Abstract Cover crops are widely used in corn ( Zea mays L.)–soybean ( Glycine max ) systems to improve soil health, yet seasonally dynamic responses of soil biological properties to long‐term cover cropping remain not fully understood, particularly in the low‐organic matter Alfisols of the eastern Corn Belt. We evaluated the effects of more than a decade of cereal rye ( Secale cereale L.) cover cropping on soil biological properties in a no‐till corn–soybean rotation in southeastern Indiana in a field experiment established in 2011. Soil samples were collected at two depths (0–10 and 10–20 cm) during fall, spring, and summer in 2023–2024 and analyzed for microbial biomass carbon and nitrogen (soil microbial biomass carbon [SMBC] and soil microbial biomass nitrogen [SMBN]), potentially mineralizable carbon (PMC), permanganate‐oxidizable carbon (POXC), autoclaved citrate‐extractable (ACE) protein, and enzyme activities associated with carbon (C), nitrogen (N), and phosphorus (P) cycling. Cover cropping increased SMBC, SMBN, and PMC, with treatment effects varying by season and soil depth. Cover crop effects on microbial biomass and PMC were most pronounced during spring and were largely confined to the 0–10 cm. In contrast, POXC, ACE protein, and enzyme responses were indicator‐specific; acid phosphatase activity increased under cover cropping and peaked in summer, whereas POXC, ACE protein, and activities of β‐glucosidase and N‐acetyl‐β‐glucosaminidase showed limited overall treatment effects. These findings indicate that long‐term cereal rye cover cropping enhances biologically mediated C and nutrient cycling in no‐till systems, with effects expressed in a seasonally and vertically stratified manner rather than as uniform, sustained increases.

Root-derived carbon (C) inputs are increasingly recognized as important precursors to soil organic carbon (SOC). However, the extent to which these inputs can be influenced by nitrogen (N) fertilizer management and plant stature remains poorly understood. This study investigated how N fertilization rate and maize hybrid stature trade off between above- and belowground performance, including investment in root traits, exudation, and soil microbial C pools. Tall- and short-stature maize (Zea mays) hybrids, from Bayer’s breeding pipeline, were grown in a pot experiment in two soil matrices (sandy and loamy), with N fertilization rates of 0, 90, 180, and 270 kg N ha⁻1. C pools in above- and belowground compartments were assessed, including root exudates, root biomass and length, soil microbial biomass C, and total soil C. Soil matrix and maize hybrids of different stature primarily explained differences in root exudation and belowground C inputs. Short-stature maize produced 22

Organic grain production continues to expand in the Midwestern United States but faces management constraints such as frequent tillage and limited cover cropping that may restrict soil health benefits. It remains unclear whether organic systems integrating reduced tillage, extended cover cropping, and biological seed treatments can improve soil function while maintaining nitrogen (N) availability, crop nutrient uptake, and productivity. This study utilized field experiments in Indiana and Wisconsin to compare a Standard Organic system (frequent tillage, limited cover crops) with an Eco-Intensive Organic system (reduced tillage, extended cover crops, and seed-applied N-fixing inoculants), and assessed short-term soil and crop responses to the Eco-Intensive Organic system during its first two years of establishment. Soil samples (0–15 and 15–30 cm) were collected at early, mid, and late stages of the growing season and analyzed for biological soil health indicators and N availability, alongside measurements of leaf N and crop yield. The Eco-Intensive Organic system had limited effects on measured biological soil health indicators during the first two years following system implementation. In contrast, soil nitrate content was generally 20–100% higher in the Standard Organic system, which coincided with 6–22% greater crop leaf N concentration and crop yield (in three of four site-years). The positive relationships between crop yield, leaf N, and soil nitrate, along with weak relationships with measured biological soil health indicators, suggest that short-term productivity was more closely associated with soil N availability than with the measured biological soil health indicators. Overall, these findings highlight the challenge of balancing short-term crop productivity with long-term soil health goals and underscore the need for integrated nutrient management to improve the overall performance of ecologically intensified organic grain cropping systems.

