• 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.
  • Authors:
    • Napit, K. B.
    • Bosch, D. J.
  • Source: Journal of Soil and Water Conservation
  • Volume: 47
  • Issue: 4
  • Year: 1992
  • Summary: Rapid expansion of the Virginia poultry industry has resulted in poultry litter production that in certain areas exceeds the potential for use in crop agriculture. If land application exceeds crop requirements, litter production may result in environmental damage. In this study, potential litter surpluses in intensive poultry-producing Virginia counties were quantified. The costs of transferring such surpluses to litter-deficient areas were compared with the economic value of litter as fertilizer. Estimates of potential cropland and pasture for spreading litter took dairy manure production into account. Use of litter surpluses by transfer was found to be economically viable. Public policy actions are needed, however, to promote such transfer.
  • Authors:
    • Cole, C.
    • Westfall, D.
    • Peterson, G.
    • Wood, C.
    • Willis, W.
  • Source: Agronomy Journal
  • Volume: 83
  • Issue: 3
  • Year: 1991
  • Summary: Soil-crop management affects the soil-N balance and, thus, has a direct bearing on soil productivity. This study determined the effects of cropping intensity (crops/time) under no-till and grassland establishment on aboveground biomass production and the system-N balance after 4 yr (1985-1989). The effects were examined across toposequences in the West Central Great Plains that had been tilled and frequently fallowed for > 50 yr. Production systems included wheat (Triticum aestivum L.)-fallow (WF), wheat-corn (Zea mays L.) or sorghum (Sorghum vulgare L.)-millet (Panicum miliaceum L.)-fallow (WCMF), and perennial grass (CG). Intense agronomic systems (WCMF) had greater aboveground production, greater N uptake, and greater percent plant residue retention than WF. Continuous grass systems had less aboveground production and N uptake but greater percent plant residue retention than agronomic systems. Soil-profile NO3-N was lower under WCMF systems than WF systems, but organic N showed the opposite trend implying that more intense systems are at less risk for NO3-N leaching, and have greater potential for replenishment of soil-organic N via enhanced immobilization. Aboveground biomass production and plant residue production increased downslope, but slope position had little effect on plant-N uptake, plant residue retention, or soil-N dynamics. Imposing no-till and perennial grassland systems created a N-balance disequilibrium, but more time will be required to ascertain the trajectory of N loss or gain due to establishment of no-till or grassland management on these soils.
  • Authors:
    • Evanylo, G. K.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 21
  • Issue: 1-2
  • Year: 1990
  • Summary: Crop response to fertilizer nitrogen (N) is dependent upon tillage management. This study was conducted to determine how tillage rotation influences non‐irrigated crop growth, N uptake and yield. The effects of tillage rotation, N rate and N timing schedule on early season dry matter production and N uptake, ear leaf N concentration at silking, and yield of corn [Zea mays (L.) Pioneer 3378] were investigated at Painter, VA, on an Altavista loam (fine‐loamy, mixed, thermic Aquic Hapludult). In 1986, maximum yields achieved in the 6‐year continuous no till (NT) [5.82 Mg/ha] and first year no till (AT) [5.64 Mg/ha] were significantly greater than that of the 6‐year continuous conventional till (CT) [3.67 Mg/ha], but no yield differences were obtained in the drier 1987 season. A higher rate of N fertilizer was required to obtain maximum yield in the first year no till (168 kg N/ha) than in the NT (112 kg N/ha) during 1986. Early 1986 N uptake and growth response with and without N at planting increased in the order CT < AT = NT and AT < CT < NT, respectively, indicating greatest immobilization of soil N occurred in the newly established no till soil. Lack of differences in critical ear leaf N values developed for NT and CT in each year imply that plant norms developed for one tillage system may accurately assess N status of corn grown under different tillage practices.
  • Authors:
    • Dalal, R. C.
