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Title: OPTIMAL APPLICATIONS OF N-FETILIZER AND IRRIGATION WATER IN CORN PRODUCTION

Author
item Lu, Yao
item Camp Jr, Carl
item Sadler, Edward

Submitted to: Western Agricultural Economics Association
Publication Type: Abstract Only
Publication Acceptance Date: 9/7/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Nitrogen fertilizer and irrigation water are major inputs to corn production and efficient use of these inputs is essential for profit maximization. To use these inputs efficiently in corn production, knowledge about corn responses to nitrogen fertilizer and irrigation water, or production functions, is needed. In this paper, we estimated corn production functions using the data from experimental plots in Florence, South Carolina, U.S.A., from 1999 through 2001. The experimental design was a split randomized complete block and irrigation water and nitrogen fertilizer application treatment combinations were in completely randomized blocks. Corn was grown under conservation tillage on a 6-ha site of relatively uniform Norfolk loamy sand. There were three irrigation treatments (0%, 75%, and 150% of the base rate) and four N-fertilizer regimes (50%, 75%, 100%, and 125 % of the base rate). Variable rate water applications were made using combinations of three sets of nozzles, each delivering a different rate. Nitrogen fertilizer was applied via fertigation by varying the application depth of water with a constant nutrient concentration. The center pivot irrigation system had been modified to permit variable applications to individual areas 9.1m by 9.1m in size. Several forms of production functions were fitted to the data and the quadratic equation was found to be most appropriate. The estimated production functions were differentiated to obtain the marginal physical products (MPP) of nitrogen fertilizer and irrigation water. The profit maximizing level of each input was obtained by equating the value of marginal product of each input, which is equal to MPP times the price of corn, with the respective input price. A demand function for each input was derived from the profit maximization conditions and demand elasticity for each input was also estimated. The results provide useful information to farmers to make nitrogen fertilizer and irrigation decisions for profit maximization and for resource conservation.