Rootworm Resistant Hybrids Increase Removal of Mineral Nutrients Compared to Non-Resistant Isolines.

Rapid adoption of corn rootworm (RW) (Diabrotica sp) resistant corn hybrids (Zea mays L.) has occurred during the past five years due to ease of insect control and distinct yield improvements. Compared to non-resistant near isolines, increased grain yield of RW resistant hybrids is probably a consequence of larger, more active root systems that allow for greater uptake of water and mineral nutrients. The objective of this study was to quantify increases in yield and mineral nutrient removal, and to determine if a re-evaluation of fertilizer recommendations is needed for modern corn hybrids containing biotech protection from corn rootworm. Hybrids were evaluated at Urbana, IL in 2008 and at Urbana and DeKalb, IL in 2009 and 2010. Treatment factors consisted of genetic background (2-7 hybrid pairs) and insect protection trait (RW resistant vs. non-resistant within a hybrid pair).

Across five site-years, non-resistant hybrids averaged a yield of 10.2 Mg ha^-1, while yield of insect protected RW hybrids averaged 11.0 Mg ha^-1 (8% increase). This increase in yield corresponded with increases in grain nutrient removal of N (7%), P (9%), K (10%), Mg (4%), S (7%), Zn (7%), B (11%) and Mn (6%). Grain nutrient removals of P, K, and B were not proportional to increases in grain yield, indicating increased concentrations of these elements.

Our data shows that transgenic rootworm protected hybrids consistently improve grain yield and increase grain nutrient removal. Increased uptake and removal of immobile nutrients such as phosphorus and potassium by RW resistant hybrids necessitates a thorough re-evaluation of fertilizer recommendations in order to realize the high yield potential brought about by advances in plant breeding and biotechnology.