Wheat Cover Crop Research Articles

Tillage and Chlorpyrifos Treatment Effects on Peanut Arthropods—An Incidence of Severe Burrower Bug Injury

Abstract A 2-yr study was conducted on the effects of tillage and soil insecticide (chlorpyrifos) treatment on peanut arthropod pests. A 3 by 2 split-plot experiment with five replications was subjected to factorial ANOVA. Main plot treatments consisted of three tillage systems: conventional moldboard plow, strip tillage into a killed wheat cover crop, and strip tillage into corn stubble residue. Subplot insecticide treatments were granular chlorpyrifos applied at early pegging (growth stage R2) and untreated. Populations of corn earworn, Helicoverpa zea (Boddie), and velevetbean caterpillar, Anticarsia gemmatalis Hübner, were lower in strip tillage systems. Chlorpyrifos applications caused corn earworm outbreaks in all tillage systems, but these applications were more disruptive in strip tillage. Chlorpyrifos treatment also increased populations of fall armyworm, Spodoptera frugiperda (J.E. Smith), but had no measurable effect on velvetbean caterpillar populations. Pod damage from lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), and wire-worms, Conoderus spp., was lower in strip tillage systems, and chlorpyrifos suppressed pod damage in all systems. Threecornered alfalfa hopper, Spissistilus festinus (Say), damage to peanut was greater in the wheat residue strip tillage system. Chlorpyrifos treatment reduced threecornered alfalfa hopper damage in all systems. Spider mite injury was not affected by tillage, but chlorpyrifos treatments resulted in mite outbreaks in all tillage systems. Burrower bug, Pangaeus bilineatus Say, injury to peanut kernels was greater in the strip tillage systems in 1999; and burrower bug injury was suppressed in the strip tillage systems by chlorpyrifos treatment. There was a significant interaction effect for burrower bug injury between tillage and insecticide treatment. Incidence of tomato spotted wilt virus also was reduced by strip tillage. Use of an effective fungicide program and a 3-yr crop rotation out of peanut production probably obscured any potential tillage effects on fungal diseases (southern stem rot, Rhizoctonia limb rot, and leaf spot). However, chlorpyrifos treatment increased Rhizoctonia limb rot incidence. Weed populations were generally greater in strip tillage systems, but postemergence herbicides effectively eliminated any potential confounding effect on yield and grade. Yield was not affected by tillage in either year, and chlorpyrifos had no effect on yield in 1998. In 1999, however, chlorpyrifos increased yield in both strip tillage systems. Neither tillage nor insecticide treatment affected grade (percentage total mature kernels) in 1998, but in 1999 grade was highest in conventional tillage and grade was improved by chlorpyrifos treatment in strip tillage systems. Crop value losses of $249 and $388/ha were attributed to burrower bug injury in untreated corn and wheat residue strip tillage systems, respectively. This injury may have been an anomaly of drought conditions but, given the potential economic impact, burrower bug merits further study in conservation tillage peanut production.

Influence of Cover Crops and Inorganic Nitrogen Fertilization on Tomato and Snap Bean Production and Soil Nitrate Distribution

ABSTRACT Commercial vegetable production depends almost solely on inorganic fertilizers. In an era of environmental sensitivity, enrichment of soils with green manures and cover crops may reduce the dependence on these fertilizers while maintaining and enhancing crop yields. The objectives of this research were to determine (1) if supplemental nitrogen (N) at 60 or 120 kg · ha−1 following winter cover crops of wheat (Triticum aestivum L.) or crimson clover (Trifolium incarnatum L.) affect yield of tomato (Lycopersicon esculentum Mill.) and snap bean (Phaseolus vulgaris L.) grown in rotation; and (2) the distribution and retention of soil nitrates in the soil profile as affected by N fertilization and cover cropping. ‘Mountain Pride’ fresh market tomato and ‘Strike’ snap bean were grown in rotation for four years. Clover and wheat cover crops increased total marketable yield of ‘Mountain Pride’ tomato in one out of four years. Total marketable tomato yield increased as fertilizer N increased to 60 kg · ha−...

