Effects of Previous Corn Hybrid On Following Hybrid's Root Weight Density and Plant Biomass.

Increasing demand for corn grain has encouraged many US growers to implement a continuous corn (corn-corn) cropping system. Research data verify the yield decrease in corn-corn compared to a corn-soybean system. However, research is limited that identifies characteristics of better performing hybrids from poorer performing hybrids in corn-corn to those in a corn-soybean system. Our research objective is to determine the relationship of the first year hybrid to the yield of the second year hybrid in multiple environments and relative to a corn-soybean rotation, focusing on root weight density and plant biomass. Root weight density and plant biomass were collected at Ames, IA (south) and Nashua, IA (north) at vegetative (V) and reproductive (R) stages: V4, V12, VT-R1, and R6. Root weight density was measured through root extractions from a known soil volume. Three hybrids were arranged as the main plot in 2007 with 12 hybrids arranged in a split-plot design in 2008 on the existing main plots. The 12 hybrids were also placed onto nearby soybean residue at each location to provide a comparison to the corn-corn plots. The same experimental design was also used in 2008 and 2009 except soybean main plots were established with the three corn hybrids. Hybrids for each research farm were chosen based on their relative maturity, disease susceptibility, and genetic background. The first year hybrid did not impact the root density or biomass of the second year hybrid.  However, root and plant weights differed among the 12 hybrids grown in 2008. These differences indicate certain hybrids produce a larger plant and more abundant root system per given soil volume. A larger plant and root system indicates that certain hybrids may perform better in a corn-corn rotation.