Nonlegume Cover Crops Research Articles

A Mixture of Summer Legume and Nonlegume Cover Crops Enhances Winter Wheat Yield, Nitrogen Uptake, and Nitrogen Balance

Cover crops protecting soil erosion during the summer fallow in the monsoon weather may enhance dryland winter wheat yield and N relations. We examined the effects of four summer cover crops (soybean (Glycine max L., SB), sudangrass (Sorghum sudanense {Piper} Stapf, SG), soybean and sudangrass mixture (SS), and no cover crop (CK)) and three N fertilization rates (0, 60, and 120 kg N ha−1) on winter wheat yield, quality, and N relations from 2017–2018 to 2020–2021 in the Loess Plateau of China. Cover crop biomass and N accumulation, soil mineral N, and winter wheat yield, protein concentration, and N uptake were greater for SB and SS than other cover crops at most N fertilization rates and years. The N fertilization rate had variable effects on these parameters. Winter wheat aboveground biomass and grain N productivities were greater for CK than other cover crops at all N fertilization rates and years. Nitrogen balance was greater for SS than other cover crops at 60 and 120 kg N ha−1 in all years. The SS with 120 kg N ha−1 can enhance soil mineral N, winter wheat yield and quality, and N balance compared to CK and SG with or without N fertilization rates.

Global synthesis of cover crop impacts on main crop yield

Incorporating cover crops into farming systems represents a potential pathway to maintaining crop productivity and achieving multiple environmental benefits. However, how cover crops impact the succeeding crop yield remained a matter of debate. Therefore, this study aims to provide a comprehensive and global scale assessment of cover crop impacts on yield. We conducted a literature synthesis of cover crop studies (104 articles) to collect field-based yield data (1027 records) and used meta-analysis to quantify the impact of cover crops on subsequent main crop yields. Our results showed that cover cropping led to an overall moderate increase in main crop yield, amounting to 2.6%. Specifically, the utilization of leguminous cover crops, cultivation in coarse soil texture and dryland areas, and the implementation of longer cover cropping durations were found to be conducive scenarios to enhance crop yields. Conversely, the use of non-legume cover crops, introducing them to fields under a short-term no-till, especially in fine-textured soils, were impaired to yields. Leguminous cover crops showed the greatest potential for increasing yield (9.8%) particularly when paired with corn. Adopting leguminous cover crops without fertilizing main crops resulted in a 21.8% yield increase. Utilizing cover crops did not affect yield if the field had already under no-till practice. Introducing cover crops on coarser soils and in rainfed drylands can increase yield by 14.1% and 11.4%, respectively. In fine-textured soils, cover crop plus conventional tillage achieved 4.8% yield increase while cover crops plus no-tillage led to a 9.5% yield decrease instead. Consequently, our findings suggested the general yield profitability of cover crops, but substantial variations remain, which was primarily affected by availability of nitrogen and soil moisture. It is advisable to maximize the nitrogen-fixing capability of leguminous cover crops as a nitrogen source for main crops, replacing fertilizer. Particular attention should be paid, and additional management practices should be adopted when using cover crops plus no-tillage in fine-textured soils to avoid yield penalties. These specific supportive measures are suggested to shorten the lag period of yield increase within the initial 1–3 years of cover cropping implementation. Our synthesis quantified the overall cover crop impacts on yield, showcasing variable yield returns across different scenarios. This holistic understanding and comprehensive information can serve to advance the appropriate and targeted adoption of cover crops by policymakers, extension services, and farmers.

Winter cover crops decreased soil mineral N contents and increased soil organic C stocks and N2O emission