Performance of reduced-tillage cropping systems for sustainable grain production in Maryland

AbstractSustainable production systems are needed to maintain soil resources and reduce environmental contamination on erodible lands that are incompatible with tillage-intensive operations. A long-term cropping systems comparison was established at Beltsville, Maryland, on a site with 2 to 15% slope to evaluate the efficacy of sustainable strategies compatible with reduced-tillage systems. All systems followed a 2-year rotation of corn the first year and winter wheat followed by soybean the second year. Treatments included (1) no-tillage system with recommended fertilizer and herbicide inputs, (2) crownvetch living mulch system with similar inputs to the no-tillage system, (3) cover crop system including a hairy vetch cover crop before corn and a wheat cover crop before soybean with reduced fertilizer and herbicide inputs, and (4) manure system including crimson clover green manure plus cow manure for nutrient sources, chisel plow/disk for incorporating manure, and rotary hoe plus cultivation for weed control. Results from the initial 4 years demonstrated the relative productivity of these systems. Corn yields were similar in the no-tillage and cover crop systems in each year; both systems averaged 7.8 Mg ha-1 compared to 5.7 Mg ha-1 in both the crownvetch and manure systems. Wheat yields were highest in the manure system in the first 2 years and in the crownvetch system in the last 2 years. Soybean yields were highest in the cover crop system in all years. The manure system usually had lower yields than the highest yielding systems, partly because of competition from uncontrolled weeds. Several measures of the efficiency of grain production were evaluated. The no-tillage system produced the most grain per total vegetative biomass throughout the rotation. The cover crop system produced the most grain per unit of external nitrogen input and, along with the no-tillage system, had the highest corn water-use efficiency. The cover crop system also recycled the most vegetative residues and nutrients of all systems. No single system performed best according to all measures of comparison, suggesting that trade-offs will be required when choosing production systems.

PHOSPHORUS AVAILABILITY AND SPECIATION IN LONG-TERM NO-TILL AND DISK-TILL SOIL

Conservation tillage results in the concentration of plant-available P near the soil surface. We studied the effects of conservation tillage on P speciation by examining the distribution of P in inorganic and organic chemical pools. Depth-incremented soil samples were collected from long-term (9- and 10-yr) no-till (NT) and disk tillage (DT) systems cropped in corn (Zea mays L.) with a wheat (Triticum aestivum L.) cover crop. Rates of P were 0, 20, and 60 kg P ha−1 yr−1. Total P (PT), organic P (PO), and available P (Mehlich-3, M3-P; Olsen NaHCO3-pH 8.5, Olsen-P) were determined. P was also extracted from the following chemical pools: non-occluded Al-bound (Al-P), non-occluded Febound (Fe-P), occluded-reductant-soluble (CBD-P), and Ca-bound (Ca-P). Total P did not vary with depth, but was greater in NT than in DT and increased with P rate. Organic P increased with P rate in the 0- to 8-cm depth. Organic P was greater in NT plots in the 8- to 60-cm depths, averaging 75 mg kg−1 for NT and 48 mg kg−1 for DT plots. Mehlich 3-P and Olsen-P were greatest in the surface 4 cm and in the 60-kg P ha−1 plots, with higher levels observed in NT plots. On average, the forms of P (as a % of total P) in NT soil was 6.2% Al-P, 33.9% Fe-P, 33.9% CBD-P, and 4.7% Ca-P. Average P distribution in DT soils was 5.4% Al-P, 35.6% Fe-P, 31.3% CBD-P, and 5.1% Ca-P. The influence of tillage on P distribution was primarily limited to the soil surface, with the exception of Al-P, which was greater in the 8- to 30-cm depths of the NT plots. Because the impact of tillage was limited to a thin, soil surface layer (<4 cm), soil P-test rating would not be affected by tillage practice. However, the improper collection of soil samples from NT (i.e., too shallow) for P-testing may provide erroneous P-test results and fertilizer recommendations.

