The soil fertility classification and constraints for rice cultivation in the Mekong Delta

Abstract

The areas of intensive rice production in the Mekong delta, Vietnam, have been rapidly enlarged but rice yield tend to be declined or need more fertilizers . Therefore, the degradation of soil fertility 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 incorporated with characteristics of soil morphology, soil physics, and soil chemistry were used for this study. Data from 300 soil profiles from rice fields and 28 field experiments on fertilizers efficiency were collected and analyzed, showing that 25 rice soil fertility types were classified in the Mekong delta, in which types of CC (clay in top and subsoil) and CCs (clay in top and subsoil and saline effected) occupied in large areas. 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-).