Source: University of Kentucky Grain Crops Update

Recently a small group of farmers were interested in trimming costs, but not yield, in 2015. They provided their soil test values, historical yields, crop history, and intended production practices for 2015. Those growers reported they were applying $124 per acre more for fertilizer than what was recommended by the University of Kentucky. Even if we factored in enough fertilizer for the following soybean crop, they were spending about $100 per acre more. They were using yield goals to make their fertilizer decisions.

Growers enjoy farming based on yield goals. Yield goals are positive thinking. They are a challenge to the grower 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. But yield goals may cost you a lot of money in 2015.

The University of Kentucky publishes AGR-1 Lime and Nutrient Recommendations every 2 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 (P), potassium (K) and zinc than what AGR-1 recommends based on soil test values. While these rates were high, the P, K and zinc were not high enough to be an in environmental risk. The additional P, K 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 2016-17, they can recoup part of their investment on the additional fertilizer. With tighter margins in 2015, the only real loss these growers 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, but they may not be the most economical approach in 2015. If we cannot convince a grower to step away from the yield goal approach for 2015, then we will suggest an adjustment to their yield goal. For 2015, consider using an Olympic average as the yield goal instead of the maximum. If a grower follows AGR-1 for fertilizer and we get a good season, then you have a great chance of beating your Olympic average.