Cover crops (CC) can contribute to climate protection as a result of their effects on soil nitrogen (N) cycling and nitrous oxide (N2O) emission and by increasing soil organic carbon (SOC) stocks. This study explored the influence of different winter CC (saia oat, winter rye and spring vetch) compared with bare fallow, followed by silage maize on N2O emissions and soil mineral N (SMN) dynamics, as well as on SOC stocks in year-round replicated field plot experiments in four fields located at two sites in northern Germany (Kiel, Uelzen) over two consecutive years (2018/19 and 2019/20). Non-legume CC decreased SMN contents in 0–30 cm during the CC period, but this did not result in decreased cumulative N2O emissions over that time. Decreased emissions during CC growth were offset by increased emissions during CC mineralisation after frost and incorporation. Higher cumulative N2O emissions during the maize period in all CC treatments compared with bare fallow (significant for non-legume CC) indicated that the incorporated CC biomass still boosted N2O emissions under the following crop. Overall, including CC in the cropping system increased annual and yield-related N2O emissions compared with bare fallow (significant only for non-legumes). The increase in annual N2O emissions of 0.84 ± 1.06 kg N2O-N ha−1 yr−1 was only partly offset by the estimated mitigation potential for indirect N2O emissions of 0.52 ± 0.14 kg N2O-N ha−1 yr−1. The mean annual increase in SOC induced by growing CC every fourth year over a 50-year period was 40–60 kg C ha−1 yr−1. In summary, CC had both positive and negative effects on greenhouse gas exchange. Site and crop rotation optimised CC systems, and a more precise and site-specific consideration of fertilising effects might help improve the net greenhouse gas budget of CC.

Soil N2 O emissions from specialty crop systems: A global estimation and meta-analysis.

Nitrous oxide (N2 O) exacerbates the greenhouse effect and thus global warming. Agricultural management practices, especially the use of nitrogen (N) fertilizers and irrigation, increase soil N2 O emissions. As a vital sector of global agriculture, specialty crop systems usually require intensive input and management. However, soil N2 O emissions from global specialty crop systems have not been comprehensively evaluated. Here, we synthesized 1137 observations from 114 published studies, conducted a meta-analysis to evaluate the effects of agricultural management and environmental factors on soil N2 O emissions, and estimated global soil N2 O emissions from specialty crop systems. The estimated global N2 O emission from specialty crop soils was 1.5 Tg N2 O-N year-1 , ranging from 0.5 to 4.5 Tg N2 O-N year-1 . Globally, soil N2 O emissions exponentially increased with N fertilizer rates. The effect size of N fertilizer on soil N2 O emissions generally increased with mean annual temperature, mean annual precipitation, and soil organic carbon concentration but decreased with soil pH. Global climate change will further intensify the effect of N fertilizer on soil N2 O emissions. Drip irrigation, fertigation, and reduced tillage can be used as essential strategies to reduce soil N2 O emissions and increase crop yields. Deficit irrigation and non-legume cover crop can reduce soil N2 O emissions but may also lower crop yields. Biochar may have a relatively limited effect on reducing soil N2 O emissions but be effective in increasing crop yields. Our study points toward effective management strategies that have substantial potential for reducing N2 O emissions from global agricultural soils.

Legume cover crops enhance soil organic carbon via microbial necromass in orchard alleyways

Cover crops may enhance soil organic carbon (SOC) sequestration, but the links among SOC fractions, microbial necromass carbon (C), and SOC sequestration potential in legume and non-legume cover-cropped orchards are unclear. We leveraged data from seven orchards with varying climatic and edaphic properties in China to assess the effects of legume and non-legume cover crops on SOC and microbial necromass C in bulk soil, particulate organic matter (POM), and mineral-associated organic matter (MAOM). Legume cover crops led to a significantly greater increase in SOC than non-legumes (23 % vs. 2 %), compared with no cover crops. The MAOM-C with legumes and non-legumes were similar but were both significantly greater than the control plots without cover crops. Legume cover crops positively influenced bacterial and fungal necromass C in all SOC fractions, while non-legume cover crops only affected fungal necromass C in bulk soil and MAOM. The effect of cover crops on the microbial necromass C to SOC ratio was negligible. Fungal necromass contributed most of the microbial necromass C to SOC accumulation, particularly in MAOM. Linear regression showed SOC, POM-C, and MAOM-C accumulated with increasing microbial necromass C. Microbial necromass C was the key factor explaining the variation in POM-C and MAOM-C compared to other climatic and edaphic factors. Partial least squares path modeling showed a causal relationship among cover crops, climate, soil substrates, soil properties, microbial necromass, and SOC and SOC fractions. Our study suggests that changes in microbial necromass C and composition may explain most of the increase in SOC in cover-cropped orchards and that MAOM-C is the principal sink of microbial necromass. This information is valuable for improving our understanding of the potential impact of microbial necromass C on enhancing SOC sequestration potential in orchard soils under cover crop management.

