Crimson Clover Residues Research Articles

Cover crop quality and quantity influences organic corn performance more than soil context

AbstractCover cropping is a common practice among organic growers, well-known for its potential to supply nitrogen (N) to subsequent cash crops. Uncertainties and challenges exist in understanding how cover crops interact with soil properties and management practices across organic farms to supply N, and if such N supply is synchronous with subsequent cash crop N demand. An on-farm study examined cereal rye (Secale cereale) versus crimson clover (Trifolium incarnatum) planted before corn (Zea mays L.) in five organic farms in Michigan with a range of soil properties and management practices. High quality crimson clover residue [Carbon (C):N ratio 15:1] was associated with higher soil inorganic nitrogen, corn chlorophyll content, tissue N content, and grain yields relative to low quality cereal rye residue (C:N ratio 25:1). There were several lines of evidence that low quality cereal rye residue coupled with substantial biomass and a dry season limited N release during peak corn N demand. Nitrogen uptake efficiency (NUE, ratio of total N removed by corn to total N input) was above 1 for corn farms with low soil organic matter (SOM), active N and C pools, and lower than 1 for farms with high SOM and active N and C pools. Overall, cover crop biomass and cover crop quality was a more important driver of corn performance than background SOM content in organic corn farms. Our research highlights the challenges of ensuring sufficient N supply in organic field production, and the importance of planting a legume cover crop before corn.

Biochemical composition of cover crop residues determines water retention and rewetting characteristics

AbstractWhen cover crop residues are left on the soil surface, their decomposition is mainly influenced by environmental conditions in residue layers, particularly residue water potential (ψresidue). Thus, models for surface residue decomposition in conservation tillage systems should include a sub‐module that can simulate hourly changes in ψresidue using available weather variables. The main goal of this study was to collect data to further improve a previously developed sub‐module within the Cover Crop Nitrogen Calculator (CC‐NCALC) that simulates water content and ψresidue in cover crop residues left on the soil surface. Specific objectives were to (1) evaluate the effect of degree of residue decomposition on the characteristic water release curves for cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.) residues, and (2) model the rate of rewetting of cereal rye and crimson clover residues by rainfall. Our results extended the data needed for equations to estimate regression parameters for water release curves of cereal rye and crimson clover residues based on changes in lignin concentration as residue decompose. Our results also indicated that the parameters of an equation describing residue wetting as a function of cumulative rainfall could be estimated from soluble carbohydrate concentrations in the residue. These results will be integrated into the ψresidue sub‐module of CC‐NCALC to further improve the estimation of hourly changes in of cover crop residues remaining on the soil surface.

Microbial processes and community structure as influenced by cover crop residue type and placement during repeated dry-wet cycles

Soil microorganisms play a critical role in cover crop (CC) residue decomposition and nutrient cycling in agroecosystems. However, the impact of CC residue management and dry-wet cycles on soil and residue microbiota and their potential ecosystem functions is largely unknown. To fill these knowledge gaps, an incubation experiment was conducted with two CC residues, crimson clover (Trifolium incarnatum L.) and cereal rye (Secale cereale L.), and two residue placements (incorporated vs surface-applied). Each CCs by placement treatment was subjected to four dry-wet cycles (20-d each) for a total of 80-d. Crimson clover residues had higher water storage capacities than cereal rye, and the rate at which water was lost from surface-applied CC residues increased after each successive wetting event. Rapid drying of surface-applied CC residues quickly suppressed CO2 fluxes, which increased immediately upon rewetting. Incorporated CC residues maintained water content for longer duration than surface-applied residues and showed greater colonization by soil prokaryotes and saprophytic fungi. Thus, significantly more C and N were mobilized from incorporated residues by 80-d than from surface-applied residues (p < 0.05). Due to differences in residue chemistry, CC residue types have a stronger impact on soil N levels than residue placement. Thus, residue chemistry strongly influenced soil prokaryotic and fungal diversity, community structure, and functionality. While crimson clover-amended soils (N-rich environments) were dominated by copiotrophs, oligotrophs dominated cereal rye-amended soils (N-poor soil environments). On the other hand, residue placement may have a greater effect than residue type in determining residue microbiota, particularly prokaryotes. Based on these findings, we can conclude that the effect of residue placement on C and N mineralization during repeated dry-wet cycles is primarily explained by differences in water dynamics between incorporated and surface-applied CC residues.

