Plant and Soil Elemental Status as Influenced by Multi-year Nitrogen and Potassium Fertilization

Abstract

Forage management of perennial grass grown under potassium (K)-limiting soil conditions is not well understood. Our objective was to evaluate the elemental status of shoots and roots of reed canarygrass (Phalaris arundinaceae L.) as well as the soil fertility profile (0–90 cm) after five years of differential nitrogen (N) and K fertilization in a two-cut management system. Three N (0, 112, or 224 kg N ha−1) and three K fertilizer treatments (0, 56, and 112 kg K ha−1) were split-applied to reed canarygrass on a Williamson silt loam (coarse-silty, mixed, active, mesic Typic Fragiudepts) soil type in central New York State. At the Fall harvest in the fifth year, plant samples from low and high K fertilized plots all at the high N fertilization rate were cut at a 10-cm stubble height and sectioned into 10 segments vertically through the canopy. In addition, forage, root and soil samples were taken from all treatments to evaluate the distribution of elements under low soil K availability. Above ground biomass samples were separated into leaf blade, stem plus sheath, and dead tissue, if present. This assessment was repeated at the first cutting in the sixth year. That same year, soil cores were taken to a depth of 90 cm, sectioned into 15 cm increments, and analyzed for soil fertility parameters. Dry matter (DM) yield and proportion of DM yield at first harvest were both significantly increased by N fertilization, but not affected by K fertilization in 2001. Elemental concentrations observed vertically through the plant canopy followed patterns controlled primarily by (leaf blade):(stem + sheath) DM ratio and the difference in concentration between leaf blade and stem + sheath. Five years of N and K fertilization of reed canarygrass resulted in an accumulation of plant available K in the top 15 cm of soil under no N and high K fertilization, while the high N/no K fertilization combination greatly depleted soil K in the top 15 cm. Decline in K availability under high N and no K fertilizer was compensated for by an increase in root biomass, particularly in the surface layer. Except for soil K, N and K fertilization did not have an effect on the availability or distribution over depth of other nutrients in the soil.