Residual effects of P on wheat in a rice-wheat sequence
1994
Goswami, J. | Barrova, S.R. | Thakuria, K. (Assam Agricultural Univ., Jorhat 785013 (India). Agronomy Dept.)
Residual effects of fertilizer P sources applied to rice on subsequent wheat growth were assessed. The soil was a loamy sand with pH 5.1, 0.59 percent organic C, 90.96 mg available N/kg (extracted in 0.32 percent KMnO4), 3.39 mg available P/kg (Bray I), and 20.45 mg available K/kg (extracted in neutral IN NH4OAc). P was applied to the rice as either single superphosphate (SSP) or diammonium phosphate (DAP) at transplanting, or mussorie rock phosphate (MRP) or purulin rock phosphate (PRP) 15 d before transplanting at a rate of 13.1, 26.2, and 39.3 kg/ha; 175 kg P/ha was applied as SSP to the wheat at sowing. Both rice and wheat also received 40 kg N/ha and 16.6 K/ha. Treatments were replicated three times in a randomized block design. Rice variety Culture 1 and wheat variety Sonalika were used. Wheat was sown at 120 kg seed/ha at a planting depth of 5 cm in rows 20 cm apart. Significant differences were observed among both sources and levels of P in their residual effects on P uptake and to a lesser extent on grain yield. Differences among sources were greater than those among levels, with the rock phosphates having the greatest residual effect. In no case did the residual effects match the benefit of directly applying P to the wheat
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