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Mulching and nitrogen (N) fertilization are the main drivers for sustainable crop production. The sole use of nitrogen fertilizer threatened both the physiology and production of maize in rain-fed areas. Therefore, we proposed that wheat straw mulching with N fertilization would increase maize yield by improving soil fertility, physiology, and nitrogen use efficiency. A two-year field study evaluated the effects of CK (control), N (nitrogen application at 172 kg ha−1), HS (half wheat straw mulch, 2500 kg ha−1), HS+N (half wheat straw, 2500 kg ha−1 plus 172 kg N ha−1), FS (full wheat straw, 5000 kg ha−1), and FS+N (full wheat straw, 5000 kg ha−1 plus 172 kg N ha−1) on maize growth, physiology, and biochemistry. Compared with the control, the FS+N treatment resulted in the increase of 56% photosynthetic efficiency, 9.6% nitrogen use efficiency, 60% nitrogen uptake, 80% soluble sugar, 59% starches, 48% biomass, and 29% grain yield of maize. In addition, the FS+N regime increased 47%, 42%, and 106% of soil organic carbon and available P and N content in comparison with the control. Maize grain and biomass yields were positively correlated with N uptake, photosynthesis, soil organic carbon, and soil available N and P contents. Conclusively, the use of wheat straw at 5000 kg ha−1, along with 172 kg N ha−1, is a promising option for building a sustainable wheat–maize cropping system to achieve optimal crop yield and improved plant and soil health in a semi-arid region of China. [ABSTRACT FROM AUTHOR]

Straw retention and wheat-soybean rotation play critical role in maintaining soil quality. However, the correlation between bacterial diversity and community structure, and soil nutrients is unknown, and a systematic understanding of their responses to straw retention is lacking. In the field experiment, the straw retention treatments included no straw (NS), half straw (HS), and total straw (TS) retention during long-term wheat-soybean rotation. The mean contents of soil total nitrogen (TN), nitrate-N (NO3−-N), and microbial biomass nitrogen (MBN) increased by 15.06%, 21.10%, and 38.23%, respectively, with straw retention relative to NS, while that of ammonium-N (NH4+-N) reduced by 3.68%. The concentration of carbon components increased as straw retention increased. The levels of soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), and soil organic carbon (SOC) increased by 4.34%, 7.63%, and 9.34%, respectively, with straw retention relative to NS. Soil bacterial alpha diversity was reduced with straw retention. Soil pH and nutrient content were identified as the main factors affecting the soil microbial diversity and structure at the phylum level. Accordingly, straw retention and soybean-wheat rotation enable sustainable agriculture in the dryland of northern China. [ABSTRACT FROM AUTHOR]

Biochar has been shown to be potentially beneficial for enhancing yields and soil properties, and diminishing nitrogen (N) losses. However, it remains unclear how biochar regulates soil carbon (C) and N to mitigate N losses induced by straw mixing with N fertilizer in dryland soils. Therefore, we investigated the effects of straw mixing (S1), S1 with biochar (SB) and no straw inputs (S0), and routine urea application rates (N1) and 70% of routine rates (N0.7) on yields and N losses, and identify the relationship between N losses and soil C and N compounds. Results showed that N0.7 and N1 were suitable for the maize and wheat seasons, respectively, contributing to mitigating N losses without reducing crop yields. Moreover, in the maize season, N0.7‐SB significantly mitigated the straw‐induced NH3‐N and N2O‐N emissions by 106% and 81%, respectively. In the wheat season, N1‐SB reduced the straw‐induced NH3‐N and N2O‐N emissions by 35% and 66%, respectively. In addition, N0.7‐SB sharply reduced soil inorganic N (SIN) storage in the maize season. Furthermore, the NH3‐N and N2O‐N emission rates were negatively correlated with dissolved organic carbon/SIN content (0–20 cm) (DOC/SIN0‐20). N losses (N2O‐N and NH3‐N emissions and SIN storage) were positively correlated with SIN0‐20, but negatively correlated with soil organic carbon / SIN0‐20 (SOC/ SIN0‐20). This study provides further evidence that biochar with an appropriate N application rate decreased SIN0‐20 and increased DOC/SIN0‐20, thus reducing SIN storage and the straw‐induced gaseous N emissions without decreasing crop yields. [ABSTRACT FROM AUTHOR]

