Forage Yield and Sucrose Response of Rhodes and Ruzi Grass to Cutting Height and Cutting Frequency Under Irrigation

The development of irrigated pastures in the Sudan is still at its infancy. The present study determined the influence of 2 cutting heights (2.5 and 5.0 cm) and 4 cutting frequencies (4-, 6-, 8-, and 10-week) on forage yield as dry matter and forage sucrose of Rhodes grass ( Chloris gayana Kunth. cv. Massaba ) and Ruzi grass ( Brachiaria ruziziensis Germain et Everard cv. Congo Signal ) under irrigated conditions. Forage yield interactions involving species X cutting height X cutting frequency were significant. These yield interactions were attributed to differences in growth period and growth rhythm of the two species. On average, Rhodes exhibited a short growth period (13 months) compared to Ruzi grass (20 months). Forage yield and forage sucrose were, on average, superior in Ruzi compared to Rhodes grass. Forage yield and forage sucrose averaged 5.2 t ha⁻¹ and 7.2 % fw sucrose in Ruzi compared to 2.8 t ha⁻¹ and 6.9 % fw sucrose in Rhodes grass. Forage yield and forage sucrose of both species were negatively correlated with cutting frequency. The highest forage yield may be obtained at an 8-week cutting frequency in Rhodes (45.6 t ha⁻¹ yr⁻¹) compared to a 10-week cutting frequency in Ruzi grass (88 t ha⁻¹ yr⁻¹). Results suggest that very high forage yields as dry matter and forage sucrose of Rhodes and Ruzi grass may be possible under irrigated conditions in the Sudan at a cutting frequency of between 8 to 10 weeks.