Use of zeolite-restoration material to suppress cadmium uptake into agricultural crops

Abstract

We describe the effect of a soil restoration material created using natural zeolite on the suppression of Cd uptake by agricultural crops in a Cd-contaminated farmland. The natural zeolite material (particle size < 1 mm), produced in the Kyushu area in Japan, demonstrates quantitative adsorption of Cd in test solutions. In this study, we prepared a restoration material consisting of the natural zeolite as a main metal-adsorbent, magnesia lime as a regulator of soil pH, and volcanic weathered clay to assist in homogeneously mixing them, for use in a test field. We refer to this prepared restoration material as a zeolite supplement. To determine the effect of applying this zeolite supplement on Cd uptake into crop, we performed tests in a double cropping farmland of rice and wheat for four consecutive years. Our results showed that Cd content was lower by 41 % and 86 %, respectively, in rice and wheat harvested from divisions where zeolite supplement was applied than the Cd content of crops in the control division where the zeolite supplement was not applied. Interestingly, the suppression of Cd uptake not only maintained for four years without further application of the zeolite supplement, but application of the supplement also resulted in the harvest of good quantities of rice and wheat. Thus, our study shows that this cultivation practice does not repeat application of large quantities of the supplement each year and is consequently a lowcost countermeasure for agricultural land contaminated with heavy metals.