Effect of cutting frequency and nitrogen application on herbage yield and nitrogen content of a degraded Panicum maximum pasture.

Abstract

The effects of cutting frequency and levels of nitrogen on revitalization of a run-down pasture were investigated in 2000 and 2001 at Nsukka, Nigeria. Grass swards were cut at intervals of 3, 6, 9 and 12 weeks and received 0, 150, 300 and 450 kg N ha' nitrogen. Grass dry matter yield was increased from 52 to 75% at the 3 and 6 weeks intervals of cutting, respectively. Weed proportion was reduced from 48 to 25% with 6-weekly cuts compared with more frequent cutting at 3 weeks interval between cuts. Cutting interval did not affect the total herbage yield. The dry matter yields of leaf blade, stem and inflorescence fractions increased significantly with increase in interval between cuts in the second year. The percentage nitrogen content was highest with 3-weekly interval of cut and decreased with high interval of cuts in the second year. Crude protein yield (kg ha') was highest with 6- and followed by 3- and 9-weekly intervals of cut and decreased with lar cutting of 12-weekly interval. Fertilizer-N treatment significantly increased total annual herbage dry matter yield from 3,460 kg ha yrl where no fertilizer N was applied to 5,233 kg ha-yr' with application of 450 kg N ha-'. Grass dry matter as proportion of the total herbage dry matter was increased from 57 to 80% with the highest N rate of 450 kg Nha compared with where N was not applied, while the weed dry matter as proportion of the total herbage dry matter was reduced from 43 to 20% with the highest N rate of 450 kg N ha compared with where N was not applied at the second year. A combination of 6-weeks interval of cutting with 450 kg N ha' gave the highest dry matter yield. It was also adequate in suppressing weed. Frequent cutting at higher levels of fertilizer N (300 - 450 kg ha'') increased the nitrogen and crude protein percentages of forage foliage while 6-weekly interval of cuts when combined with higher N levels gave the highest crude protein yield per hectare per year in the foliage herbage.