19602015
  • Authors:
    • Li, C.
  • Source: Soil Management and Greenhouse Effect
  • Year: 1995
  • 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:
    • Coffin, D. P.
    • Burke, I. C.
    • Lauenroth, W. K.
  • Source: Ecological Applications
  • Volume: 5
  • Issue: 3
  • Year: 1995
  • Summary: Although the effects of cultivation on soil organic matter and nutrient supply capacity are well understood, relatively little work has been done on the long-term recovery of soils from cultivation. We sampled soils from 12 locations within the Pawnee National Grasslands of northeastern Colorado, each having native fields and fields that were historically cultivated but abandoned 50 yr ago. We also sampled fields that had been cultivated for at least 50 yr at 5 of these locations. Our results demonstrated that soil organic matter, silt content, microbial biomass, potentially mineralizable N, and potentially respirable C were significantly lower on cultivated fields than on native fields. Both cultivated and abandoned fields also had significantly lower soil organic matter and silt contents than native fields. Abandoned fields, however, were not significantly different from native fields with respect to microbial biomass, potentially mineralizable N, or respirable C. In addition, we found that the characteristic small-scale heterogeneity of the shortgrass steppe associated with individuals of the dom- inant plant, Bouteloua gracilis, had recovered on abandoned fields. Soil beneath plant canopies had an average of 200 g/m2 more C than between-plant locations. We suggest that 50 yr is an adequate time for recovery of active soil organic matter and nutrient availability, but recovery of total soil organic matter pools is a much slower process. Plant population dynamics may play an important role in the recovery of shortgrass steppe ecosystems from disturbance, such that establishment of perennial grasses determines the rate of organic matter recovery.
  • Authors:
    • McIntosh, M. S.
    • Mulford, F. R.
    • Meisinger, J. J.
    • Decker, A. M.
    • Clark, A. J.
  • Source: Agronomy Journal
  • Volume: 87
  • Issue: 3
  • Year: 1995
  • Summary: Hairy vetch (Vicia villosa Roth) can fix N-2 for subsequent release to a corn (Zea mays L.) crop, but kill date effects on vetch N accumulation, soil water, and subsequent corn production have not been studied. A hairy vetch cover crop can deplete soil water through transpiration, but cover crop mulches can conserve soil water for no-till corn. In order to determine optimum spring kill date and corn fertilizer N (FN) rates, hairy vetch was killed early April, late April, or mid-May, followed by three corn planting dates and four FN rates (0, 45, 135, and 202 kg N ha(-1)). From early April to mid-May, hairy vetch aerial phytomass and N content increased significantly, from 2800 to 4630 and 96 to 149 kg ha(-1), respectively. Corn grain yields ranged from 5.2 to 10.1 Mg ha(-1) and were significantly greater following mid or late kill, compared with early kill of vetch, regardless of corn planting date or FN rate. Gravimetric soil water under mid- or late-kill vetch was often significantly greater than after early-kill vetch. We conclude that soil water conservation by late-killed vetch mulches had a greater influence on corn production than vetch spring water use. Optimum N production and water conservation occurred when vetch was killed the last week of April. Early-kill vetch sacrificed N production and minimized soil water conservation, resulting in reduced corn grain yield. Late kill did not add significant N benefits, but could deplete soil water or interfere with timely corn planting.
  • Authors:
    • Porter, P.
  • Source: Journal of Production Agriculture
  • Volume: 8
  • Issue: 2
  • Year: 1995
  • Summary: A study was conducted on an Orangeburg loamy sand (fine-loamy, siliceous, thermic Typic Paleudults) near Blackville, South Carolina in 1990-92 to determine the effect of deep tillage on both canola [rape] and wheat, the subsequent response of doublecropped soyabeans, and response of wheat grown following the soyabean crop when controlled traffic and minimum tillage practices were used. Canola yields averaged 37.8 bu/acre in 1991 and 43.2 bu/acre in 1992, whereas wheat yields were 58.0 and 72.5 bu/acre, respectively. In both years, deep tillage (chiselling to 11 in) had no effect on wheat yields when compared with discing. Deep tillage increased canola yields by 12.5% in the drier of the two growing seasons. Soyabean yields were not significantly affected by the tillage used for the previous crops. Subsoiled soyabeans yielded 33.7 vs. 31.9 bu/acre for no-till soyabeans in 1991, and 22.6 vs. 19.4 bu/acre in 1992. In 1992, soyabean tillage following wheat did not affect soyabean yield but following canola, in-row subsoiling resulted in greater soyabean yields than no-till. Wheat following soyabeans was not affected by the tillage practice used for the previous winter crops, and the 1992 wheat yields were unaffected by previous winter crop or soyabean tillage. In 1993, soyabean tillage did not affect subsequent wheat yield but following canola, in-row subsoiling resulted in greater wheat yields than no-till. It is suggested that canola has no adverse effect on either soyabeans or wheat when grown in sequence on a Coastal Plain soil.
