Winter Legume Cover Crops Research Articles

Economic and Biological Benefits of Intercropping Berseem Clover with Oat in Corn-Soybean-Oat Rotations

Sustainability of Iowa agriculture may require change from predominantly a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation to more diverse cropping systems. Alternative crops are vital for providing temporal diversity. Reincorporating small grains into a three-crop rotation with corn and soybean can provide greater temporal diversity, especially if a forage legume is included as a companion crop. A field study was established in 1991 on a Kenyon (fine-loamy, mixed, mesic Typic Hapludoll) soil to evaluate the economic and biological benefits of an oat (Avena saliva L.) crop underseeded with berseem clover (Trifolium alexandrinum L.) in a three crop rotation. Two rotation treatments were compared: (i) corn-soybean-oat and (ii) corn-soybean-oat intercropped with berseem clover. In 1992, 1993, 1994, and 1995, oat grain yield was not significantly changed when berseem clover was underseeded with the oat crop. However, in 5 yr, oat underseeded with berseem clover produced up to 70% more biomass (harvested material without the grain) than sole-crop oat straw. The biomass (40% oat straw and 60% berseem clover forage) also had adequate digestible material (51%) to be considered as low quality forage. Berseem clover regrowth after oat grain harvest produced an average 1.2 tons/acre of forage, which could have been harvested for hay or left in the field as green manure. During this trial, berseem clover regrowth was left as groundcover and green manure, which contributed an average of 39 lb N/acre to the succeeding corn crop. Corn grain yields following berseem clover were 10% higher over the trial period. Soybean grain yields were the same for both treatments. Intercropping berseem clover with oat returned an average of S39/acre more than sole-crop oat. This study demonstrated both economic and biological advantages for more diverse cropping practices.

Suitability of Sunn Hemp as an Alternative Late‐Summer Legume Cover Crop

AbstractThe tropical legume ‘Tropic Sun’ sunn hemp (Crotalaria juncea L.) may have potential as an alternative legume cover crop or as forage for cattle in southern temperate regions. This study determined dry‐matter production, chemical composition, and N release from sunn hemp residue under conventional and no‐tillage systems as might be used in corn (Zea mays L.) production. Sunn hemp was sown in mid‐August and mowed in early December on a Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudult) and a Lucedale fine sandy loam (fine‐loamy, siliceous, thermic Rhodic Paleudult) in Alabama (1991–1992). Mesh bags were used to determine residue decomposition and N release. Average dry‐matter production was 5.9 Mg ha−1 9 to 12 wk after planting. At mowing, residue N content averaged 126 kg ha−1. Residue overwintered on the soil surface until early April. During the first 4 wk following mowing, N release from residue was 50%. In April, N remaining in overwintered residue was only 38% of that after mowing in December (45 kg N ha−1). Nitrogen release from residue during the subsequent corn growing season was 13% in no‐tillage and 43% in conventional tillage. Sunn hemp produced sufficient dry matter to cover and protect the soil from erosion and provided sufficient N to benefit a succeeding summer crop. In addition, forage quality of leaves was suitable to provide late summer and fall grazing. Sunn hemp has potential to be managed as an alternative to winter legume cover crops in warm temperate regions.

Influence of management practices on soil organic matter, microbial biomass and cotton yield in Alabama's ?Old Rotation?