Integrating Cover Crops and POST Herbicides for Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Control in Corn

Field experiments were conducted in 2013 and 2014 in Jackson, TN, to evaluate the efficacy of integrating cover crops and POST herbicides in corn to control glyphosate-resistant (GR) Palmer amaranth. Crimson clover and hairy vetch were planted in the fall and accumulated greater than 1,600 kg ha−1aboveground biomass by time of termination. Crimson clover and hairy vetch provided 62% and 58% Palmer amaranth control 14 d before application, respectively. POST herbicide treatments of glyphosate +S-metolachlor + mesotrione + atrazine, thiencarbazone-methyl + tembotrione + atrazine, and glyphosate + atrazine were applied when Palmer amaranth reached 15 cm tall. The herbicide treatments provided greater than 95% control of Palmer amaranth 28 d after application. In addition to Palmer amaranth suppression, corn was taller at V5 and V7 following a hairy vetch cover crop. Hairy vetch and crimson clover residues provided early season weed suppression because of biomass accumulation. Palmer amaranth in the nontreated control plots reached 15 cm 4 and 3 d ahead of the cover-treated plots in 2013 and 2014, respectively. This could potentially increase POST herbicide-application flexibility for producers. Results of this trial also suggest that cover crops alone are not a means of season-long control of GR Palmer amaranth. From a herbicide resistance-management perspective, the integration of cover crops with herbicide mixtures that incorporate multiple sites of action should aid in mitigating the further selection of herbicide resistance in Palmer amaranth.

Cover crop, tillage, and herbicide effects on weeds, soil properties, microbial populations, and soybean yield

A field study was conducted during 1997 to 2001 on a Dundee silt loam soil at Stoneville, MS, to examine the effects of rye and crimson clover residues on weeds, soil properties, soil microbial populations, and soybean yield in conventional tillage (CT) and no-tillage (NT) systems with preemergence (PRE)-only, postemergence (POST)-only, and PRE plus POST herbicide programs. Rye and crimson clover were planted in October, desiccated in April, and tilled (CT plots only) before planting soybean. Both cover-crop residues reduced density of barnyardgrass, broadleaf signalgrass, browntop millet, entireleaf morningglory, and hyssop spurge but did not affect yellow nutsedge at 7 wk after soybean planting (WAP) in the absence of herbicides. Densities of these weed species were generally lower with PRE-only, POST-only, and PRE plus POST applications than with no-herbicide treatment. Total weed dry biomass was lower when comparing CT (1,570 kg ha−1) with NT (1,970 kg ha−1), rye (1,520 kg ha−1) with crimson clover (2,050 kg ha−1), and PRE plus POST (640 kg ha−1) with PRE-only (1,870 kg ha−1) or POST-only (1,130 kg ha−1) treatments at 7 WAP. Soils with crimson clover had higher organic matter, NO3–N, SO4–S, and Mn, and lower pH compared with rye and no–cover crop soils. Total fungi and bacterial populations and fluorescein diacetate hydrolytic activity were higher in soil with crimson clover, followed by rye and no cover crop. Soybean yields were similar between CT (1,830 kg ha−1) and NT (1,960 kg ha−1), no cover crop (2,010 kg ha−1) and rye (1,900 kg ha−1), and rye and crimson clover (1,790 kg ha−1), but they were higher in PRE plus POST (2,260 kg ha−1) than in PRE-only (1,890 kg ha−1) or POST-only (1,970 kg ha−1) treatments.

405 No-till Vegetable Production in the Sand Hill Region of North Carolina

An experiment was established to determine the effect of different winter cover crops residues on yields of no-till pumpkins, yellow summer squash, and sweet corn. Residue treatments of fallow, triticale, crimson clover, little barley, and crimson clover + little barley were fall established and killed before spring no-till planting in 1998 and 1999. All summer vegetables received recommended fertilizer rates and labeled pesticides. Spring cover crop growth and biomass measurements ranged from 1873 to 6362 kg/ha. No-till sweet corn yields among the various cover residue treatments were greater where crimson clover and crimson clover + little barley (mixture) were used as residue in 1999, but not significantly different in 1998. No-till pumpkins showed the beneficial affect cover crop residue had on vegetable yields when dry conditions exist. Triticale and crimson clover + little barley (mixture) residues reduced soil water evaporation and produced more numbers of fruit per hectare (5049 and 5214, respectively) and greater weights of fruit (20.8 and 20.9 Mg/ha) than the other residue treatments (3725 to 4221 fruit/ha and 11.8 to 16.1 Mg/ha, respectively). No-till summer squash harvest showed steady increases in yield through time by all treatments with crimson clover residue treatment with the greatest squash yields and triticale and little barley residue treatments with the lowest squash yields. We found that sweet corn and squash yields were greater where legume cover residues were used compared to grass cover residues, whereas, pumpkin yields were higher where the greatest quantity of mulch was present at harvest (grass residues).

