Influence of dicarboxylic acid polymer in enhancing the growth and productivity of sweet potato (Ipomoea batatas L.) in acidic soil

The available phosphorus (P) in acid sulfate soils (ASSs) is low because of fixation by aluminum (Al) and iron (Fe), resulting in decreased P use efficiency and crop yield. At present, the use of dicarboxylic acid polymer (DCAP) coated on P fertilizer is expected to improve P use efficiency and plant productivity. However, the influence of DCAP on P solubility and on the yield of sweet potato cultivated in acidic soils has not been elucidated. Thus, the aimed of this study was to evaluate the effect of the use of DCAP-coated P fertilizer on the availability and nutrient uptake of P as well as the yield of sweet potato. Under the greenhouse condition, the use of DCAP significantly improved P availability (~3 mg P kg(−1)), increasing tuber diameter and length by ~0.5 and ~1.0 cm, respectively. Thus, the productivity of sweet potato in the treatment 40-kg P(2)O(5) and 60-kg P(2)O(5) ha(−1) coated with DCAP was higher by about 100 g pot(−1) than that in the same rate of P fertilizers (40- and 60-kg P(2)O(5) ha(−1)) not coated with DCAP. In the field experiment, P accumulation (82.7 kg P(2)O(5) ha(−1)) and tuber yield (22.0 t ha(−1)) in the treatment of DCAP-coated with 60-kg P(2)O(5) ha(−1) were not significantly different compared with that in the treatment of 80-kg P(2)O(5) ha(−1) (82.1 kg P(2)O(5) and 21.7 t ha(−1), respectively). Furthermore, the use of DCAP combined with 75% P fertilizer increased the P availability by the same amount as that with the use of 100% P fertilizer. Hence, the use of DCAP reduced about 25% of the chemical P fertilizer applied in soil.