  • Authors:
    • Coady, S. A.
    • Clark, R. T.
    • Schneekloth, J. P.
    • Klocke, N. L.
    • Hergert, G. W.
  • Source: Journal of Production Agriculture
  • Volume: 8
  • Issue: 3
  • Year: 1995
  • Summary: Declining groundwater levels in parts of the Great Plains could lead to reduced irrigation and a decline in the economies of those areas. Improved irrigation efficiency has helped slow the rate of decline in aquifer levels but adoption of limited irrigation and water conserving rotations could slow the decline even more. The objective was to estimate the riskiness and profitability of these alternatives with and without farm commodity programs. Three water levels-rainfed, limited irrigation (6 in./yr water allocation) and full irrigation (meet crop evapotranspiration demands) were established for continuous corn (Zea mays L.), winter wheat (Triticum aestivum L.)-corn-soybean [Glycine max (L.) Merr.], and corn-soybean rotations. The profitability of each rotation under each water level was estimated using results of field experiments conducted since 1981 in west central Nebraska and cost estimates based on a typical center pivot irrigation system covering 126 acres. Stochastic dominance techniques were then applied to the data by using combinations of prices for corn, wheat, and soybean to generate cumulative distribution functions. Profitability and riskiness were estimated with and without participation in the wheat and feed grain programs and with alternate acreage conservation reserve (ACR) levels. Results showed that the government program improved income levels and reduced income variation for each water level and all rotations. Program participation did encourage monoculture corn under full irrigation and under limited irrigation with low ACR requirements. Under rainfed conditions the relative ranking of the three rotations was not changed by program participation.
  • 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:
    • Unger, P. W.
  • Source: Journal of Soil and Water Conservation
  • Volume: 50
  • Issue: 3
  • Year: 1995
  • Summary: Crop residue management was chosen as a key practice to help control erosion on nearly 75% of the highly erodible land covered by conservation plans. This study determined the effects of treatments that involved retaining all residues on the surface (NT+Res), removing some residues at harvest (NT-ResH) or at planting (NT-ResP), and conventional tillage (ConvT) on soil water storage and use, and yields of continuous winter wheat (Triticum aestivum L.) produced with limited irrigation. Water storage between crops was greater with NT+Res (95 mm) and NT-ResH (100 mm) than with ConvT (79 mm), but soil water depletion was not affected by treatments. Grain yield was greater with NT+Res (4.56 Mg ha(-1)), than with ConvT (4.26 Mg ha(-1)) and NT-ResH (4.18 Mg ha(-1)), but straw yield was not affected by treatments. Grain and straw yield differed among crops. Continuous wheat production with limited irrigation resulted in an estimated 2.2 Mg ha(-1) of residues on the surface at planting with the NT-ResH and NT-ResP treatments. The initial amount was 9.0 Mg ha(-1) with the NT+Res treatment, and much of this remained on the surface at planting of the next crop. In all cases, the residue amounts provided considerably more (a minimum of about 70%) than the 30% surface cover usually required to control erosion on highly erodible land. Hence, use of limited irrigation and no-tillage can help producers meet the surface residue requirements established for their conservation plans for highly erodible lands in the southern Great Plains.
  • 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:
    • Lindemann, W. C.
    • Salazarsosa, E.
    • Gill, L. R.
    • Christensen, N. B.
  • Source: Agronomy Journal
  • Volume: 86
  • Issue: 2
  • Year: 1994
  • Summary: Soil nitrogen and organic carbon differences between no-till and conventional tillage systems are often dramatic and well documented, but these differences between no-till and stubble mulch tillage systems are more subtle. Our objective was to evaluate changes in soil inorganic N, organic N, organic C, surface soil moisture and grain yield on the southern High Plains as affected by stubble mulch and no-till tillage systems from 1988 to 1992. The cropping system was a sorghum (Sorghum bicolor (L.) Moench)-sorghum-fallow-wheat (Triticum aestivum L.) rotation conducted on a Pullman sandy clay loam (fine, mixed, thermic Torrertic Paleustoll) under dryland conditions near Clovis, NM. Tillage treatments were main plots and N fertilization treatments were subplots. Averaged over 5 yr and 37 sampling dates, the no-till treatment had 2.0 mg kg-1 less inorganic N, 40 mg kg-1 more organic N, and 617 mg kg-1 more organic C than the stubble mulch treatment. Although differences between tillage systems were generally small, they were most noticeable during sorghum planting and development. No-till unfertilized treatments often showed N deficiency symptoms during development. Nitrogen fertilization was more important than tillage system in determining sorghum and wheat yields in wet years. In dry years, N-fertilized stubble mulch treatments had the lowest yields. Since conversion to either stubble mulch or no-till in 1987, organic C levels under both systems have continually increased.