NITROGEN-FERTILIZER MANAGEMENT TO IMPROVE CROP TOLERANCE TO CORN-ROOTWORM LARVAL FEEDING DAMAGE

Widespread use of crop management practices that reduce the effect of corn rootworm (Diabrotica spp.) larval feeding damage on maize (Zea ma ys L.) plant lodging or grain yield production would reduce grower rel iance on chemical pesticides. Nitrogen fertilizer placement can affect root system morphology and distribution within the soil profile. This study was conducted to determine if N fertilizer placement can be use d as a tool to improve maize tolerance to rootworm infestation. The ef fects of planting time broadcast or split-applied (planting-cultivatio n) banded N (UAN; 28-0-0 N-P-K) treatments on root larval feeding dama ge, root pull resistance, lodging, grain yield, and survival of larvae to adult stage under different levels of controlled rootworm larval i nfestation were investigated. Results of the 3-yr field experiment sug gest that root systems were generally larger (greater root pull resist ance) under banded N (85 kg plant(-1)) than under broadcast N (68 kg p lant(-1)) at the time when rootworm larval feeding had ceased. Lodging (stem greater than 30 degrees from vertical) in broadcast N plots (51 %) was greater than that seen in banded N plots (41%). If tolerance to rootworm larval feeding damage is defined by the presence of a large root system and by the ability of the stem to stand erect, then banded N fertilizer placement can help improve tolerance to corn rootworm la rval feeding damage.