Effect of application of molasses to paddy soil on the concentration of cadmium and arsenic in rice grain

Abstract

Molasses, a liquefied by-product of sugar production from sugarcane, is one of the most easily decomposable organic substances. We investigated the effect of the application of diluted molasses in paddy rice (Oryza sativa L.) fields on cadmium (Cd) and arsenic (As) absorption in rice grains as a measure of the shortage of irrigation water or rainfall. The application of diluted molasses on to the top of the soil surface at one week before or after heading led to a decrease in the redox potential of the soil. The Cd concentration in the rice grains was significantly decreased with the application of molasses (2000 kg ha−1) at heading or one week after heading. However, early application of molasses (one week before heading) did not decrease the Cd concentration in the rice grains with downsizing of grain particle size. Meanwhile, As concentration in the rice grains did not change with early application at one week before heading, while it increased with application of molasses at heading or one week after heading. This method is useful especially for decreasing Cd concentration in rice grains in a region under lack of irrigation due to drought.