Non-leguminous Cover Crops Research Articles

Long-term effects of agronomic practices on winter wheat yield and NUE in dryland regions of USA and China: a long-term meta-analysis

Dryland agriculture is fundamental to global crop production and vital to food security. Conservation tillage is extensively practiced in USA wheat cultivation. Meanwhile, the adoption of conservation tillage by Chinese farmers is limited. This meta-analysis compared the yield and nitrogen use efficiency (NUE) between conservation tillage and conventional tillage (CT) with different types of cropping systems, mulching methods, levels of nitrogen fertilizer (NF), and addition of manure. The meta-analysis presented that conservation tillage at high-NF enhanced the yield and NUE, and reduced the yield and NUE at low-NF, compared to CT. The interaction of conservation tillage with leguminous cover crops (LCC) and manure application increased the yield and NUE at low-NF, compared to CT. Non-leguminous cover crops (NLCC) increased the yield and NUE under high-NF than low-NF. The interaction of conservation tillage with management practices showed that the no-tillage (NT) with leguminous cover crops (LCC) significantly increased wheat yield by 58% and NUE by 47% under low-NF compared to CT. However, increasing the rate of NF did not increase the yield under such interaction. Cropping systems, mulching types, and manure application mainly determined the effects of conservation tillage on wheat yield and NUE. The adverse impact of CT on yield and NUE could be alleviated with the application of LCC and manure under moderate NF. We demonstrate that adding LCC and manure have a generally substitutive relationship with N fertilizer, resulting in a significant increase in wheat yield and NUE at low-NF doses as at high N fertilizer dosages. Therefore, based on the obtained results, moderate NF with LCC and manure application is recommended for growing winter wheat in dryland regions of the USA and China.

Plant and soil N of different winter cover crops as green manure for subsequent organic white cabbage

Leguminous cover crops used as green manures can reduce fertilizer inputs by supplying nitrogen (N) via mineralization of incorporated N-rich biomass derived from biological N2 fixation. In a multi-year trial at three locations in Germany, the effects of leguminous, non-leguminous and mixed green manure crops on the yield of the subsequent cash crop white cabbage (Brassica oleracea convar. capitata var. alba) were investigated. The winter cover crop treatments were forage rye (Secale cereale L.), a mixture of forage rye with winter Hungarian vetch (Vicia pannonica Crantz), sole-cropped winter Hungarian vetch, winter pea (Pisum sativum L.), and winter faba bean (Vicia faba L.) with bare soil as a control. Sole-cropped legumes showed higher marketable cabbage head yields (head weight > 1.0 kg) compared to the other cover crop treatments, with 25.5, 25.9 and 28.1 Mg ha− 1 for vetch, pea and faba bean, respectively. The aboveground biomass of the legume winter cover crop treatments had higher N offtakes with 185, 177 and 159 kg N ha− 1 for vetch, pea and faba bean, respectively, with significantly lower carbon (C)/N ratios compared to rye and rye with vetch. The constant C/N ratio of the aboveground biomass of leguminous cover crops throughout the growing period indicates that the optimum incorporation date to achieve high N mineralization rates is less time dependent in leguminous compared to non-leguminous cover crops. The results of the present study show that leguminous winter cover crops do not reduce the soil N availability for a succeeding high N demanding cabbage crop resulting in yields comparable to agricultural practice without winter cover crops.

Cover Crop Identity Differently Affects Biomass Productivity as well as Nitrogen and Phosphorus Uptake of Maize (Zea mays L.) in Relation to Soil Type

Cover crop integration in agriculture rotation is associated to multiple agronomic and environmental benefits. However, the effect of cover crop identity on the following cash crop productivity and nutrient uptake is still uncertain, particularly in relation to soil types. We set up an experiment to test the effects of four different cover crop species (Indian mustard, lupine, field pea, and oat) on maize above- and belowground biomass as well as on nitrogen and phosphorus nutrition after incorporation of the cover crop litter in two soil types (clay and sandy soil). We observed that aboveground and belowground biomass of maize was always higher in sandy than clay soil likely due to better soil physical properties. On general, in clay soil, the presence of a preceding cover crop promoted or did not modify the aboveground and the belowground maize productivity compared to bare soil. On the other hand, in sandy soil, the decomposing litter of non-leguminous cover crops decreased maize aboveground productivity whereas any preceding cover crop decreased maize root biomass. The burial of leguminous litter significantly increased the N uptake by maize in both soil types. For what concerns the phosphorus uptake by maize, it appears that due to high phosphorus soil availability, the selected cover crops did not play a major role in improving P uptake, with the only exception of field pea. Our data show that leguminous cover crops improved the N status of maize particularly under conditions of low N fertilization rates.