Context or problem: Maize (Zea mays L.) is a widely cultivated crop with high nitrogen (N) demand. While modern hybrids and intensive N fertilization have increased yields, they may have compromised root phenes and biological soil health. The belowground performance of newly introduced short-stature maize hybrids, however, remains unknown. Objective or research question: The objective of this study was to evaluate root phene aggregates of short-stature vs. conventional tall maize hybrids and soil health indicators under varying N rates across two locations. Methods: To address this knowledge gap, we conducted field experiments encompassing two contrasting soils in Indiana, U.S.A., to compare short-stature vs. tall maize hybrids under four N rates (0, 100, 200, and 300 kg ha(-1)). Root and soil samples (0-120 cm) were collected at the R2 maize growth stage to quantify key root phenes, root carbon (C) and N, and soil health indicators. Results: Short-stature maize, with similar to 28.6% reduced height, produced 1.35 times more root biomass and 1.42 times greater total root length than its tall counterpart, with noticeable differences observed down to 120 cm depth in high-organic matter (OM) soils in west-central Indiana. Most root aggregate values peaked at 200 kg N ha(- 1), with the strongest responses observed in the top 30 cm soil layer. In poorly drained, low-OM soils in southeastern Indiana, however, root biomass of short-stature maize was not significantly different from its conventional tall counterpart. Across sites, the short-stature hybrid produced slightly lower grain yield than the tall-stature hybrid, with a reduction of 2.6% at high-OM and 11.5% at low-OM; N effects on yield were significant only at high-OM, and no hybrid x N interaction was observed. Root phene aggregates of short-stature hybrid were generally positively associated with soil health indicators, but these relationships lacked statistical significance. Conclusions: Short-stature maize hybrids exhibited enhanced root biomass and length under optimal N fertilization in high-OM soils, with minimal impact on soil biological indicators. Implications or significance: These findings suggest that optimizing N application rates in combination with hybrids exhibiting greater root growth and aggregated root phene plasticity can improve enhance belowground C input, and support more resilient and sustainable maize production under variable environmental conditions.

Soil organic carbon (SOC) is a fundamental component of the global carbon cycle, underpinning ecosystem health, climate regulation, and sustainable land management worldwide. The conversion of natural forests to plantation systems in humid tropical regions has emerged as a critical global issue, leading to significant reductions in SOC stocks and compromising the carbon sequestration potential of soils. To assess these impacts, we compared SOC concentrations in plantation and natural forests across five humid tropical zones, including the globally significant Southern Western Ghats (SWG) of India- a recognized biodiversity hotspot and one of the world's most complex forest ecosystems. A stratified random sampling design was used across five agroecological zones to select paired natural forests and adjacent long-rotation teak (Tectona grandis) plantations (40-50 years old). Soil samples were collected from four horizons (O, A, B, and C) within 1 m depth profiles. SOC concentration (CHNS analyzer), bulk density, texture (hydrometer method), cation exchange and pH were determined. SOC stocks were calculated using bulk density and horizon depth. Our analysis shows that natural forests maintain substantially higher average SOC concentrations (16.61 g/kg) than plantation forests (11.82 g/kg). In natural forests, SOC ranged from 9.53 g/kg to 26.09 g/kg, while plantation forests ranged from 6.93 g/kg to 17.73 g/kg, reflecting similar trends observed in the SWG and other tropical regions. SOC concentrations were significantly greater in the surface layers of natural forests compared to deeper layers (P < 0.05), with more than 70% of SOC typically stored in the upper 30 cm. Correlation analysis showed a significant negative relationship between SOC and soil pH in natural forests (r = -0.37, P < 0.05), whereas plantation soils exhibited a positive relationship (r = 0.03, P < 0.05). Forest soils also showed a positive correlation between SOC and clay content (r = 0.16, P < 0.05) and a weak negative correlation with sand content (r = -0.04, P < 0.05). These findings underscore a global challenge: land use change from natural forest to plantation reduces SOC stocks, alters soil health, and diminishes the resilience of tropical soils to environmental change. Maintaining and restoring natural forests-both globally and in biodiversity hotspots like the SWG-is essential for maximizing soil carbon sequestration, supporting soil fertility, and achieving climate mitigation targets. This study provides a scientific foundation for sustainable land management and carbon storage strategies in tropical regions globally.

