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Soils with high organic carbon (SOC) have been shown to enhance crop yields while minimizing climate-induced losses. However, the resilience impacts and mechanisms by which high SOC enhances crop performance have not been fully explored. Here, eight-year rotations of winter wheat and summer maize managed with chemical fertilizer input alone (CF) or with cattle manure (OM) or with peat and vermiculite (PV) were conducted, and various soil properties were measured alongside crop growth, nitrogen (N) uptake, and grain yield, with seasons categorized as dry or normal based on precipitation amounts. The OM and PV treatments increased SOC by 57% and 78% relative to the CF, respectively, and improved soil nutrient availability and the soil quality index. Soil moisture content in the 0–30 cm layer increased by 3.5–26.6%, but was less influenced in the 30–90 cm soil layers. Annual yield of wheat plus maize increased by 13% and 12% in OM and PV compared to the CF, and the yield sustainability index increased by 29% and 17%. Yield gains were more pronounced in dry compared to normal seasons, ranging from 19% to 28% and 12–15% for wheat. At least in part, the relative advantages of OM and PV treatments under drying conditions were associated with accelerated growth and N uptake rate from sowing to stem elongation for wheat and maize. Among the factors influencing yield in the present study, soil moisture exerted the greatest positive total effect on yield. Overall, the results highlight that enhanced SOC resulting from combined application of organic amendments and mineral fertilizer was positively associated with yield by promoting soil quality and water availability, with a more pronounced benefit under water-limited conditions. [Display omitted] • Improved soil quality and moisture enhance wheat and maize yield and stability. • Combined inorganic fertilizer and organic amendments increased soil moisture in the 0–30 cm but not in deeper layers. • Better soils with high SOC enhanced wheat and maize yield and stability during dry seasons. • Accelerated vegetative growth and nutrient uptake by high SOC contributed to productivity resilience. [ABSTRACT FROM AUTHOR]

The use of "green manure"—crops that are cultivated specifically to be incorporated into the soil to increase its organic matter content—has been proposed as an alternative to chemical fertilizer because of its benefits in terms of crop yield. Nonetheless, the differential impacts of green manure on ammonia volatilization remains underexplored. In this study, the influence of various green manure management strategies on ammonia volatilization in maize cultivation were examined. Field experiments conducted from 2020 to 2022, the field experiment applied common vetch after the spring wheat harvest, with five distinct treatments: conventional tillage without green manures as a control (CT); tillage with total green manure incorporation (TG); no-tillage with total green manure mulching (NTG); tillage with only root incorporation (T); and no-tillage with removal of aboveground green manure (NT). The results showed that under TG and NTG, the maize yields were 12.3%-33.2% higher than under CT, and 6.8%-18.8% higher than under T and NT. Compared with CT, all four green manure management practices also significantly increased NH 3 emissions in maize fields, and they increased ammonia volatilization by 12.0%-13.7% in NTG and TG compared to root retention patterns, with NTG exhibiting higher rates than TG. NTG significantly increased soil organic matter, total nitrogen, mineral nitrogen, water-filled pore space (WFPS), microbial biomass carbon and nitrogen, and C: N, and it decreased soil pH compared to TG. Regression analysis showed that these factors were correlated with NH 3 volatilization. In addition, soil urease and ammonia-oxidation functional genes (amo A) showed differences under green manure management practices. Structural equation modeling showed that NH 4 +-N had the greatest positive impact on NH 3 , and urease activity and total nitrogen had positive effects on NH 4 +-N. Furthermore, microbial biomass carbon and pH had positive and negative effects on urease activity, respectively, both of which were only related to SOM. At the same time, WFPS had a positive impact on total nitrogen. In summary, no-tillage with total green manure mulching increases maize yield but also increases NH 3 emissions. NH 4 +-N formed by the hydrolysis of urea by soil urease and the conversion of total nitrogen were found to be the main reasons for high NH 3 emissions. In addition, SOM can promote urease activity, increase NH 4 +-N content and NH 3 volatilization by increasing MBC and decreasing soil pH. [Display omitted] • No-tillage combined with total green manure retention can enhance soil quality and crop yield. • NH 3 volatilization is mainly a physicochemical process caused by the control of NH 4 +-N. • Urease activity and total nitrogen have significant effects on NH 4 +-N. • Increasing microbial biomass carbon and decreasing soil pH can promote urease activity. [ABSTRACT FROM AUTHOR]