Effect of soil fertility level on growth of cover crop mixtures and residual fertilizing value for spring barley

The use of cover crops may play an important role in ecological intensification of farming systems through their impacts on cycling and the availability of essential nutrients. However, little is known about the effect of soil fertility on the performance of cover crops and consequent nutrient dynamics. We performed a two-year field trial to quantify the effect of two soil fertility levels (low and moderate) on the growth and nutrient content of different leguminous and non-leguminous cover crop species and their mixtures, and on their fertilizing value for the succeeding crop.Overall, the growth and shoot nutrient content of cover crops in autumn was influenced by the species, mixture choices and soil fertility level. The growth of some species was less affected by fertility level than others. Among the legumes, fertility levels had no effect on the growth of lupin. Among the non-legumes, buckwheat had the highest biomass production as well as C:N ratio at a low fertility level, and in the first year was affected least by soil fertility level. However, buckwheat and lupin grown as a single species or in mixtures did not lead to yield improvements in the subsequent crop. Generally, legumes produced more biomass than non-legumes in the mixtures at the low fertility level, whereas non-legumes produced more biomass at the moderate fertility level. Growing a mixture of vetch and radish achieved the best synergetic effect and highest shoot N content. In both years, the greatest improvements in barley yields were achieved after vetch grown as a single species and in a mixture with radish (by up to 46 %). Rye was less competitive in mixtures than radish and buckwheat, and in the second year it had a negative effect on barley yield at the low soil fertility level, presumably due to pre-emptive competition for nitrogen. Soil fertility level had a greater effect on barley yields than cover crop treatments, as yield increments at the moderate fertility level amounted to 48 % in the first year and 64 % in the second year compared with the low fertility level.These results demonstrate that the cultivation of winter-persistent legumes alone or in a mixture with oilseed radish offers a promising tool for improving the yields of subsequent crops through nitrogen input and nutrient cycling on farms where soil fertility level is low.

Soil and crop management practices and the water regulation functions of soils: a qualitative synthesis of meta-analyses relevant to European agriculture

Abstract. Adopting soil and crop management practices that conserve or enhance soil structure is critical for supporting the sustainable adaptation of agriculture to climate change, as it should help maintain agricultural production in the face of increasing drought or water excess without impairing environmental quality. In this paper, we evaluate the evidence for this assertion by synthesizing the results of 34 published meta-analyses of the effects of such practices on soil physical and hydraulic properties relevant for climate change adaptation in European agriculture. We also review an additional 127 meta-analyses that investigated synergies and trade-offs or help to explain the effects of soil and crop management in terms of the underlying processes and mechanisms. Finally, we identify how responses to alternative soil–crop management systems vary under contrasting agro-environmental conditions across Europe. This information may help practitioners and policymakers to draw context-specific conclusions concerning the efficacy of management practices as climate adaptation tools. Our synthesis demonstrates that organic soil amendments and the adoption of practices that maintain “continuous living cover” result in significant benefits for the water regulation function of soils, mostly arising from the additional carbon inputs to soil and the stimulation of biological processes. These effects are clearly related to improved soil aggregation and enhanced bio-porosity, both of which reduce surface runoff and increase infiltration. One potentially negative consequence of these systems is a reduction in soil water storage and groundwater recharge, which may be problematic in dry climates. Some important synergies are reductions in nitrate leaching to groundwater and greenhouse gas emissions for nonleguminous cover crop systems. The benefits of reducing tillage intensity appear much less clear-cut. Increases in soil bulk density due to traffic compaction are commonly reported. However, biological activity is enhanced under reduced tillage intensity, which should improve soil structure and infiltration capacity and reduce surface runoff and the losses of agro-chemicals to surface water. However, the evidence for these beneficial effects is inconclusive, while significant trade-offs include yield penalties and increases in greenhouse gas emissions and the risks of leaching of pesticides and nitrate. Our synthesis also highlights important knowledge gaps on the effects of management practices on root growth and transpiration. Thus, conclusions related to the impacts of management on the crop water supply and other water regulation functions are necessarily based on inferences derived from proxy variables. Based on these knowledge gaps, we outlined several key avenues for future research on this topic.

