• Authors:
    • Deibert, E. J.
  • Source: Agronomy Journal
  • Volume: 81
  • Issue: 4
  • Year: 1989
  • Summary: Information on response of soybean [Glycine max (L.) Merr.] cultivars to reduced tillage systems in northern dryland areas is limited. A 4-yr field study (1984 to 1987) was conducted to evaluate the effect of tillage system, weed control method, and cultivar maturity on soybean seed yield variables. An early and a late-maturing soybean cultivar were grown on a Fargo clay (fine, montmorillonitic frigid Vertic Haplaquoll) on established tillage plots. Tillage systems included conventional (moldboard plow) and three reduced tillage systems (sweep, intertill, and no-till) with herbicides or herbicides plus cultivation for weed control. Climatic conditions resulted in differences among years in seed yield, seed weight, seed moisture, seed oil concentration, and seed oil yield. These seed variables were not significantly influenced by tillage system, weed control method, or cultivar maturity when grown in rotation with barley (Hordeum vulgare L.), but showed significant interactions. Cultivation for weed control depressed seed yield and weight of only the early cultivar. Early plant water stress (June and July) lowered yield of the early cultivar more than the late cultivar. Early cultivar no-till yields (1240 kg ha−1) were greater than tilled system yields (average 1070 kg ha−1). while late cultivar yields were similar among systems (average 1420 kg ha−1). An early maturing cultivar performed similarly to a late-maturing cultivar irrespective of tillage system unless early plant water stress was encountered. Fall application of granular herbicide provided good weed control, but cultivation for weed control was not beneficial for the yields parameters measured.
  • 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:
    • Rohde, C. R.
    • Rasmussen, P. E.
  • Source: Soil Science Society of America Journal
  • Volume: 52
  • Issue: 4
  • Year: 1988
  • Summary: Maintaining or improving soil organic matter has high priority in agriculture because of its beneficial effect on soil physical, chemical, and biological properties. Soil organic N and C were measured 44 yr after establishment of a long-term experiment to evaluate tillage and fertilizer effects in a winter wheat (Triticum aestivum L.)-fallow rotation on a coarse-silty mixed mesic Typic Haploxeroll. Main treatments consisted of three primary tillage systems, one conventional (moldboard plow) and two stubble mulch (offset disc, subsurface sweeps). Subplots consisted of six N treatments, 493, 728, 986, 1221, 1714, and 2207 kg N ha−1 applied over 44 yr. Organic N and C in the top 75 mm of soil were 26 and 32% higher, respectively, in the two stubble mulch systems than in conventional tillage, and equal below 75 mm. Stubble mulch plots contained 245 kg more N ha−1 than conventionally tilled plots, representing the conservation of 5.7 kg N ha−1 yr−1. Nitrogen fertilization increased soil N linearly in all tillage treatments, with 18% of the applied N incorporated into the soil organic fraction. Applied N also increased soil C linearly on plots with previous S application. Soil C was higher on plots with no previous S than on comparable plots with previous S, however, which suggests an S deficiency that altered S, but not N, transformations in soil. Identical N fertilization effects on soil organic N and C in both stubble mulch and conventional tillage suggests that N transformations were the same in both systems.
  • Authors:
    • Harman, W.
    • Jones, O.
    • Smith, S.
  • Source: Optimum erosion control at least cost. Proceedings of the National Symposium on Conservation Systems, December 14-15, 1987, Chicago, IL, USA
  • Year: 1987
  • Summary: Graded-terraced field-size watersheds have been cropped in a dryland wheat - fallow - sorghum - fallow (2 crops in 3 years) sequence with no-till and conventional (stubble-mulch) tillage systems at Bushland, Texas since 1982. No-till had little effect on wheat yields but increased sorghum yields 14% due to reduced evaporation, as a result of surface residue. No-till reduced erosion by 66%; however, soil loss with conventional tillage was also low due to terracing and contouring. NPK loss was very low. Economically, no-till performed very well, due mainly to reduced equipment inventories and lower operating costs. No-till gave increased storm runoff due to soil crusting, and there were problems with grass weeds. A system consisting of successive no-tillage and stubble-mulch tillage is proposed.
  • Authors:
    • Raun, W. R.
    • Sander, D. H.
    • Olson, R.A.
  • Source: Soil Science Society of America Journal
  • Volume: 51
  • Issue: 4
  • Year: 1987
  • Authors:
    • Miranowski, J.
    • Shortle, J.
  • Source: Applied Agricultural Research
  • Volume: 1
  • Issue: 2
  • Year: 1986
  • Authors:
    • Dyke, P. T.
    • Jones, C. A.
    • Williams, J. R.
  • Source: Transactions of the ASAE
  • Volume: 27
  • Issue: 1
  • Year: 1984
  • Summary: A mathematical model called EPIC (Erosion-Productivity Impact Calculator) was developed to determine the relationship between soil erosion and soil productivity throughout the U.S. EPIC continuously simulates the processes involved simultaneously and realistically, using a daily time step and readily available inputs. Since erosion can be a relatively slow process, EPIC is capable of simulating hundreds of years if necessary. EPIC is generally applicable, computationally efficient, and capable of computing the effects of management changes on outputs. The model must be comprehensive to define the erosion-productivity relationship adequately. EPIC is composed of physically based components for simulating erosion, plant growth, and related processes and economic components for assessing the cost of erosion, determining optimal management strategies, etc. The EPIC components include weather simulation, hydrology, erosion-sedimentation, nutrient cycling, plant growth, tillage, soil temperature,economics, and plant environment control. Typical results are presented for 15 of the 163 tests performed in the continental U.S. and Hawaii. These results generally indicate that EPIC is capable of simulating erosion and crop growth realistically.
  • Authors:
    • Paul, E. A.
    • Rennie, D. A.
    • Aulakh, M. S.
  • Source: Journal of Environmental Quality
  • Volume: 13
  • Issue: 1
  • Year: 1984
  • Summary: The gaseous losses of N from conventional-till (CT) and zero-till (ZT) crop fields were 3 to 7 and 12 to 16 kg N ha-1 y-1, respectively. In contrast, losses from CT and ZT fallow were severalfold higher, namely, 12 to 14 and 34 kg N ha-1, respectively. The more dense surface soil and consistently higher moisture content (lower air-filled porosity) were identified as major factors affecting increased denitrification under ZT. The potential denitrification rates were markedly higher under ZT, and the population of denitrifiers was up to six times higher than in CT soil samples. The contribution of lower soil horizons towards gaseous N losses was found to be low on both CT and ZT fields, and this finding was confirmed from a survey carried out on three other widely differing soils. Volumetric soil moisture and air temperature were the only two of several factors that accounted for a significant portion of the variations in gaseous N fluxes under field conditions. The average mole fraction of N2O ranged from almost 100% to as low as 28% of the total gaseous products and showed a negative relationship with soil moisture.
  • Authors:
    • Elharis, M. K.
    • Cochran, V. L.
    • Elliott, L. F.
    • Bezdicek, D. F.
  • Source: Soil Science Society of America Journal
  • Volume: 47
  • Issue: 6
  • Year: 1983
  • Authors:
    • Fenster, C. R.
    • Mannering, J. V.
  • Source: Journal of Soil and Water Conservation
  • Volume: 38
  • Issue: 3
  • Year: 1983