Evaluating the contribution of diverse nitrogen (N) sources in agricultural systems is pivotal for optimizing sustainable farming practices. While knowledge exists about the roles of various N sources, there's limited comprehensive data on the relative contributions of manure compost, fertilizer, and root residues to subsequent plant uptake. A comprehensive field study was conducted in Shandong Province, China, utilizing 15N labeling techniques to clarify these contributions. Four treatments were established, each incorporating four exogenous nitrogen sources (manure compost + urea + maize root + residual urea) applied concurrently at wheat seeding, with only one source being 15N labeled per treatment. Additional two treatments served as controls, one without 15N labelling and another without manure compost. During a wheat growing season, the N contribution from each individual source to subsequent wheat growth was quantified. Manure contributed 10% of the wheat seed N, while urea contributed 18% and maize root contributed 0.3%. Nitrogen recovery in distinct components of the wheat plant (seeds, straw, and roots) was assessed, revealing urea's superior use efficiency within the total wheat biomass at 55%. In contrast, both manure compost and maize root showed a recovery rate of 29%. Although this study spans only one-year, it offers fresh perspectives on the differential contribution and use efficiency of key N sources under field conditions, emphasizing their role in bolstering crop health and productivity for sustainable agriculture. [Display omitted] • Manure contributes 10% of N in wheat seeds, more than maize root (0.3%), but less than urea (18%). • Soil and other contributes 72% of the seed N, 71% of the straw N, and 65% of the root N. • N use efficiency in wheat biomass is comparable for manure and maize root (29%). • Urea shows superior N use efficiency in wheat total biomass at 55%. • Grains per spike, not spike number or grain weight, influence yield differences. [ABSTRACT FROM AUTHOR]

Cover crops (CCs) are a recognized best management practice to reduce surface water runoff and nutrient loss from agroecosystems. This 4-yr study was conducted in a tile-terraced field to assess the effects of CCs on nutrient loss compared to without CC (no CC) in a corn (Zea mays L.)-soybean (Glycine max L.) rotation. The 3xCCmix (wheat (Triticum aestivum L.), radish (Raphanus raphanistrum subsp. Sativus), and turnip (Brassica rapa subsp. Rapa)) was aerial seeded in soybean at R6 in 2018 and 2020. Cereal rye (Secale cereale) was drill seeded after the corn harvest in 2019 and 2021 (corn-cereal rye-soybean-3xCCmix). Water samples from individual flumes were collected using automated samplers and analyzed for concentrations and loads of nitrate-N (NO 3 -N), total phosphorus (TP), dissolved phosphorus (PO 4 -P), and total suspended solids (TSS). The 3xCCmix and cereal rye had 16% and 12% lower discharge, respectively, than no CC. The 3xCCmix reduced TSS load 50% compared to CC, while cereal rye had no effect. Cover crops reduced NO 3 -N load 20%, 54%, and 68% during the corn, cereal rye, and soybean growing periods, respectively. Over the full rotations, cumulative discharge and nutrient loads were greater during the 2018–20 crop rotation year because of increased precipitation in 2019. The variability in effectiveness of CCs in reducing nutrient losses was likely affected by different climatic and management factors including CC planting and termination dates. This study highlights the benefits of CCs for reducing sediment and nutrient loss over crop rotation, as well as the continued need for enhanced fertilizer management systems to reduce nutrient loss. • On average, CCs reduced NO 3 -N load in discharge by 20%, 54%, and 68% during the corn, cereal rye CC, and soybean seasons, respectively. • The effect of CC on discharge varied with total rainfall and growing season. • Grass cover crops showed potential to reduce sediment losses in runoff. [ABSTRACT FROM AUTHOR]