The planting effect of cover crop in Sanjiang Plain, Northeast China

The planting effect and the planting potential of 12 cover crops (Leguminous: alfalfa, smooth vetch, hairy vetch, red clover, white clover, common vetch; non-leguminous: sudangrass, green radish, Nitro radish, rape, kale, endive) in the Sanjiang Plain of Northeast China were comprehensively evaluated by soil penetration resistance, pre-winter biomass, root characteristics, and plant nitrogen accumulation. The results showed that all the 12 cover crops grew normally during the experimental sowing period. Compared with the control, all the cover crops successfully reduced soil compactness. The planting of green radish, nitro radish, and sudangrass decreased soil penetration resistance by 47.1%, 43.4% and 33.4%, respectively. The pre-winter total fresh biomass of cover crop populations was between 3.38 and 13.98 kg·m-2, and the total dry matter mass was between 0.78 and 2.43 kg·m-2. The biomass of non-leguminous cover crops was significantly higher than that of the leguminous cover crops. The group roots of radish, rape and endive had large volumes. In particular, the nitro radish roots had a vo-lume of 4018.5 cm3·m-2, and the root system of sudangrass extended over the widest horizontal range. The ash content of leguminous cover crops was significantly lower than that of non-leguminous species, which could provide more organic matter with high decomposability. The total nitrogen accumulation of cover crops varied from 18.72 to 53.09 g·m-2. Kale and endive accumulated the highest amount of nitrogen and large biomass, which could facilitate nitrogen fixation and accumulation. According to the type of main crops in Sanjiang Plain and canopy structure, planting leguminous (clover, vetch, and alfalfa) and non-leguminous (radish, kale and sudangrass) cover crops to plant inter-row or in a line mixed cropping pattern could regulate soil structure and promote nutrient cycing, with positive effects on the fertility of black soil in the Sanjiang Plain.

Weed Flora Dynamics in Maize (Zea mays L.) Field as Influenced by Cover Crop Types and Planting Densities at Jalingo, Northeast, Nigeria

Aim: Competition from weeds is an obstacle to profitable maize production. Knowledge of weed species limiting productivity is essential for sustainable management. A two years field experiment was conducted to evaluate the effect of a leguminous cover crop, akidi (Vigna unquiculata sub-sp sequipedalis) and two non-leguminous cover crops (melon and sweet potato) planted at three densities on weed flora composition and shift in maize at Jalingo, North-eastern Nigeria.
 Study Design: There were 11 treatments replicated three times in a randomized complete block design.
 Methodology: Low, moderate and high densities (20,000, 30,000 and 40,000 stands/ha respectively) of Akidi, Melon and Sweet potato (A1, A2, A3, M1, M2, M3, S1, S2, S3) with weeded (C1) and unweeded (C2) checks constituted the treatments laid out in a randomized complete block design replicated three times. Weed flora abundance, percentage density, percentage frequency, frequency index and percentage contributions were determined from a 50cm x 50cm quadrat thrown twice per plot at various phases of maize growth.
 Results: Thirteen weed families made up of 11 broad leaves, one grass and one sedge were identified. The abundance was in the order Broad leaf > Grass > Sedges. The most abundant weed species were: Imperata cylindrica L (3.8), Mucuna utilis (3.0), Oldenlandia herbacea L. (2.6) Sida acuta Burm F, Tridax procumbens L. (2.5 each), Leucas martinicensis, Pennisetum pedicellatum (2.3 each). Commelina benghalensis, Cyperus difformis (3.5), Digitaria horizontalis, Fimbristylis littoralis (2.8 each). The influence of selected cover crops on individual weed percentage the contribution shows: Commelina benghalensis ( C2<C1 < M <S< A), Euphorbia hyssopifolia (C2<M/S < A<C1), Euphorbia heterophylla (M<S<A), Leucasmartinicensis (C1<C2<M<A<S), Mucunautilis (S<M<C1<C2<A) and Sida acuta (M<S<A<C2<C1) while grassy weeds, Imperata cylindrical (A<C2<S<M), Pennisetum pedicellatum (A<C2), Digitaria horizontalis (C1/ C2< A < M <S), Kyllinga squamulata (M/S <C2<A <C1). Commelina spp. increased in status from an accessory (21.2%) to abundance (66.7%) while others increased from rare to accessory (from 0.0 to 20-40%).
 Conclusion: Akidi was more effective on broad-leaved weeds while melon and sweet potato were more effective on grasses and Commelina benghalensis need to be monitored.

