Yield Response to Starter Fertilizers Mixes Containing Either N, P, or K On High Testing Soils for Two Corn Hybrids in Minnesota.

Farmers in the northern Corn Belt utilize starter fertilizer to speed plant growth under shorter growing seasons.  Typically starter fertilizer is applied to corn (Zea Mays L.) in spite of high P and K levels in the soil and broadcast fertilizer application.  This study examined yield effects of N, P, and K on two corn hybrids.  Starter fertilizer was applied 5 cm besides and below the seed in combinations of no starter (chk), N starter, N+P starter, K starter, N+K starter, and N+P+K starter at 10 locations over two years testing high in P or K.  Rates applied 11 kg N, 10 kg P, or 19 kg K ha^-1 for all starter combinations and hybrids consisted of a near isoline with (+BtRW) and without (-BtRW) the Bt rootworm (Diabrotica sp.) gene.  Corn yield was increased by starter P at one location and K at one location.  Starter N did not increase yields at any location and differing combinations of nutrients did not have additive effects of the nutrients alone.  Yields differed between hybrids at 3 of 10 locations with higher significantly higher yields for the +BtRW hybrid at one location and –BtRW hybrid at two locations.  There was no difference in response to starter between treatments for each hybrid across locations.  Data from this study indicate a small probability of a yield increase from starter N, P, or K under conventional tillage when soil test levels for P and K are high.