Abstract
Phosphorus (P) is an endemic soil constraint to crop production in rainfed semi-arid regions like the 1.82-Mha Pothohar Plateau in Pakistan, where we monitored the P status of rainfed wheat (Triticum aestivum L.) and determined crop responses to P application by broadcast and banding methods. Nutrient indexing of young whole shoots and associated soils revealed severe to moderate P deficiency in most fields. In a 3-year field trial on P-deficient soils, grain yield increases were 130-233% with broadcast and 175-239% with banded P; fertilizer requirement for optimum crop yield was twice as high for broadcasting than banding. Fertilizer use was highly profitable, especially with banding, and increased both available soil P and organic matter. This comprehensive approach of soil-plant nutrient indexing and selective field trials provided a rational economic basis for P fertilizer use in rainfed agriculture and serves as a model strategy for stimulating crop productivity in developing countries.