Integrating cover crops into conventional cropping systems can improve soil health, but field management, soil type, and climate can limit the rate of improvements. This study evaluated the effects of cereal rye (Secale cereale) cover crops on soil organic carbon (SOC) content and physical properties in a no-till, corn-soybean rotation on a poorly structured silt loam in southeastern Indiana. An earlier assessment of this trial found cover crops had increased aggregate stability after just 4 years but had no significant effect on bulk density (BD), water dynamics, or SOC. Revisiting this trial after an additional 6 years, we observed significant improvements across multiple soil health indicators. Cover crops increased SOC by 7.5% and total nitrogen by 12.9%, alongside improvements in BD (-2.9%) and water holding capacity (+8.6%). Aeration porosity was significantly enhanced (+7.7% at 0-10 cm, +9.0% at 10-20 cm, and +30.1% at 20-40 cm), indicating potential improvements in water infiltration. Aggregate stability remained a strong indicator of cover crop benefits, higher by 33% in the top 10 cm and by 35% at 10-20 cm as compared to no cover plots. These results align with findings from similar long-term trials and underscore how aggregate stability may be a valuable early predictor of broader improvements. Our findings support cereal rye as an effective strategy to enhance soil health and resilience in Midwestern no-till corn-soybean systems. Plain Language Summary Cover crops are plants grown in the off-season between harvested crops. Cover crops can support crop production by adding carbon to soil and improving soil structure. Other farming practices, soil type, and climate can limit these improvements. It is critical to see how cover crops perform under different conditions. For this study, soil was collected from field plots with or without cereal rye cover crops under a unique combination of practices (no-till), soil type (poorly structured silt loam), and climate (temperate). Improvements to soil were limited after 4 years but significant after 10 years. Other long-term trials have similarly found that it can take close to a decade for cover crops to improve soil structure. The results of this study provide evidence that cereal rye cover crops can improve the long-term sustainability of growing no-till corn and soybeans on poorly structured soils in temperate climates.

Soil organic matter (SOM) declines under agricultural production have been well documented, despite efforts to maintain or enhance SOM through practices like rotational diversity and increased carbon (C) input quantity and quality. However, a critical knowledge gap remains in understanding how system management alters the microbial processes that drive C input turnover and stabilization across time and soil depths. This study addresses this gap by leveraging a long-term cropping systems trial to investigate microbial mechanisms of SOM turnover and stabilization across a representative range of cropping systems in the North Central US. We assessed microbial and chemical soil characteristics at two key sampling times throughout the growing season and linked these measurements to indicators of SOM persistence. Particulate organic matter (POM) C:N exhibited significant (P < 0.001) variation across cropping systems, depth, and time reflecting a gradient of system C input quality. POM-C was greatest in pasture systems (P < 0.001) at both time points, suggesting stability of the relationship between POM inputs and decomposition across the growing season. Additionally, microbial growth and respiration were highest in pasture (P > 0.001), which was consistent across time, indicating an active microbial community that facilitates SOM turnover and stabilization. Our findings provide novel insights on the role of rotational and plant input diversity for enhancing microbial turnover and slowing SOM decline through POM substrate quality, particularly in pasture systems, across time and soil depths. This research will serve to inform future cropping system-level soil management strategies aimed at improving SOM persistence.

