Chad Lee, Extension Professor, Grain Crops, University of Kentucky
Producers enjoy farming based on yield goals. Yield goals are positive thinking. They are a challenge to the producer to try to reach higher yields. Annual budgets have yield goals. Loans require an estimate of income which requires a projected yield. Yield goals are easy to market and easy to understand. Yield goals also could cost you a lot of money in 2015.
The University of Kentucky publishes AGR-1 Lime and Nutrient Recommendations every two years. These recommendations are based on decades of research on soil test values, fertilizer rates and yields in Kentucky. The rates in AGR-1 are based off of these research results. Many yield goal strategies include fertilizer rates to meet the expected crop removal rate. Often, those crop removal rates are much higher than the agronomic response of fertilizer reported in AGR-1.
The farmers in that small group were applying more phosphorus, potassium and zinc than what AGR-1 recommends based on soil test values. While these rates were high, the phosphorus, potassium and zinc were not high enough to be an in environmental risk. The additional phosphorus, potassium, and zinc should increase soil test values and a portion of each should be available for subsequent crops. As long as these fields are managed by the same growers in 2016 and 2017, they can recoup part of their investment on the additional fertilizer. With tighter margins in 2015, the only real loss these producers face is the additional expense on fertilizer that likely will not increase yields a single bushel.
While a yield goal method tends to recommend more fertilizer on fields that soil test in the moderate to high range (Table 1), the yield goal method could suggest less fertilizer on fields that soil test low or very low (Table 2). In these low-testing fields, AGR-1 is attempting to increase soil test values in addition to providing enough nutrients for the crops. So, a yield goal method likely over-fertilizes fields that soil test high and possibly under-fertilizes on fields that soil test low.
Again, yield goals are fun to talk about and are easy to understand. They may not be the most economical approach in 2015. If we cannot convince you to step away from the yield goal approach for 2015 then we will suggest an adjustment to your yield goal. For 2015, consider using an Olympic average as your yield goal instead of the maximum. If you follow AGR-1 for fertilizer and we get a good season, then you have a great chance of beating your Olympic average.