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Background and aims Soil microbial communities influence nutrient cycling, chemistry and structure of soil, and plant productivity. In turn, agronomic practices such as fertilization and crop rotation alter soil physical and chemical properties and consequently soil microbiomes. Understanding the long-term effects of agronomic practices on soil microbiomes is essential for improving agronomic practices to optimize these microbial communities for agricultural sustainability. We examine the composition and substrate-utilization profiles of microbial communities at the Morrow Plots in Illinois. Methods Microbial community composition is assessed with 16S rRNA gene sequencing and subsequent bioinformatic analyses. Community-level substrate utilization is characterized with the BIOLOG EcoPlate. Results Fertilizer and rotation treatments significantly affected microbial community structure, while substrate utilization was affected by fertilizer, but not croprotation treatments. Differences in relative abundance and occurrence of bacterial taxa found in fertilizer treatments can explain the observed differences in community level substrate utilization. Conclusion Long-term fertilization and crop-rotation treatments affect soil microbial community composition and physiology, specifically through chronic nutrient limitation, long-term influx of microbes and organic matter via manure application, as well as through changes in soil chemistry. Relatively greater abundance of Koribacteraceae and Solibacterales taxa in soils might prove useful as indicators of soil degradation.

Farms in the US Midwest are experiencing disruptive heavy rainfall during the spring planting window and more intense droughts during the summer growing season. Recent analyses of field experiments suggest that increasing crop rotational complexity (RC) builds resilience to climate change, especially when rotations include overwintering cover crops that assimilate and retain nutrients and increase organic matter inputs to soil. However, evidence from working farms is lacking. We used field-scale remote sensing to assess relationships between crop diversification and agroecosystem climate resilience from 2008 to 2019 in Michigan, the most agriculturally diverse state in the US Midwest. Using panel fixed effects models and linear regressions, we assessed how corn and soybean yield and temporal yield stability (measured as the coefficient of variation) respond to: (1) an index of crop RC that encompasses species turnover and functional diversity, and (2) replacing bare fallows with winter cover crops. We also tested how cover crops influence corn and soybean planting dates as an indicator of resilience to heavy spring rainfall. We found that crop diversification was linked to higher corn and soybean yields, but cover crops showed more promise for improving yield stability than overall RC. Cover crops reduced planting delays associated with heavy spring rainfall, and did not interfere with primary crop planting under average weather conditions. However, cover crop benefits for resilience took multiple years to appear on farms, highlighting the importance of technical and financial support during the early phases of transition. Together these findings may promote cover crop adoption by reducing concerns that cover crops interfere with primary crop planting, and instead showing that they are a crucial tool for minimizing risk from increasingly variable and extreme climatic conditions.

Background Overyielding (i.e., mixtures of crops yielding higher than expected when compared with monocultures) and increased nutrient acquisition have been found in many intercropping systems. However, there are very few published studies on long-term changes in soil chemical and biological properties in intercropping systems compared to sole cropping. Methods A field experiment was established in 2003 in Gansu province, northwest China. The treatments comprised three intercropping systems (either continuous or rotational wheat/maize, wheat/faba bean, maize/faba bean intercropping), rotational cropping (wheat-maize, wheat-faba bean, faba bean-maize, and wheat-maize-faba bean rotations), and monocropping (sole wheat, faba bean and maize) systems. In 2011 (ninth year of the experiment) and 2012 (tenth year) the yields and some soil chemical and biological properties were examined after all crop species were harvested. Results There was overyielding by 6.6 % and 32.4 % in wheat/maize intercropping in 2011 and 2012, respectively. Faba bean/maize intercropping was enhanced by 34.7 % and 28.6 %, respectively but not wheat/faba bean intercropping. Soil organic matter, total nitrogen, Olsen P, exchangeable K and cation exchange capacity in all intercropping systems did not differ from the monocultures except for soil pH in wheat/maize and faba bean/maize intercropping in 2011 and soil exchangeable K and cation exchange capacity (CEC) in 2012. Soil pH in wheat/maize and faba bean/maize intercropping was significantly reduced by 3.2 % and 1.9 %, respectively. Soil exchangeable K in wheat/maize, faba bean/maize and wheat/faba bean intercropping declined markedly by 15 %, 21.7 % and 12.1 %, respectively. Soil cation exchange capacity in wheat/maize, faba bean/maize and wheat/faba bean intercropping was notably lower than the corresponding monocultures by 17.5 %, 23.3 % and 18.3 %, respectively. Soil enzyme activities after 9 and 10 years of intercropping differed little from monocultures or rotations. Conclusions The results indicate that intercropping overyielded compared with monocropping or rotational cropping and also maintained the stability of most of the soil chemical and enzyme activities relative to rotations and monocropping in the relatively fertile soil studied.

