Phosphorus dynamics and phosphatase activity of soils under corn production with supplemental irrigation in humid coastal plain region, USA

Abstract

A 3-year (2013–2015) field study was conducted to evaluate the effect of integrated nutrient management (NM) and three irrigation scheduling methods (IS): irrigator pro (IPro); normalized difference vegetative index (NDVI) and soil water potentials (SWP) on phosphorus (P) dynamics and phosphatase activity in four Coastal Plains soil types (ST) at various growth stages (CS: V6, six leaves; V16, sixteen leaves; and R1, silking) of corn (Zea mays L.). Nitrogen fertilizer was applied at two rates: 157 and 224 kg ha−1 through the irrigation system in three applications. Phosphorus dynamics and phosphatase activity varied significantly (p ≤ 0.0001) with year (Y), CS and ST, but not with NM. Phosphorus uptake of corn had an increase of about 1200% from V6 to R1. Both the Mehlich extractable P and water soluble P showed declining trends from V6 to R1. Concentration of P in pore water differed significantly (p ≤ 0.05) with IS in 2014 and 2015, but not in 2013. The order of the concentrations of P in pore water (averaged across ST) as affected by IS is as follows: 2013 (IPro = NDVI = SWP); 2014 (SWP = IPro < NDVI); and 2015 (IPro < NDVI < SWP). Concentration of phosphatase among the different ST was affected by CS, from V6 to R1 and soil depth, but not with NM. The difference in phosphatase concentration between the upper and lower soil horizons (averaged across Y and ST) was about 67.7 μg g−1 h−1. Our results have significant implication on P mobility, availability and management in areas where inputs of P in fertilizers may have had exceeded P output in harvested crops. Our results further suggest that understanding of P inputs and outputs which include P accumulation in soils and plants, as well as P losses is critical to determining the environmental balance and accountability of P in agricultural ecosystem. It is imperative to have a holistic understanding of P dynamics from soil to plant by optimizing P management and improving P-use efficiency.