Influences of Soil Environment on Biomass and Nitrogen Accumulation Rates of Orchardgrass

Abstract

AbstractGrasslands are the basis for a stable agriculture in the northeast USA. However, knowledge of the interactive effects of the diverse soils and climate of this region on grassland production remains scant. Our objective was to quantify the effect of soil environment on grassland biosmass and N accumulation. The study was conducted for 3 yr on four sites in central Pennsylvania selected for soil water holding capacity and temperature regime. Orchardgrass (Dactylis glomerata L.) was treated with a split application (50%/50%) of 0, 84, and 168 kg N ha−1 of 15N depleted ammonium nitrate. Biweekly biomass samples were taken starting 30 April of each year and continuing until the grass heading stage. At heading, plots were cut at a 7.5‐cm stubble height and all herbage removed. Plots were refertilized with the second half of the N and monthly biomass sampling commenced on 31 July and continued until 31 October. Biomass samples were dried at 60 °C and weighed for yield. Subsamples of the dried material were analyzed for N and isotope ratio. Spring biomass accumulation rates ranged from 60.0 to 112.0 kg ha−1 day−1. Soil N, N fertilization and temperature all were factors controlling spring biomass accumulation rate. Fall biomass accumulation rate was controlled by N fertilization alone. Spring fertilizer N accumulation rates range from 0.078 to 0.72 kg ha−1 day−1 and were largely controlled by N fertilization. Spring total N uptake rates ranged from 0.461 to 2.20 kg ha−1 day−1 and were controlled by soil N levels and N fertilization. Fertilizer N recovery was about 42% for the spring growth period but only about 15% for the fall growth period.