Effect of minimum tillage, sowing rate, and sowing time on the yield of a sorghum-sudangrass hybrid in the Manawatu, New Zealand

Abstract

Abstract A forage sorghum (Sorghum bicolor (L.) Moench. × Sorghum sudanense (piper) Stapf) cv. Sudax ST-6 was investigated as a means of increasing summer forage production in the Manawatu, New Zealand. An experiment comparing pre-sowing treatments showed no advantage in spraying with paraquat or rotary-hoeing before ploughing. In a second experiment, Sudax was direct-drilled into either a perennial ryegrass-white clover (nil herbicide) or white clover (herbicide) sward at 15,30,45, or 90 em row widths to give seed rates of 25, 12.5, 8.3, and 4.2 kg/ha. Sudax yields were unsatisfactory, increasing from 0.1 to 0.6 t dry matter (DM)/ha as seed rate increased in the ryegrass-white clover sward; in the white clover sward yields increased from 0.5 to 2.7 t DM/ha as seed rate increased with an advantage for total herbage of 1.1 t DM/ha over a control sward. A third experiment compared yields from eight sowing dates at weekly intervals from 5 November 1975. Frost damage occurred on the first three sowings, but m...