Nitrogen fractions and soluble carbohydrates in Italian ryegrass II.—Effects of light intensity, form and level of nitrogen

Abstract

Abstract S.22 Italian ryegrass grown in a glasshouse during June on clay loam soil at three light intensities (100, 68 and 44% of daylight), was given 6 amounts of N (0–500 ppm) as NH 4 + ‐N or NO 3 − ‐N. Grass grew best in 100% daylight, and with NH 4 + ‐N yields were most at 500 ppm and with NO 3 − ‐N at 200 ppm. Total‐N, total soluble‐N and nitrate‐N, were much more, and protein‐N, amide‐N (psrticularly asparagine‐N) and α‐amino‐N much less in grass given NO 3 − ‐N than in grass given NH 4 + ‐N. These differences increased with increasing amounts of applied N. Shading, or increasing the amount of N increased total‐N, total soluble‐N, soluble organic‐N and nitrate‐N, and decreased protein‐N and soluble carbohydrates. Light intensity had most effect on the amount of solyble carbohydrates in grass given 100 ppm of N and the effect decreased with increasing amounts of N. ‘N‐Serve’ indirectly influenced the chemical composition of grass by maintaining N in the soil in the NH 4 + ‐N form.