Introduction Growing academic attention has been given to the crucial role of soil microorganisms in the net loss of soil organic carbon (SOC) under climate warming and the effectiveness of straw-C sequestration to replenish the SOC stock. However, the lack of empirical investigations in anaerobic paddy soils hinders accurate estimation of the global soil C-climate feedback and development of countermeasures. Objectives This study aimed to unravel the impact of warming on the complexity of the microbial community network of the paddy soil in response to warming, and correspondent changes of microbial metabolic functions relevant to the transformation of straw-C in SOC pools. Methods We added 13C/15N-labeled rice straw into a long-term paddy soil and incubated under three temperature treatments (25, 35 and 45 °C) for 140 days to quantify straw-C sequestration in various SOC fractions, and further deployed metagenomic sequencing and solid-state 13C NMR analyses to explore relevant biochemical mechanisms. Results Warming (35 °C and 45 °C vs. 25 °C) enhanced SOC decomposition, but straw amendment did not replenish the loss C in mineral-associated C, a major SOC fraction of this soil, especially at 45 °C. Compared to 25 °C, temperature increases to 35 °C and 45 °C led to decreases in microbial diversity indices by an average of 19 % and 43 %, respectively. Warming also destabilized the microbial community network with less connectivity and keystone nodes in the paddy soil. Furthermore, warming decreased the abundances of organic C- and N-mineralization genes. Those genes encode enzymes involved in the degradation of both labile and recalcitrant organic compounds, including starch, cellulose, hemicellulose, chitin, pectin and aromatics, as well as in N mineralization, such as glutamate dehydrogenase and glutamate synthase. A subsequent deficiency in the synthesis of those enzymes appeared to suppress the transformation of straw-C and N, thereby reducing their sequestration efficiency in the mineral-associated C fraction in the paddy soil. Conclusion The detrimental impact of warming on the microbial metabolic profiles lowered the role of straw amendment in sustaining SOC stability under warming. An improved understanding of the warming-induced loss of microbial community diversity and correspondent weakening metabolic functions for the turnover of exogenous C should be accounted for global mitigation practices in paddy fields under climate warming.

The role of nitrogen (N) fertilization in enhancing crop yields and mixed cropping in reducing continuous cropping obstacles have been well documented. However, N fertilization and mixed cropping on rhizosphere and bulk soil microbial diversity, community structure, and plant growth remain controversial. To address this knowledge gap, we conducted a pot experiment of two plant species (peanut (Arachis hypogaea L.) and maize (Zea mays L.)), three N addition levels (0, 150, and 225 kg N hm-2), and two cropping systems (monoculture and mixed cropping). To investigate rhizosphere and bulk soil prokaryotic and fungal community response to N addition in different cropping systems, high-throughput sequencing technology was used in this study. Overall, under the mixed cropping condition, compared with N0 addition level, N2 addition level increased maize aboveground biomass (AGB) by 205.62 % and maize belowground biomass (BGB) by 45.36 %, but reduced peanut AGB by 12.60 % and peanut BGB by 24.07 %. Moreover, with increased N fertilization, the BGB/AGB ratio of peanut under mixed cropping decreased first from 0.22 to 0.18, and then increased up to 0.23. The alpha-diversity of soil prokaryotic community decreased significantly with increasing N addition levels, while the observed ASVs of the rhizosphere fungal community was significantly lower than that of bulk soils. The results of non-metric multidimensional scaling (NMDS) combined with PERMANOVA analysis showed that the clustering of soil microbial communities was mainly dominated by the rhizosphere and N effects. In addition, Mantel test results showed that the changes of the rhizosphere environmental factors drove the changes in fungal community composition, while the changes of bulk soil environmental factors drove the changes in prokaryotic community composition. Microbial network co-occurrence analysis indicated that N addition increased the complexity of the soil prokaryotic network structure, but reduced the complexity of the soil fungal network structure. Meanwhile, the network structure complexity of prokaryotic and fungal communities in the rhizosphere were higher than that in bulk soils. The above results comprehensively suggested that N addition mainly changed soil prokaryotic community composition, while rhizosphere effects primarily altered soil fungal community composition. This may be caused by the survival strategy of soil microbes (r/K strategists) and the background environmental differences between the rhizosphere and bulk soils.

