The amount of erosion, E, expressed in tons per acre per annum, that will occur from a given agricultural field can be expressed in terms of equivalent variables as: E = f(I′, K′, C′, L′, V) where I′ is a soil erodibility index, K′ is a soil ridge rougness factor, C′ is a climatic factor, L′ is field length along the prevailing wind erosion direction, and V is equivalent quantity of vegetative cover. The 5 equivalent variables are obtained by grouping some and converting others of the 11 primary variables now known to govern wind erodibility. Relations among variables are extremely complex. Charts and tables have been developed to permit graphical solutions of the equation. The equation is designed to serve the twofold purpose of providing a tool to (i) determine the potential erosion from a particular field, and (ii) determine what field conditions of soil cloddiness, roughness, vegetative cover, sheltering by barriers, or width and orientation of field are necessary to reduce potential erosion to a tolerable amount. Examples of these applications of the equation are presented. Weaknesses in the equation and areas needing further research are discussed.
Although crop‐fallow systems stabilize production in the semiarid northern Great Plains, fallow often wastes water, minimally controls water and wind erosion, and contributes to the saline‐seep problem. Developing alternate cropping systems which rely less on fallow requires additional crop residue and more specific soil fertility management guidelines. To optimize the potential of a spring wheat‐winter wheat‐fallow rotation for the northern Great Plains, we examined the effects of spring wheat (Triticum aestivum L. ‘Norana’) stubble management (conventional‐till vs. no‐till stubble at heights of 15, 28, and 38 cm) and N fertilization (rate, timing, and source) on winter wheat yields. Grain yields were significantly higher for ammonium nitrate (NH4NO3) than for urea applied at 67 kg N/ha early (1 May) or late (23 May). Maximum grain yields were 2,620 and 2,540 kg/ha for winter wheat seeded directly (no‐tillage) into 15‐ and 28‐cm stubble heights, respectively, with 67 kg/ha of N applied in early May as NH4NO3. With 22 or 45 kg/ha of N applied early (1 May), grain yield increases for NH4NO3 and urea were similar. With a later application at the same rates, NH4NO3 was significantly superior. Nitrogen topdressing of winter wheat in a recropping system must be completed early, either before or soon after spring growth begins and definitely before the end of tillering.
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