The Effects of Soil Temperature and Form and Level of Nitrogen on Growth and Chemical Composition of Italian Ryegrass

Abstract

Abstract Italian ryegrass was grown in a clay loam soil in a greenhouse at 3 soil temperatures 11°, 19.5° and 28°C. with 6 levels of N (0 to 500 ppm.) as NH 4 + (treated with “N serve”) or NO 3‐ . Tops grew best at 19.5° and roots at 11°C. At 19.5° yields of tops with NO 3 ‐N were maximal at 100 ppm. and with NH 4 ‐N at 200 ppm. Increasing NO 3 ‐N above 100 ppm. greatly decreased yields of tops, but increasing NH 4 ‐N did not. Yields of tops were larger with NO 3 ‐N than with NH 4 ‐N at low levels of N but were smaller at higher levels. Root weights were similar with both forms of N, but whereas the roots were well distributed throughout the soil with NH 4 ‐N, with NO 3 ‐N, they were mainly confined to the top half of the soil. Form of N greatly influenced the composition of the grass. Increasing NO 3 ‐N decreased the concentrations of P, Cl and S, and NH 4 ‐N decreased the concentrations of Ca. Percent N was larger with NO 3 ‐N than with NH 4 ‐N. Raising the soil temperature greatly increased % Ca and % Mg but had little influence on concentrations of N, P, S, Na, and K. Percent Cl was always largest at 11°C.