Maximizing soil organic carbon stocks under cover cropping: insights from long-term agricultural experiments in North America

Cover crops are widely advocated for increasing soil organic carbon (SOC) levels, thereby benefiting soil health improvement and climate change mitigation. Few regional-scale studies have robustly explored SOC stocks under cover cropping, due to limited long-term experiments. We used the unique experimental data from the North American Project to Evaluate Soil Health Measurements conducted in 2019 to address this issue. This study included 19 agricultural research sites with 36 pairs of cover cropping established between 1896 and 2014. Explanatory variables related to site-specific environmental conditions and management practices were collected to identify and prioritize contributing factors that affect SOC stocks with cover crops, by coupling the Boruta algorithm and structural equation modeling. Overall, cover crops significantly (P < 0.05) improved several indicators of soil health, including greater SOC (concentration: +8%; stock: +7%), total nitrogen (+8%), water-stable aggregates (+15%), and potential carbon mineralization (+34%), on average, compared to no cover crop control. Likewise, on average, cover crops sequestered SOC 3.55 Mg C ha-1 (0–15 cm depth), with a sequestration rate of 0.24 Mg C ha-1 yr-1. In addition, we found climate (Hargreaves climatic moisture deficit) was important in explaining the variation of SOC stocks with cover crops, followed by soil properties (e.g., soil clay content). In terms of management practices, cover crop type had a significant positive (0.36) effect on SOC stocks, with non-legumes showing a greater impact, compared to legumes and mixtures. Crop rotational diversity also had a positive (0.28) effect on SOC accumulation. Our findings suggested that integrating non-legume cover crops into diverse crop rotation is likely to be a promising strategy to maximize SOC stocks with cover crops across North America.

Nitrogen release dynamics and carbon sequestration by legume and non-legume cover crops under pure and mixed planting conditions

Abstract Synchronizing crop residue decomposing and releasing nitrogen with subsequent cash crop needs provides benefits for ecosystems, but it is difficult to carry out. This study aimed to investigate the trend of decomposition of vetch (Vicia sativa), rye (Secale cereale) and mixed (rye + vetch) cover crop residues as well as nitrogen release after incorporating them into the soil during 12 weeks of the potato growth season by using the mesh bag method. Vetch residues decomposed very quickly in the spring and their nitrogen is released due to their higher nitrogen content and consequently a lower Carbon/Nitrogen (C/N) ratio. However, rye residues decomposed at a slower rate compared to mixed treatment, and their nitrogen content was immobilized mainly due to a higher C/N ratio. A better understanding of cover crops residues decomposition dynamics leads to maximizing the cover crop effects and higher nutrient uptake by subsequent main crops. The results of this study showed that the input level of nitrogen fertiliser can be reduced by implementing management strategies in farming potatoes and using cover crops, which will reduce the harmful environmental effects and increase the economic benefit for farmers.

Assessing long-term impacts of cover crops on soil organic carbon in the central US Midwestern agroecosystems.

Cover crops have been reported as one of the most effective practices to increase soil organic carbon (SOC) for agroecosystems. Impacts of cover crops on SOC change vary depending on soil properties, climate, and management practices, but it remains unclear how these control factors affect SOC benefits from cover crops, as well as which management practices can maximize SOC benefits. To address these questions, we used an advanced process-based agroecosystem model, ecosys, to assess the impacts of winter cover cropping on SOC accumulation under different environmental and management conditions. We aimed to answer the following questions: (1) To what extent do cover crops benefit SOC accumulation, and how do SOC benefits from cover crops vary with different factors (i.e., initial soil properties, cover crop types, climate during the cover crop growth period, and cover crop planting and terminating time)? (2) How can we enhance SOC benefits from cover crops under different cover crop management options? Specifically, we first calibrated and validated the ecosys model at two long-term field experiment sites with SOC measurements in Illinois. We then applied the ecosys model to six cover crop field experiment sites spanning across Illinois to assess the impacts of different factors on SOC accumulation. Our modeling results revealed the following findings: (1) Growing cover crops can bring SOC benefits by 0.33 ± 0.06 MgC ha-1 year-1 in six cover crop field experiment sites across Illinois, and the SOC benefits are species specific to legume and non-legume cover crops. (2) Initial SOC stocks and clay contents had overall small influences on SOC benefits from cover crops. During the cover crop growth period (i.e., winter and spring in the US Midwest), high temperature increased SOC benefits from cover crops, while the impacts from larger precipitation on SOC benefits varied field by field. (3) The SOC benefits from cover crops can be maximized by optimizing cover crop management practices (e.g., selecting cover crop types and controlling cover crop growth period) for the US Midwestern maize-soybean rotation system. Finally, we discussed the economic and policy implications of adopting cover crops in the US Midwest, including that current economic incentives to grow cover crops may not be sufficient to cover costs. This study systematically assessed cover crop impacts for SOC change in the US Midwest context, while also demonstrating that the ecosys model, with rigorous validation using field experiment data, can be an effective tool to guide the adaptive management of cover crops and quantify SOC benefits from cover crops. The study thus provides practical tools and insights for practitioners and policy-makers to design cover crop related government agricultural policies and incentive programs for farmers and agri-food related industries.

