EFFECTS OF N, P, AND K ON CHEMICAL COMPOSITION OF BARLEY GROWN ON A LOW-FERTILITY PODZOL SOIL IN THE GREENHOUSE

Abstract

Chemical composition of Herta barley (Hordeum distichon L.) grown in the greenhouse on an extremely low-fertility Podzol soil as influenced by N, P, and K fertilization was investigated in relation to feed quality and straw strength. Two experiments, a 6 × 6 NP factorial on the low-P soil and a 6 × 6 NK factorial on the low-K soil, were simultaneously conducted to examine chemical composition of barley sampled at early vegetative, mid-vegetative, and mature stage of growth. Percent protein N and nonprotein N (NPN) in vegetative tissue and grain increased with successive rates of N, whereas they decreased as P and K rates were increased. The N × K interaction effects on grain yield and protein N were greater than the N × P interaction effects. Percent NPN was considerably higher in vegetative tissue than in grain. It appeared that a low-percent K and a high-percent Ca rather than a high-percent NPN in vegetative tissue were associated with lodging. Percent Ca and Mg in vegetative tissue increased with increasing rates of P and decreased with increasing rates of K, but showed little response to N.