The “Old Rotation” cotton experiment was designed to aid farm managers in implementing rotation schemes that not only increase yield, but also improve soil quality. Six different crop rotation treatments were imposed since 1896. Rotations were: IA, cotton (Gossypium hirsutum L.) grown every year without a winter legume and without N fertilization; IB, cotton grown every year with a winter legume and without N fertilization; IC, cotton grown every year without a winter legume and with 134 kg N as NH4NO3 ha-1 year-1; IIA, 2-year cotton-corn (Zea mays L.) rotation with a winter legume and without N fertilization; IIB, 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 as NH4NO3; and III, 3-year cotton-corn- alternating soybean [Glycine max (L.) Merr.] or rye (Secale cereale L.) rotation with a winter legume and with 134 g N as NH4NO3 ha-1 year-1. Crimson clover (Trifolium incarnatum L.) was the winter legume cover crop. The 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 (IIB) and the 3-year cotton-corn soybean/rye rotation with a winter legume and with 134 kg N ha-1 year-1 (III) had higher amounts of soil organic matter, soil microbial biomass C and crop yield than the other four treatments. The cotton grown every year without a winter legume or N fertilizer (IA) had a lower amount of soil organic matter, soil microbial biomass C and N and cotton seed yield than all other rotations. In 1988 and 1992 cotton seed and legume yield were correlated in positive, curvilinear relationships with soil organic matter (r 2 ranged from 0.72 to 0.87). In most months, soil microbial biomass C and N was lower in the cotton grown every year without winter legumes or fertilizer (IA) than the other five rotations. In 1994, microbial biomass C and the Cmic:Corg ratio correlated in positive, curvilinear relationships with seed cotton yield (r 2=0.87 and 0.98, respectively). After 99 years of management the “Old Rotation” cotton experiment indicates that winter legumes increase amounts of both C and N in soil, which ultimately contribute to higher cotton yields. Microbial biomass C and the Cmic:Corg ratio are poor predictors of annual crop yield but may be an accurate indicator of soil health and a good predictor of long-term crop yield.

Winter Legume Cover Crop Benefits to Corn: Rotation vs. Fixed‐Nitrogen Effects

AbstractThe use of winter legume cover crops for erosion control and to provide additional N to the soil is well established. Other potential benefits to legume cover crops besides N additions have been recognized, but have not been quantified. The objective of this study was to separate the fixed‐N effects from the rotation effects in a winter legume cover cropping system. A field study was initiated in 1989 on a Norfolk loamy sand (fine, loamy, siliceous, thermic Typic Kandiudult) in east‐central Alabama. Corn (Zea mays L.) was grown following (i) ‘Tibbee’ crimson clover (Trifolium incarnatum L.), (ii) a partially ineffective‐nodulating crimson clover, CH‐1, (iii) rye (Secale cereale L.), and (iv) winter fallow. The plots were split into four rates of fertilizer N (0, 56, 112, and 168 kg N ha−1) in a split‐plot experimental plan. An evaluation of different methods of distinguishing fixed‐N vs. rotation effects of the winter annual legume cover crop to a subsequent corn crop was made. Regression analysis of the effect of N application rates on N2 fixation by crimson clover (fertilized with 45 kg N ha−1) indicated that CH‐1 clover biomass contained approximately 40 and 101 kg N ha−1 and Tibbee clover contained approximately 51 and 119 kg N ha−1 in 1990 and 1991, respectively. In both years of the study, crimson clover substantially increased corn yield compared with winter fallow, with a yield increase at the highest fertilizer N application level of 7 and 22% for 1990 and 1991, respectively. Estimates of yield increases due to rotation ranged from negative to 40%. The data indicated that winter cover crops improve corn yield and that besides soil N availability, there was very little difference between the beneficial effects of clover and the rye cover crops to corn.

Amelioration of soil compaction by a cover-crop for no-tillage lettuce production

Excessive cultivation in many horticultural areas results in soil structural decline and poor utilization of water and nutrients. There are no reliable techniques for growing irrigated vegetables without cultivation. This work explores the hypothesis that a winter legume cover-crop can overcome the soil limitations of no-tillage and provide an alternative to excessive cultivation in the vegetable industry. We grew lettuce (Lactuca sativa) under no-tillage in field trials on a sandy loam soil following a bare winter fallow or a cover-crop of subterranean clover (Trifolium subterraneum), and compared this with cultivation by rotary hoe. The clover died naturally in early summer or was desiccated in the spring to form a mulch of at least 5 t ha-1 on the soil surface. The experiment was carried out over a 2.5 year period. The first crop was grown during hot weather and the soil in the no-tillage treatments was only moderately compacted. The yield of lettuce was similar in the no-tillage and cultivated treatments, and increased by about 30% when a mulch was added to each treatment. The soil was artificially compacted after the first crop. The second crop was grown 18 months later, during cooler spring weather, and following two further cover-crops. The yield of no-tillage lettuce was only 40% of that obtained with cultivation. Yield in the no-tillage treatment was doubled in two different ways: (1) by the addition of a surface mulch, and (2) through changes to soil structure stimulated by a cover-crop in the absence of a mulch. The experiments showed that a well-managed cover-crop can significantly ameliorate a compacted sandy soil by modifying soil temperature, soil strength, and by stimulating the formation of biopores.

