Illinois Fertilizer & Chemical Association
Supply · Service · Stewardship

Utilizing Omission And Inclusion Plot Techniques To Increase Yields Of Soybeans And Wheat

S. A. Ebelhar, E. D. Nafziger, J. Niekamp, R. Higgins and C. A. Bradley
Over the past 30 years, corn yields in Illinois have increased by 65% from an average of 102.7 bu/acre to 169.8 bu/acre. At the same time soybean yields have only risen 37% (from 34.5 to 47.3 bu/acre) and wheat yields have only risen 35% (from 45.1 to 60.6 bu/acre). There are reports of 160 bu soybeans/acre and 151 bu soft red winter wheat/acre. Both trials emphasize the need for a more holistic approach to high yield management.

Traditional research trials contained factorial arrangements that were particularly useful as they would allow for interaction effects among variables to be evaluated. However, because of the multiplicative nature of factorial designs, experiments became too large if more than 2 or 3 factors were evaluated at the same time. The use of omission plot techniques would allow for a much larger number of variables to be included in a study (the “all-in” or “combined effect” treatment, so to speak). These factors could be best management practices or elevated rates of products or new products or practices which have shown some promise of increased yields. Then one would drop out one factor at a time to see what effect that particular treatment contributed (the “individual” effect) to grain yields.

The objectives of this study are to 1) determine the individual effects and the combined effects of several nutrient, pest management, and other growth enhancing products for improving wheat and soybean yields through the use of omission and inclusion plot techniques; and 2) evaluate new technologies and compounds, as appropriate, which might be added to the omission/inclusion study over time.