Tillage, Seeding Rates, and Fertilizer Placement for Corn Grown in Claypan Soil Under Low-Yield Environments.

Corn grown in claypan soil of southeastern Kansas requires good management, especially in years when the yield potential is low.  Data are limited regarding tillage, seeding rate, and fertilizer placement decisions for corn grown in the area.  The experiment was conducted at the Mound Valley Unit (Site 1) and the Parsons Unit (Site 2) of the Southeast Agricultural Research Center for four years each (Site 1: 2009-2012; Site 2: 2010-2013). The experimental design was a split-plot arrangement of a randomized complete block with three replications. The whole plots were three tillage systems: conventional, strip tillage, and no-till. Conventional tillage consisted of chisel and disk operations in the spring. Strip tillage was done with a Redball strip-till unit in the spring prior to planting. The subplots were a 5 × 2 factorial combination of five seed planting rates (18,000, 22,000, 26,000, 30,000, and 34,000 seeds/a) and two fertilizer placement methods: surface band (dribble) on 30-in. centers near the row and subsurface band (knife) at 4 in. deep. At the Mound Valley site, N and P nutrients were supplied as 28% urea ammonium nitrate and ammonium polyphosphate (10-34-0) applied at 125 lb/a N and 40 lb/a P₂O₅. Based on initial soil tests, at the Parsons site only N was applied by the two placement methods.  In all years at either site, corn yield was low and overall averaged less than 105 bu/a.  Since corn yields averaged <30 bu/a, data from 2011 were omitted.  In the six other low-yielding site-years, the treatment effects on yield and yield components were inconsistent.  In some site-years, conventional tillage and knife placement of fertilizer increased corn yield, partially because of improved stand and more kernels per ear, respectively.  Although increasing seeding rate increased stand, decreases in the number of ears per plant and kernels per ear often mitigated yield increases.