Impact of cover crop and mulching on soil physical properties and soil nutrients in a citrus orchard.

BackgroundCover crops and mulching can ameliorate soil porosity and nutrient availability, but their effects on the physical characteristics and nutrients in the raised bed soils are unclear.MethodsThe field experiment was conducted in a pomelo orchard from 2019 to 2021, with an area of 1,500 m2. The treatments included control (no cover crop), non-legume cover crop (Commelina communis L.), legume cover crop (Arachis pintoi Krabov & W.C. Gregory), and rice straw mulching (Oryza sativa L.). At the end of each year (2019, 2020, and 2021), soil samples were collected at four different layers (0–10, 10–20, 20–30, and 30–40 cm) in each treatment. Soil bulk density, soil porosity, and the concentration of nutrients in the soil were investigated.ResultsThe results revealed that soil bulk density at two depths, 0–10 and 10–20 cm, was reduced by 0.07 and 0.08 g cm−3 by rice straw mulch and a leguminous cover crop, thus, increasing soil porosity by ~2.74% and ~3.01%, respectively. Soil nutrients (Ca, K, Fe, and Zn) at topsoil (0–10 cm) and subsoil (10–20 cm) layers were not significantly different in the first year, but those nutrients (Ca, K, Fe, and Zn) improved greatly in the second and third years.ConclusionsLegume cover crops and straw mulch enhanced soil porosity and plant nutrient availability (Ca, K, Fe, and Zn). These conservation practices best benefit fruit orchards cultivated in the raised bed soils.

Cover crops and N fertilization affect soil ammonia volatilization and N2O emission by regulating the soil labile carbon and nitrogen fractions

Introducing cover crops in monocropping systems to improve soil health has been broadly adopted worldwide. However, the impacts of different cover cropping systems on soil emissions and related soil fractions and their regulatory mechanism remain elusive. In this study, four cropping systems, i.e., relay intercropping with Orychophragmus violaceus L./cotton (OvC), Vicia villosa Roth/cotton (VvC), a cover crop mixture (Ov and Vv)/cotton (MSC) and a fallow field–cotton (FFC) system, were combined with four N application rates in a two-rotation cycle (2019–2021) to evaluate the effects on soil greenhouse gases (GHGs) emission, ammonia (NH3) volatilization, and labile carbon (C) and nitrogen (N) fractions and their relationships. Compared with the FFC system, the cumulative NH3 volatilization and nitrous oxide (N2O) emissions of OvC are noticeably reduced 13% and 58%, respectively, and those of VvC are comparable, while those of MSC are markedly increased by 15% and 24%, respectively. N fertilization significantly affects soil NH3 volatilization and N2O emissions, and a higher N rate results in more gaseous N emissions. In addition, NH3 volatilization and N2O emission are positively correlated with the soil microbial biomass N (MBN), dissolved organic N (DON), NH4+-N and NO3--N but negatively correlated with microbial biomass C (MBC) and dissolved organic C (DOC). OvC system decreased gaseous N emission by high soil MBC/MBN ratio, Vv as cover crop indirectly promote soil N2O emission through increased soil MBN, DON and MBC content, while cover crop mixtures increase soil labile C and N fractions and enhance gaseous N emission ultimately. Overall, application of N fertilizer and cover crop mixture both promoted soil NH3 and N2O emissions; the relay intercropping nonlegume cover crop Ov noticeably mitigates N2O and NH3 emissions through an increase in the soil MBC and reduce in the labile N, while introduction of the legume cover crop Vv increases N2O emissions but reduces soil NH3 volatilization due to a lower soil MBC/MBN ratio.

