Changes on phosphorus fractions and paddy yield using different single super phosphate and rock phosphate rates under acid soil

Abstract

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.