The results of a case study conducted in Betulia (Sucre, Colombia) in May-Dec. 1983 to evaluate the competition for land between cassava cultivation (monocropped or in association with maize or yam) and cattle raising are discussed. In general, profits from cassava either in association or in monoculture are much higher than for cattle raising. Regarding labor requirements, cassava cultivation and cattle raising are equally attractive from an economic viewpoint.

The effect of land use on the availability of soil nitrogen (N) was studied by separating total soil N into one labile and one stable fraction by oxidation and extraction of labile N with potassium permanganate. The nitrogen management index (NMI) was calculated according to Blair et al. (1995) for the carbon management index. In all systems, labile N released by potassium permanganate was a better indicator for nitrogen availability than were total and stable N. The NMI was a good indicator for N availability but gave no information on the total amount of N.

Land degradation is a great threat for the future and it requires great effort and resources to ameliorate. The major causes of land degradation in Ethiopia are the rapid population increase, severe soil loss, deforestation, low vegetative cover and unbalanced crop and livestock production. Inappropriate land-use systems and land-tenure policies enhance desertification and loss of agrobiodiversity. Utilization of dung and crop residues for fuel and other uses disturbs the sustainability of land resources. The supply of inputs such as fertilizer, farm machinery and credits are very low.

Summarises the literature on the alleged defects of traditional systems of land tenure in Nigeria. Reviews the provisions of the land use decree and their implications for rural land tenure.

Frontier areas in Latin America have been characterized by land speculation, abandonment and exploitation. This paper analyzes a frontier cattle ranching area in the savanna where intensification has occurred in spite of land speculation. A whole farm livestock production model is used to quantify the determinants of intensification. Results show that land speculation has simultaneously increased the profitability of cattle ranching while slowing down intensification and impeding the adoption of sustainable practices.