Effects of season, maturity and rate of nitrogen fertilizer on ensilage of Setaria sphacelata

Abstract

A study was made of the chemical composition and silage fermentation of Setaria sphacelata CV. Nandi. The grass was ensiled at three periods of the growing season, with two maturities at harvest, and grown with two levels of nitrogen fertilizer. On each harvest day cuts were taken in the morning, at noon, and in the afternoon. The object was to measure the variation that occurred under field conditions in south-eastern Queensland. The water soluble carbohydrate content of the grass was always below 6 per cent of its dry weight, and the silage had very low contents of lactic acid, high contents of volatile acids and high pH values. Volatile base contents were usually well below 20 per cent of the total nitrogen, showing that degradation of protein was not extensive. By traditional standards of silage quality the S. sphacelata was poorly preserved. On the other hand a degree of preservation was achieved as shown by the moderate amount of protein breakdown and small losses of dry matter and nitrogen during storage. Variation in the extent of fermentation changes, and of losses during ensilage, demonstrated that grass cut at five weeks was more effectively preserved than grass cut at eight weeks. Also, on any one harvest day, grass cut during the morning had lower dry matter contents, and was not as well preserved as cuts made later during the day.