Effects of Non-Leguminous Cover Crops on Yield and Quality of Baby Corn (Zea mays L.) Grown under Subtropical Conditions

Effects of non-leguminous cover crops and their times of chopping on the yield and quality of no-till baby corn (Zea mays L.) were evaluated during two kharif seasons (May-August in 2014 and 2015) under subtropical climatic conditions of Punjab, India. The experiment was laid out in a split-plot design with four replications at Punjab Agricultural University’s Research Farm. Three cover crops (pearl millet (Pennisetum glaucum L.), fodder maize (Zea mays L.), and sorghum (Sorghum bicolor L.)) and the control (no cover crop) were in the main plots and chopping time treatments (25, 35, 45 days after planting (DAP)) in the subplots. During both kharif seasons, the yield (cob and fodder yield) and dry matter accumulation of baby corn following cover crop treatments, especially pearl millet, were significantly (p ≤ 0.05) higher than the control, and improved with increments in chopping time from 25 to 45 DAP. The effect of cover crops on baby corn quality (i.e., protein, starch, total soluble solids, crude fiber, total solid, and sugar content) did not differ among treatments, while increasing increments in chopping time had a significant effect on the protein and sugar content of baby corn. The use of cover crops and increment in chopping time helped in enhancing topsoil quality, especially available nitrogen; yet, the effect of cover crops and their times of chopping on topsoil organic carbon, phosphorus, and potassium did not differ among treatments. During both seasons, there was no significant interaction between cover crop and time of chopping among treatments with respect to baby corn yield and quality, as well as topsoil quality parameters.

Carbon and nitrogen mineralization differ between incorporated shoots and roots of legume versus non-legume based cover crops

Cover crops (CC) have been widely used to improve soil quality and sustain agricultural productivity. However, the turnover of carbon (C) and nitrogen (N) from different species and parts of CCs incorporated into the soil under Northern European conditions remains unclear. In this study, we examined mineralization of C and N from isolated shoots and roots of two leguminous and two non-leguminous CCs labeled with 15N tracers in a 100-day incubation experiment at 10 °C. After 100 days incubation, the average net N mineralization was 33% from the leguminous CCs and 20% from the non-legumes. Net N mineralization from shoots was 1–15% (% of the N input) higher than that from the corresponding roots, and the net C mineralization accounted for 53–62% and 18–39% of the total C applied with CC shoots and roots, respectively. The C/N ratio of plant residues was a good predictor for net N mineralization, while the lignin concentration was a good predictor for C mineralization from both roots and shoots. Roots of both legume and non-legume CCs caused net immobilization of (unlabeled) soil N, whereas no significant soil N immobilization occurred from shoots with low C/N ratios. Our results indicate that different CC characteristics (C/N ratio and lignin) control the turnover of residue N and C, respectively, in the soil. Our results further showed very limited interactions with soil N turnover (no priming effects) when materials with low C/N ratios were applied to soil.

Cover Crops Reduce Nitrate Leaching in Agroecosystems:A Global Meta-Analysis.

Cover crops are well recognized as a tool to reduce NO leaching from agroecosystems. However, their effectiveness varies from site to site and year to year depending on soil, cash and cover crop management, and climate. We conducted a meta-analysis using 238 observations from 28 studies (i) to assess the overall effect of cover crops on NO leaching and subsequent crop yields, and (ii) to examine how soil, cash and cover crop management, and climate impact the effect of non-leguminous cover crops on NO leaching. There is a clear indication that nonleguminous cover crops can substantially reduce NO leaching into freshwater systems, on average by 56%. Nonlegume-legume cover crop mixtures reduced NO leaching as effectively as nonlegumes, but significantly more than legumes. The lack of variance information in most published literature prevents greater insight into the degree to which cover crops can improve water quality. Among the factors investigated, we identified cover crop planting dates, shoot biomass, and precipitation relative to long-term mean precipitation as potential drivers for the observed variability in nonleguminous cover crop effectiveness in reducing NO leaching. We found evidence indicating greater reduction in NO leaching with nonleguminous cover crops on coarse-textured soils and during years of low precipitation (<90% of the long-term normal). Earlier fall planting and greater nonleguminous shoot biomass further reduced NO leaching. Overall, this meta-analysis confirms many prior studies showing that nonleguminous cover crops are an effective way to reduce NO leaching and should be integrated into cropping systems to improve water quality.

