The Impact Of Cultivation On Rangeland Above Ground Herbaceous Primary Production And On Some Soil Properties. A Case Study Of Ol Moran Location, Laikpia District
Muthiani, Elizabeth N
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Rangelands are traditionally used for livestock and wildlife production but have increasingly been put under crop cultivation in the recent past. Consequently, land use conflicts, which include crop farmers versus pastoralists, wildlife versus livestock and human versus wildlife, are common. This has been exacerbated by the subdivision of large-scale pastoral lands and ranches into small-scale units that cannot support a viable livestock enterprise. This practice is fuelled by the most common held principle that, communal land tenure, common in rangelands, is the main impediment to increased productivity and prosperity. Studies that elucidate the effects of cultivation on both rangeland primary production and soils are few as well as those comparing primary production from communal and privately managed ranches. A study was carried out to investigate the effect of cultivation on above ground herbaceous primary production and on some vegetation attributes in 01 Moran location, Ng'arua Division, Laikipia District. The impact of cultivation on some soil physical and chemical properties was evaluated and the rate of encroachment of crop farming was assessed . Above ground herbaceous primary production and soil properties were determined from cultivated and uncultivated areas under continuous cultivation and grazing respectively. Crop production of maize and beans was determined from plots cultivated for over three and ten years respectively each with three treatments; Planted without manure or fertilizer (Tl), Planted with manure (T2) and planted with fertilizer (T3). Production from cultivated plots was compared with herbaceous primary production from Private commercial ranch (PR) and Communal grazing area (CG) , which was determined by clipping. Two sites, Mlima Fisi and Quarry were sampled in PR while in the CG, 01 Moran and Mutaro were sample. Above ground herbaceous primary production was significantly different (F 7,14=23.17, df=7 p<0.05) across the land use treatments with cultivated farms recording the lowest overall. Above ground standing crop from uncultivated plots was about double that from plots cultivated with no manure or fertilizer. There was no significant difference between primary production from PR and that from plots cultivated for ten years with fertilizer. Primary production from CG did not differ significantly from that of plots cultivated for three years with fertilizer. Species richness and basal cover did not differ significantly between CG and PR. Cultivated sites had significantly lower species richness and woody vegetation species density than the uncultivated. The two sites in PR had significantly different woody species density with Quarry having a higher density than Mlima Fisi and the difference was attributed to the differential levels of use by wild herbivores and especially elephants. Cultivated areas recorded higher soil fertility, better soil texture and lower bulk densities than the uncultivated areas. The latter was attributed to the returning of crop residue in the cultivated fields and probably due to the use of fire in the uncultivated fields. However, soil fertility was generally low across all the land use treatments. Cultivated soils had better texture and lower bulk densities-than the uncultivated. Contrary to the expected results, forest cover increased by 58 %, while as expected, cultivated farms increased from 50 Km-2 to 524 Km-2• Area of bushed grassland decreased by 29% from 1770 Km-2 to 1257 Km-2 Rainfall amount and distribution was observed as the major limiting factor to crop farming. Despite the addition of crop residue in the crop fields, soil fertility was generally low in the study area. Therefore, rangeland cultivation should be accompanied by prudent soil fertility management. Further, forage production in the rangelands can be increased by improving rangeland soil fertility. While factors constraining proper range use should be controlled, research should look for alternative sources of livelihood other than cultivation in the rangeland.