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In the past two years, ICRISAT, in collaboration with other International Agricultural Research Centres, National Agricultural Research and Extension Systems, has been evaluating and promoting point or hill application of fertilizer along with "Warrantage" in three West African countries, namely, Burkina Faso, Mali and Niger. The hill application of fertilizers consists of applying small doses of fertilizer in the planting hills of millet and sorghum. The combination of strategic hill application of fertilizer with complementary institutional and market linkages, through an inventory credit system (known as "Warrantage") offers a good opportunity to improve crop productivity and farmers' incomes. Results from the two year on-farm trials showed that, on average, in all the three countries, grain yields of millet and sorghum were greater by 44 to 120% while incomes of farmers increased by 52 to 134% when using hill application of fertilizer than with the earlier recommended fertilizer broadcasting methods and farmers' practice. Substantial net profits were obtained by farmers using "Warrantage". Farmers' access to credit and inputs was improved substantially through the "Warrantage" system. The technology has reached up to 12650 farm households in the three countries and efforts are in progress to further scale-up and out the technology to wider geographical areas.

In the West African Sahel, farmers use the zai technique to reclaim degraded cropland. Although the nutrients released by the decomposition of the amendments are central to the success of the technique, little is known regarding the impact of the zai pits on the decomposition process and whether the nutrient release is synchronized with plant requirements. The decomposition of millet stalks and cattle manure applied in zai pits or at the soil surface was studied in Niger using litterbags, under controlled irrigation on-station in 1999 and on-farm in 1999 and 2000 at two locations (Damari and Kakassi) with contrasting soils. In addition, a satellite trial was conducted in 2000 on-farm at the same locations to study the relative contribution of termites to manure decomposition. Only at Damari did termite presence enhance manure decomposition, by a factor three for surface placement compared to the zai pits. At Damari, zai pits enhanced the decomposition when termite activity was suppressed. Whereas manure decomposition proceeded two to three times faster than that of millet stalks at Damari, the type of amendment had no effect on decomposition rate at Kakassi. Nutrient release followed the trend of organic amendment decomposition except for K. When applied prior to the rainy season, nutrient release rate of organic amendments strongly exceeded plant nutrient uptake, which could lead to important leaching losses during the first 4-6 weeks after sowing, especially for N and to a lesser extent for K. However, at harvest, total nutrient absorption by plants was generally higher than the total amount released. The results indicate a highly site-specific response of amendment decomposition to zai and the need for a better timing of amendment application to reduce potential leaching losses, possibly through a split application.

Pearl millet (Penisetum glaucum (L.) R.Br.) is a major food crop grown on impoverished sandy soils in the Sahel. A 9-year long-term study was undertaken in the Sahel to test the hypothesis that integrated use of millet crop residues retained on farm ®elds after harvest and mineral fertilizers results in greater and more sustainable yields and conserve soil fertility better than either the use of residue or fertilizer alone. The four treatments compared were: (1) control (crop residue removed and no fertilizer applied), (2) crop residue alone, (3) 30 kg N 13 kg P ha À1 (fertilizer) alone and (4) crop residue fertilizer. Use of crop residue fertilizer increased grain yield fourfold over the control; use of fertilizer doubled millet yield relative to the control and crop residues resulted in 1.2 times more yield than the control. Crop residues signi®cantly improved nutrient-use ef®ciency of the applied fertilizer. Sustainability yield index (SYI), a measure of an upward trend in yield over time, was greatest in crop residue fertilizer plots as are soil organic carbon, available P and pH. Stability analysis indicated that crop residue fertilizer treatment gave in greater yields and returns over fertilizer cost in the various seasons than either crop residue or fertilizer.

The fertilizer microdosing technology deals with the application of small quantities of fertilizers in the planting hole, thereby increasing fertilizer use efficiency and yields while minimizing input costs. In drought years, microdosing also performs well, because larger root systems are more efficient at finding water, and it hastens crop maturity, avoiding lateseason drought. Recent research found that solving the soil fertility problem unleashes the yield potential of improved millet varieties, generating an additional grain yield of nearly the same quantity. Recognizing that liquidity constraints often prevent farmers from intensifying their production system, the warrantage or inventory credit system helps to remove barriers to the adoption of soil fertility restoration. Using a participatory approach through a network of partners from the National Agricultural Research and Extension Systems (NARES), non-governmental organizations (NGOs), farmers and farmer groups and other international agricultural research centres, the microdosing technology and the warrantage system have been demonstrated and promoted in Burkina Faso, Mali, and Niger during the past few years with encouraging results. Sorghum and millet yields increased by up to 120%, and farmers' incomes went up by 130% when microdosing was combined with the warrantage system. This chapter highlights the outstanding past results and the ongoing efforts to further scale up the technology using Farmer field schools (FFS) and demonstrations, capacity and