EFFECT OF STARTER FERTILIZER ON CORN-SILAGE YIELDS ON MEDIUM AND HIGH FERTILITY SOILS

Use of a starter fertilizer banded near the row with the planter is an efficient method of fertilizer application for corn (Zea mays L.), but application of excessive rates is uneconomical and can contribute to nutrient loading to surface and ground water. The objective of this study was to evaluate yield response to starter fertilizer in the silage production systems common in the dairy farming areas of the northeastern USA. Three N-P-K starter fertilizer rates-none, low (11 to 14 lb P/acre), and high (22 to 22 to 28 lb P/acre)-were compared on 12 on-farm sites in northwestern Vermont from 1986 to 1989. All soils tested medium or higher in P and K; most were poorly or somewhat poorly drained; and most sites received dairy manure before planting. Three of the five sites testing medium in P and/or K showed a yield increase from starter fertilizer application, primarily the low rate, while a fourth showed an increase only in early plant growth (EPG). These four responsive sites were on poorly or somewhat-poorly drained soils, while the nonresponsive site was well drained. None of the seven sites with medium-high or higher soil tests showed an increase in EPG and only one had a small increase in silage yield. Concentration of P or K in EPG samples increased with the use of fertilizer on some, but not all, of the responsive sites. These results show a high probability of yield response to starter fertilizer on sites testing medium in P or K, especially on soils with limited drainage, but only low rates were needed. The probability of response is much lower on soils testing higher in P and K.