• Authors:
    • Voroney, R.
    • Vyn, T.
    • Janovicek, K.
  • Source: Agronomy Journal
  • Volume: 89
  • Issue: 4
  • Year: 1997
  • Summary: Research in Ontario, Canada in 1989, 1990, and 1995 evaluated no-till maize yield response to various preceding crops and examined whether in-row residue removal affected no-till maize response to rotation crops. The soil was an imperfectly drained loam (medium, mixed, weakly to moderately calcareous Typic Hapludalf). The preceding crops were: maize harvested for grain or whole-plant silage; hard red spring wheat; barley; red clover ( Trifolium pratense) cover crops, following barley, that were killed by spraying either 3 weeks (early-kill) or 1 day (late-kill) prior to sowing maize; canola [rape]; and soyabeans. In-row residue was either retained while sowing or cleared using planter-mounted, notched-disc row cleaners. Clearing in-row cover crop residue increased early-season maize growth and was associated with yield increases of 0.61 t ha -1 (8%) following early-killed red clover and 0.43 t ha -1 (6%) ( P = 0.10) following late-killed red clover. In 2 of 3 years, maize yields following early-killed red clover were similar to following soyabeans and greater than following grain maize, provided that in-row residue was cleared. Following the other crops, grain yield response to clearing in-row residue was smaller and less consistent over years. Preceding cropping affected early-season maize growth, with the largest plants at 5 weeks after sowing following either soyabeans or silage maize and the smallest following either red clover or grain maize. In 2 of 3 years, when preceding crop effects on grain yield were statistically significant, yields following either soyabeans or spring wheat were more than 1.05 t ha -1 (16%) higher than after grain maize. That yield increase occurred regardless of in-row residue placement. Removing maize stover by harvesting as silage increased maize yield by 0.86 t ha -1 (12%) over yield following grain maize. During 1995, maize yield following silage maize was less than after soyabeans, canola, barley, or wheat; thus, no-till maize yield response to rotation is not exclusively due to the presence of surface-placed stover. In-row residue placement and preceding cropping practices affected in-row soil temperature, but this could not totally account for the treatment effects on early-season maize growth and yields.
  • Authors:
    • Yoo, K. H.
    • Shirmohammadi, A.
    • Yoon, K. S.
    • Rawls, W. J.
  • Source: Journal of Environmental Science and Health . Part A: Environmental Science and Engineering and Toxicology
  • Volume: 31
  • Issue: 3
  • Year: 1996
  • Summary: A Continuous version of distributed parameter model, ANSWERS (ANSWERS 2000) was applied to a field-sized watershed planted to cotton in the Limestone Valley region of northern Alabama. The field was cultivated for three years with conventional tillage followed by three years of conservation tillage. Overall, the ANSWERS model simulated runoff and nutrient losses in surface runoff within an acceptable range for the conventional tillage system conditions in continuous simulation mode. But the sediment losses predicted by ANSWERS were initially on the order of fifteen times or more higher than measured regardless of tillage systems. In order to duplicate measured data, the sediment detachment coefficient of rainfall and flow had to be reduced for calibration. The model poorly predicted soluble nutrient losses for the conservation tillage system due to the model's weakness in representing the surface application of fertilizer under this practice. The model simulates only one soil layer, in which soil moisture, nutrient concentration, and soil characteristics are assumed homogeneous. Currently, the model does not consider vertical nutrient concentration variation in soil profile. During the conservation tillage system, corn stalk and the residue of a winter cover crop were spread on the soil surface. However, the model did not properly represent surface spreading of crop residue, thus the model was unable to consider the organic-nitrogen contribution from crop residue to the erodible soil surface. This resulted in poor prediction of sediment-bound TKN, especially for conservation tillage system.
  • Authors:
    • Kalejaiye, A. S.
    • Akinyemi, J. O.
  • Source: International Journal of Tropical Agriculture
  • Volume: 14
  • Issue: 1/4
  • Year: 1996
  • Summary: To protect the fragile soils of the tropics under the continuous cultivation systems, some farming conservation techniques have been advocated. A survey of the farming systems and the extent of erosion were carried out on a tropical rain forest of Nigeria with respect to the current status of the soil management practices. The results showed that ~85% of the farmers reported of the severe erosion problems on their farms. The rural farmers found that cover cropping was the most effective means of soil management and shifting cultivation was the most common farming system in this area. Approximately 83% of the farmers have their farms scattered at the different locations which makes the implementation of adequate soil conservation practices very difficult unless new and innovative cropping/farming systems are developed. The various strategies suggested for improving the farm conservation practices, particularly those that can be easily adopted by the rural farmers, are discussed.