Cover crop composition drives changes in the abundance and diversity of nitrifiers and denitrifiers in citrus orchards with critical effects on N2O emissions

• Cover crop C and N effects linked to N-cycling community abundance and diversity. • Lower soil N 2 O fluxes with legume + non-legume cover crops vs non-legumes. • Cover crop mixture had significant effects on nirK and nosZ I community diversity. • nirK and nosZ I community composition attributed to soil properties and CC mixtures. • amoA AOA, nirK, and nosZ I species potential indicators of CC N 2 O changes. Tree crops contribute to global agriculture production, but they are usually cultivated in soils with low nutrient availability. Cover crops (CCs) have been reported as a sustainable management strategy to improve soil nutrient availability for vegetable systems, but less is known about their influence on soil nutrient cycling, greenhouse gas emissions (GHG), and the soil microbiome in tree crops. We examined the effect of replacing the traditional weedy row middles of a commercial Florida citrus orchard with two different mixtures of CCs (legumes and non-legumes, LG + NL; and non-legumes only, NL) compared to a grower standard control (GSC) over a period of two years. Both CC mixtures significantly increased soil carbon (C) availability, microbial abundance, and soil respiration in the row middles compared to the GSC. Significant increases in soil nitrogen (N) concentrations and abundance of genes associated with N-fixation and nitrification were observed in soils treated with LG + NL. Planting LG + NL significantly increased the abundance of nosZ -type denitrifiers compared to NL and the GSC treatments, and significantly reduced nitrous oxide (N 2 O) emissions. The use of both CC mixtures reduced bacterial diversity and affected the composition of nirK and nosZ I communities. The composition of nosZ I communities differed between CC mixtures, possibly due to changes in soil moisture and carbon. Specific amoA ammonia-oxidizing archaea, nirK, and nosZ I species were identified as potential indicators for changes in N 2 O emissions after planting CCs. Our results show that CCs can be a good strategy to improve soil nutrient cycling in the row middles of tree crops and that CC composition drives changes in the abundance and diversity of N-cycling communities which ultimately impact GHG emissions.

Winter cover crops increased nitrogen availability and efficient use during eight years of intensive organic vegetable production.

Efficient use of nitrogen (N) is essential to protect water quality in high-input organic vegetable production systems, but little is known about the long-term effects of organic management on N mass balances. We measured soil N and tabulated N inputs (organic fertilizers, compost, irrigation water, atmospheric deposition, cover crop seed, vegetable transplant plugs and fixation by legume cover crops) and exports in harvested crops (lettuce, broccoli) over eight years to calculate soil surface and soil system N mass balances for the Salinas Organic Cropping Systems study in Salinas, CA. Our objectives were to 1) quantify the long-term effects of compost, cover crop frequency and cover crop type on soil N, cover crop and vegetable crop N uptake, and yield, and 2) tabulate N balances to assess the effects of these factors on N export in harvested crops, soil N storage and potential N loss. Results show that across all systems only 13 to 23% of N inputs were exported in harvest. Annual compost applications increased soil N stocks but had little effect on vegetable N uptake or yield, increasing the cumulative soil system N balance surplus over eight years by 999 kg ha-1, relative to the system receiving organic fertilizers alone. Annually planted winter cover crops increased N availability, crop uptake and export; however, biological N fixation by legumes negated the positive effect of increased harvest exports on the balance surplus in the legume-rye cover cropped system. Over eight years, rye cover crops improved system performance and reduced the cumulative N surplus by 384 kg ha-1 relative to the legume-rye mixture by increasing N retention and availability without increasing N inputs. Reduced reliance on external compost inputs and increased use of annually planted non-legume cover crops can improve efficient N use and cropping system yield, consequently improving environmental performance.

Regulation of Soil Microbial Community Structure and Biomass to Mitigate Soil Greenhouse Gas Emission.