Assessing Short‐Term Impacts of Management Practices on N2O Emissions From Diverse Mediterranean Agricultural Ecosystems Using a Biogeochemical Model

AbstractCroplands are important sources of nitrous oxide (N2O) emissions. The lack of both long‐term field measurements and reliable methods for extrapolating these measurements has resulted in a large uncertainty in quantifying and mitigating N2O emissions from croplands. This is especially relevant in regions where cropping systems and farming management practices (FMPs) are diverse. In this study, a process‐based biogeochemical model, DeNitrification‐DeComposition (DNDC), was tested against N2O measurements from five cropping systems (alfalfa, wheat, lettuce, vineyards, and almond orchards) representing diverse environmental conditions and FMPs. The model tests indicated that DNDC was capable of predicting seasonal and annual total N2O emissions from these cropping systems, and the model's performance was better than the Intergovernmental Panel on Climate Change emission factor approach. DNDC also captured the impacts on N2O emissions of nitrogen fertilization for wheat and lettuce, of stand age for alfalfa, as well as the spatial variability of N2O fluxes in vineyards and orchards. DNDC overestimated N2O fluxes following some heavy rainfall events. To reduce the biases of simulating N2O fluxes following heavy rainfall, studies should focus on clarifying mechanisms controlling impacts of environmental factors on denitrification. DNDC was then applied to assess the impacts on N2O emissions of FMPs, including tillage, fertilization, irrigation, and management of cover crops. The practices that can mitigate N2O emissions include reduced or no tillage, reduced N application rates, low‐volume irrigation, and cultivation of nonleguminous cover crops. This study demonstrates the necessity and potential of utilizing process‐based models to quantify N2O emissions from regions with highly diverse cropping systems.

Nitrous oxide emissions from soils amended by cover-crops and under plastic film mulching: Fluxes, emission factors and yield-scaled emissions

Assessment of nitrous oxide (N2O) emission factor (EF) for N2O emission inventory from arable crops fertilized with different nitrogen sources are under increased scrutiny because of discrepancies between the default IPCC EFs and low EFs reported by many researchers. Mixing ratio of leguminous and non-leguminous cover crop residues incorporation and plastic film mulching (PFM) in upland soil has been recommended as a vital agronomic practice to enhance yield and soil quality. However, how these practices together affect N2O emissions, yield-scaled emissions and the EFs remain uncertain. Field experiments spanning two consecutive years were conducted to evaluate the effects of PFM on N2O emissions, yield-scaled emissions and the seasonal EFs in cover crop residues amended soil during maize cultivation. The mixture of barley (Hordeum vulgare) and hairy vetch (Vicia villosa) seeds with 75% recommended dose (RD 140 kg ha−1) and 25% recommended dose (RD 90 kg ha−1), respectively, were broadcasted during the fallow period and 0, 25, 50 and 100% of the total aboveground harvested biomass that correspond to 0, 76, 152 and 304 kg N ha−1 were incorporated before maize transplanting. It was found that the mean seasonal EFs from cover crop residues amended soil under No-mulching (NM) and PFM were 1.13% (ranging from 0.81 to 1.23%) and 1.49% (ranging from 1.02 to 1.63%), respectively, which are comparable to the IPCC (2006) default EF (1%) for emission inventories of N2O from crop residues. The emission fluxes were greatly influenced by NH4+N, NO3−-N, DOC and DON contents of soil. The cumulative N2O emissions markedly increased with the increase in cover crop residues application rates and it was more prominent under PFM than under NM. However, the yield-scaled emissions markedly decreased under PFM compared to NM due to the improved yield. With relatively low yield-scaled N2O emissions, 25% biomass mixing ratio of barley and hairy vetch (76 kg N ha−1) under PFM could be recommended to enhance yield and to mitigate N2O emissions in an upland maize cropping system.

Susceptibility of cover crop plants to Fusarium virguliforme , causal agent of soybean sudden death syndrome, and Heterodera glycines , the soybean cyst nematode

Greenhouse studies were conducted to evaluate the susceptibility of cover crop species to infection by Fusarium virguliforme (Fv), a soilborne fungus that causes sudden death syndrome (SDS) of soybean (Glycine max [L.] Merr.), and the soybean cyst nematode (SCN; Heterodera glycines), both important soybean pathogens. In the SDS experiments, cover crops were planted in Fv-infested soil, and plants were assessed for fresh biomass, root rot severity, foliar symptoms, and amount of Fv DNA in roots. Inoculated alfalfa (Medicago sativa L.), crimson clover (Trifolium incarnatum L.), red clover (Trifolium pratense L.), and pea (Pisum sativum L.) had more root necrosis than the noninoculated controls, and Fv DNA quantities in roots did not differ from those found in soybean roots. Inoculated alfalfa, corn (Zea mays L.), crimson clover, oat (Avena sativa L.), red clover, sorghum (Sorghum bicolor L.), and turnip (Brassica rapa L.) plants had lower biomass compared to noninoculated controls, although corn, oat, and turnip had no root necrosis. Biomass reduction and root necrosis were not observed in inoculated hairy vetch (Vicia villosa Roth), false flax (Camelina sativa [L.] Crantz), millet (Pennisetum glaucum [L.] R.Br.), mustard (Brassica juncea L.), rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), triticale (Triticale hexaploide Lart.), and wheat (Triticum aestivum L.), and Fv DNA quantity in the roots of these species was lower than in soybean. These results suggest that the legume species tested are hosts of Fv whereas grasses and Brassicas spp. are nonhosts or poor hosts. In the SCN experiment, select leguminous and nonleguminous cover crop plants were grown in soil naturally infested with SCN, and the number of females formed per root after 30 days was determined. There were very few (zero to five) SCN females on the roots of multiple varieties of leguminous cover crop species studied. No females were recovered from the roots of any of the nonleguminous species studied, except for a single female on four plants from three different species. None of the cover crop plants studied were susceptible hosts for SCN. With the increasing interest in using cover crops as a soil conservation practice in corn–soybean production systems, it is important to understand how this practice would impact major soybean diseases. Knowing the impact that cover crops may have on SDS and SCN is important to help farmers make better decisions when planting cover crops in areas with history of these diseases.