  • Authors:
    • Schulbach, K. F.
    • Jackson, L. E.
    • Wyland, L. J.
  • Source: The Journal of Agricultural Science
  • Volume: 124
  • Year: 1995
  • Summary: Winter non-leguminous cover crops are included in crop rotations to decrease nitrate (NO3-N) leaching and increase soil organic matter. This study examined the effect of incorporating a mature cover crop on subsequent N transformations. A field trial containing a winter cover crop of Merced rye and a fallow control was established in December 1991 in Salinas, California. The rye was grown for 16 weeks, so that plants had headed and were senescing, resulting in residue which was difficult to incorporate and slow to decompose. Frequent sampling of the surface soil (0-15 cm) showed that net mineralizable N (anaerobic incubation) rapidly increased, then decreased shortly after tillage in both treatments, but that sustained increases in net mineralizable N and microbial biomass N in the cover-cropped soils did not occur until after irrigation, 20 days after incorporation. Soil NO3-N was significantly reduced compared to winter-fallow soil at that time. A N-15 experiment examined the fate of N fertilizer, applied in cylinders at a rate of 12 kg N-15/ha at lettuce planting, and measured in the soil, microbial biomass and lettuce plants after 32 days. In the cover-cropped soil, 59% of the N-15 was recovered in the microbial biomass, compared to 21% in the winter-bare soil. The dry weight, total N and N-15 content of the lettuce in the cover-cropped cylinders were significantly lower; 28 v. 39% of applied N-15 was recovered in the lettuce in the cover-cropped and winter-bare soils, respectively. At harvest, the N content of the lettuce in the cover-cropped soil remained lower, and microbial biomass N was higher than in winter-bare soils. These data indicate that delayed cover crop incorporation resulted in net microbial immobilization which extended into the period of high crop demand and reduced N availability to the crop.
  • Authors:
    • Rowell, A. L.
    • Weinrich, K. B.
    • Barnwell, T. O.
    • Jackson, R. B.,IV
    • Patwardhan, A. S.
    • Donigian, A. S.
  • Source: Soil Management and Greenhouse Effect
  • Year: 1995
  • Authors:
    • Sweeney, D. W.
    • Moyer, J. L.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 26
  • Issue: 1-2
  • Year: 1995
  • Summary: Legumes provide benefit in crop rotations, but data are limited on soil inorganic nitrogen (N) and soil strength responses to spring- or fall-seeded legumes as green manures for grain sorghum [Sorghum bicolor (L.) Moench] production on the prairie soils of the eastern Great Plains of the United States. With increased emphasis on conservation tillage, information is also needed on combining conservation tillage with the use of legume cover crops. This experiment was established to examine the effects of i) red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth.) as previous crops to grain sorghum compared with continuous grain sorghum, ii) reduced or no-tillage, and iii) fertilizer N rate on changes in soil inorganic N and soil strength. At two adjacent sites (Parsons silt loam; fine, mixed thermic Mollic Albaqualf) differing in initial pH and phosphorus (P) and potassium (K) fertility, soil nitrate-nitrogen (NO3-N) was as much as fourfold higher following kill-down of red clover or hairy vetch than following continuous grain sorghum. At the higher fertility site, soil total inorganic N [TIN: sum of ammonium-nitrogen (NH4-N) and NO3-N] shortly following kill-down of red clover exceeded TIN following hairy vetch by more than 35% and that with continuous grain sorghum by 110%; however, at the lower fertility site, the trend for soil TIN to be higher following legumes was not significant. Tillage did not affect soil NO3-N levels in the spring following legume kill-down. However, subsequent soil NO3-N levels under no-tillage tended to be higher in the spring, but lower in the fall than with reduced tillage. Increases in soil TIN by legumes and fertilizer were related to grain sorghum yield, but likely were not the only factors affecting yield. Legumes and tillage used in grain sorghum production may also provide other non-N benefits as suggested by soil penetration resistance measured at the end of the study.
  • Authors:
    • Clark, L. E.
