Pautsch, Gregory R.

December, 1999

By: Pautsch, Gregory R.; Babcock, Bruce A.; Breidt, F. Jay
Studies examining the value of switching to a variable rate technology (VRT) fertilizer program assume producers possess perfect soil nitrate information. In reality, producers estimate soil nitrate levels with soil sampling. The value of switching to a VRT program depends on the quality of the estimates and on how the estimates are used. Larger samples sizes, increased spatial correlation, and decreased variability improve the estimates and increase returns. Fertilizing strictly to the estimated field map fails to account for estimation risk. Returns increase if the soil sample information is used in a Bayesian fashion to update the soil nitrate beliefs in nonsampled sites.

December, 1998

By: Babcock, Bruce A.; Pautsch, Gregory R.
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 0.5 bushels per acre, and would reduce fertilizer costs by $1.19 to $6.83 per acre.