Sustainable reduction of fertilization with technology acquisition for improving soil quality and realizing green food production is a major strategic demand for global agricultural production. Introducing legume (LCCs) and/or non-legume cover crops (NLCCs) during the fallow period before planting main crops such as wheat and corn increases surface coverage, retains soil moisture content, and absorbs excess mineral nutrients, thus reducing pollution. In addition, the cover crops (CCs) supplement the soil nutrients upon decomposition and have a green manure effect. Compared to the traditional bare land, the introduction of CCs systems has multiple ecological benefits, such as improving soil structure, promoting nutrient cycling, improving soil fertility and microbial activity, controlling soil erosion, and inhibiting weed growth, pests, and diseases. The residual decomposition process of cultivated crops after being pressed into the soil will directly change the soil carbon (C) and nitrogen (N) cycle and greenhouse gas emissions (GHGs), and thus affect the soil microbial activities. This key ecological process determines the realization of various ecological and environmental benefits of the cultivated system. Understanding the mechanism of these ecological environmental benefits provides a scientific basis for the restoration and promotion of cultivated crops in dry farming areas of the world. These findings provide an important contribution for understanding the mutual interrelationships and the research in this area, as well as increasing the use of CCs in the soil for better soil fertility, GHGs mitigation, and improving soil microbial community structure. This literature review studies the effects of crop biomass and quality on soil GHGs emissions, microbial biomass, and community structure of the crop cultivation system, aiming to clarify crop cultivation in theory.

Assessing the impacts of cover crops on maize and soybean yield in the U.S. Midwestern agroecosystems

• Non-legume cover crops cause 3.9 % yield penalty for maize, no penalty for soybean. • Legume cover crops have no significant impacts on maize and soybean yield. • Pathways for yield penalty are N and O 2 deficiency, water stress and cooler soil. • Optimizing cover crop growth windows could maximize the benefit from cover crops. • The ecosys model is an effective tool to quantify cover crop impacts on crop yield. Growing cover crops is one of the most promising conservation practices with multiple benefits. However, the impacts of cover crops on the productivity of the maize-soybean [ Zea mays L. - Glycine max (L.) Merr.] rotation system in the U.S. Midwest still have large uncertainties based on results obtained from field experiments, specifically across different soil properties, climate conditions, and land management practices. Process-based models fully validated with data from field experiments across these diverse conditions provide an effective tool to quantify cover crop impacts on cash crop productivity and optimize the management of cover crops accordingly. In this study, we aim to answer the following questions: (1) What are the impacts of cover crops on cash crop yield in the U.S. Midwest agroecosystems? (2) What are the mechanistic pathways of cover crop to affect cash crop yield (e.g. through influencing soil water, nitrogen and O 2 dynamics)? (3) What management practices can be used to mitigate the negative impacts on cash crop yield caused by cover crops? To address these questions, we calibrated and validated a sophisticated process-based agroecosystem model, ecosys , using field experimental data from 2013 to 2018 across Illinois, and then used ecosys to assess the impacts of winter cover crops on maize and soybean yield under different management practices. Our study revealed the following findings: (1) planting non-legume cover crops can cause 3.9 ± 3% yield reduction for maize and no significant impacts on soybean yield, while planting legume cover crops has no significant impact on the yield of either maize or soybean; (2) the maize yield reduction caused by planting cover crops can be mainly explained by nitrogen deficiency induced by increased immobilization, water competition in dry areas, cooler soil surface and oxygen competition; (3) later termination of non-legume cover crops before maize can result in larger maize yield loss due to intensive competition for resources (e.g. water and nitrogen), and the impacts of non-legume cover crops on maize yield reduction can be minimized by optimizing cover crop termination time in the spring. Overall, in the U.S. Midwestern maize-soybean rotation system, we found that although non-legume cover crops cause yield reduction for maize through resource competition, this yield reduction can be minimized through management practices, such as controlling termination time of cover crop and proper fertilizer management.

Changes in microbial and physicochemical properties under cover crop inclusion in a degraded common bean monoculture system

The expansion of the common bean monoculture system along with intensive agricultural practices focused on productivity has generated a misuse of natural resources, accompanied by a significant decline of the soil ecosystem services. The aim of this study was to analyze the short-term effect (3 years) of the inclusion of different cover crops (legumes, non-legumes and mixtures) on the physicochemical, biological properties and crop yield in a degraded common bean monoculture system in the north region of Argentina. The inclusion of legumes (vetch and melilotus) and non-legumes (oat and wheat) as sole cover crops over three consecutive years significantly increased the abundance of the main microbial groups, microbial biomass C and N (MBC and MBN) and the activity of the common bean rhizosphere microbial community, which resulted into a fast improvement of soil quality and rhizosphere microbiota compared with bean monoculture. However, mixed cover crops (oat + vetch) had a positive but lower impact on rhizosphere microbial community abundance compared to legume or non-legume cover crops when used as sole cover crops. The information generated in this study will contribute to the evaluation of the inclusion of specific cover crops as a conservation strategy to recover soil health and minimize soil degradation, while maintaining crop yields.