Subsurface drainage is an important agricultural practice that has been widely utilized in the US Midwest to improve the productivity of poorly drained soils. Although widely adopted, long‐term yield benefits of drainage, particularly with varying spacings, in an ever‐changing climate are largely unknown. The goals of this study were to assess how various drainage spacings (5, 10, and 20 m) impacted crop yields compared to the undrained control in a long‐term trial (started in 1984) in southeastern Indiana and how these effects were influenced by the amount of rainfall of specific periods of the growing season. Drainage treatments led to an increase in corn (Zea mays) yields (by 12%–17%) but did not significantly affect soybean (Glycine max) yields compared to the control. In the initial 10 years of the experiment, drainage benefits were subtle and corn yields did not vary significantly across spacing treatments, whereas in the most recent 10 corn years, the drainage treatment effects became more pronounced, likely due to the combined effects of long‐term drainage system and conservation practices of no‐till and cover crops. Over 37 years, corn yields remained stagnant in the undrained plots but progressively increased in the drained treatments. Both corn and soybean yields showed a negative correlation with rainfall 14 days post‐planting, while drainage spacing treatments partially mitigated this negative effect. Our findings underscore the importance of effective drainage as a necessary prerequisite for realizing the potential benefits of conservation practices and improved crop genetics for increased crop productivity.

Understanding nitrous oxide (N2O) production as well as reduction in response to grazing and mowing is essential for designing better management strategies to improve sustainability of grassland ecosystems. We evaluated how four years of grazing or mowing altered N2O production and reduction potential, gene abundance, and expression of microbial functional groups pertinent to N2O production in situ on a typical grassland in Inner Mongolia. In our study, we found that grazing dramatically raised soil ammonium (NH4+-N) and nitrate (NO3--N) concentrations, AOB gene abundance and potential of N2O production through nitrification (N-N2O) and denitrification (D-N2O) in summer, but lessened the expression of nosZ clade II gene in all seasons. Mowing had minor effect on soil inorganic nitrogen (N) concentrations. Mowing diminished the quantity of denitrification genes (narG and nosZ), expression of nosZ and nosZ clade II genes, and D-N2O concentration. The expression and abundance of nosZ clade II gene were related to D-N2. These results suggested that short-term grazing could enhance N2O production potential in peak growing season, while the reduction in abundance and expression of nosZ calde II gene might be an important contributor to the enhanced N2O production of semi-arid typical steppe grasslands.

Conventional aerobic methanotrophs oxidize methane (CH4) and covert CH4-derived carbon (C) into biomass at the oxic-anoxic interface of inundated rice paddy fields, playing indispensable role in mitigating greenhouse gas emissions and loss of organic C from methanogenesis. Two phylogenetically distinct groups of methanotrophs, type I (γ-proteobacteria) and type II (α-proteobacteria) methanotrophs, often co-exist in rice paddy soil and compete for CH4 biotransformation. Since these two methanotrophic groups also possess differential kinetics of CH4 oxidation and pathways of C assimilation, the consequence of their niche differentiation and metabolic differences in soil is expected to affect the CH4 oxidation rate and C conversion efficiency. Here, we examined the microbiology, chemistry, and CH4 metabolism in 24 geographically different paddy soils, covering four climate zones of eastern China. High-throughput sequencing of pmoA gene displayed a clear separation of in situ methanotrophic compositions between temperate (warm and mid-temperate) and warmer (subtropics and tropics) climate zones, likely driven by soil pH. Both methanotrophic groups were detected in soils but proportions of type I methanotrophs increased in temperate soils of higher pH (accounting for 76.1 ± 12.4