Ecology ofParatrichodorus allius and its relationship to the corky ring-spot disease of potato in the Pacific Northwest

Paratrichodorus allius, a vector of the tobacco rattle virus which causes the corky ringspot disease (CRS) in potato, was identified in soil samples from Oregon and Washington. Two populations from potato fields in Pasco, WA and Umatilla, OR reproduced successfully on alfalfa, wheat, and corn which are commonly rotated with potato, and most weeds associated with this crop in the Pacific Northwest. Greenhouse studies showed thatP. allius was sensitive to low soil moisture, and increased 10 and 100 fold on Samsun NN tobacco in soil above field capacity compared to 1/2 and 1/3 field capacity, respectively. Population dynamic studies for 1996 and 1997 on a potato-wheat cropping sequence showed thatP. allius declined after the winter wheat cover crop was disked in the spring of 1996, and remained low on potato at the 0–90 cm soil profile, with no evidence of downward migration. In 1997,P. allius declined early in the season on wheat, and remained low until June–July when it peaked before declining again. In soil columns,P. allius placed 30 cm below a confined tobacco root system was able to reach and transmit tobacco rattle virus. The nematodes below 30 cm transmitted the virus only when plant roots were allowed to grow to that depth.

RUNOFF AND SOIL LOSS FROM COTTON PLOTSWITH AND WITHOUT STIFF-GRASS HEDGES

The performance of grass hedges and the effectiveness of no-till cropping systems in reducing soil loss wasevaluated on standard erosion plots. No-till cotton with grass hedges, no-till cotton without grass hedges, conventional-tillcotton with grass hedges, conventional-till cotton without grass hedges, and no-till cotton without grass hedges but with awinter wheat cover crop produced average annual soil losses of 2.2, 5.2, 12.3, 48.5, and 2.0 t/ha, respectively. The annualratio of soil loss for no-till cotton plots with grass hedges to those without hedges averaged 0.43. The annual ratio of soilloss for conventional-till plots with grass hedges to without hedges was 0.25. Averaged over all plots (with and withoutgrass hedges, but not including winter cover plots), no-till plots reduced soil loss from conventional-till plots by 88%. Notillplots without grass hedges had 57% less soil loss than conventional-till plots with grass hedges. Although grasshedges were effective in reducing soil loss on erosion plots with similar cropping practices as compared to plots withouthedges, other studies of contoured grass hedges on field-sized areas are needed to determine their applicability on largerareas with greater concentrations of runoff.

Long-term evaluation of cover crop and strip-tillage on tomato yield, foliar diseases and nematode populations

A 6-yr (1987–1992) experiment, continuous on the same site, evaluated potential problems for yield, nematodes and diseases with tomatoes (Lycopersicon esculentum Mill.) grown in a strip-till system. Treatments consisted of conventional tillage (CT) and strip tillage (ST), rye (Secale cereale L.), wheat (Triticum aestivum L.) and perennial ryegrass (Lolium perenne L.) cover crops and a 2-yr rye-tomato rotation. Results of the first 5 yr indicated a decrease in tomato yield over time for both tillage treatments and cover crops. However, yield rebounded overall for treatments in 1992 with the highest yield in the rye-tomato rotation. We suspect this was a result of high populations of root-knot nematodes which collapsed over the winter of 1991/1992. Tomato yields were lower following wheat and perennial ryegrass than rye. In only 1 yr out of 6, strip-tillage reduced yield compared with conventional tillage. Bacterial speck/spot symptoms on foliage, although minor, were significantly greater in ST than in CT plots during the last 3 yr. No major trends in incidence and severity of bacterial and fungal diseases and of disorders of fruit were evident during the 5-yr period and neither fruit yield nor quality were significantly affected by these factors. Root-knot nematodes (Meloidogyne hapla Chitwood) were numerically less in the rye-tomato rotation than in other treatments; both root-knot and root lesion nematodes (Pratylenchus penetrans [Cobb]) tended to be less numerous under CT than under ST. Strip-tillage is feasible for machine harvest processing tomatoes. However, we are concerned about the tendency of tomatoes grown under reduced tillage to have lower yields than those grown under conventional tillage. More work is required on the interactions of cultivars, cover crops and nematodes in soil conservation systems. Key words: Tomato, bacterial speck/spot, foliar diseases, root-knot nematodes, root lesion nematodes, tillage

