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

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 maximum yields at harvests in February, March, and April were from the first two sowings. Total yields in April increased from 11.8 to 21.3 t DM/ha for the latest to earliest sowing.

Keywords:

• Sorghum bicolor × Sorghum sudanense
• sudangrass hybrid
• Manawatu
• sowing date
• yield
• digestibility
• direct-drilling
• seed rate