Soil fertility management as a factor in weed control: the effect of crimson clover residue, synthetic nitrogen fertilizer, and their interaction on emergence and early growth of lambsquarters and sweet corn

Previous experiments have shown that crimson clover (Trifolium incarnatum L.) used as a green manure may supply weed control benefits as well as nitrogen (N) to a subsequent crop of corn (Zea mays L.). In contrast to use of synthetic N fertilizer, use of fresh, incorporated crimson clover residue as an N source has been found to suppress lambsquarters (Chenopodium album L.) aboveground drymatter accumulation but to only temporarily reduce that of sweet corn. One possible cause of the clover's suppressive effect is the initial low availability of N that may occur after residue incorporation in the soil. A factorial treatment combination of +/− crimson clover residue and four rates of N fertilizer was used in two field experiments to further document the clover's influence on early plant growth and development and to test the hypothesis that low initial N availability is responsible for the clover's previously observed suppressive effects. The presence of crimson clover residue was found to reduce total emergence of lambsquarters by 27%, while application of N fertilizer increased lambsquarters emergence by almost 75%. Lambsquarters emergence was also delayed by the residue treatment. Addition of N did not alleviate the clover's suppressive effect on total emergence or emergence rate of lambsquarters. Sweet corn emergence and emergence rate differed by less than 5% in 0 N/+residue and 0 N/−residue treatments. Applications of N to residue plots suppressed rather than enanced sweet corn emergence. Lambsquarters aboveground biomass accumulation was 46% tower in the residue than nonresidue treatments at 23 days after planting (DAP) and remained 26% lower at 53 DAP. Addition of N did not alleviate the suppressive effect of the clover residue on lambsquarters aboveground drymatter accumulation. Sweet corn aboveground biomass accumulation was not affected by the presence of the clover residue. The results of the experiments indicate that the suppressive effect of crimson clover residue on lambsquarters emergence and growth is not attributable to initial low availability of N. However, given the stimulatory effect of N fertilizer on lambsquarters development, use of crimson clover as an N source would appear to provide weed control benefits both as a direct suppressant of weed emergence and growth and as a substitute for fertilizer N.

Carbon and Phosphorus Losses from Decomposing Crop Residues in No‐Till and Conventional Till Agroecosystems

AbstractAn increased knowledge of crop residue decomposition characteristics is a critical component for nutrient cycling studies in agroecosystems. Carbon and P losses from shoot residues of maize (Zea mays L.), wheat [Triticum estivum (L.), emend. Thell], soybean [Glycine max (L.) Merr.], and shoot and root residues of crimson clover (Trifolium incarnatum L.) were compared in no‐till and conventional till systems. Grain crop residues were generally collected from senescent plants following harvest and placed in fiberglass mesh litter bags. Soybean leaf residues, however, were sampled following preharvest abscission, while crimson clover residues were collected at spring anthesis and buried only in a conventional till system. Generally, the changes in C and P content of residues were best described by exponential and/or logarithmic functions. Losses of C and P from crop residues were consistently greater, and more rapid when residues were buried vs. left on the soil surface. Crimson clover shoots lost C and P more rapidly than root residues. Generally, greater initial losses of P than of C occurred in most residues. The lack of correlation between C and P losses is believed to be due to an inital and probably variable inorganic P content that is readily leached prior to the decomposition and mineralization losses of C. Differences in the rate and magnitude of C losses were related to seasonal effects, the initial N and P content, and/or the proportional amount of lignin in the plant residues. Tillage is clearly an important regulator or driving variable for element cycling in agroecosystems.