The Influence of Winter Legume Cover Crops on Soilborne Plant Pathogens and Cotton Seedling Diseases

The influence of winter legume cover crops on soilborne plant pathogens and seedling diseases of cotton was examined at two locations over 2 yr. The Clarkedale site was a long-term cover crop experiment established in 1972. The Lewisville site was established in a production field with a history of cotton monoculture. Soil populations of Thielaviopsis basicola and isolation frequency of this pathogen from cotton seedlings were reduced following a hairy vetch cover crop compared with winter fallow at Clarkedale, the only site with moderate to high soil populations of this pathogen. Isolation of Rhizoctonia solani from cotton seedlings and soil populations of Rhizoctonia spp. at planting were increased following hairy vetch compared with winter fallow at Lewisville. A similar trend was found for Rhizoctonia spp. following hairy vetch at Clarkedale. Soil populations of Pythium spp. were greater at both locations following a legume cover crop compared with winter fallow; however, no differences among cover crop treatments were found for isolation frequency of this genus from seedlings. The other cover crop treatments (common vetch, hairy vetch plus rye, or crimson clover plus rye) were intermediate between winter fallow and hairy vetch in their influence on pathogen populations and isolation frequency. Bacterial and fungal populations were greater in the cropping system containing a hairy vetch cover crop compared with winter fallow at Clarkedale. The influence of winter legume cover crops on the seedling disease complex depended on the prevalent pathogens at each location. Winter legumes do not appear to increase the risks of cotton seedling diseases sufficiently to deter their use in reducing soil erosion and providing nitrogen to a subsequent cash crop, and can reduce the risk of black root rot

Profitability of No-Tillage Corn following a Hairy Vetch Cover Crop

Hairy vetch (Vicia villosa Roth subsp. villosa), as a winter legume cover crop, fixes atmospheric N 2 for following crops and improves the soil. A 3-yr field study (1985-1988) was conducted in the Maryland Coastal Plain and Piedmont to assess the agronomic and economic characteristics of a hairy vetch cover crop on no-till corn (Zea mays L.) compared with corn systems preceded by winter fallow and winter wheat (Triticum aestivum L.) cover crops. No-till corn following a hairy vetch cover crop yielded more than no-till corn following winter fallow and winter wheat cover crops at comparable fertilizer N rates in the Coastal Plain and Piedmont over 3 yr. The highest yielding combinations were a hairy vetch cover crop with 120 Ib N/acre in the Coastal Plain and a hairy vetch cover crop with 40 Ib N/acre in the Piedmont [...]

Residual Effects of Interseeded Hairy Vetch on Soil Nitrate-Nitrogen Levels

Increased use of winter legume cover crops has renewed interest in legume N mineralization patterns. This study was conducted to monitor the residual effect of a hairy vetch (Vicia villosa Roth) cover crop and fertilizer N on surface soil NO3-N concentration in no-till and conventional-till corn (Zea mays L.) in northeastern Nebraska on a Nora silty clay loam (fine-silty, mixed, mesic Udic Halplustoll). The experimental design was a split-split-split plot with three replicates. Main plots of conventional tillage and no-till were split into 0, 67, and 134 kg N ha−1 with and without hairy vetch. Soil samples were taken from the 0− to 7.5− and 7.5− to 15−cm depths five times during the 1987 growing season and three times in 1988. Inclusion of a hairy vetch cover crop interseeded during the previous growing season increased soil NO3-N concentration in the surface 7.5 cm between 50 and 64 d after corn planting and in the 7.5- to 15-cm soil layer between 50 and 78 d after corn planting during 1987. In 1988 (a dry growing season), hairy vetch did not significantly increase soil NO3-N concentration in the 0- to 7.5-cm soil layer at any sampling time, but did increase soil NO3-N concentration in the 7.5- to 15-cm depth 103 d after planting. This increase in soil NO3-N concentration occurred in hairy vetch plots after silking, which probably resulted in the additional N not being available for plant growth in 1988. Increased available N resulting from a legume cover crop like hairy vetch may be beneficial in N management programs in lower rainfall areas of the USA when amounts of precipitation are adequate for plant growth and N mineralization.

