Agricultural soils are usually deficient in phosphorus (P), causing yield reduction. To boost crop production and P availability in acid soil, rock phosphate (RP) can be used with single super phosphate (SSP), which can also supply available P for the long-term during a crop cycle. The study was conducted to show the effect of SSP and rock RP on the P release and fixation pattern and its uptake by paddy variety CAU-R1 in acid soil. The experimental design was randomized block design having six treatments, where P supplied through i) only SSP, ii) only RP, iii) 3/4th SSP + 1/4th RP, iv) half SSP + half RP, v)1/4th SSP + 3/4th RP and vi) control. The addition of P in general increased all inorganic P forms with time over untreated control. There was an increase in saloid-P, Aluminum-P, Iron-P, Calcium-P, and available P concentration reaching maximum on 50th day with gradual decline till harvest. Phosphorus application significantly increased P uptake, dry matter yield, tiller number, and plant height of paddy during the entire growth period. Comparatively higher P uptake and grain yield were observed in soil applied with SSP and RP at 1:1, as SSP predominantly supplied P at the earlier growth stage and RP released P slowly. Therefore, the combined use of SSP and RP at 1:1 can provide a constant pool of available P and improve agronomic efficiencies under acid soil.
