Do new corn hybrids and yield levels influence potassium fertilizer management?

The frequency of potassium (K) deficiency symptoms in corn has increased in recent years. Observations in Iowa and neighboring states have shown that the reason for these symptoms was a low soil K level in about two-thirds of the instances reported. In the rest of the instances, however, the K deficiency symptoms resulted from a variety of reasons related to limitations in root growth or water uptake and/or K uptake by plants. It is known that factors that limit root activity and growth greatly inhibit K uptake and yield because K is a relatively immobile nutrient in soils. A strong root system and continuous growth of fine roots are required to supply sufficient K to high yielding crops. However, there has not been research on K use efficiency or K fertilizer need of genetically modified modern hybrids with traits that may directly or indirectly affect the physiological needs for K or the plant capacity for K uptake. Of particular interest is the rootworm resistance trait, because a healthier root system without a need for root insecticides and higher yield could result on different root size or surface area that, in turn, can affect K uptake and the yield response to K fertilization. Therefore, a research project has been investigating since 2006 the K nutrition of corn hybrids with or without the rootworm resistance trait