Well -drained upland soils generally have stronger microbial catabolism during organic C transformation than water-logged paddy soils. However, the intensity of microbial anabolism and necromass formation processes in these contrasting agricultural soils is unclear. To quantify these processes, 40 pairs of adjacent upland and paddy soils collected from four climates (mid -temperate, warm temperate, subtropics, and tropics) across eastern China were incubated with 13C -labeled root exudates under simulated field water conditions for 50 days. Upland soil collected from warm temperate exhibited a higher 13C incorporation into living microbial biomass than other climates. In contrast, the lowest newly formed necromass was detected due to the inhibition of fungal anabolism under the high pH condition. Paddy soils collected from cooler climates (mid -temperate and warm temperate) exhibited faster microbial biomass growth than those from warmer climates (subtropics and tropics). Still an opposite trend was observed for microbial necromass accumulation, possibly because of the faster turnover rate of microbial biomass induced by the high N availability in warmer climates. Regardless of climates, 13C incorporated into living microbial biomass (phospholipid fatty acids) was 1.4-2.6 times higher in upland than paddy soils, resulting in 1.8-3.9 times greater accumulation of newly -formed microbial necromass in the former. This was mainly caused by the stronger fungal anabolism (2.5-5.6 times higher) due to the oxygen -sufficient condition of upland soil. Our findings highlighted the weaker accumulation but stronger stability of organic C stored in upland soils because of the greater microbial catabolism and anabolism during organic C transformation.

Aim: Species-area relationships (SAR) are widely utilized for estimating the species richness and its spatial turnover across various scales. Despite the prevalent characterization of SAR using the power law in many microbial community studies, its efficacy remains unvalidated. This study aims to characterize the microbial SAR and its mechanisms in alpine grassland soils on the Qinghai-Tibet Plateau (QTP). Location: Qinghai-Tibet Plateau, China. Time Period: August 2014. Major Taxa Studied: Soil bacteria. Methods: Soil samples were collected from five alpine grassland sites on the QTP. Employing a nested sampling strategy at each site, soil samples were collected in plot sizes ranging from 0.5 x 0.5 m(2) to 2048 x 2048 m(2). Soil bacterial communities were analysed by sequencing 16S ribosomal RNA gene amplicons using an Illumina MiSeq. Results: The bacterial SAR exhibited a logarithmic power law (R-2: 0.952-0.999), outperforming the power law (R-2: 0.701-0.852). Consequently, the most widely adopted power law led to an overestimation of species richness by up to 15.07% in areas >256 x 256 m(2), and the regional maximum theoretical richness based on Chao1 by up to 9.88%. Mechanistically, the passive sampling hypothesis was refuted through the rarefied species richness analysis, and the disproportionate effect hypothesis was rejected based on analyses of the effective numbers of species number conversions for the probability of interspecific encounters (S-PIE). Notably, Pearson and multiple linear regression analyses indicated that the spatial turnover of bacterial richness was determined by the environmental heterogeneity (R-2: 0.855-0.999), rather or better than environmental variables themselves, supporting the 'environment heterogeneity hypothesis'. Main Conclusions: Soil bacterial SAR in alpine grasslands exhibited a logarithmic power relationship. Spatial turnover was primarily governed by the environmental heterogeneity. In contrast, the traditional power law leads to an overestimation of soil bacterial diversity at the regional scale.

Labile organic carbon (C) substrates could accelerate microbial transformation of soil N pool by stimulating the decomposition of large molecule organic N. However, it remains unclear how gross N transformation processes (protein depolymerization, amino acid uptake, microbial N mineralization and NH4+-N uptake rates) in response to individual C substrates. Typical paddy soil was incubated with the supplement of oxalic acid or glucose under simulated field water conditions for 16 days to assess the gross N transformation rates by 15N pool dilution assays. A mixture of 15N labeled amino acid was applied to gross protein depolymerization and amino acid uptake rates measurement, and 15N-(NH4)2SO4 was used to gross microbial N mineralization and NH4+-N uptake rates analyses. Oxalic acid supplement promoted the gross protein depolymerization, gross microbial uptake of amino acid, and gross N mineralization rates at the early stage. It was attributed that oxalic acid supplement urged microbes to decompose large molecular organic N to acquire amino acid derived C and excluded the superfluous N via mineralization as evidenced by the increase of NH4+-N. By contrast, glucose supplement diminished the gross N transformation processes, since microbes prefer to utilize the native NH4+-N to meet their N demand supported by the decreasing NH4+-N concentration in soil, and consequently inhibited the decomposition for the large molecule organic N. With the increase of microbial growth, especially for bacteria, glucose amendment stimulated the large molecular organic N depolymerization to acquire amino acid to maintain the microbial C/N stoichiometric balance. Compared to glucose treatment, oxalic acid supplement stimulated more N allocation into microbial growth but not for mineralization, and thus led to higher microbial N use efficiency, which was adverse for available inorganic N supply for rice growth in paddy ecosystem. Overall, this study emphasizes that low molecular organic C substrates of organic acid and glucose exerted contrasting influences on gross N transformation, and help to improve our understanding of the mechanism of the coupling biotransformation of C and N in paddy soil.

