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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]

Soil health assessment is fundamental to guiding sustainable soil management practices, ensuring healthy soil, crop productivity, and provision of other ecosystem services. Interpretation of soil health in intensive agriculture in the North China Plain (NCP) is still lacking due to an over emphasis on soil chemical management and large variations among smallholders' farmlands. The objectives of this study were to (i) compare soil health assessment approaches in response to fertilization regimes, (ii) quantify relationships between soil health and agronomic outcomes, (iii) develop a minimum data set to simplify soil health assessment, and (iv) validate soil health assessment frameworks in smallholders' fields on the NCP. We collected soil samples from eight wheat-maize rotation long-term experiments which were divided into three fertilization regimes: (1) NPK, application of chemical fertilizers only; (2) M, application of organic materials only; and (3) MNPK, combined application of organic materials with chemical fertilizer application. Three soil health indexing (SHI) approaches, Comprehensive Assessment of Soil Health (SHI-CASH), linear (SHI-L) and sigmoidal (SHI-Sig) were evaluated. SHIs in the M and MNPK treatments were significantly higher than those in the NPK treatment across assessment approaches and were positively correlated with maize yield. A minimum data set including subsurface hardness, wet aggregate stability, available K, available Fe, soil organic carbon and soil protein was established using best subset regression. The soil health indices of smallholders' farmlands using CASH and MDS were 0.58 (0.42–0.73) and 0.63 (0.40–0.87), respectively. More than 60% smallholders' fields was at middle or low level. The relationship between SHI-CASH and SHI-MDS (Sig) was better than those for the CASH and linear methods. Our results demonstrate that an MDS based on best subset regression is applicable for evaluating soil health in wheat-maize rotation systems in the NCP. Soil health assessment in smallholders' farmland indicates that soil health constraints are related to soil and biomass management, which provides insights on pathways towards addressing soil health gaps. • Soil health index in the M and MNPK treatments was significantly higher than that in the NPK treatment. • The minimum data set (MDS) included SubHard, AgStab, AK, Fe, SOC and protein. • The MDS is applicable for soil health assessment of smallholder fields. • Organic input is important for improving soil health. [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]

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]