Straw retention is an effective method to conserve soil water content and improve soil carbon stocks. However, how soil carbon dynamics respond to different straw retention practices remains unclear. In this study, we investigated soil respiration and soil carbon sequestration at depths of 0–100 cm. We conducted a two-year field experiment with three crop rotation treatments and three straw retention treatments in northwest China. The straw retention treatments included no straw retention (NS), retention of half the straw (HS), and retention of the total amount of straw (TS). The crop rotations treatments included winter wheat plus summer soybean (WS), winter wheat plus summer maize (WM), and winter wheat plus summer fallow (WF). Mean soil respiration rates under WS, WM, and WF treatments were 5.14, 6.53, and 5.49 μmol·m-2·s-1; and 5.67, 5.47, and 6.03 μmol·m-2·s-1 under TS, HS, and NS treatments. The mean soil water content were 15.50%, 15.57%, and 15.74% under WS, WM, and WF rotations, and 15.81%, 15.41%, and 15.50% under TS, HS, and NS treatments. The soil organic carbon (SOC) concentration was higher with increased straw retention, and lower at deeper soil depths. Mean SOC concentrations under different rotations and straw treatments of TS, HS, and NS, respectively were as follows: WS: 6.91, 6.63, 6.39 g/kg; WM: 6.90, 6.72, 6.57 g/kg; and WF: 6.49, 6.52, 6.37 g/kg. Soil temperature was the main determinant of soil respiration rates. We conclude that WS rotation resulted in lower soil respiration, WM rotation resulted in a higher soil carbon sequestration potential, and WF rotation resulted in higher soil water content. However, continued, long-term monitoring is needed to confirm the effect of rotations and straw retention on soil respiration and carbon sequestration in dryland cropping systems in northern China. [ABSTRACT FROM AUTHOR]

Field experiments were conducted to study soil properties, soil enzymes activities, water use efficiency (WUE) and crop productivity after six years of soya bean straw mulching in the semi‐arid conditions of China. The experiment included four treatments: CK (Control), N (240 kg N ha‐1), H (soya bean straw mulching at half rate 700 kg ha‐1 with 240 kg N ha‐1) and F (soya bean straw mulching at full rate 1,400 kg ha‐1 with 240 kg N ha‐1). Soil organic carbon (SOC), soil labile organic carbon (LOC), soil available N (AN), available P (AP) and enzyme activities were analysed after wheat harvesting in 2016 and 2017. Results show that straw amounts had positive effects on the soil fertility indices being higher for treatment F. The SOC, LOC, AN, AP and enzyme activities (i.e. saccharase, urease and alkaline phosphatase) were in the order of F > H > N > CK. High wheat grain yield and WUE were observed for F treatment. A total of six years mulching along with 240 kg ha‐1 nitrogen fertilizer application is sufficient for wheat yield stability and improving soil properties except urease activities in the semi‐arid condition of China. However, the straw mulching amount should be further studied with minimum nitrogen fertilizer for an environment‐friendly and effective approach for improving the soil biological properties with adequate crop production on a sustainable basis in the semi‐arid region of China. [ABSTRACT FROM AUTHOR]

Dairy manure (DM), chicken manure (CM) and wheat straw were used to investigate the possibility of optimizing the methane (CH4) potentials in anaerobic co-digestion of multiple substrates. Response surface methodology (RSM) was used to evaluate the individual and interactive effects of four variables [carbon/nitrogen (C/N) ratio, the feeding composition (DM/CM), initial substrate loading and inoculum-to-substrate ratio (ISR)] in the digestion process. All four variables had significant effects on CH4 potentials. Interactive effects of C/N and DM/CM ratios, C/N ratio and ISR, initial substrate loading and ISR were significant The optimum conditions were a C/N ratio of 26.31, a DM/CM ratio of 42.96:57.04, an initial loading of 15.90 g volatile solids (VS)/l and an ISR ratio of 2.34, with the maximum CH4 potential being 394 ml/g VS. The RSM model was appropriate for optimizing CH4 production in the process of anaerobic co-digestion of multiple substrates. [ABSTRACT FROM AUTHOR]

