Is starter phosphorus fertilizer necessary for corn grown on Atlantic Coastal Plain soils?

Abstract

Abstract Producers managing Coastal Plain soils in Maryland have reported visual symptoms of P deficiency in corn (Zea mays L.) grown on soils with P concentrations above the agronomic optimum range (e.g., 40–84 mg kg–1 Mehlich 3‐extractable phosphorus [M3P]). Yet, corn yield response to starter P fertilizer on soils with M3P concentrations above this range has not been consistently demonstrated in the literature. The objective of this study was to evaluate corn yield response to application of starter P fertilizer to soils with varying M3P concentrations. This study was conducted at three locations in Maryland where, following 14 yr of phytoremediation by continuous cropping and no P applications, M3P concentrations ranged from 34 to 237 mg kg–1 in soil samples collected from plots prior to study commencement. Beginning in 2015, half of each main plot received inorganic P application prior to corn planting in 3 yr, with corn yield measured in each split plot in each year. We observed no interaction effect of starter P fertilizer and soil P category on corn yield at any location. When the data were analyzed by site‐year, we observed no interaction effect, an effect of soil P category in 5 of 9 site‐years, and a yield response to starter fertilizer in 2 of 9 site‐years, with a positive yield response in 1 site‐year and a negative yield response in the other. Based on these results, we do not recommend Mid‐Atlantic farmers invest in starter P fertilization for corn grown on Coastal Plain soils when not recommended by soil testing.