Winter cover crops alter methanotrophs community structure in a double-rice paddy soil

Methanotrophs play a vital role in the mitigation of methane emission from soils. However, the influences of cover crops incorporation on paddy soil methanotrophic community structure have not been fully understood. In this study, the impacts of two winter cover crops (Chinese milk vetch (Astragalus sinicus L.) and ryegrass (Lolium multiflorum Lam.), representing leguminous and non-leguminous cover crops, respectively) on community structure and abundance of methanotrophs were evaluated by using PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) and real-time PCR technology in a double-rice cropping system from South China. Four treatments were established in a completely randomized block design: 1) double-rice cropping without nitrogen fertilizer application, CK; 2) double-rice cropping with chemical nitrogen fertilizer application (200 kg ha–1 urea for entire double-rice season), CF; 3) Chinese milk vetch cropping followed by double-rice cultivation with Chinese milk vetch incorporation, MV; 4) ryegrass cropping followed by double-rice cultivation with ryegrass incorporation, RG. Results showed that cultivating Chinese milk vetch and ryegrass in fallow season decreased soil bulk density and increased rice yield in different extents by comparison with CK. Additionally, methanotrophic bacterial abundance and community structure changed significantly with rice growth. Methanotrophic bacterial pmoA gene copies in four treatments were higher during late-rice season (3.18×107 to 10.28×107 copies g–1 dry soil) by comparison with early-rice season (2.1×107 to 9.62×107 copies g–1 dry soil). Type I methanotrophs absolutely predominated during early-rice season. However, the advantage of type I methanotrophs kept narrowing during entire double-rice season and both types I and II methanotrophs dominated at later stage of late-rice.

Topography Mediates the Influence of Cover Crops on Soil Nitrate Levels in Row Crop Agricultural Systems.

Supplying adequate amounts of soil N for plant growth during the growing season and across large agricultural fields is a challenge for conservational agricultural systems with cover crops. Knowledge about cover crop effects on N comes mostly from small, flat research plots and performance of cover crops across topographically diverse agricultural land is poorly understood. Our objective was to assess effects of both leguminous (red clover) and non-leguminous (winter rye) cover crops on potentially mineralizable N (PMN) and levels across a topographically diverse landscape. We studied conventional, low-input, and organic managements in corn-soybean-wheat rotation. The rotations of low-input and organic managements included rye and red clover cover crops. The managements were implemented in twenty large undulating fields in Southwest Michigan starting from 2006. The data collection and analysis were conducted during three growing seasons of 2011, 2012 and 2013. Observational micro-plots with and without cover crops were laid within each field on three contrasting topographical positions of depression, slope and summit. Soil samples were collected 4–5 times during each growing season and analyzed for and PMN. The results showed that all three managements were similar in their temporal and spatial distributions of NO3 —N. Red clover cover crop increased by 35% on depression, 20% on slope and 32% on summit positions. Rye cover crop had a significant 15% negative effect on in topographical depressions but not in slope and summit positions. The magnitude of the cover crop effects on soil mineral nitrogen across topographically diverse fields was associated with the amount of cover crop growth and residue production. The results emphasize the potential environmental and economic benefits that can be generated by implementing site-specific topography-driven cover crop management in row-crop agricultural systems.

