AbstractThe main uses to which marginal and arid rangelands are put involve livestock production, tourism based on wildlife and ethno-tourism, and agriculture, i.e. crop production. There is minimal dry land forestry, sometimes as agro-forestry. The emphasis placed on these three main uses varies according to the ecological potential (i.e. climate, topography and soils) and accessibility to the areas.Taking the Kenyan example, approximately 20% of the land is arid and used almost exclusively for livestock production while ethno-tourism runs a poor second in dry seasons because of inaccessibility. Current technology in Africa precludes extensive irrigation. Peak production of livestock is in the late wet season and early dry with marketing mostly in dry seasons. Over 50% of the land is semi-arid where all three uses are practised. Livestock production is still the most important and agriculture the least important, because rainfall is unreliable and erratic, wildlife populations are larger and so tourism is more important (e.g. Amboseli, Isiolo, Samburu). Agriculture occurs particularly in wet years and wet seasons.Although land is only very locally suited to agriculture, permanent water sources, rivers and springs may enable year round settlement. Farmers of non-pastoral backgrounds (and even some pastoralists) wish to follow their traditions and attempt cultivation. This is occasionally successful in above average years of rainfall (two years in five) on good soils but fails in dry years when it also deprives livestock of essential traditional dry season grazing reserves.Marginal areas occupy perhaps 12% of the land but are in high demand for all three use categories. Pastures are ideal for fattening livestock bred in more arid areas and they have a rapid turn-over. Wildlife populations are often at their highest in these areas, e.g. Laikipia, Mara and Nairobi park. Areas are relatively accessible on tarmac roads for year round viewing of wildlife. Agricultural resettlement has spilled over from higher potential lands where human populations are exceeding the carrying capacity.Increasing food requirements have led to a greater demand for efficient land use and to diversification into new areas, e.g. eco-tourism, ostrich farming or the intensification of traditional uses such as camel rearing.Lailipia District, situated mostly in marginal and semi-arid land is used as a case study. Here, successful conservation measures on mostly private land, which was formerly used by Maasai for subsistence pastoralism, has led to the largest population of wildlife in Kenya outside parks and reserves. At the same time land is used in part for crop production especially in the higher potential areas, but also wherever land is available for co-operative arable farmers to purchase. Livestock production remains however, the most widespread form of land use. The main seasonal variation in use is with crop production in the rains and game viewing in the dry seasons but extremes are less than in the lower rainfall areas.Recent preliminary analysis of the economics of various forms of land use in Laikipia indicate that in those limited areas where agriculture is reliable (e.g. irrigated areas near rivers) returns may be as high as US$ 132 to 166 per ha per annum. Wildlife tourism which prevails in less well watered areas may yield US$ 4 to 5 per ha, while conventional livestock rearing yields from US$ 0.2 to 1.4 per ha per annum. Game cropping is the least well developed and the least productive but is accepted as a necessity by the Kenya Wildlife Service, particularly with regard to zebra which compete with livestock for resources. It yields only US$ 0.2 to 0.4 per ha per annum.Wildlife and livestock occur together, except where there has been considerable outlay on electric fencing. Predators, especially lions and hyenas, are incompatible with livestock and together with certain wildlife which may act as disease vectors (e.g. buffalo) reduce income by US$ 0.5 per ha per annum. By contrast, the addition of camels, which are eco-friendly milk and meat producers, with no reduction of conventional stock, may increase livestock yields by US$ 0-4 per ha per annum.Combined wildlife tourism, cropping and livestock, including camels, may yield US$ 4.7 to 6.4 per ha per annum, which although still less than 5% of agricultural yield, is the best that may be achieved at present on a sustainable basis. Crop production is highly dependent on rainfall which becomes less predictable the more arid the land. It may not be sustainable in the long term in its present form.Current returns on investment are low for all forms of land use. Constraints to increasing returns are outlined. Research agendas need to be tailored to provide answers which could help minimize them. In particular, we need to refine our knowledge concerning the economics of the different options, both conventional and non-conventional.
A County-Level Assessment of Manure Nutrient Availability Relative to Crop Nutrient Capacity in Iowa: Spatial and Temporal Trends