Effects of Phosphorus Blended with Dicarboxylic Acid Polymer (DCAP) on Yield of Sweet Potato, Cassava and Yam in Acid Sulphate Soils in the Mekong Delta

Abstract

     The phosphorus fertilizer use efficiency in acid sulphate soils usually is low because Fe²⁺ and Al³⁺ ions fix phosphate ions under low pH conditions. The objective of this study was to evaluate the influence of phosphorus fertilizer blended with DCAP on growth and yield of sweet potato, cassava and yam cultivated in acid sulphate soils in Long My - Hau Giang. The on-farm research was conducted in three farmer’s fields. The treatments included (i) no phosphorus application; (ii) 30 kg P₂O₅ ha^-1; (iii) DCAP (2‰) combined with 30 kg P₂O₅ ha^-1; (iv) 60 kg P₂O₅ ha^-1; (v) and DCAP (2‰) combined with 60 kg P₂O₅ ha^-1. Results showed that application of phosphorus blended with DCAP at 30 kg P₂O₅ ha^-1 increased the diameter, number of tubers and yield on sweet potato and cassava, which were comparable with the application of 60 kg P₂O₅ ha^-1. Thus, this practice seemed to be effective in reducing phosphorus fertilizer application. However, phosphate fertilizer blended with DCAP did not increase yam yield. It is needed to further test the efficiency of phosphate fertilizer blended with DCAP on sweet potato and cassava cultivated on larger area in acid sulfate soils in the Mekong Delta.