Contribution of Cover Crops to the Productivity of Maize‐Based Conservation Agriculture Systems in Zimbabwe

ABSTRACTResearch in Latin America has shown numerous benefits of rotations with cover crops under conservation agriculture (CA) to manage N and weeds; however, information from Zimbabwe is limited. The objective of the study was to investigate the benefits of rotating maize (Zea mays L.) with different leguminous and nonleguminous cover crops on maize yield, weed management, and decomposition rates of residues. A study was conducted at University of Zimbabwe (UZ), Domboshawa Training Centre (DTC), and two sites at Henderson Research Station (HRS) with contrasting soil types (clay and sand) from 2008 to 2014. Nine different cover crops were rotated with maize and compared with maize monocropping. During the 2012 to 2013 and 2013 to 2014 cropping seasons, a litter‐bag experiment was set within the experiment at UZ and DTC to investigate residue decomposition rates. Decreases in weed numbers of up to 94% were observed in maize–black sunnhemp (Crotalaria juncea L.) treatment at DTC. At UZ, maize after jack‐bean [Canavalia ensiformis (L.) DC.] (7823 kg ha−1) showed up to 61% more yield than continuous maize (4851 kg ha−1). Maize yields after fodder radish (Raphanus sativus L. var. oleiformis Pers.) were, in most cases, not significantly different from those of uniform maize. Decomposition rates were faster in leguminous residues, with velvet‐bean [Mucuna pruriens (L.) DC. var. utilis (Wall. ex Wight) Baker ex Burck] residues being generally the fastest and therefore not suitable for ground cover. Despite the positive effects of rotations, not a single cover crop was identified that provided all the benefits. There is need to characterize niches for specific cover crops within the farming system to assist farmers in their choices and spatial arrangements of cover crops on their farms.

Biomass yield and nitrogen content of annual energy/forage crops preceded by cover crops

In order to reduce input costs and improve sustainability of energy/forage crops in the northern Great Plains (NGP), preceding cover crops can be included into existing annual crop systems. The objective of the study was to determine biomass yield and quality of five annual energy/forage crops, grown after six different, leguminous and non-leguminous cover crop species. The experiment was conducted at two locations, Fargo and Prosper, ND, from 2010 to 2012. The experimental design was a randomized complete block with three replicates, in a split-plot arrangement where the preceding season's cover crop was the main plot and the forage crop was the sub-plot. Six cover crops, forage pea (Pisum sativum L.) cv. Arvika, Austrian winter pea (Pisum sativum ssp. arvense (L.) Poir), hairy vetch (Vicia villosa Roth.) forage radish (Raphanus sativus var. niger) cv. Daikon, turnip (Brassica rapa var. rapa) cv. Purple Top, and forage turnip (Brassica campestris x napus) cv. Pasja, were planted no-till on 8 to 9 August in 2010 and 2011 into oat (Avena sativa L.) residue. In the following spring, five energy/forage crops, maize (Zea mays L.), forage sorghum and sweet sorghum (Sorghum bicolor L.), oat, and barley (Hordeum vulgare L.) were planted no-till onto the winter-killed cover crops residue. Results across locations and years indicated forage pea and forage radish, produced the highest dry matter yield (3.3Mgha−1) in the fall. Total plant N content was 116kgNha−1 in forage peas and 76kgNha−1 in forage radish, respectively. Results across locations and years indicated all energy/forage crops had greater biomass yield, and total N content when preceded by a legume cover crop compared with a non-legume or the check, in the previous year. Forage sorghum had the highest average biomass yield among the five energy/forage crops, with 17.8Mgha−1, followed by sweet sorghum with 15.3Mgha−1. In conclusion, forage pea was the most suitable cover crop to provide additional N for the subsequent crops in the NGP. Forage sorghum and sweet sorghum can be considered as the most productive energy/forage crops, especially when preceded by a legume cover crop.

Effects of groundcover management on soil properties, tree physiology, foliar chemistry and growth in a newly established Fraser fir (Abies fraseri [Pursh] Poir) plantation in Michigan, United States of America

Incorporating cover crops into Christmas tree plantations may potentially improve soil fertility, tree growth and quality and be an alternative to commercial nitrogen (N) fertilizers. However, cover crops may compete with the trees for water and other nutrients than N. This study was carried out to assess whether soil fertility, tree survival and growth could be improved by incorporating leguminous and non-leguminous cover crops into the Fraser fir (Abies fraseri) production system. Dutch white clover (Trifolium pratense), alfalfa (Medicago sativa) and perennial ryegrass (Lolium perenne) were grown in a newly established Fraser fir plantation using two cover crop management practices; no banding (NB) by growing each cover crop throughout the entire plot and banding (B) by creating a 61 cm-wide bare zone centered on the tree rows. A conventionally-managed system (CONV) was used as a control. The cover crop aboveground biomass and N content were assessed. Soil available N (NO3− and NH4+) and N mineralization were measured at 0–15, 15–30 and 30–45 cm soil depths. Tree survival, growth, photochemical efficiency of photosystem II (Fv/Fm), branch water potential (Ψw) and foliar nutrients were also evaluated. Biomass production was as high as 13.9, 10.2 and 5.9 Mg DM ha−1 year−1 for clover, alfalfa and ryegrass, respectively. Cover cropping increased soil available N by 1.5- and 2.2-fold relative the CONV in the top soil layer in 2007 and 2008, respectively. Tree seedling survival and growth in the B and CONV systems were similar. In contrast, NB treatments resulted in poor seedling survival and growth relative to the B and CONV plots. Plant Ψw and Fv/Fm decreased significantly for A. fraseri seedlings on the NB treatments relative to their counterparts on the B and CONV plots. However, cover cropping had marginal effects on foliar nutrients. Cover cropping with banding can be an efficient strategy for maintaining productivity in Fraser fir Christmas plantations.

