Assessment of soil phosphorus supplying capacity in some rice paddy fields in the Mekong River Delta of Vietnam using deffusive gradient in thin films technique

Abstract

The study aimed to evaluate the soil P-supply capacity for the crop uptake using the Deffusive gradient in thin films (DGT) technique and the P absorption interaction between two groups: soil available P and dissolving P in Bac Lieu and Can Tho provinces using the DGT method. Soil samples were collected in the experimental fields where were applied with different P fertilizer rates: no P fertilizer, 40 kg P2O5 per ha, and 60 kg P2O5per ha. The DGT tool which was designed with three gel layers was directly put onto the soil surface within 24 hours. The results showed that the soil P availability rate in no P fertilizer and 40 kg P2O5/ha treatments were higher than that in 60 kg P2O5/ha treatment in both Bac Lieu and Can Tho provinces. However, there were no significant differences in the soil P availability rate in the treatments applied with 0 and 40 kg P2O5/ha compared with the 60 kg P2O5/ha treatment (P>0.05). The P which was analysed by DGT (PDGT) has a close interaction with Olsen-P (r>0.73) and dissolving P in soil solution (r> 0.95). The DGT technique could substitute for the Olsen and Malachite Green methods to determine the soil available P. Applying the DGT technique can evaluate exactly the P resleased from soil solution, thereby increasing the P use efficiency in the rice cultivation.