Timing Nitrogen Applications for Corn in a Winter Legume Conservation‐Tillage System

AbstractFertilizer N efficiency of corn (Zea mays L.) in conservation‐tillage systems with winter legumes such as crimson clover (Trifolium incarnatum L.) can possibly be improved by better synchronization of legume‐N release, fertilizer‐N application time, and crop demand for N. The objective of this 3‐yr (1986‐1988) field experiment was to determine the effect of N application time on dry matter accumulation, N uptake, and grain yield of corn grown in a winter legume conservation‐tillage system. Corn was planted with unit planters into crimson clover residue following in‐row subsoiling. The clover was killed at midbloom every year. Treatments were a factorial arrangement of fertilizer N rates and application time. Nitrogen as NH4NO3 was broadcast at rates of 34, 67, and 134 kg ha−1. Zero‐N checks were also included in both clover and rye (Secale cereal L.) plots. Application times were at planting, or 3, 6, or 9 wk later. In addition, split applications (1/3 at planting and the remainder 6 wk later) of the 67 and 134 kg N ha−1 rates were included. In 2 of 3 yr, dry matter accumulation was not affected by N application time. In 1987, however, dry matter production was greater when N was applied at planting compared to split applications or applications later than 3 wk after planting. Application time affected N uptake patterns during the growing season, but generally did not affect total N uptake at the end of the season. With the exception of the first year, split N applications resulted in equivalent or reduced N uptake compared to application of all N at planting. Based on linear regression models, maximum yield was obtained with 134, 116, and 93 kg N ha−1 in 1987, 1988, and 1989, respectively. After the first year, applying N later than 6 wk after planting reduced grain yield and split applications of N were not effective in increasing grain yield. These results suggest that the fertilizer N requirement of corn grown in winter legume conservationtillage systems on Coastal Plain soils decreases with successive years in the system and that the optimum management practice for conservation of N, energy, time, and labor would be to apply all fertilizer N at planting.

Resource quality and trophic responses to simulated throughfall: Effects on decomposition and nutrient flux in a no-tillage agroecosystem

Effects of simulated throughfall additions on microbial and microfaunal abundances, decomposition and N, P, Ca, Mg and K flux from winter rye ( Secale cereale L.) and crimson clover ( Trifolium incarnatum L.) residues in a no-tillage agroecosystem were quantified during the summer of 1986. Clover residues, with higher initial nutrient concentrations and lower C-to-element ratios, had a greater rate of decomposition, greater net mineralization and higher mean concentrations of all five elements than rye. Overall mean densities of both fungi and bacteria were also greater on clover and these in turn supported greater overall mean densities of fungivore microarthropods and bacterivore nematodes. Throughfall additions to low resource quality rye residues enhanced microbial immobilization of N, P and Ca in the absence of high grazer abundances. Microfloral densities and nutrient retention were diminished under higher grazer-fauna densities. No consistent throughfall effects were observed for the higher resource quality crimson clover residues. Significantly lower net N mineralization from rye (0.95 mgg −1 of initial litter) vs clover (12.69 mgg −1 of initial litter) and enhanced N retention in throughfall-treated rye suggest the limiting nature of this element. The additional amounts of N and P retained in throughfall-treated rye residues over controls were greater than could be accounted for by throughfall inputs and suggest that low level nutrient additions may stimulate immobilization of elements from other sources.

Release of Nitrogen from Crimson Clover Residue under Two Tillage Systems

AbstractThe N contained in winter cover crops (particularly legumes) is a potentially important source of N for succeeding crops. The purpose of this study was to determine N release from crimson clover (Trifolium incarnatum L.) residue under no‐tillage and conventional tillage conditions. Residues contained in nylon mesh (53 µm) bags placed either on the surface of no‐tillage plots or buried at plowlayer depth in conventional tillage plots were removed for dry matter, C, and N determinations at 1, 2, 4, 8, and 16 weeks after placement in mid‐May. The rate of N disappearance was more rapid under conventional than no‐tillage conditions. The percentage of initial residue N remaining at 4 and 16 weeks under conventional tillage conditions was 40 and 31, respectively. The corresponding values for no‐tillage were 63 and 36% at 4 and 16 weeks. The C/N ratio of the residue remained relatively unchanged over the 16‐week period under no‐tillage conditions. However, under conventional tillage conditions, the C/N ratio declined from 15.9 to 12.7. Under humid, subtropical conditions, release of N from both surface and buried residue from winter legumes, is sufficiently rapid to be of significant benefit to the summer crop.