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Background: Phosphorus, an essential element, plays a central role in cell metabolism and reproduction. It is a structural component of energy transferring molecules (ATP, ADP and AMP), nucleic acids, coenzymes, phosphor-proteins, phospholipids and sugar phosphates. In soils, the P does not occur abundantly as nitrogen or potassium. Despite its importance, only a proportion (~ 0.1-1.0%) of it is available for use by plants and microorganisms because phosphorous has poor solubility and gets fixed in soil. Many studies had been done regarding nutrient management of soil in various parts of the world, but limited study was done in India and in North- East India, it is relatively unexplored. Thus, the main aim of this experiment was to find out how nutrient management influencing P fractions under protected cultivation. Methods: The investigation area from which soil samples were collected i.e., Horticultural Farm, Assam Agricultural University, Jorhat-13, Assam. The study was carried out under protected poly house condition in the year 2017-18. The test crop was Capsicum (Capsicum annum var. Swarna). The design of the experiment was Split-Split plot technique. Random soil samples were collected from different treatments under protected cultivation at a depth of 0-15 cm. The soil samples were collected at two different stages of the crop viz., flowering and fruiting stages at 45 and 115 days after planting respectively. Result: The present study revealed that single factor effect of nitrogen (N), phosphorus (P) and potassium (K) had a significant effect on different forms of P The readily available P forms tend to increase in the fruiting stage while the iron bound phosphates registered a decrease. This implies that iron bound phosphate form predominantly controlled available P in acid soils under protected cultivation. The study indicates that iron bound P may be considered as slowly available labile P for fertilizer scheduling under protected cultivation. The present study also revealed that single factor effect of nitrogen (N) and phosphorus (P) had a significant effect on yield of capsicum. Among the various P fractions, Pi-water and Pi-Fe contribute more towards yield of capsicum. [ABSTRACT FROM AUTHOR]