Effects of the Level of Fertilizer Input on Dry Matter Productivity of Napiergrass and Kinggrass

Abstract

Growth of napiergrass (Pennisetum purpureum Schumach) and kinggrass, the hybrid between napiergrass and pearl millet (Pennisetum typhoides), was measured under three levels of chemical fertilizer supply during the growing season. Plants were grown in 1/2000 a wagner pot by transplanting single tillers and growing them under natural conditions in 1999 and 2000. Plant length, total expanded leaf number per shoot (TELN/S), total dry matter weight (TDMW), stem dry matter weight, root dry matter weight and mean tiller dry matter weight (MTW) increased with time for both grasses and increased with an increase in the level of fertilization. Top per root ratio in both grasses increased but the ratio of leaf blade per stem with leaf sheath did not vary with an increase in the level of fertilization. Crop growth rate (CGR) and leaf area index (LAI) increased for both grasses as the level of fertilization increased. The relationship between TELN/S and LAI was quadratically negative for each level of fertilization in both napiergrass and kinggrass, and the change in TELN/S with time was one of the major factors contributing to the change in LAI. The increase in LAI was linearly related to that in CGR, which was affected by the increase in level of fertilization. With an increase in level of fertilization, tiller number (TN) and TELN/S increased, which resulted in an increase in TDMW because of the change in LAI. It was suggested that these were plant factors that increased TDMW of both grasses both years under higher input of fertilizer. The difference in dry matter productivity between napiergrass and kinggrass was negligible because the increases in TN, TELN/S and MTW compensated for each other in both species as affected by the increase in fertilization.