Dallisgrass yield, quality and nitrogen recovery responses to nitrogen and phosphorus fertilizers

Publisher Website
Google Scholar
Abstract
Nitrogen applications to dallisgrass grown on Oliver silt loam, an Aquic Fragiudalf, increased forage yield, forage digestibility, nutrient concentrations and nutrient contents as N rates increased to 896 kg ha"-1. Expressing yield as a function of N application rate resulted in quadratic prediction equations that account for 75 to 98% of the variability in yield during five years. Eighty-six percent of the maximum yield was obtained during the five years at 448 kg of N ha-1. Plant concentrations of N, Ca and Mg were increased more than concentrations of the other macronutients as N rates increased. Plant contents of N, Ca and Mg in the forage increased 4.0, 3.2 and 3.5-fold as N rates increased to 448 kg ha-1, while that of P, K and S increased 2.5 to 2.8-fold. Residual N accumulations in the soil profile were apparent at the 896 kg ha-1 rate at the end of the growing seasons but were not detected the following March, indicating N losses by leaching and/or denitrification occurred at that N rate. Phosphorus applications increased forage P concentration but did not increase forage yield nor available P levels in the surface 15 cm of soil. Maximum yields were obtained at forage P concentrations and Bray No. 2 soil P levels as low as 2.0 g kg-1 and 17 mg kg-1, respectively.