This chapter discusses the principles and approach to optimize fertilizer use, which involve linear programming that aid in developing fertilizer optimization tools (FOTs) that aid farmers in their choice of crop-nutrient-rate combinations likely to be most profitable given a budget constraint. Development and use of Excel and paper FOTs is also described.

Africa's fertilizer use averages only 8 kg per hectare per year. Available fertilizer recommendations in Africa are high, and vary between countries. The recommendations are generally out dated, and/or "blanket" recommendations that are not site, or crop specific. Recommendation de-* Corresponding author.

Sorghum [Sorghumbicolor (L.) Moench] is an important food crop grown by subsistence farmers in Africa for its seeds and fodder with little or no fertilizer. Information is scarce for sorghum response to nutrient application for many production areas in west Africa. Research was conducted to determine macro and micronutrients response in an Integrated Soil Fertilizer Management (ISFM). The experiment was conducted both in farmerss field of Angoual Mata and at station in Tarna. Four N levels (0, 20, 40, 60 kg ha-1) were combined with five P levels (0, 7.5, 15, 22.5, 30) and four K levels (0, 10, 20, 30) to constitute 15 treatments. An additional treatment of N-P-K-Kieserite-Zn-B (40-22.5-20-15-2.5-0.5) was used to test the effect of micronutrient deficiency. These 16 treatments were tested in a randomized complete-block design with three replications at each site. The number of ears, the dry weight of ears, the weight of dry stem and grain yield were measured at maturity. Added N and P, increased yield and yield component but K did not influence these parameters. The combination of NPK with Kieserite-Zn-B yielded the highest number of ears (82) and ears weight (2300 g). On the station, the highest grain yield (1334 kg ha-1) was obtained with NPK with Kieserite-Zn-B.On farmerss field, the N-P-K combinations (40-30-0 40-22.5-20 40-22.5-30) and with Kieserite-Zn-B gave similar and highest grain yield. NPK supplementation with micronutrients such as kieserite, zinc and boron improves the number and the weight of the ears of sorghum in our studying area.