. From October 2013 to September 2015, the effects of a fertilizer mixture (polymer coating of sulfur-coated urea, polymer coated urea, and normal urea with N ratios of 3: 3: 4, respectively, during the wheat growing season, and 3.5: 3.5: 3, respectively, during the maize season) on crop yields and nutrients uptake were investigated in a field using a wheat ( Triticum aestivum L.) and maize (Zea mays L. ) rotation system. Crop residues were returned into the field at the end of the growing season. Before planting each crop, the fertilizer mixture was applied once as basal dressing at two application rates of 225 kg N ha −1 (CRU1) and 150 kg N ha −1 (CRU2). Meanwhile, the equivalent rates of normal urea (BBF1 and BBF2) used as twice-split fertilization, 60% at pre-plant and 40% at jointing stage of wheat or V12 (twelve leaf collar) stage of maize as the control. The results suggested that blended applications of CRU and normal urea fulfilled the wheat and maize plants demand for nitrogen during the entire growth periods with crop residues were returned into the field. The yields in the CRU1 treatment were increased by 7.9–10.3% for wheat and 9.1–21.0% for maize, compared with normal urea treatment at the same nitrogen application rates. The NUEs in the mixture treatments were increased by 33.7–56.4% for wheat and 16.7–48.5% for maize, respectively, and the average annual net profit was also increased by 14.5–19.9%, compared with normal urea treatments at the same nitrogen application rates. Although the treatment of CRU2 supplied one-third less N, its yield was similar with that of urea at 225 kg N ha −1 . However, the BBF2 treatment supplied one-third less N, the yields were significantly decreased by 6.1–11.1% for wheat and 7.2–9.4% for maize than that the urea at 225 kg N ha −1 . In addition, the mixture treatments significantly increased the quality and quantity of tillering of wheat. Furthermore, the NO 3 − -N and NH 4 + -N concentration in soil were enhanced especially during the later crops stages, and leaching of soil nitrogen was reduced by using the fertilizer mixture. These results demonstrate that combining CRU and normal urea improved crop yields and NUEs while decreasing costs of fertilizer and the labors required for fertilizer application. [ABSTRACT FROM AUTHOR]

Deep-injected straw incorporation (DI-SI) is a novel soil tillage and straw management, which allowed for the formation of maize straw layer structure in the subsoil (20–38 cm) in wheat-maize rotation systems. However, little is known about how DI-SI affects soil physicochemical and enzymatic processes, as well as crop productivity. Therefore, we conducted a field experiment during 2018–2020 in the North China Plain to determine whether DI-SI would improve soil structure, nutrients, enzyme activities, and crop yield. Three treatments were included: straw removal (SR), conventional straw incorporation (SI), and DI-SI. The results showed that DI-SI improved soil structure and water retention through decreasing the bulk density and penetration resistance in 20–40 cm soil layer. DI-SI significantly increased soil organic C (67.5%), total N (61.3%), and available nutrients (i.e. NO 3 -, NH 4 +, dissolved organic C) compared with SI in the subsoil (20–40 cm), while no differences were detected among straw managements in the topsoil (0–20 cm). This was mainly attributed to the accumulation of microbial biomass C and C-, N-acquisition enzymes in the straw layers, which promoted the straw decomposition and nutrient release. Finally, with the combined effects of soil ecological processes, DI-SI significantly increased the grain yields of wheat and maize by 12.0% and 11.8% compared with SI in the second year, respectively. Our study suggested that deep placement of straw would better promote the utilization of crop residue for farming, and deep-injected straw incorporation represents a viable strategy to improve subsoil physical, chemical, and biological processes, and subsequently crop productivity in wheat-maize rotation systems. [Display omitted] • DI-SI improves soil structure and water retention through decreasing the bulk density. • DI-SI considerably increases the SOC, TN, and available nutrients in the subsoil. • DI-SI stimulates microbial and C-, N-acquisition enzymes activities in the straw layers. • Wheat and maize yields were increased under DI-SI, especially in the second year. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nitrogen loss in runoff was primarily nitrate-nitrogen. [•] In leachate, nitrogen loss was equal parts nitrate-nitrogen and ammonium-nitrogen. [•] Runoff accounted for more than two-thirds of inorganic nitrogen loss through water. [•] Using control-release nitrogen fertilizer would decrease nitrogen loss. [•] Incorporation of wheat straw to the soil would decrease nitrogen loss. [Copyright &y& Elsevier]

