- 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:
- 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:
- Source: Energy in World Agriculture
- Volume: 2
- Year: 1987
- Authors:
- Schirmer, S. L.
- Wilson, T. A.
- Source: U.S. Department of Transportation, Federal Highway Administration
Milestones: A History of the Kansas Highway Commission and the Department of Transportation, Kansas Department of Transportation, December 1986.
(A second publication by a combination of
- Year: 1986
- 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:
- Bremner, J. M.
- Breitenbeck, G. A.
- Source: Biology and Fertility of Soils
- Volume: 2
- Issue: 4
- Year: 1986
- Summary: Field studies to determine the effect of different rates of fertilization on emission of nitrous oxide (N2O) from soil fertilized with anhydrous ammonia showed that the fertilizer-induced emission of N2O-N in 116 days increased from 1.22 to 4.09 kg ha-1 as the rate of anhydrous ammonia N application was increased from 75 to 450 kg ha-1. When expressed as a percentage of the N applied, the fertilizer-induced emission of N2O-N in 116 days decreased from 1.6% to 0.9% as the rate of fertilizer N application was increased from 75 to 450 kg N ha-1. The data obtained showed that a 100% increase in the rate of application of anhydrous ammonia led to about a 60% increase in the fertilizer-induced emission of N2O. Field studies to determine the effect of depth of fertilizer injection on emission of N2O from soil fertilized with anhydrous ammonia showed that the emission of N2O-N in 156 days induced by injection of 112 kg anhydrous ammonia N ha-1 at a depth of 30 cm was 107% and 21 % greater than those induced by injection of the same amount of N at depths of 10 cm and 20 cm, respectively. The effect of depth of application of anhydrous ammonia on emission of N2O was less when this fertilizer was applied at a rate of 225 kg N ha-1.
- Authors:
- Source: Proceedings, North Central Weed Control Conference
- Issue: Vol. 41
- Year: 1986
- Summary: Results are summarized of a long-term study started in 1985 at Boone County, Iowa, to determine the effect of several annual and perennial cover crops on maize and soyabean yields. Best soyabean yields were obtained with annual cover crops, Kentucky bluegrass ( Poa pratensis) and the bare soil control. Best maize seed yields were obtained with the bare soil control, winter rapeseed and winter barley cover crops.
- 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:
- 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.
- Authors:
- Fenster, C. R.
- Mannering, J. V.
- Source: Journal of Soil and Water Conservation
- Volume: 38
- Issue: 3
- Year: 1983
