Rice Soil Fertility Classification and Constraints in the Mekong Delta

Abstract

In the Mekong Delta, Vietnam, areas of intensive rice production have been rapidly enlarged. Soil fertility degradation in this system can be one of the most important factors contributing to the yield decline. Information on soil fertility and recommendations on improving soil constraints will provide basic data for proper soil management, land evaluation and land use planning. A Fertility Capability Classification (FCC) system incorporates characteristics of soil morphology, soil physics, and soil chemistry. Data from 300 soil profiles in rice fields and 28 field experiments on fertilizers efficiency were collected, showing that there were 25 rice soil fertility types, in which types CC (clay in top and subsoil) and CCs (clay in top and subsoil and saline effected) occupied in large extent. The major soil constraints for rice cultivation can be listed as follows: low organic carbon content (o); high P fixation and high Fe toxicity potential (i); potential salinity (s^-); low available P (p); high acidity and Al toxicity (a); the separation of actual acid sulfate soils (c, c^-) and potential acid sulfate soils (f, f^-).