Straw incorporation with half-plastic film mulch is a promising approach for enhancing soil quality in dryland farming. However, its effects on soil greenhouse gas (GHG) and NH 3 emissions remain poorly understood. This study aims to optimize the mulch practice to balance the plastic film input with comprehensive benefits and examine the temporal dynamics and influencing factors of soil GHG and NH 3 emissions. A 3-year field experiment was conducted in a wheat-maize cropping system in north-western China with a complete randomized design including three treatments replicated thrice: (a) no straw incorporation or half-plastic film mulch (CT), (b) straw incorporation without half-plastic film mulch (S), and (c) straw incorporation with half-plastic film mulch (SP). The study revealed that S treatment significantly enhanced crop yield and soil cumulative N 2 O, CO 2 , and NH 3 emissions during the maize season by 8.26%, 113.51%, 31.78%, and 64.92%, respectively, compared to CT treatment. SP treatment significantly decreased N 2 O and NH 3 emissions by 30.66% and 23.74%, respectively, and slightly stimulated CO 2 emissions by 8.73% relative to S treatment throughout the three maize seasons. The average maize yield gap between S and SP treatments ranged from 517 to 800 kg ha−1. N 2 O and NH 3 emissions were significantly associated with soil water content (SWC), soil N components, and enzyme activity (nitrate and nitrite reductase), whereas CO 2 emissions were significantly influenced by soil temperature. Compared with S treatment, half-plastic film mulch increased SWC (16.77%), reduced soil N content and inhibited activity of nitrate (12.15%) and nitrite reductase (8.40%), eventually mitigated straw incorporation-induced N 2 O and NH 3 emissions by 30.66% and 23.74%, respectively. Overall, we demonstrated that straw incorporation with half-plastic film mulch is an innovative practice for enhancing the sustainability of dryland farming by increasing maize yield and mitigating N 2 O and NH 3 emissions. [Display omitted] • Nitrogen cycle- related enzyme activities are key to regulating gas emissions. • S significantly increased N 2 O, CO 2 , and NH 3 emissions compared with CT. • SP significantly reduced N 2 O and NH 3 emissions and increased yield compared to S. • SP is an innovative practice for promoting the sustainability of dryland farming. [ABSTRACT FROM AUTHOR]

• Straw return and fertilization improve the soil nutrient status. • Straw return with nitrogen fertilizer reduced soil CO 2 emissions by 270.01%, compared with straw return. • Enzyme stoichiometry showed that soil microorganisms of winter wheat were carbon and nitrogen limited under straw-return conditions. • Microorganisms use their stoichiometric flexibility to regulate soil CO 2 emissions. Straw return is the key measure of green agricultural production. Nitrogen (N) and phosphorus (P) play pivotal roles in crop growth and carbon (C) cycling in agroecosystems. However, the mechanism of soil CO 2 emissions and enzyme stoichiometry regulation by straw return with N and P application remain unknown. Therefore, this study is aimed to use enzyme stoichiometry to investigate the effects of straw return with N and P fertilizer application on soil CO 2 emissions, enzyme activity, and microbial nutrient limitation through a two-year field experiment. A split-plot experimental design was used (straw as the main plot and fertilizer as the sub plot). The results indicated that the addition of N, P (SNP) increased CO 2 emissions by 25.54 %, and N application (SN) reduced CO 2 emissions by 27.01 %, compared with straw return (SW). Enzyme stoichiometry indicated that straw return with N and P application exhibited significant C and N limitations. In soil nutrients and nutrient stoichiometry, compared with the S 0 W treatment, straw return with fertilizer (SNP, SN) significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON); SNP treatment increased β-1,4- n −acetylaminoglucosidase (NAG) enzyme activity by 53.72 %, increased l −leucine aminopeptidase (LAP) enzyme activity by 58.11 %, and increased one P-acquiring enzyme alkaline monoalkaline phosphatase (AKP) enzyme activity by 39.49 % (P < 0.05). Structural equation modeling suggested that straw return and fertilization can influence microbial biomass phosphorus (MBP) and vector length (VL) by affecting MBN, which, in turn, affects CO 2 emissions. Soil microbes regulate CO 2 emissions using stoichiometric flexibility to maintain a stoichiometric balance of nutrients and microbes. Therefore, straw return with N and P fertilizers to winter wheat soils can meet the requirements of microbial stoichiometry, modulate microbial and extracellular enzyme activities, and effectively regulate CO 2 emissions and resource limitations. [ABSTRACT FROM AUTHOR]