  • Source: Soil Science Society of America Journal
  • Volume: 53
  • Issue: 5
  • Year: 1989
  • Summary: There is a paucity of information on the long-term effects of crop residue management under no-tillage culture on properties of clay soils in tropical and subtropical regions. The objective of this study was to compare the effects of 13 yr of conventional tillage vs. no tillage, crop residue retained vs. burned, and no fertilizer N vs. application of 23 and 69 kg N ha-1 yr-1 on organic C content, total N, mineralizable N, pH, electrical conductivity, chloride, exchangeable sodium percentage (ESP), and aggregation index (undispersed fraction <20 fim silt + clay) in a fine-textured Vertisol (650 g clay kg-1 soil). Highest concentrations of organic C and total N were found in the surface soil (0-0.1 m) with a combination of no-tillage, crop residue retained, and fertilizer N. Mineralizable N followed similar trends. Soil pH to 0.3-m depth and electrical conductivity to 1.2-m depth were significantly lower under no-tillage than under conventional tillage. Aggregation index of the surface soil (0-0.1 m), was higher under no-tillage. The ESP was lowest in the surface soil (0- 0.04 m) under no-tillage with crop residues retained; the soil profile (0-1.2 m) under this treatment also contained far less NaCl-equivalent salts (0.8 Mg ha-1) than under conventional tillage with crop residue burned (7.3 Mg ha-1). Available water and nitrate were lower in the surface soil but greater at depths (0.6-1.2 m) under no-tillage than in tilled soil. Thus tillage and crop residue management can substantially affect soil organic matter and microbial activity in the surface layers, and water relations and salt movement to at least 1.2-m depth, even in a fine-textured Vertisol.
  • Authors:
    • Ojima, D. S.
    • Cole, C. V.
    • Schimel, D. S.
    • Parton, W. J.
  • Source: Soil Science Society of America Journal
  • Volume: 51
  • Issue: 5
  • Year: 1987
  • Summary: We analyzed climatic and textural controls of soil organic C and N for soils of the U.S. Great Plains. We used a model of soil organic matter (SOM) quantity and composition to simulate steady-state organic matter levels for 24 grassland locations in the Great Plains. The model was able to simulate the effects of climatic gradients on SOM and productivity. Soil texture was also a major control over organic matter dynamics. The model adequately predicted aboveground plant production and soil C and N levels across soil textures (sandy, medium, and fine); however, the model tended to overestimate soil C and N levels for fine textured soil by 10 to 15%. The impact of grazing on the system was simulated and showed that steady-state soil C and N levels were sensitive to the grazing intensity, with soil C and N levels decreasing with increased grazing rates. Regional trends in SOM can be predicted using four site-specific variables, temperature, moisture, soil texture, and plant lignin content. Nitrogen inputs must also be known. Grazing intensity during soil development is also a significant control over steady-state levels of SOM, and since few data are available on presettlement grazing, some uncertainty is inherent in the model predictions.
  • Authors:
    • Seastedt, T. R.
    • Knapp, A. K.
  • Source: BioScience
  • Volume: 36
  • Issue: 10
  • Year: 1986
  • Summary: Focuses on the reduction in the amount of tallgrass prairie in North America. Study conducted by the International Biological Program; The three dominant warm-grasses which tallgrass prairie is divided into; Reasons why tallgrass prairie flourished; Effects of prairie fires on nitrogen levels; Efforts to remove detritus.
  • Authors:
    • Doran, J. W.
    • Linn, D. M.
  • Source: Soil Science Society of America Journal
  • Volume: 48
  • Issue: 4
  • Year: 1984
  • Summary: Surface soils from long-term tillage comparison experiments at six U.S. locations were characterized for aerobic and anaerobic microbial populations and denitrification potential using an in situ acetylene blockage technique. Measurements of soil water content, bulk density, and relative differences in pH, NO-3-N, water-soluble C, and total C and N contents between tillage treatments were also determined at the time of sampling. Numbers of aerobic and anaerobic microorganisms in surface (0-75 mm) no-till soils averaged 1.35 to 1.41 and 1.27 to 1.31 times greater, respectively, than in surface-plowed soils. Bulk density, volumetric water content, water-filled pore space, and water-soluble C and organic C and N values were similarly greater for surface no-till soils compared to conventionally tilled soils. Deeper in the soil (75-300 mm), however, aerobic microbial populations were significantly greater in conventionally tilled soils. In contrast, below 150 mm, the numbers of anaerobic microorganisms differed little between tillage treatments. In no-till soils, however, these organisms were found to comprise a greater proportion of the total bacterial population than in conventionally tilled soils. Measurements of the denitrification potential from soils at three locations generally followed the observed differences in anaerobic microbial populations. Denitrifying activity, after irrigation with 15 mm of water, was substantially greater in surface 0- to 75-mm no-till soils than in conventionally tilled soils at all locations. At the 75- to 150-mm soil depth, however, the denitrification potential in conventionally tilled soils was the same or higher than that of no-till soils. In surface no-till soils, increased numbers of anaerobic microorganisms and a substantially greater denitrification potential, following irrigation, indicate the presence of less-aerobic conditions in comparison to conventionally tilled soils. This condition appears to result from greater soil bulk densities and/or water contents of no-till soils, which act to increase water-filled porosity and the potential for water to act as a barrier to the diffusion of oxygen through the soil profile.