Cover crops promote primary crop yield in China: A meta-regression of factors affecting yield gain

• We analyse the effects of cover crops (CCs) on subsequent crop yield in China. • On average over whole China, CCs significantly increased subsequent crop yield by ca. 10 % compared to fallow. • CC type, CC season and N input were key factors influencing the effect of CCs on crop yield. • Results provide a basis for advising farmers on the use of CCs for increasing crop yields. Inclusion of cover crops (CCs) in cropping systems can improve soil quality, reduce agricultural inputs, and improve environmental sustainability. While CCs have been widely promoted in China in recent years, a quantitative assessment of CC effect on crop yield across China is lacking. There is also no overarching analysis on factors explaining variation in yield effects. Here, we carried out a meta-analysis to evaluate the effects of CCs on subsequent primary crop yield in China, based on 53 published studies reporting 442 yield ratios with and without CCs. We found that CCs increased subsequent primary crop yields by 9.7 % on average when compared with fallow across China. The effects of CC varied with different factors related to climatic zone, field management and soil properties. CC type (legume or not), CC season (growing in winter or summer) and nitrogen input were factors substantially influencing primary crop yield. We identified high yield benefits in subtropical rice systems with winter CCs (12.9 ± 3.9 %) but no significant yield benefits in temperate wheat systems with summer CCs (1.9 ± 6.6 %). Within subtropical rice systems, both legume and non-legume CCs were tested widely, and the effects of legume CCs (14.6 ± 4.0 %) on primary crop yield were greater than those of non-legume CCs (7.9 ± 3.7 %). The yield benefits of CCs decreased with increasing fertilizer inputs. These results may be used for developing policy recommendations to improve primary crop yield by integrating targeted CCs associated with nitrogen management into cropping systems in China.

Impact of the mixture verses solo residue management and climatic conditions on soil microbial biomass carbon to nitrogen ratio: a systematic review.

Cover crops (CCs) have been increasingly cultivated to boost soil quality, crop yield, and minimize environmental degradation compared with no cover crops (NCCs). There is no consensus of CCs under different climatic conditions on soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and soil microbial biomass carbon and nitrogen ratio (SMBC/SMBN) are yet documented. Thus, a global meta-analysis of 40 currently available literature was carried out to elucidate the effect of CCs on SMBC and SMBN, and its ratio for cash and cover cropping systems was conducted. Our findings demonstrated that CCs increased SMBC, SMBN, and SMBC/SMBN ratios by 39, 51, and 20%, respectively, as compared to NCCs. The categorical meta-analyzes showed that the mixture of legume and nonlegume CCs decreased the SMBC, SMBN, and SMBC/SMBN ratios relative to the sole legume or nonlegume CCs. Nonlegume CCs enhanced the SMBC, SMBN, and SMBC/SMBN ratio compared to legume CCs. When CCs residues were incorporated into the soil or surface mulched, the SMBC and SMBN increased compared to the removal of residues. The effect of CCs on the SMBN and SMBC/SMBN ratio was higher in medium-textured soils compared to coarser or fine-textured soils, but coarser-textured soils have a higher SMBC. The effect of CCs on SMBN and SMBC/SMBN ratio was prominent on medium-textured soils having soil organic carbon (SOC) in the range of 10-20 mg g-1, pH > 6.5, and total nitrogen (TN) in the range of 1-2%. It was concluded that CCs enhanced SMBC, SMBN, and its ratio compared to NCCs. The response, however, varied depending on the soil properties and climatic region. Cover crops can boost the biological soil's health by increasing the microbial population's abundance compared to NCCs.

The effects of ground cover management on fruit yield and quality: a meta-analysis

ABSTRACT An important management strategy for the development of sustainable agriculture in orchards is the management of ground cover. However, there is a knowledge gap regarding the effects of ground cover on fruit yield and quality. We performed a meta-analysis of 580 observations collected from 116 peer-reviewed field studies, to assess the effects of ground cover on fruit yield and quality indicators. Overall, ground cover significantly increased fruit yield, soluble solid content, sugar content, and vitamin C content by 6.98%, 6.77%, 7.83%, and 14.59%, respectively, and significantly reduced fruit acidity by 10.63%. The effects of ground cover on fruit yield and quality were greater in subtropical regions and semi-humid, humid zone. These effects also mostly depended on ground cover types. Cover crops and mulch both significantly improved fruit quality. However, compared to clean tillage practice, legume cover crops substantially enhanced fruit yield while non-legume cover crops significantly decreased fruit yield. This effect was attributed to greater soil moisture and fertility with legume cover crops. Our analysis synthesized the scientific evidence on ground cover management to help orchard managers and policy makers improve orchard fruit yield and quality.

