Response of panlcum maximum jacq. Anderagrqstls superba peyr. To Simultaneous pressure of soil water deficit and simulated grazing In the south central semi-arid rangelands of Kenya

Abstract

Kenya's arid and semi-arid areas have been exposed to frequent droughts and overgrazing for a long period of time. The consequence of this has been the degradation of the range forage resources. This study was therefore undertaken at Kiboko National Range Range Research Station to investigate the interactive effects of grazing intesity and soil moisture deficit on tillering, regrowth and forage yields of Panicum maximum Jacq. and Eragrostis superba Peyr., the key Kenyan range forage grasses. The research layout consisted of three macroplots each measuring 12m x 4m which were demarcated and replicated twice. Each macroplot was further subdivided into 24 (lm x 1m) microplots. Twelve microplots within each macroplot were randomly transplanted with Panicum maximum Jacq. and the other 12 with Eragrostis superba Peyr. splits. Adequate watering was maintained until the grass splits were properly established. Before initiating water and defoliation treatments, all the grass plots were clipped down to 2 ern stubble heights. Soil moisture deficits were generated by withholding water for a variable 2, 7, and 14 days while defoliations were effected at 4 (four) defoliation levels viz. unclipped controls, clipping that left 20, 10, 5cm stubble heights. The effect of defoliation on Panicum maximum Jacq. on tillering ability, regrowth height and forage yield was significantly greater under higher soil moisture deficit compared to that of Eragrostis superba Peyr. It is thus concluded that under conditions of favourable soil moisture, the superior perfomance of Panicum maximum Jacq. to defoliation, as evidenced by its greater foliage production, higher tillering ability and regrowth height, makes it more suitable as a forage source than Eragrostis superba Peyr. in the areas within the semi-arid rangelands with relatively higher mean annual rainfall. On the other hand, the results of this study show that Eragrostis superba Peyr. was more tolerant to defoliation under less favourable moisture conditions than Panicum maximum Jacq. and is therefore more suited to the relatively more arid parts of Kenya's south central semi-arid rangelands.