Effect of Organic and Inorganic Sources of Phosphorus and Potassium on their Different Fractions under Potato-Radish Cropping Sequence in a Brown Hill Soil

Field experiments were conducted during 2004–05 to 2006–07 at Central Potato Research Institute's farm on brown soils in mid hills of Shimla to investigate the role of organic and inorganic sources of phosphorus and potassium on different fractions of phosphorus and potassium in soil after three cycles in a potato-radish sequence. The eight manurial treatments consisted of inorganic and organic sources of nutrients. The potato crop received differential doses of phosphorus and potassium from inorganic fertilizers or FYM as per schedule of treatments whereas succeeding radish crop received only N. Application of recommended dose of N along with 50% PK from inorganic fertilizers and rest from FYM (on K basis) in potato resulted in the highest dry matter yield of potato (5.72 t ha⁻¹). This treatment also gave highest dry matter yield of following radish crop (1.89 t ha⁻¹). Therefore, for the higher productivity of the potato-radish system, 25 to 50% of the recommended dose of P and K fertilizers could be replaced with FYM in the mid hill soils of Himachal Pradesh. Results showed significant variations in different fractions of phosphorus and potassium and soil chemical properties. Highest soil pH (6.50) was obtained with application of 100% PK from farmyard manure (FYM on K basis). Likewise, integrated use of 50% PK from inorganic fertilizers and 50% from FYM resulted in highest organic carbon and available P content in soil. Total N and available K were, however, higher when 75% PK was applied though inorganic fertilizers and 25% from FYM. Fractionation studies revealed significant increase in saloid-P, AI-P, Ca-P and various forms of K under integrated use of inorganic fertilizers and FYM.