Background Crop rotation is an important agricultural practice that often affects the metabolic processes of soil microorganisms through the composition and combination of crops, thereby altering nutrient cycling and supply to the soil. Although the benefits of crop rotation have been extensively discussed, the effects and mechanisms of different crop combinations on the soil microbial community structure in specific environments still need to be analyzed in detail. Materials and methods In this study, six crop rotation systems were selected, for which the spring crops were mainly tobacco or gramineous crops: AT (asparagus lettuce and tobacco rotation), BT (broad bean and tobacco rotation), OT (oilseed rape and tobacco rotation), AM (asparagus lettuce and maize rotation), BM (broad bean and maize rotation), and OR (oilseed rape and rice rotation). All crops had been cultivated for > 10 years. Soil samples were collected when the rotation was completed in spring, after which the soil properties, composition, and functions of bacterial and fungal communities were analyzed. Results The results indicate that spring cultivated crops play a more dominant role in the crop rotation systems than do autumn cultivated crops. Crop rotation systems with the same spring crops have similar soil properties and microbial community compositions. pH and AK are the most important factors driving microbial community changes, and bacteria are more sensitive to environmental responses than fungi. Rotation using tobacco systems led to soil acidification and a decrease in microbial diversity, while the number of biomarkers and taxonomic indicator species differed between rotation patterns. Symbiotic network analysis revealed that the network complexity of OT and BM was the highest, and that the network density of tobacco systems was lower than that of gramineous systems. Conclusions Different crop rotation combinations influence both soil microbial communities and soil nutrient conditions. The spring crops in the crop rotation systems had stronger dominating effects, and the soil bacteria were more sensitive than the fungi were to environmental changes. The tobacco rotation system can cause soil acidification and thereby affect soil sustainability, while the complexity of soil microbial networks is lower than that of gramineous systems. These results provide a reference for future sustainable applications of rotation crop systems.

AimBalanced crop nutrition is key to improve nutrient use efficiency and reduce environmental impact of farming systems. We developed and tested a dynamic model to predict the uptake of P and K in long-term experiments to better understand how changes in soil nutrient pools affect nutrient availability in crop rotations.MethodsOur RC-KP model includes labile and stable pools for P and K, with separate labile pools for placed P and organic fertilizers including farm yard manure (FYM). Pool sizes and crop-specific relative uptake rates determined potential uptake. Actual crop uptake from labile pools was based on concepts developed by Janssen et al. (Geoderma 46:299-318, 1990). The model was calibrated on three long-term experiments from Kenia (Siaya), Germany (Hanninghof) and the United Kingdom (Broadbalk) to estimate parameter values for crop-specific relative uptake rates and site-specific relative transfer rates.ResultsThe model described N, P and K uptake accurately with a Nash-Sutcliff modelling efficiency of 0.6–0.9 and root mean squared errors of 2.6–3.4 kg P ha−1 and 14–20 kg K ha−1. Excluding organic labile pools did not affect model accuracy in Broadbalk in contrast to Hanninghof where Mg deficiencies affected crop uptakes in treatments without Mg or FYM.ConclusionsThis relatively simple model provides a novel approach to accurately estimate N, P and K uptake and explore short- and long-term effects of fertilizers in crop rotations. Interactions between limiting nutrients affecting actual nutrient uptake were captured well, providing new options to include N, P and K limitations in crop growth models.

