Agronomic Evaluation of Phosphorus Sources in Lowland Rice Production

Abstract

Phosphorus (P) deficiency is one of the most yield-limiting factors in lowland rice production on Brazilian Inceptisol. The objective of this study was to evaluate eight P sources for lowland rice production. The P sources were simple superphosphate (SSP), polymer-coated simple superphosphate (PSSP), ammoniated simple superphosphate (ASSP), polymer-coated ammoniated simple superphosphate (PASSP), triple superphosphate (TSP), polymer-coated triple superphosphate (PTSP), monoammonium phosphate (MAP), and polymer-coated monoammonium phosphate (PMAP). These P sources were applied in four rates (i.e., 50, 100 200, and 400 mg P kg⁻¹) + one control treatment (0 mg P kg⁻¹). Plant height, straw yield, grain yield, panicle number, and root dry weight were significantly increased in a quadratic fashion with increasing P levels from 0 to 400 mg kg⁻¹ of all the P sources evaluated. However, overall maximum root length and P-use efficiency were significantly less at greater P levels. Based on regression equation, maximum plant height was obtained with 262 mg P kg, maximum straw yield was obtained with 263 mg P kg⁻¹, maximum grain yield was obtained with 273 mg P kg⁻¹, and maximum panicle density was obtained with 273 mg P kg⁻¹. Plant growth and yield components had significant positive association with grain yield, except maximum root length. Based on grain yield and average P rate of maximum grain yield, which is 273 mg kg⁻¹, P sources were classified for P-use efficiency in the order of PSSP = TSP > PTSP > PASSP > SSP > MAP > ASSP. Soil chemical properties [pH; P; potassium (K); calcium (Ca); magnesium (Mg); hydrogen (H) + aluminum (Al); cation exchange capacity (CEC); base saturation; Ca, Mg, and K saturation; acidity saturation; Ca/Mg, Ca/K, and Mg/K ratios] changed significantly with the addition of different P treatments.

Keywords:

• Grain yield
• P-use efficiency
• root growth
• yield components

Acknowledgement

Polymer-coated P sources were supplied by Produquímica/Wirstchat Com. & Ind. S.A., São Paulo, Brazil.