Legume Cover Crops as a Nitrogen Source for No‐Till Corn and Grain Sorghum

AbstractIncreasing use of conservation tillage has brought about a renewed interest in growing winter legume cover crops. Field experiments were conducted to determine the fertilizer N equivalency of hairy vetch (Vicia villosa Roth), bigflower vetch (Vicia grandiflora W. Koch var. Kitailbeliana), and rye (Secale cereale L.) to no‐tillage corn (Zea mays L.) and grain sorghum [sorghum bicolor (L.) Moench]. A fallow treatment, consisting of stalk residue only, was used as a comparison. Fertilizer N rates for corn were 0, 50, or 100 kg N ha−1 for 1980 to 1983 and 0, 85, or 170 kg N ha−1 for 1984 to 1987. Hairy vetch produced the most cover crop dry matter with the highest percentage of N. During 1980 to 1983, corn grain yields were significantly higher with the vetch treatments than with rye or fallow treatments at the 0 and 50 kg N ha−1 rates with a tendency toward higher yields at the 100 kg N ha−1 rate. During 1984 to 1987, corn yields from the vetch treatments were significantly higher than the other cover treatments at all N levels. Grain sorghum, like corn yields, were greater with the vetch treatments than with the rye or fallow treatments, although the bigflower vetch treatment was not significantly higher than the fallow treatment at the 170 kg N ha−1 rate. The estimated fertilizer‐N equivalency of the hairy vetch‐N in the corn experiment was 75 kg N ha−1 and bigflower vetch was 65 kg N ha−1. Fertilizer N equivalency values in the grain sorghum experiment were estimated to be 125 kg N ha−1 for hairy vetch and 135 kg N ha−1 for bigflower vetch.

Winter Legume Effects on Soil Properties and Nitrogen Fertilizer Requirements

AbstractWinter legume cover crops have been shown to provide significant amounts of N to subsequent nonleguminous crops, but benefits beyond those directly attributed to N are rarely cited. A 3 yr field study at two Georgia locations utilizing a randomized, complete‐block, split‐plot design with four replications was begun in 1985 to measure the equivalent fertilizer N supplied by winter annual legumes and to monitor changes in soil physical and chemical properties. Corn, Zea mays L. was grown on a Rome gravelly clay loam soil (fine‐loamy, mixed, thermic Typic Hapludult) at the Limestone Valley location, and grain sorghum [Sorghum bicolor (L) Moench] on a Greenville sandy clay loam soil (clayey, kaolinitic, thermic Rhodic Paleudult) in the Coastal Plain. Main plots were cover crops of hairy vetch (Vicia villosa Roth.), crimson clover (Trifolium incarnatum L), berseem clover (Trifolium alexandrinum L), winter pea [Pisum sativum subsp. arvense (L) poir], wheat (Triticum aestivum L), and fallow. Subplots were broadcast NH4NO3 fertilizer of varying rates. Hairy vetch and crimson clover replaced the greatest amount of fertilizer N averaging 123 and 99 kg N ha−1, respectively. More water‐stable aggregates were found following cover crops than fallow in the 0‐ to 0.025‐m depth at the Coastal Plain location. Higher infiltration rates were found following cover crops than fallow at both locations and infiltration rates were greater following hairy vetch than following wheat at the Coastal Plain site. An adapted winter legume cover crop can replace all of the fertilizer N necessary for optimum rain‐fed grain sorghum and up to two‐thirds of that required for corn production, and improve soil physical properties.