  • Source: Beltwide Cotton Conferences. Proceedings. 1995. or Winter Cover Crops in Conservation Tillage Systems for Cotton Production in the Rolling Plains of Texas. In M. R. McClelland, et al. (eds.) Conservation-tillage Systems for Cotton – A Review of Research
  • Volume: 2
  • Year: 1995
  • Summary: Austrian winter peas, Pisum sativum, and wheat, Triticum aestivum, as winter cover crops, were evaluated in 1993 and 1994 at two sites on the Chillicothe Research Station in the northern Rolling Plains of Texas. Tests compared the cover crops as an alternative to maintaining bare soil during winter and spring months in annual cotton (Gossypium hirsutum) cv. CAB-CS production systems. Site 1 was located in an area with a history of an intermittent high water table, and site 2 was located in an area that historically is drought prone. Weight of residue and percent ground cover were adequate at both sites and in both years to meet SCS Conservation Compliance Plan requirements for highly erodible soils. Cover crops had no significant effect on early development of cotton plants in either year, but no significant wind or water damage occurred in either year. Mean lint yields were 576 and 425 lb of lint/acre from sites 1 and 2, respectively, in 1993. Respective yields were 368 and 238 lb from the two sites in 1994, in which precipitation amount and distribution were less favourable than in 1993. Yields among treatments were not significantly different except at site 2 in 1994 (the drought prone site). In this test, cotton lint yield following wheat was lowest, and yield following peas was lower than continuous cotton. Water use efficiency followed the same trend as yield at site 1, but differed slightly at site 2. Historical cotton yields from the Chillicothe Research Station are approximately 350 lb/acre.
  • Authors:
    • Copeland, S. M.
    • Tanaka, D. L.
    • Power, J. F.
    • Allmaras, R. R.
  • Source: Conservation Tillage in Temperate Agroecosystems
  • Year: 1994
  • Authors:
    • Lindwall, C. W.
    • Roman, E. S.
    • Moyer, J. R.
    • Blackshaw, R. E.
  • Source: Crop Protection
  • Volume: 13
  • Issue: 4
  • Year: 1994
  • Summary: Soil erosion by wind or water is a serious problem in North and South America. When no-till or reduced tillage is used to control erosion, the density of certain annual and perennial weeds can increase and new weed control techniques are usually required. The effects of conservation tillage on annual and perennial weeds, weeds that are spread by wind, plants from rangelands and pasture as weeds and volunteer plants as weeds arc reviewed. Current weed control methods with minimum tillage, herbicides, cover crops and other cultural practices in conservation tillage systems in North and South America are described. Some producers are successfully controlling weeds in continuous summer cropping systems in North America and in double cropping systems that include wheat in the winter and soybean or corn in the summer in Brazil, Argentina and southeastern United States. Successful conservation tillage systems usually involve cropping sequences of three or more crop types and several herbicides. In these cropping sequences, the ground is covered with a crop during most of the period in which the climate is favourable for weed growth. Perennial weeds are a problem in all tillage systems and there is a general dependence on glyphosate for perennial weed control. In successful conservation tillage systems, the amount and cost of herbicides used is similar to that for herbicides used in conventional tillage systems.
  • Authors:
    • Sweeney, D. W.
    • Moyer, J. L.
  • Source: Soil Science Society of America Journal
  • Volume: 58
  • Issue: 5
  • Year: 1994
  • Summary: With increased emphasis on conservation tillage, information is needed on the use of spring- or fall-seeded legumes as green manures for eastern Great Plains grain sorghum [Sorghum bicolor (L.) Moench] production. This study was conducted to determine whether legumes can be beneficial to subsequent grain sorghum crops grown in conservation tillage systems on prairie soil. Comparisons included the effects of (i) red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth) before grain sorghum vs. continuous grain sorghum, (ii) reduced or no-tillage, and (iii) fertilizer N rates on grain sorghum grown on two sites of a Parsons silt loam (fine, mixed, thermic Mollic Albaqualf). Surface soil at Site 1 was higher in pH (7.2 vs. 6.2), P (12 vs. 4 mg kg(-1)), and K (80 vs. 60 mg kg(-1)) than at Site 2. Yield of the first sorghum crop after legume kill-down in 1987 ranged from 79 to 131% more than for continuous grain sorghum. At the higher fertility Site 1, red clover residual increased yields to 3.7 from 2.7 Mg ha(-1) with continuous grain sorghum in the third year; at the lower fertility Site 2, the legume residual did not influence yield after the first year. First-year grain sorghum yielded 1.1 to 1.6 Mg ha(-1) more with reduced tillage than with no-tillage, but the difference was less in subsequent years. In 1987, yield was not affected by fertilizer N even following grain sorghum, but the response was significant in subsequent years. Low N response on this high organic matter prairie soil contributed to uncertain fertilizer N equivalencies and suggested other non-N benefits from the legumes.