Nitrogen-15 labelling and tracing techniques reveal cover crops transfer more fertilizer N to the soil reserve than to the subsequent crop

Estimating the capacity of cover crops (CC) to capture soil nitrogen (N) and to transfer captured N to subsequent crop remains a challenge because CC biomass production, N content and decomposition rate vary depending on environmental conditions and management practices. The objectives of this study were (1) to compare biomass production and N accumulation by a mixture of red and white clovers intercropped with barley, and oat, field pea and oilseed radish grown as catch crops after barley harvest, (2) to determine the capacity of different CCs to catch and transfer fertilizer N (mineral or pig slurry) to subsequent wheat and the soil reserve, and (3) to determine the influence of CC type on yield of spring wheat in the next year. A 2-y crop rotation (barley – wheat) was repeated twice on a sandy loam using 15N-labelled fertilizers applied at the time of CC establishment. Fertilization increased above-ground biomass yield in oat and oilseed radish, but had little effect on legume CCs. The legume CCs accumulated more total N in their biomass (63–127 kg N ha−1) than non-legume CCs (47–68 kg N ha−1). However, oat and oilseed radish were more efficient at capturing the applied fertilizer 15N (33–51 %) than legume CCs (2–36 %). Intercropped clovers resulted in the largest increases in subsequent wheat yields (23–92 %), followed by oilseed radish and field pea. At the end of the 2-y rotation (wheat harvest), the recovery of fertilizer 15N by subsequent wheat was < 10 %, whereas 26–60 % were still present in the 0−30 cm soil layer. We conclude that non-legume CCs have a good capacity to capture applied fertilizer N, whereas legume CCs (especially clovers) had a limited capacity. Nevertheless, clovers CC resulted in the greatest wheat yields in the following year, likely due to efficent transfer of symbiotically fixed N and improved soil quality, whereas fertilizer N captured by non-legume CCs was mainly routed to the soil N reserve, with potential to supply N to subsequent crops through a legacy effect.

Cover cropping enhances soil microbial biomass and affects microbial community structure: A meta-analysis

Cover crops have been increasingly grown for improving soil health and crop production and minimizing environmental impact compared to no cover crop. Systematic documentation of cover cropping effects on soil microbial abundance and community structure, however, is scarce. A meta-analysis including data from 81 available studies was conducted to elucidate the effect of “cover crop” versus “no cover crop” on soil microbial community abundance and structure. Microbial biomass C and N (MBC and MBN) and total phospholipid-derived fatty acids (PLFA) were taken as proxies for soil microbial abundance, and total fungi, total bacteria, gram-positive and -negative bacteria, actinomycete, and arbuscular mycorrhizal fungi (AMF) for microbial community structure. Compared to no cover crop, cover crop overall enhanced PLFA, MBC, and MBN by 24, 40, and 51%, respectively. Soil total bacteria and total fungi, and the groups in them increased by 7–31% with cove crop compared to no cover crop. Fungi were affected more by cover crop than bacteria as indicated by the greater fungi/bacteria ratio. In depth categorical meta-analyses revealed that the legume and nonlegume cover crop mixture reduced MBC, PLFA, and actinomycete compared to legume or nonlegume cover crop alone. Legume cover crop enhanced actinomycete in comparison to nonlegume or the cover crop mixture. Incorporation of cover crop residue into the soil increased PLFA, total bacteria, AMF root colonization, and spore density, but decreased gram-positive and -negative bacteria and AMF compared to residue placed at the surface or removed from the soil. Microbial parameters due to cover crop compared to no cover crop were related to soil properties and annual precipitation. Medium-textured soils showed greater response of cover crop on PLFA, total bacteria and fungi, and actinomycete than fine- or coarse-textured soils. We conclude that cover crops enhance soil microbial community biomass and affected community structure compared to no cover crop and the responses of microbial parameters to cover crop varied with soil and climatic conditions. Cover crops can enhance biological soil health by enhancing microbial community abundance compared to no cover crop.