Cover crop effects on nitrous oxide emission from a manure-treated Mollisol

Agriculture contributes 40–60% of the total annual N 2O emissions to the atmosphere. Development of management practices to reduce these emissions would have a significant impact on greenhouse gas levels. Non-leguminous cover crops are efficient scavengers of residual soil NO 3, thereby reducing leaching losses. However, the effect of a grass cover crop on N 2O emissions from soil receiving liquid swine manure has not been evaluated. This study investigated: (i) the temporal patterns of N 2O emissions following addition of swine manure slurry in a laboratory setting under fluctuating soil moisture regimes; (ii) assessed the potential of a rye ( Secale cereale L.) cover crop to decrease N 2O emissions under these conditions; and (iii) quantified field N 2O emissions in response to either spring applied urea ammonium nitrate (UAN) or different rates of fall-applied liquid swine manure, in the presence or absence of a rye/oat winter cover crop. Laboratory experiments investigating cover crop effects N 2O emissions were performed in a controlled environment chamber programmed for a 14 h light period, 18 °C day temperature, and 15 °C night temperature. Treatments with or without a living rye cover crop were treated with either: (i) no manure; (ii) a phosphorus-based manure application rate (low manure): or (iii) a nitrogen-based manure application rate (high manure). We observed a significant reduction in N 2O emissions in the presence of the rye cover crop. Field experiments were performed on a fine-loamy soil in Central Iowa from October 12, 2005 to October 2, 2006. We observed no significant effect of the cover crop on cumulative N 2O emissions in the field. The primary factor influencing N 2O emission was N application rate, regardless of form or timing. The response of N 2O emission to N additions was non-linear, with progressively more N 2O emitted with increasing N application. These results indicate that while cover crops have the potential to reduce N 2O emissions, N application rate may be the overriding factor.

Changes of Soil Microbial Biomass Carbon and Nitrogen with Cover Crops and Irrigation in a Tomato Field

ABSTRACT In order to understand how soil microbial biomass was influenced by incorporated residues of summer cover crops and by water regimes, soil microbial biomass carbon (C) and nitrogen (N) were investigated in tomato field plots in which three leguminous and a non-leguminous cover crop had been grown and incorporated into the soil. The cover crops were sunn hemp (Crotalaria juncea L., cv ‘Tropic Sun’), cowpea (Vigna unguiculata L. Walp, cv ‘Iron clay’), velvetbean (Mucuna deeringiana (Bort) Merr.), and sorghum sudangrass (Sorghum bicolor × S. bicolor var. sudanense (Piper) Stapf) vs. a fallow (bare soil). The tomato crop was irrigated at four different rates, i.e., irrigation initiated only when the water tension had reached −5, −10, −20, or −30 kPa, respectively. The results showed that sorghum sudangrass, cowpea, sunn hemp, and velvetbean increased microbial biomass C by 68.9%, 89.8%, 116.8%, and 137.7%, and microbial N by 58.3%, 100.0%, 297.3%, and 261.3%, respectively. A legume cover crop, cowpea, had no statistically significant greater effect on soil microbial C and N than the non-legume cover crop, sorghum sudangrass. The tropical legumes, velvetbean and sunn hemp, increased the microbial biomass N markedly. However, the various irrigation rates did not cause significant changes in either microbial N or microbial C. Soil microbial biomass was strongly related to the N concentration and/or the inverse of the C:N ratio of the cover crops and in the soil. Tomato plant biomass and tomato fruit yields correlated well with the level of soil microbial N and inversely with the soil C:N ratio. These results suggest that cover crops increase soil microbiological biomass through the decomposition of organic C. Legumes are more effective than non-legumes, because they contain larger quantities of N and lower C:N ratios than non-legumes.