Winter wheat cover cropping, VA mycorrhizal fungi and maize growth and yield

The relationships among winter cover cropping, inoculum potential of vesicular-arbuscular mycorrhizal (VAM) fungi, and the growth and yield of a subsequent maize crop were investigated. In the first experiment, an autumn-sown winter wheat cover crop increased VAM fungal inoculum potential of a field soil as measured by an in situ maize bioassay during the following growing season. Infective extra-radical hyphal densities were significantly increased by cover cropping as interpreted from the effect of soil disturbance on infection of the maize bioassay plants. In a second experiment the following year, the winter wheat cover crop again increased VAM fungal inoculum potential as assessed by an in situ maize bioassay during the following growing season. Moreover, the degree of mycorrhizal infection of maize was correlated with maize growth and yield. This study suggests that the management of mycorrhizal fungi by cover cropping may be a useful practice in sustainable agriculture.

Starter fertilizer and the method and rate of potassium fertilizer effects on cotton grown on soils with and without winter grazing by cattle1

A three‐year field study was conducted on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudult) in North Alabama. The objective of the study was to evaluate the effects of winter grazing by cattle on the potassium (K) and starter fertilizer needs of cotton (Gossypium hirsutum L.) the following season. Grazed and non‐grazed treatments were established by planting a wheat (Triticum aestivum L.) cover crop in the fall and allowing cattle to graze half of the treatment area for 35 to 65 days in late winter‐early spring. After grazing, the grazed and non‐grazed wheat was killed and cotton was planted using a strip‐tillage system. Test areas had medium to high soil test ratings for K. Fertility treatments consisted of three rates of K (0, 37, and 74 kg K ha‐1), three methods of K application (surface broadcast; in‐row, band application at a depth of 30.5 cm; and surface banding using a spacing of 50.8 cm) and two rates of starter fertilizer (no starter and 168 kg#lbha‐l of a liquid 15–15–0). Seed cotton yields were affected by grazing of the winter cover crop prior to planting, but not by the method of K fertilizer application. During the two years that a yield reduction was observed, winter grazing reduced seed cotton yields by an average of 14%. Cotton responded to K rate only under the ungrazed system. During the first and second year of the test, an application of 37 kg K ha‐1 increased seed cotton yields by an average of 351 kg#lbha‐1. Starter fertilizer consistently gave slightly higher yields with a significant response occurring in two out of the three years.

Suppression of Phytophthora Blight in Bell Pepper by a No-Till Wheat Cover Crop

ABSTRACT Four mechanisms of dispersal of propagules of Phytophthora capsici were investigated through modifications in cultural practices and fungicide applications in field plots of bell pepper (Capsicum annuum). Dispersal of soil inoculum was suppressed, and final incidence of disease was 2.5 to 43% when stubble from a fall-sown, no-till, wheat cover crop was present. Final disease incidence was 71 to 72% and pathogen spread occurred within and across rows when all dispersal mechanisms were operative in plots of pepper planted into bare soil. Final disease incidence was 42 to 78% with black plastic mulch when a sporulating pepper fruit placed on the surface served as the source of initial inoculum. The fungicide metalaxyl applied in the irrigation system did not suppress within-row spread of surface inoculum from a sporulating fruit on plastic, but did limit across-row spread; final disease incidence in metalaxyl-treated plots was 11.5 to 14%. Pathogen dispersal mechanisms were modified most dramatically by the no-till cropping system. Thus, simple changes in cultural practices can have dramatic effects on the development of Phytophthora epidemics. Ecologically based disease management strategies have the potential to reduce our reliance on agrichemicals in this and similar pathosystems.