Subterranean Clover Cover Crop Used to Increase Rice Yield

AbstractManagement systems for flooded rice (Oryza sativa L.) production that include a winter legume cover crop and no‐till planting are of interest to farmers seeking lower‐cost production methods. Field experiments were performed at Crowley and Baton Rouge, LA. The purpose was to determine the effects of N fertilization (0, 56, 112, and 168 kg urea‐N ha−1) and tillage (rototilling or no‐tillage) on the yield and yield components of rice planted in fallow plots or in plots containing subterranean clover (Trifolium subterraneum L.) that had produced mature seed. Rice was dry‐seeded 1 wk after clover was desiccated with an herbicide or tilled into the soil. A permanent flood was established 30 d after planting. The presence of a clover cover crop increased rice yields about 10% in tilled and no‐till plots receiving various rates of N fertilizer. Flag‐leaf N concentrations and the amounts of total N assimilated into above‐ground biomass at harvest were greater in rice after clover than in rice after fallow, but the presence of a winter clover cover did not reduce the amount of N fertilizer required to produce maximum yield. The maximum yields of rice obtained by no‐till management were similar to or greater than those obtained by tillage. After rice harvest, stands of reseeded subterranean clover were better in no‐till plots than in plots where clover residues had been incorporated into the soil prior to rice planting.

Influence of legume cover crops and conservation tillage on soil populations of selected fungal genera

The influence of winter legume cover crops and of tillage on soil populations of fungal genera containing plant pathogenic species in the subsequent summer sorghum crop were examined in field studies. Legume cover crops significantly increased populations of Pythium spp. throughout the sorghum crop compared with a rye cover crop or no cover crop. This stimulation of the populations of Pythium spp. was not solely due to colonization of cover-crop residue, as populations were significantly greater at the time the legume cover crop was desiccated. Removal of aboveground residue generally decreased populations of Pythium spp. in soil. Incorporation of residue by tillage increased populations of Pythium spp. at some sampling dates. Legumes differed in the magnitude of stimulation, with hairy vetch stimulating Pythium spp. more than crimson clover. Cover crop treatments did not consistently influence soil populations of Fusarium spp., Rhizoctonia solani, Rhizoctonia-like binucleate fungi, or Macrophomina phaseolina. Macrophomina phaseolina populations were significantly greater under no tillage.

Legume Cover Crops for Improving Crop and Soil Management in the Southern United States

Abstract Legumes were an important component of crop rotations in the southern United States before World War II. In the post-war years, however, inexpensive and abundant fertilizer N diminished the role of N-fixing plants in cropping systems. There has been little research since 1960 on winter legumes in terms of their contribution to soil and crop management. Recent escalated costs of fertilizer N manufacture and concern over soil erosion has renewed interest in legumes and their role in cropping systems. Winter legume cover crops may provide significant quantities of fixed N while conserving soil and water resources and sustaining or improving soil productivity. This review presents both old and new information on the role of legumes in improving soil and crop management, particularly in the southern United States.

Winter Legumes as a Nitrogen Source for No‐Till Grain Sorghum1

AbstractBecause winter legume cover crops may provide significant quantities of N while conserving soil and water resources, the role of legumes in conservation tillage production systems warrants renewed attention. The objectives of this study were (i) to determine the N contribution of several legumes to a subsequent crop of grain sorghum [Sorghum bicolor(L.) Moench] under no‐tillage management and (ii) to determine the influence of legume cover crops on soil fertility status. A field experiment was conducted in which four winter legumes, one nonlegume, and a no cover crop treatment were studied over a 3‐yr period. In addition, four fertilizer N rates (0, 28, 56, and 112 kg N ha−1) were applied to no‐till grain sorghum. Grain sorghum did not respond to fertilizer N when following a legume cover crop but responded to as much as 99 kg N ha−1when following a nonlegume cover crop or no cover crop. A mean estimate of 72 kg N ha−1was obtained for the fertilizer N replaced by the legume. The effects of the legume cover crops on soil fertility status included: (i) a lower pH, (ii) a redistribution of K+to the soil surface from deeper in the soil profile, and (iii) a lower C/N ratio in soil organic matter. Since fertilizer N represents a sizeable portion of the fossil fuel energy required for nonleguminous row crop production, the estimated N contribution of legume cover crops represents a significant energy savings, enhancing the conservation value of a no‐tillage production system.