Effect of harvesting interval and N-fertilizer application on the gross energy, digestibility and crude fibre content of field swards.

摘要

A field experiment was conducted in 1986 using grass swards established at the University of Nigeria farm in Nsukka, Nigeria, to determine the harvesting frequency in the growing season and the level of nitrogen (N) fertilizer that would give good quality herbage throughout the growing season. The effect of four application levels of N fertilizer in the form of urea (0, 150, 300 and 450 kg/ha) and six harvesting intervals (3, 4, 5, 6, 8 and 10 weeks after planting) on field swards of Northern gamba grass (Andropogon gayanus), Guinea grass (Panicum maximum cv. S112) and star grass (Cynodon polystachyus) were studied over 30 weeks period in 1986. A significant reduction in dry matter (D values) of total herbage was observed with the interval extended from 3 to 6 weeks and a further significant reduction with extension from 6 to 10 weeks in the three species. The highest D-value of 75.3% was obtained from plots cut every 3 weeks and was slightly greater than 54.2% obtained from plots cut every 10 weeks. A progressive reduction in D-value was observed when N application rates increased from 150 to 450 kg/N per ha. There was a significant increase in gross energy (GE) content by increasing N application and a greater increase by increasing interval between harvests. The crude protein content of the herbage was significantly affected by the treatment combinations. A slightly significant increase of 8.2% crude fibre was observed when intervals between harvests increased from 3, 4 and 5 weekly cut to a 6, 8 and weekly-cut. Thus, harvesting every 4, 5 and 6 weeks for Northern gamba, Guinea and star grasses and fertilizing at a rate of 300 kg N/ha are suggested as good management practices that would significantly increase forage production and maintain a more sustainable productive stand..