Improving soil nitrogen (N) supply capacity is recognized as a viable solution for sustaining cereal production for food security, since more than half of N absorbed by crops comes from the soil through the gross N mineralization (GNM) process. However, significant uncertainties exist regarding GNM patterns driven by commonly used fertilization practices in croplands. Based on soils collected from 13 long-term fertilization trials spanning over 30 years across China's uplands by using the 15N dilution technique, we found that manure amendment led to the highest increase in GNM (1.9-9.7 folds), followed by straw return (0.8-4.7 folds) and chemical fertilizer application (0.07-3.9 folds), compared to the unfertilized treatment. Fertilization-induced GNM changes were primarily influenced by the initial soil pH in the chemical fertilizer and straw treatments, and by soil clay content in the manure treatment. Application of chemical fertilizer and straw in higher pH soils and manure in higher clayey soils had a greater promotion on GNM, mainly due to the enhanced soil properties (e.g., total dissolved N) and associated microbial attributes (e.g., N-acquiring enzyme activity, bacterial and fungal biomass). Manure amendment also facilitated GNM in low pH soils by promoting microbial attributes. These findings underscore the importance of differentiated fertilization managements at the district level to maximize soil N supply across China's uplands, with prioritizing application of chemical fertilizer and straw in neutral and alkaline soils and manure in acidic and heavier texture soils. This knowledge is crucial for developing policies aimed at buttress food security and reduce soil N loss in China.

Regularly flooded rice paddies usually show greater soil organic C and microbial-derived C contents than adjacent upland counterparts, but the soil microbial physiological traits under these two different land uses spanning regions remain unclear. Here, we collected 40 pairs of adjacent paddy and upland soils from four different climates (mid temperate, warm temperate, subtropics, and tropics) across eastern China to determine the microbial growth, respiration, and C use efficiency using the 18O-H2O incubation method. Upland soils from warmer climates exhibited lower microbial growth but higher respiration normalized to microbial biomass C (qGrowth and qRespiration, respectively) than those from cooler climates, since the lower soil pH and higher clay content in warmer climates induced a shift from microbial growth to respiration. Whereas, paddy soils from warmer climates had consistently lower qGrowth and qRespiration than cooler climates, probably due to the long term water-logged condition decreased the sensitivity of microbial metabolism in response to lower pH. Paddy soils had higher qGrowth, but lower qRespiration than upland soils, resulting in a greater C use efficiency regardless of climate zones. The difference in microbial C use efficiency between paddy and upland soils was positively correlated to their difference in soil organic C content. From the perspective of microbial C metabolism, the greater organic C accumulation in paddy than that in upland soils is attributed to the weaker microbial uptake of organic C and stronger microbial anabolism under the water-logged condition.