The emerging environment-associated issues due to the overuse of inorganic fertilizers in agricultural production are of global concern despite the benefit of high yields. Eco-friendly organic materials with the capability to fertilize soil are encouraged to partially replace mineral fertilizer. The N cycle conducted by soil microorganisms is the most important biogeochemical process, dictating the N bioavailability in farmland ecosystems; however, little is known about how organic material amendment affects soil microbial N cycling under chemical fertilizer reduction. Hence, a fixed field trial with five fertilization practices was implemented to experimentally alter microorganisms essential for the soil N cycle, including conventional chemical fertilization (NPK), reduced chemical fertilization (NPKR), reduced chemical fertilization plus straw (NPKRS), reduced chemical fertilization plus organic fertilizer (NPKRO), and reduced chemical fertilization plus organic fertilizer and straw (NPKROS). The microbial N-cycling gene abundances and associated N-converting genetic potentials were evaluated using real-time quantitative PCR. In comparison to conventional chemical fertilization (NPK), organic addition significantly increased the amounts of heterotrophic microbes involved in organic N decomposition, N fixation, and N reduction; however, it reduced autotrophic microbes performing ammonia oxidization. Consequently, the overall proportion of heterotrophic microbes was remarkably enhanced, and the autotrophic proportion was correspondingly lowered. The fertilization practice shift significantly improved N fixation and gaseous N emission potentials, whereas it suppressed NO 3 - leaching potential. A significant discrepancy among five fertilization treatments was observed based on functional gene abundances (PERMANOVA, P =0.002),as revealed by distance-based redundancy analysis (db-RDA), with NH 4 + as the dominant factor. Organic fertilizer addition was beneficial for heterotrophic N functional microorganisms, with simultaneous input of straw augmenting such an effect. Pearson's correlation analysis revealed that N storage and gaseous N emission potentials were both substantially negatively correlated with NH 4 + ; NO 3 - leaching potential was notably negatively associated with SOC and TN but significantly related to NH 4 + . In conclusion, chemical fertilizer reduction combined with organic material amendments, a main fertilization recommendation, may enhance soil N storage, diminish N loss by leaching, and mitigate the environmental risk of N 2 O emission. This deserves attention considering that healthy and sustainable agricultural soil environment can be cultivated from the view of microbial N-cycling.

CO2 flux was measured continuously using the eddy covariance technique in a wheatmaize rotation system in the North China Plains from October 2002 to October 2006. The annual and seasonal variation of ecosystem respiration and the bio-environmental controls on them were investigated. The results show that ecosystem respiration (Rec) in the cropland increased exponentially with soil temperature at 5 cm depth. The temperature sensitivity coefficient (Q10) for ecosystem respiration varied from 3.5 to 5.4 for wheat and from 2.4 to 4.5 for maize. In the wheat growing season, monthly average R0 (ecosystem respiration at 0°C) increased linearly with soil temperature and logarithmically with leaf area index (LAI). Monthly average Q10 decreased logarithmically with R0. Residual Rec was significantly correlated with LAI. After considering LAI, the modified Q10 model could estimate Rec better than before. The simulation results show that annual ecosystem respiration in the wheat-maize rotation system in the North China Plains was 1327, 1348, 1040 and 1171 gC m-2 yr-1 for the 4 years of the study. As a 4-year average, seasonal mean ecosystem respiration in wheat (2.60 gC m-2 day-1) was much lower than in maize (6.09 gC m-2 day-1). However, integrated ecosystem respiration for the wheat growing season (566 gC m-2) was slightly higher than that for maize (520 gC m-2). These account for 46.4 and 42.6% of the annual values, respectively. [ABSTRACT FROM AUTHOR]

