Rootworm Resistance Affects Corn Grain Nutrient Concentration.

The planted area of corn rootworm (Diabrotica spp.) resistant hybrids (RWH) has been steadily increasing in the last growing seasons. The suppression of rootworm larval feeding protects the root system and this could affect grain nutrient content and concentration, but this effect has not been studied even though it has important implications for nutrient and crop management. Two pairs of RWH and their near-isogenic non-RWH of 111 and 113 relative maturities were evaluated at Champaign, IL. These hybrids were grown under five N rates (0 kg ha-1 to 270 kg N ha-1) applied as ammonium sulphate. Yield, nutrient concentration and nutrient content were determined. Averaged across N rates, the grain yield was 1.4 Mg ha-1 higher for the RWH but there was no effect of relative maturity. Nitrogen, P, K and Zn grain concentration were significantly higher for the RWH whereas Cu and Mg were higher for the non-RWH. Grain nutrient content was higher for the RWH compared to the non-RWH (except for Cu). The shorter season hybrids had significantly larger P, Mg, Mn, Fe and B concentration but lower S and Zn than the longer season hybrids. Increased N and S availability decreased grain P, K, Mg, Zn, and B concentration, increased N and S, and did not affect Mn, Fe, and Cu. Grain content of all nutrients increased with N and S availability.