Background and aims Crop rotation can effectively alleviate the obstacles of continuous cropping and restore the agroecological balance, and then determining the optimal length of crop rotation is the cornerstone of effective crop rotation. To delve into this issue, we conducted a six-year rotation experiment aimed at exploring how different rotation lengths impact sugar beet yield, soil properties, and microbial communities. Methods Conduct field experiments to gather rhizosphere soil samples from treatments with different rotation lengths of sugar beet and analyze their physicochemical properties and microbial characteristics. Subsequently, establish a model linking sugar yield with the physicochemical properties and microbial characteristics of the rhizosphere soil. Results Sugar beet, sugar content, and sugar yield significantly increased while decreasing disease symptoms, with increases in crop rotation length. Longer rotations significantly ameliorated soil acidification and improved soil fertility. On the other hand, extending the crop rotation length significantly altered the community structure of microbial sub-communities with varying abundances. Additionally, the fungal diversity increased and ecological network became more complex, and a multitude of potentially beneficial microbiota were enriched in the rhizosphere soil with rotation length. Conclusion These results demonstrate that extending the crop rotation length improved soil conditions, and increased sugar beet yield. In addition, we recommend that sugar beet rotation length should be at least three years or more.

Earth's water resources are critical for supporting livelihoods and food security but are being increasingly overexploited to support global agriculture. Diversifying cropping systems could potentially resolve unsustainable water use but trade‐offs with other aspects of sustainability and food security have not yet been assessed. We performed a detailed analysis of 31 different field crop rotations conducted during 1990–2019 in the North China Plain, to assess the potential impact of crop diversification on actual evapotranspiration (ETa), changes in regional groundwater table, grain yield, economic output, and water use efficiency (WUE) and to identify configurations that can achieve co‐benefits across multiple dimensions. We found that a combination of lowering the cropping index (i.e., harvest frequency), incorporating fallow periods, and introducing higher‐value crops into the currently dominant winter wheat–summer maize double cropping system can reduce growing season ETa by as much as 31%, mitigate groundwater decline by 19% or more, and increased economic output and economic WUE by more than 11% and 3%, respectively. We also found that multiple diversified wheat‐maize–based rotations—all with rotation lengths greater than 2 years—achieve co‐benefits across all evaluated dimensions. This study provides new empirical evidence of the opportunities for diversified crop rotations to balance the multiple objectives of food production, sustainable groundwater use, and farmer profitability. Extending this solution to other water‐stressed agricultural regions could be an effective strategy in achieving more sustainable food production system globally. This study assessed the potential impact of crop diversification on water use and food production. Introducing fallowing period and certain cash crop into intensive double cropping system saves groundwater and increase the economic output. Cropping configurations could achieve co‐benefits across multiple dimensions.

  Conservation agriculture is often assumed to reduce soil N 2 O emissions. Yet, studies analyzing the specific effect of conservation agriculture practices on N 2 O emissions give contradictory results. Herein, we synthesized a comprehensive database on the three main conservation agriculture practices (cover crops, diversified crop rotations, and no-till and/or reduced tillage (NT/RT)) to elucidate the role of conservation practices on N 2 O emissions. Further, we used a random meta-forest approach to identify the most important predictors of the effects of these practices on soil N 2 O emissions. Averaged across all comparisons, NT/RT significantly decreased soil N 2 O emissions by 11% (95% CI: –19 to –1%) compared to conventional tillage. The reductions due to NT/RT were more commonly observed in humid climates and in soils with an initial carbon content < 20 g kg –1 . The implementation of cover crops and diversified crop rotations led to variable effects on soil N 2 O emissions. Cover crops were more likely to reduce soil N 2 O emissions at neutral soil pH, and in soils with intermediate carbon (~20 g kg –1 ) and nitrogen (~3 g kg –1 ) contents. Diversified crop rotations tended to increase soil N 2 O emissions in temperate regions and neutral to alkaline soils. Our results provide a comprehensive predictive framework to understand the conditions in which the adoption of various conservation agriculture practices can contribute to climate change mitigation. Combining these results with a similar mechanistic understanding of conservation agriculture impacts on ecosystem services and crop production will pave the way for a wider adoption globally of these management practices.

