Journal ofAgricultural and Resource Economics 23(2):385-400 Copyright 1998 Western Agricultural Economics Association Moving from Uniform to Variable Fertilizer Rates on Iowa Corn: Effects on Rates and Returns

This study develops a model based on the yield potential of various soil types in 12 Iowa counties to estimate the potential value of switching from uniform to variable fertilizer rates. Results indicate modest increases in the gross returns over fertilizer costs, ranging from $7.43 to $1.52 per acre. The net profitability of variable-rate technology (VRT) is sensitive to the per acre costs of moving to a VRT program. Under the assumptions of the model, applying variable rates would increase yield by 0.05 to 0.50 bushels per acre, and would reduce fertilizer costs by $1.19 to $6.83 per acre. Key words: nitrogen fertilizer, precision farming, single-rate technology, site-specific management, variable-rate technolog