Mulching can effectively maintain and improve soil health and functionality. The mechanisms, however, have not been fully elucidated. Therefore, the effects of temperature on the biogeochemical properties of soil were investigated in the present study in relation to nitrogen management and soil functionality. The results of the 3-year field experiments showed that integrated straw mulch (S) and nitrogen fertilizer (N) treatments enhanced the activities of soil urease, invertase, alkaline phosphatase, and catalase by >1.8, 2.1, 2.0 and 1.4 fold, respectively, compared with the control treatment. Furthermore, these treatments increased soil available N by 28%, phosphorus by 45%, and potassium by 55%. In general, the soil organic carbon, dissolved carbon and labile organic carbon content in the treated plot were approximately 1.2–2.9 folds greater than in the control plot. These improvements in soil fertility and carbon indices increased the biomass and grain yield of soybean (67 and 75%, respectively) during the three-year study period. During 2015–2017, the straw mulch and nitrogen fertilizer treatment increased the soil moisture (23%) and decreased the soil temperature (8%) in comparison to the control in the 0–0.2 m soil depth and, therefore, improved soil enzyme activities, nutrient availability, and carbon stocks, and ultimately, soil functionality and sustainability, in the semiarid region. Unlabelled Image • Integrated use of straw mulch with nitrogen fertilizer improved soil carbon pool. • S + N regime improved soil nutrients and soil water content in 0–0.4 m soil layer. • S + N treatments significantly decreased the soil temperature. • Soil enzyme activities were positively correlated with nutrient dynamics. • Soybean yield was significantly enhanced by straw mulch with nitrogen fertilizer. [ABSTRACT FROM AUTHOR]

Straw incorporation is widely applied to improve crop productivity, and biochar amendment may be an effective countermeasure for mitigating greenhouse gas (GHG) emissions; however, the comprehensive evaluation of straw return and biochar amendment coupled with different N application rates on soil organic carbon (SOC) sequestration rate, GHG emissions, and reactive N losses have been inadequately recorded. Consequently, the field experiment had six treatments and three replications including two mineral N fertilization rates (conventional N fertilizer application (N 1) and 30% reduced N fertilizer application (N 0.7)) and three types of straw and biochar management variations (no straw incorporation (S 0), straw incorporation (S), and straw incorporation with biochar amendment (SB)) and the results were based on three years of soil SOC and GHGs emission data in wheat-maize agroecosystem. Our finding revealed that N 0.7 reduced the GHG emissions (CO 2 : 13.9%; N 2 O: 34.2%; CH 4 : 32.5%), greenhouse gas intensity (GHGI; 32.7%), carbon footprint (CF; 35.1%) and nitrogen footprint (NF; 24.5%), but had no significantly different crop yields compared with N 1 (p > 0.05). Straw incorporation had no significant impact on CF and yield-scaled CF but increased NF (29.7%) because the stimulated GHG emissions would be offset by SOC sequestration. Under S, the wheat and maize yields increased by 9.7% and 5.4%, respectively, whereas the GHGI increased by 59.6% compared with S 0. Biochar amendment reduced GHG emissions (CO 2 : 19.9%; N 2 O: 29.9%), GHGI (32.7%), CF (26.7%) and yield-scaled CF (29.2%), while improving crop yields (wheat: 5.8% (p < 0.05); maize: 1.5% (p > 0.05)) and SOC sequestration rate (74.5%) compared with that under S. Overall, N 0.7 SB exhibited enormous potential for enhancing wheat-maize agroecosystem productivity and drastically mitigating their CF and NF in the semi-arid conditions of the Guanzhong Plain. [Display omitted] • Soil quality, crop productivity, and environmental benefits of different field managements were evaluated. • Reduce N application mitigated GHG emissions, carbon and nitrogen footprints, but had no effect on crop yields. • Biochar inhibited the stimulation of GHG emissions by straw incorporation and increased the SOC sequestration. [ABSTRACT FROM AUTHOR]