Crop production and water productivity may be impacted by diverse crop rotation and management practices. A field study was conducted from 2017-2020 in the Loess Plateau to evaluate the effects of crop rotation sequences on pre-planting and post-harvest soil water storage (SWS), annualized crop yield, water use, and water productivity. Crops in rotation included oil flax ( Linum usitatissimum L.) (F), wheat ( Triticum aestivum L.) (W), potato ( Solanum tuberosum L.) (P). Twelve 4-year-cycle crop rotation treatments, along with a continuous oil flax treatment as a baseline, were included. The results showed that the average soil water content under the 0-150 cm soil layer in all treatments was increased after one rotation cycle, and the PWFW treatment achieved the highest SWC (17.1%). The average soil water storage (winter fallow season) and evapotranspiration (ETa) (growing season) under different crop rotation sequences were lower than those under continuous oil flax cropping. The ETa of FFFF increased by 28.9, 2.7, 15.3, and 28.4%, compared to average crop rotations in 2017, 2018, 2019, and 2020, respectively. Crop rotation had a significant effect on average annual yield and water use efficiency (WUE), which varied by year and rotation sequence. The crop rotations with the highest grain yield of oil flax were FFWP (2017), WFWP (2018),WPFF (2019) and FWPF (2020); the grain yield of wheat was highest when the two pre-crops (previously cultivated crops) were F-F, and potato yield was highest when the two pre-crops were W-F (except 2018). On average, the WUE of oil flax was 8.6, 38.7, 22.7, and 42.1% lower with FFFF than other diversity crop rotations in 2017, 2018, 2019, and 2020. We found that the WUE was not the largest when the grain yield of oil flax and wheat was highest. The treatments with maximum grain yield and WUE were not consistent. Our findings also revealed that wheat-potato-oil flax or potato-wheat-oil flax rotation could increase oil flax grain yields while wheat-oil flax-potato-oil flax markedly improved oil flax WUE.

Aims Evaluate crop rotation diversity, perenniality, carbon (C) inputs, and C input quality as predictors of soil organic carbon (SOC) concentration and aggregate mean weight diameter (MWD). Methods At a crop rotation trial in its 37th year in Ontario, Canada, species in rotations included corn (C, Zea mays L.), alfalfa (A, Medicago sativa L.), soybean (S, Glycine max (L.) Merr.), winter wheat (W, Triticum aestivum L.), and red clover (rc, Trifolium pratense L.). Rotations were: CC, CCAA, CCSS, CCSW, CCSWrc, AA. Soils (0–20 cm) were analyzed for aggregate MWD, aggregate C, and SOC concentrations. We estimated C inputs from historical yields and C input quality (C:N, lignin: N, or NMR-derived index) from structural plant tissues. C stabilization efficiency was estimated as the ratio of SOC stock per unit total or root C input. Results Crop rotation diversity failed to increase SOC concentrations or aggregate MWD. Perennialized rotations (CCSWrc, CCAA, AA) maintained the numerically highest SOC concentrations, and root C input increased SOC concentration. Out of 12 statistical tests relating C input quality to C stabilization efficiency, only 3 indicated a positive effect and 6 tests indicated a negative effect. Conclusions Including a perennial forage such as alfalfa and limiting soybean frequency promotes aggregate MWD and SOC concentration more so than optimizing crop rotation diversity. Quality of structural plant inputs does not explain differences in C stabilization efficiency, possibly due to overriding influence of living root inputs.