Effect of N and P Starters On Short-Season Corn Grown in Conservation Tillage Systems On a Claypan Soil.

Recent use of short-season cultivars to avoid mid-summer drought has increased corn acreage on the upland, claypan soils of southeastern Kansas.  However, fertility and tillage options are not well defined on these soils.  Thus, the objective of this research was to determine the effect of N and P rates in starter fertilizers on short-season corn planted with reduced or no tillage.  The experimental design was a split-plot arrangement with tillage system as whole plots and starter N-P combinations as subplots.  Rainfall was variable in both 2006 and 2008 and though yield and yield components were affected by year, there were few treatment effects.  Average yield was about 15% greater with the fertilizer treatments than with the no N or P control, likely due to a similar increase in the number of kernels per ear.  There were no differences in yield or yield components between tillage systems, starter N rates, or starter P rates, nor were there any meaningful interactions between tillage and starter fertilizer treatments.  In contrast to yield, average dry matter production was affected by tillage at V6, V12, and R1 growth stages and by P starter early in the season prior to reproductive growth.  However, the response was greater in 2006 as indicated by significant interactions of tillage and P starter with year.  At V6, reduced tillage resulted in about 20% more growth than with no tillage.  Reduced tillage resulted in significantly greater dry matter production throughout the season, but the difference became non-significant as the plant reached late growth stages.  Early in the season, increasing P rate in the starter resulted in significantly greater dry matter production.  However, this response declined rapidly and was not significantly different by the time the corn plant entered reproductive growth.