Fungal parasitism of soybean cyst nematode, Heterodera glycines (Nemata: Heteroderidae), in differing cropping-tillage regimes

A 2 year field study was designed to determine if soybean-wheat double-cropping and reduced or no tillage altered the soil mycoflora antagonistic to the soybean cyst nematode, Heterodera glycines. Six treatments were sampled monthly: disc 10 cm deep, followed by roller harrow; chisel plow 20 cm deep, followed by disc and roller harrow; moldboard plow 15 cm deep, followed by disc and roller harrow; non-tillage in the previous year's soybean stubble (NT-Soy); non-tillage in standing wheat cover crop (NT-1); non-tillage after wheat cover crop (NT-7). Each treatment had been applied to the same plots for up to 7 years. At appropriate monthly intervals, nematode cysts, females, and eggs were collected and assayed for the presence of fungi, which were identified to species-level taxa. Effects of cropping-tillage regimes on numbers of infective juveniles, numbers of eggs within cysts, and vertical distribution of cysts were determined. Similarities of egg and female mycofloras in this study to those of previous studies were examined. A total of 61 species-level fungal taxa were identified, along with 20 non-sporulating isolates distinguished from one another by appearance, growth pattern, and color. Fusarium solani was the most frequent of 47 species infesting cysts. Fusarium solani and F. oxysporum were the most frequent of 20 taxa isolated from field-collected females; in females produced on soybean plants grown in field soil in the greenhouse, F. oxysporum was the most frequent of 21 taxa. Paecilomyces lilacinus was the most common fungus among the 38 species isolated from eggs. For all fungi, percentages of parasitized females and eggs were similar in all treatments, but some treatments affected the parasitism rates of Paecilomyces lilacinus and Verticillium chlamydosporium. Parasitism of females was relatively low in July and August, but tripled in September. Egg parasitism was generally below 10% regardless of sampling time. Vertical distribution of cysts had no discernible effect on sampling precision, since cysts were concentrated in the top 25 cm in two dissimilar treatments (moldboard plow, NT-7). No consistent treatment effects were seen on densities of soil-borne infective juveniles in winter or spring, nor on average numbers of eggs per cyst. Based on similarity indices among this study and four previous studies, a biogeography of H. glycines mycofloras is proposed.

YIELD RESPONSE OF TOMATOES AND BEANS TO COVER CROPS OVER TIME

Tomatoes and beans were grown in rotation for 4 years with three cover crop treatments (bareground, wheat, and crimson clover) and three nitrogen rates (0, 60, and 120 kg N/ha). Over the course of the study, when no additional N was provided, lowest yields of tomatoes and beans were obtained with the wheat cover crop. With the highest N rate, however, there was little difference in yields of beans or tomatoes with any of the cover crop treatments. Considering the benefits associated with the use of cover crops, it is encouraging to see that with proper N amendment, yields obtained with cover crop systems can be comparable to conventional bareground systems.

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 [...]

POTENTIAL OF NO-TILL TOMATO PRODUCTION IN TENNESSEE

No-till (NT) culture has worked well with many agronomic crops; however, NT culture has been less successful with vegetable crops. `Mountain Pride' tomatoes were grown under (NT) and conventional-till (CT) culture at the Plateau Experiment Station. During the first two years of the study, both NT and CT plots were tilled in the fall and sowed in a winter wheat cover crop. In the third year of the study, a continuous NT culture was maintained. Tomato yields were identical from the two tillage practices in the first year. In the second year, yields were significantly higher from NT tomatoes than CT tomatoes. The trend reversed in the third year with CT producing significantly more yield than NT culture. In addition, NT tomato plants were stunted and roots were observed to grow laterally near the soil surface. Production of NT tomatoes following a winter wheat cover crop appears feasible; however, continuous NT was not promising.