The application of large amounts of nitrogen (N) fertilizer can result in soil N accumulation and consequently N loss. To address these problems in a wheat-maize rotation area of the North China Plain, a two-year field experiment (2016-2017) was conducted to examine the effects of three different N fertilizer strategies on crop yield, N uptake, N loss and soil inorganic N content. The treatments were: controlled-release fertilizer, microbial fertilizer, nitrification inhibitor and farmer's practice (control). The results showed that the wheat yield from the microbial fertilizer treatment in 2016 was significantly lower than that from the controlled-release fertilizer treatment and the nitrification inhibitor treatment, but was not significantly different from conventional farmer fertilization. The N uptake of wheat and annual crops in the microbial fertilizer treatment was significantly reduced. There was no significant difference in crop yield and N uptake among the treatments in 2017. Soil fertility of the tillage layer was maintained or improved in all three treatments compared with the control, and the contents of alkali-hydrolyzed nitrogen, available potassium and organic matter increased with the increase of plant growth period in the microbial fertilizer treatment. Microbial fertilizer and nitrification inhibitor reduced the inorganic N content in the 40-100 cm soil profile, while controlled-release fertilizer increased the inorganic N content in the 0-40 cm soil layer. N loss through ammonia volatilization was higher than that through leaching, which was greater than the loss through N 2 O emission. Runoff loss was negligible. Among the treatments, N loss in farmer's practice treatment was the highest. Microbial fertilizer significantly reduced N loss through ammonia volatilization, but the loss through leaching was larger. In conclusion, with reduced N application compared with the farmer's practice, controlled release fertilizer and nitrification inhibitor could maintain crop yield and N uptake, and microbial fertilizer could ensure crop yield and N uptake for a longer plant growth period. The results suggested that inorganic N content in the 40-100 cm soil layer could be reduced in the soil by adding microbial fertilizer and nitrification inhibitors, and the amount of inorganic N was not reduced significantly by application of controlled release fertilizer. Several N reduction measures could reduce N loss. The microbial fertilizer treatment needed to be modified to reduce N leaching.

In order to compare the differences in carbon sequestration and greenhouse gas mitigation between straw and straw-derived biochar amendment, a field experiment was conducted with simultaneous measurement of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) emissions, crop yield, soil organic carbon (SOC) content and net global warming potential (NGWP) in a wheat-maize rotation cropping system from the loess plateau of China. Five treatments were included:control (no straw incorporation, no straw-derived biochar amendment and no fertilization, CK), fertilization (no straw incorporation and no straw-derived biochar amendment, F), straw with fertilization (wheat straw incorporated at 8 t·hm -2 , FS), low straw-derived biochar (8 t·hm -2 ) with fertilization (FBlow) and high straw-derived biochar (16 t·hm -2 ) with fertilization (FBhigh). Wheat yield increased by 30.9%, 66.3% and 36.6% under FS, FBlow and FBhigh treatment, as compared to the F treatment, respectively. However, maize yield decreased by 14.1%, 18.0% and 24.6% under FS, CK and FBhigh treatment as compared to the F treatment, respectively. There was no significant difference between FBlow and F treatment. Annual CO 2 emission increased by 60.2% under FS treatment, but decreased by 14.4% under FBhigh treatment as compared to the F treatment, respectively. Annual N 2 O emission decreased by 27.6% and 38.7% under FBlow and FBhigh treatment as compared to the F treatment, respectively. However, no significant difference was observed under straw application. Overall, the NGWP decreased by 24.13 and 58.44 t·hm -2 under FBlow and FBhigh treatment as compared to the F treatment, respectively. And the NGHGI decreased by 1.78 and 5.06 t·t -1 under FBlow and FBhigh treatment as compared to the F treatment, respectively. In summary, we conclude that the fertilization with 16 t·hm -2 biochar amendment can be used as an effective management to improve the crop yield and reduce the net global warming potential under the wheat-maize rotation system.

Irrigation can influence greenhouse gas (GHG) emission and carbon footprint in agricultural production. In this study, annual GHG emissions (including CO 2 , CH 4 , and N 2 O) were monitored with static opaque chamber and gas chromatography from a wheat-maize rotation system under different irrigation treatments in the Guanzhong Plain of China during 2014-2015. A total of four different irrigation treatments were conducted, e.g. W 0 , W 120 , W 180 , and W 240 , where the subscripts represented the irrigation amounts in mm. Net global warming potential (NGWP) and carbon footprint were used to evaluate the influence of different irrigation amounts on GHG emission and composition of carbon footprint of crop production. Compared with treatment W 0 , wheat yield of treatments W 120 , W 180 , and W 240 increased by 31.3%, 44.3% and 33.7%, while corn yield increased by 9.9%, 22.6%, and 33.8%, respectively. Similarly, annual CO 2 emission increased by 22.2%, 24.3% and 15.1% and annual N 2 O emission by 18.6%, 67.8%, and 91.5%, respectively, while annual CH 4 absorption decreased by 51.7%, 79.6% and 97.8%, respectively. The values of NGWP increased by 20.1%, 31.6%, and 31.4%, respectively. The carbon footprint of treatment W 120 was 19.1% lower than that of W 0 , while W 180 and W 240 showed no significant difference. Treatments W 120 and W 240 increased carbon footprint per unit crop yield by 44.5% and 23.3%, respectively, while W 180 showed no significant difference. Considering both the economic and environmental effects of different irrigation amounts, we recommend the irrigating amount of 180 mm for the wheat-maize rotation system in the Guanzhong Plain of China for the purposes of water saving and carbon sequestration.