Browsing by Author "Ess, Daniel R."

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    Cover crop residue effects on machine-induced soil compaction
    Ess, Daniel R. (Virginia Tech, 1994-07-05)
    Crop production systems which utilize the biomass produced by rye (Secale cereale ) to suppress weed growth and conserve soil moisture have been developed at Virginia Tech. The success of alternative, reduced-input crop production systems has encouraged research into the potential for breaking the traffic-tillage cycle associated with conventional tillage crop production systems. The fragile residues encountered in agricultural crop production, whether incorporated into the soil or distributed on the soil surface, provide minimal protection against compaction by wheeled vehicles. The potential of an intact cover crop to reduce machine-induced effects on soil properties that affect primary crop growth was the subject of this study. A randomized complete block experiment was conducted at the Whitethorne Farm in Montgomery County, Virginia. One set of plots was arranged on a terrace adjacent to the New River in a fine, mixed, mesic, Aquic Argiudolls. Another set of plots was arranged on an upland site, a river terrace tread, in a fine-loamy, mixed, mesic, Typic Hapludults. Three rye cover crop treatments were examined. In one, a live cover crop was completely undisturbed prior to tracking by a wheel-type tractor. In another, the cover crop was chemically desiccated, and in the third treatment, all above-ground biomass was removed from plots prior to machine traffic. The treatments permitted investigation of the effects of crop condition on machine-induced soil compaction and the contribution of root reinforcement to the alteration of soil response to machine traffic. A fall-tilled fallow treatment served as an experimental control. Three levels of traffic were investigated: one pass, three passes, and five passes. Undisturbed soil core samples were analyzed to determine machine-induced effects on dry bulk density, pore size distribution, and saturated hydraulic conductivity. The treatments affected soil response to machine traffic. The cover crop treatments altered the soil-plant microenvironment, affecting soil parameters that influence compactibility. Soil compaction was attenuated by the reinforcing effect of a network of undisturbed roots within the soil. There was no convincing evidence that above-ground biomass contributed directly to the reduction of machine-induced compaction effects. Soil response to machine traffic was limited to the uppermost 15 cm of the soil profile.
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    Energetics of low-input corn production
    Ess, Daniel R. (Virginia Tech, 1990-12-05)
    This study compares the energy costs of synthesizing, distributing, and applying manufactured nitrogen fertilizer to the overall energy costs associated with nitrogen-fixing legume production and use. The energetics of com silage and com grain production under standard and alternative practices are examined. Economic analyses of crop production practices are used to aid the selection of recommended alternative practices. In corn silage production, cover-cropped treatments had a significant advantage over standard practice treatments in terms of overall energy expenditures for field operations. Cover-cropped no-till treatments required an average energy expenditure of 9026 MJ/ha compared to 19,763 MJ/ha required by the standard-practice no-till treatment. Cover-cropped treatments that used disking to kill the cover crops required an average energy expenditure of 9781 MJ/ha compared to 18,488 MJ /ha required by the standard-practice winter-fallow treatment. Alternative-practice treatments that utilized vetches to provide nitrogen for com production performed significantly better than standard-practice treatments in terms of energy use per unit of crop output. In addition, the alternative hairy vetch - no-till treatment produced a $33/ha greater average net revenue than the standard-practice no-till treatment. Weed control energy requirements for cover-cropped ridge-tillage com grain production were compared. Broadcast application of pre-emergence herbicides required an energy expenditure of 1160 MJ fha. Cultivation of ridges to control weeds consumed 380 MJ/ha. Economic costs of ridge cultivation were $14/ha. Broadcast application of pre-emergence herbicides cost $49/ha.