Effect of Prices and Moisture Stress on Nitrogen Rates that Maximize Two Economic Criteria for Corn1
- Emilio Escamilla,
- Regis Voss and
- J. R. Webb2
Fertilizer rates, which maximize certain economic criteria for crop production, are affected by the yield response to fertilizer, the ferti1izer:crop-price ratio, the crop price, and the cost of production. The purpose of this study was to evaluate the effects of different fertilizer N:crop-price ratios (P,), corn (Zea mays L.) prices (Py), and moisture-stress levels (S) on the rates of fertilizer N that maximize net return (m) and rate of return (M) to total investment in corn production per unit of land area.
Fifteen site-years of data were used from two continuous-corn fertilizer rate experiments conducted under different crop management and environmental conditions. Moisture stress had a different effect in each experiment on yield and yield response to N.
Net return from corn production and the rate of return to investment per hectare at the economic optimum N rate were affected by all factors considered. They were affected more by decreasing Py by half from 13.77 to 6.88¢/kg than by increasing the Pr ratio fourfold from 2.8 to 11.2 on a kg N:kg corn-price basis. Only a severe deleterious effect of moisture stress on yields and yield reponse to N decreased the net return and rate of return more than decreasing the price of corn.
At a constant PrM, decreasing the corn price caused the N rate that maximized M to increase and approach the economic optimum N rate. At a constant N price and a decreasing corn price, the economic optimum N rate decreased, but the N rate that maximized M remained static. In either case, these two N rates approached each other. A deleterious moisture-stress effect also caused both N rate to decrease but approach each other.
These results suggest that, if there are increasing production costs and(or) decreasing crop prices, an overreduction of a divisible responsive input such as fertilizer N on corn could markedly affect the return to total investment on per-land-area basis.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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