The West African semi-arid tropics is home to the world's poorest people. According to the recent United Nations Development Programme (UNDP) Human Development Index, which ranks countries in terms of life expectancy, education, and income, Sahelian countries fall in the bottom 15 percent of the 174 countries ranked. Niger sits in the 174th slot. Gray clouds engulf this last frontier.

Ninety percent of the people in this area live in villages, gaining livelihood from subsistence agriculture. Recurrent droughts and consequent crop failures in recent years have led to near destruction of the rural economy of the region. The low and erratic rainfall, high soil and air temperatures, soils with poor native fertility, surface crusting and low water-holding capacity, and recurrent water deficits during the crop season are some of the main factors limiting crop production.

In traditional agricultural systems, when crop yields declined to unacceptable levels, overcropped parcels of land were left fallow to restore fertility while new pockets were opened. But increasing population pressure has reduced the availability of land and resulted in reduced duration of fallow relative to the duration of cropping, to the point that shifting cultivation is losing its effectiveness. As a result, soil fertility is decreasing.

The soils of the West African semi-arid tropics have inherently low fertility with negative plant nutrient balances characteristic of many cropping systems. This striking feature makes the farming system unsustainable, low in productivity, and destructive to the environment.

"Phosporous deficiency is a major constraint to crop production in West Africa and response to nitrogen is substantial when both moisture and phosphorus are non-limiting. For many years, research has been undertaken to assess the extent of soil phosphorous deficiency, to estimate the phosphorus requirement of major crops, and to evaluate the agronomic potential of various phosphate fertilizers including phosphate rocks (PR) indigenous to the region, such as those found in Tahoua in Niger and Tilemsi in Mali. Despite the widespread and acute phosphate deficiencies in West African soils, very little phosphorus fertilizer is used by local farmers, partly because of the high cost of imported fertlizers," said Dr Andre Bationo, IFDC Principal Scientist, Soil Chemistry, based at ICRISAT, Niamy.

Long-term experiments allow a practical approach to address the difficult issues associated with the quantitative assessment of sustainability in agriculture. The survey and interpretation of data from the 24 long-term experiments on soil management conducted in semi-arid Africa have produced unique information on two fundamental soil processes; soil organic matter decline, and soil acidification. These processes control the sustainability of crop productivity under continuous cropping systems in the semi-arid countries of West Africa. Statistics show that sorghum has responded favorably to the fertilizer+manure treatment over the last 30 years.

One reason for the increases in millet yields after the application of mulch crop residues is changes in soil chemical properties, that lead to a better availability of nutrients, mainly phosphorus. Mulched crop residues also improve plant establishment and dry matter production of millets under the agroclimatic conditions that prevail in the Sahel. These beneficial physical effects are complemented by a decrease in the mechanical resistance of the surface soil, which may lead to better water infiltration and increases in root growth of millets after crop residue application. The relative importance of chemical versus physical effects of crop residues on millet growth depends on the soil's susceptibility to wind erosion, and the crop growth stage at which the damage occurs.

Water-use efficiency increased drastically with the addition of plant nutrients. Several technologies for land surface management and water-harvesting techniques, appropriate cropping systems,and varietal choices have been developed to optimize soil water use. Future research should focus more on studies on water and nutrient interactions and on understanding why present technologies are not adopted by farmers, by using the farmer's participatory approach.

The future of food security in Sahelian Africa is no longer uncertain. The farmers have started adopting innovations that will enhance the productivity of the soil. Govern-ment policies, according to the USAID Famine Early Warning System Bulletin, have also become more favorable for agriculture, with understanding increasing towards the need to encourage production and lessen risk. There is an upswing in the long-term climatic cycle, bringing greener days.