Corn Response to Phosphorus Based Starter Fertilizer Application on the Seed.

The use of fertilizer banded directly on the corn seed at planting for corn (Zea Mays L.) is common in central and western Minnesota.  Soils in these areas can vary in their soil test P due to soil pH levels which can range from 6.0 to 8.5 within a field.  The purpose of this study was to determine if rates of starter fertilizer applied directly on the corn seed should be changed based on soil test level and in the presence or absence of a high rate of P broadcast before planting.  Eight locations were studied from 2012 to 2014.  Sites were selected that had variation in soil chemical properties, particularly soil P tests.  Treatments were applied using a split plot design and were replicated sixteen times.  Main plots were an application of 0 or 59 kg P ha^-1.  Main plots were subdivided into four subplots where 0, 13.1, 26.2, and 39.3 kg ha^-1 of an 10-15-0 (N-P-K) fertilizer was applied with the corn planter on top of the seed.  In-furrow application of P fertilizer increased early plant mass and P uptake across soil test P categories regardless of the use of broadcast P fertilizer.  Corn grain yield was increased by in-furrow starter fertilizer across initial P soil test classes when broadcast P was nota applied.  The lowest in-furrow starter application rate increased yield and no further response occurred for the 26.2 and 39.3 kg ha-1 rates.  Broadcast fertilizer increased yield but only when soils tested less in the medium classification (<12 mg P kg^-1 by the Olsen P test).  The data suggests that a P based in-furrow starter fertilizer program can enhance corn production but the use of in-furrow fertilizer is best for low soil test levels and only when P is not broadcast at high application rates.