Cover crop residue retention on the soil surface can suppress weeds and improve organic no-till soybean (Glycine max) yield and profitability compared to a tilled system. Appropriate cereal rye (Secale cereale) fall planting date and termination methods in the spring are critical to achieve these benefits. A plot-scale agronomic experiment was carried out from September 2018 to October 2021 in Kutztown, PA, USA to demonstrate the influ-ence of cereal rye planting date (September or October) and mechanical termination method [no-till (I & J roller-crimper, Dawn ZRX roller, and mow-ted) and tilled (plow-cultivate)] on cover crop regrowth density, weed biomass, soybean yield, and economic returns. In one out of three years, the September rye planting accumulated more cover crop biomass than the October planting, but the regrowth of the rye after roller-crimping was greater with this plant-ing date. Cover crop planting date had no effect on total weed biomass and demonstrated varying effects on soybean grain yield and economic returns. The Dawn ZRX roller outper-formed the I & J roller-crimper in effectively terminating cover crops, while the I & J roller-crimper demonstrated more uniform weed suppression and led to greater soybean yields over a span of three years. Organic no-till strategies eliminated the need for tillage and reduced variable costs by 14% over plow-cultivated plots, and generated similar to 19% greater net revenue across the study period (no-till vs tillage = US $845 vs US $711 ha-1). Terminating cereal rye with roller-crimping technology can be a positive investment in an organic soybean production system.

The persistence of carbon (C) in soils strongly depends on its biophysiochemical formation pathways. However, the contributions of physical, chemical and microbial processes to organic C accrual across various landscapes and climates remain unclear. In this study, we employed a combination of physical fractionation and biomarker analysis to investigate soil organic C subjected to microbial anabolism and protected by aggregates and free minerals in typical agricultural lands across a climatic gradient across eastern China. Results showed that the proportion of aggregate-protected C in total C decreased progressively from mid-temperate (62 %) to tropical regions (20 %), while free mineral-associated C increased from 24 % to 58 %. This suggests a shift from aggregate protection as the primary pathway for soil organic C formation in cooler climates to a mineralogical association in warmer climates. Compared to free minerals, the stronger C acquisition in aggregates was characterized by greater occluded mineral-associated C probably due to the enriched reactive minerals and cations. However, less microbial-derived C detected in aggregates than in free minerlas (especially in warmer climates) because of spatial isolation. The enhanced soil organic C preservation in paddy fields compared to adjacent uplands was attributed to the strengthened microaggregate formation and increased C sequestration capacity of free minerals induced by long-term flooding conditions. To enhance C storage in agricultural soils, it is crucial to adopt strategies such as improving aggregation, strengthening microbial anabolism in cooler regions, and incorporating calcium-enriched inorganic amendments in warmer climates.

Tillage reduction is an increasingly common goal of farmers worldwide to reduce soil erosion and improve agroecosystem sustainability. Reduced tillage is usually achieved by different strategies in conventional and organic agricultural systems, yet it is unclear if these different strategies have contrasting effects on soil health. To compare how reduced-till strategies affect soil health under conventional and organic management, we evaluated soil health of a long-term field crop trial in Pennsylvania, USA. This trial was established in 1981 with three side-by-side management systems: an agrochemical-based conventional maize-soybean system (CNV), a legume-based low-input organic grain system (LEG), and a manure-based organic grain and forage system (MNR). Ten years after reduced-till treatments were introduced in 2008, herbicide-based no-till in the CNV system did not affect soil organic matter (SOM), cation exchange capacity, permanganate oxidizable carbon (POXC), or autoclaved-citrate extractable (ACE) protein content under conventional field crop production. Reducing tillage in the conventional system significantly increased potentially mineralizable carbon (PMC) by 23 +/- 11%, and led to more severe surface compaction, reflected by 23 +/- 9% shallower penetration resistance at 300 psi. In the LEG and MNR systems, tillage was reduced through cover crop-based rotational no-till, where maize and soybeans were no-till planted following the use of a roller-crimper to terminate fall-planted cover crops. In these two organic systems, moderately reducing tillage did not cause significant changes in individual soil health indicators except for a 17 +/- 8% increase of PMC in the MNR system. Individual soil health indicators and Comprehensive Assessment of Soil Health (CASH) scores generally did not differ between the CNV and LEG systems, and were significantly higher in the longer-rotation, manure-based MNR system. These results suggest that soil health in organic systems was determined more by diversified crop rotations and adequate organic inputs than by reducing tillage frequency, whereas in conventional systems other co-adapting soil health prac-tices might be necessary to alleviate surface compaction and realize the full benefits of reduced tillage.