Much of the Upper Great Plains consists of a rolling or gently rolling landscapes. Fields can be described as having hilltops, side hills and bottom ground. Soil test values, crop yields and water holding capacity are generally quite different in these landscape positions. Hilltops generally have higher pH values, lower phosphorus, potassium, sulfur, zinc and organic matter. Bottom ground generally is the opposite of hilltops in these soil test values, with side hills being in between these two. Crop yields and plant available water are usually the lowest on the hilltops and greatest in the bottom ground and side hills. Yields on poorly drained bottom ground is highly variable from year to year. Yields may be very low in years with excess water or high in drier years.

Plant population research and observations have shown that higher seeding rates on hilltops, with limited moisture, will likely result in lower yields when compared to a lower plant population. Bottom ground and side hill areas of a field can usually support higher seeding rates, which can translate into higher yields.

Fertility research on small grains, corn and soybeans has shown that crop production yield goals can be managed differently across these landscape positions. Breaking up fields into these various crop potential zones, soil testing these zones separately and fertilizing them accordingly can increase crop production. For example, a corn yield goal of 100-125 bu/acre for the hilltops and 150 bu/acre for the side hills and if the bottom ground is well drained, 150-175 bu/acre. In this case, the appropriate amount of fertilizer is placed in each area of a field, instead of a blanket one-rate uniform broadcast application.

By incorporating variable rate seeding and variable rate fertility based upon these management zones, growers may be able to reduce input costs, increase their yields and maximize profits on their farms. University and Industry research is ongoing in managing fields in this way.

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