This was also visible in aerial photos. In general, differences between plots with and without starter fertilizer were clear. However, differences between plots with various types of starter were small or undetectable. Yield increases were smaller in 1998 than in 1996 or 1997. Research has not determined why response to starter fertilizer is more in some years than others.
Slower planting is another cost of using starter fertilizer.
On average, using starter slows the planting operation by about ten to fifteen percent. The value of this lost time depends on the individual farming operation. There did not appear to be any yield benefit to using in-furrow starter in addition to placed starter, nor to the addition of starch, S, Zn, or B in the experiments where those materials were used. The starch treatment was tried because researchers in Idaho have reported yield gains from using row-placed starch for wheat. This helps confirm that substantial yield responses to starter are often observed in Missouri conditions.