Effect of plant height at cutting, source and level of fertiliser on yield and nutritional quality of Napier grass (Pennisetum purpureum (L.) Schumach.)

Abstract

Napier grass (Pennisetum purpureum (L.) Schumach.) was studied using a 5 x 3 factorial experiment arranged in a randomised complete block design with three replications. The treatments were five fertiliser applications (0kg ha^-1 N, 46kg ha^-1 N and 92kg ha^-1 N, 1t ha^-1 and 2t ha^-1 cattle manure) and three plant heights at cutting (0.5m, 1m and 1.5m). The mean dry matter (DM) yield was 8.21t ha^-1 per cut but increased when the plant height at cutting increased and when the level of N fertilisation increased (P<0.05). Neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), cellulose, calcium, in vitro dry matter digestibility (IVDMD) and metabolisable energy were significantly (P<0.05) affected by plant height at cutting while total ash, crude protein (CP), ADF-ash, hemicelluose and phosphorus were affected by both plant height at cutting and fertiliser level. As plant height at cutting increased from 0.5m to 1.5m, IVDMD declined from 71.74% to 61.03% (P<0.05). Correlations between IVDMD versus CP, NDF, ADF, ADL, cellulose and hemicellulose were high with r = 0.92, -0.94, -0.96, -0.98, -0.83 and 0.74, respectively. CP yield per hectare per day of growth was highest for the 0.5m height at cutting, whereas the digestible DM yield was highest at both the 0.5m and 1.0m cutting height. The results of the present study suggest that Napier grass could be categorised under medium to high quality forage if cut at 0.5m or 1.0m height.