Dry matter accumulation and changes in forage quality during primary growth and three regrowths of irrigated winter cereals

Abstract

Selected cultivars of oats (3), barley (2), wheat (3), cereal rye (1) and triticale (3) were grown under irrigation at Trangie, N.S.W., in 1978 and 1980. Dry matter accumulation and changes in the moisture, nitrogen and phosphorus content and dry matter digestibility of forage were monitored at intervals of about 21 days during uninterrupted primary growth (June-September 1980). In a split-plot design the crops were cut at 80 days, 80 and 122 days, and 80, 122 and 164 days after sowing. Regrowth was sampled on two or three occasions to determine dry matter yield and quality. Most cultivars accumulated 16-20 t/ha of dry matter by the end of sampling in late September; cereal rye only yielded 14 t/ha. Early maturing Minhaffer oats produced the highest yield when uncut but regrew poorly after cutting. Under a 42-day cutting interval oats and barley yielded 12-13 t/ha, winter wheat yielded 10-11 t/ha and triticale yielded 10-1 2 t/ha. The nitrogen and phosphorus content of all forages decreased linearly during primary growth. Oats and wheat had similar digestibilities and these began to decrease rapidly 40-50 days before head emergence (mid-August). The early maturing barley and triticale cultivars had lower digestibilities than oats. Regular cutting maintained the nitrogen content and digestibility of all cultivars above 2.7% and 72% respectively. Dry matter accumulation was described by mathematical equations which allowed cultivars to be compared under different cutting regimes. They also allowed dry matter and digestible dry matter yields from different systems of cutting to be predicted for irrigated cereals in western New South Wales.