Response of Dryland Soybeans to Nitrogen in Full-Season and Doublecrop Systems

The addition of N fertilizer to soybeans [ Glycine max (L.) Merr.] has been adopted by many producers in Virginia without knowing the potential yield benefit or loss. The objective of this study was to evaluate the response of soybeans (seed yield, maturity, plant height, lodging, seed weight, seed quality, and seed protein and oil content) to N applied near planting or at flowering in dryland full-season and doublecrop soybeans in Virginia's Coastal Plain soils. At Suffolk and Warsaw in 1988 and 1989, N treatments (0 and 25 lb N/acre of 30% urea NH4NO3 or UAN) were the whole plots and six maturity group (MG) V soybean cultivars were the subplots in a randomized complete block (RCB) experimental design. Nitrogen was applied with burndown herbicides to kill a winter wheat (Triticum aestivum L.) cover crop 21 to 42 d prior to planting full-season, no-till soybeans. In full-season studies in 1990, N (0 or 50 lb/acre) was applied to the soil surface at flowering to seven MG V cultivars in a RCB experimental design at Painter, Suffolk, and Warsaw. In doublecrop studies in 1990, N (control, 50 lb/acre at planting, or 50 lb/acre at flowering) was applied to the soil surface to seven MG V cultivars in a RCB experimental design at Painter, Suffolk, and Warsaw. Nitrogen significantly (P < 0.05) increased seed yield in only one of 10 enviroments, in which N (25 lb/acre) was applied before planting in a full-season system at Warsaw (a dry, low-yielding environment). In the doublecrop study at Suffolk, N significantly decreased seed yield when applied at flowering. Averaged over cultivars and environments, however, N did not significantly affect seed yield, maturity, lodging, plant height, seed quality, or seed oil content. Nitrogen (25 lb/acre applied before planting) significantly increased seed weight by 91 seeds/lb in the 1988 and 1989 studies, but did not affect seed weight in other tests. In the 1990 full-season tests, N applied at flowering significantly reduced seed protein content, but protein content was unchanged in the doublecrop tests. The cultivar × N, N × environment, and cultivar × N × environment interaction effects were not significant for any of the traits measured. These results suggest that a yield response to the addition of N (50 lb or less of N/acre) applied near planting or at flowering is unlikely in dryland soybeans in Coastal Plain soils of the southeast USA.

Effects of Wheat and Soybean Planting Date onHeterodera glycinesPopulation Dynamics and Soybean Yield with Conventional Tillage

The influence of winter wheat (Triticum aestivum) cover crop vs. winter fallow and of soybean (Glycine max) planting date on the populations dynamics of soybean cyst nematode (Heterodera glycines) (SCN) was determined during a 2-yr period. Numbers of SCN cysts, eggs, and second-stage juveniles were unaffected by wheat as opposed to winter fallow. Delay in soybean planting associated with double-cropping wheat, however, allowed for a significant decline in the numbers of SCN between early May and late June. Midseason densities of early May soybean plantings were greater than those of mid-June to late June plantings (.)

Evaluation of Conservation Tillage Cropping Systems for Cotton on the Texas Southern High Plains

T~e Texas Southern High Plains is a major coUon (Gossypi. um hirsulum L.) producing region in which a conventional till· age cotton monocuUure has evolved during the last 15 yr. Decreased profitability in cotton production in the region, as well 8S soil erosion concerns, have increased interest in conser· vation tillage systems. Initial adoption, acceptance, and widespread use of conservation Iillage systems will depend on how their economic perfonnance compares with current produc· Hon practices. In this study I two conservation tillage syslems for the Texas Southern High Plains (TSHP) were evaluated in 1986 and 1987 as a means of increasing profitability of coUon. Conservation tillage systems with and without a winter wheat (Triticum aes(ivum L.) cover crop were compared with conven· tional lilIage for cotton under both irrigated and dryhind COD· ditibns. The two conservation tillage systems either irrigated or dryland, increased profitability over currenl conventional till· age cotton practices used in the Texas Southern High Plains. Cotlon production in conservation tillage systems is a viable alternative for the Texas Southern High PlaiDS and its adop. lion could result in net revenue increases.

Variation of Runoff Characteristics Under Conservation Tillage Systems

ABSTRACT Tillage systems of cotton were studied for three years to determine differences between their effects on four parameters of runoff characteristics: runoff volume, runoff as percent of rainfall, peak flow rate, and SCS runoff curve number. The tillage systems included: reduced tillage without a cover crop (RT), reduced tillage with a winter wheat cover crop (RTC) and conventional tillage (CT). Three paired tests of the tillage systems (RT vs. RTC, CT vs. RT, and CT vs. RTC) were used to evaluate differences between effects. Statistical comparisons were conducted for three data sets separately; all storm events, storm events during the growing period (planting to the last harvesting), and storm events during the non-growing period. The runoff parameters were affected by the three tillage systems and these effects varied by the periods. Effects of the storm events on the runoff parameters were higher during the growing period than during the non-growing period. The RTC system was the most effective in reducing runoff volume and peak flow rate. All runoff parameters of the CT system other than the runoff as percent of rainfall were not different from those of the RT system. The SCS runoff curve number from RT and CT were higher than RTC for all storm events. No difference was found for this parameter between CT and RT.

Surface Runoff and Sediment Yield from Various Tillage Systems of Cotton

ABSTRACT THREE tillage systems of cotton were studied to determine their effects on surface runoff and sediment yield during growing period of 1985 and 1986 in the Tennessee Valley region of northern Alabama. They include; reduced tillage without a cover crop (RT), reduced tillage with a winter wheat cover crop (RTC) and conventional tillage (CT). Sediment yield was in the order of CT > RT > RTC in 1985. Runoff was the lowest from the RTC system followed by the CT and RT systems. In 1986, runoff from the CT was the lowest, followed by the RTC and RT, while sediment yield was in the order of CT > RTC > RT. The growth stage of cotton and the cultivations of the CT system influenced the patterns of runoff and sediment yield. More than 85% of the measured sediment yield and 50 to 70% of the runoff occurred during the first 2 months after planting. Seed cotton yields for all tillage systems were above average in 1985, but the highest yield occurred with the RT system. However, a drought during the critical stage of growth in 1986 caused reduced yield with all systems and the lowest yield occurred with the RT system.

The influence of winter wheat cover crop management on first-year Poa pratensis L. and Festuca rubra L. seed crops.

In field trials at 3 locations in the Netherlands in 1978-84, P. pratensis or F. rubra was sown simultaneously with a wheat cover crop in Sep.-Nov. or sown in Dec.-Apr. into an Oct. sown wheat crop. Wheat was sown at 110 or 160 kg/ha with between-row spacings of 12.5, 25.0, 37.5 or 50 cm, and given 140 kg N/ha as a single or split dressing. Light interception of several wheat cultivars was measured in concurrent government cultivar trials. Mean seed yield of P. pratensis was lowest with Feb.-Apr. sowing (0.80 t/ha) and highest with Sep. sowing (1.34 t). Mean F. rubra yield was lowest with Sep. sowing (1.26 t) and highest with Oct.-Nov. sowing (1.42 t/ha). Tillering of the grasses ceased if &gt;85% of the solar radiation was intercepted by the cover crop. Grass production was enhanced by using a wheat cultivar with a late-closing canopy, decreased cover crop sowing rate and split application of N. (Abstract retrieved from CAB Abstracts by CABI’s permission)