Effect of ground rubber vs. ZnSO4 on spinach accumulation of Cd from Cd-mineralized California soil
Abstract:Certain soils derived from marine shale in Salinas Valley, CA, USA, contain significant levels of natural Cd but normal levels of Zn, all derived from the soil parent materials. Crops grown on these soils contain high levels of Cd, and because of the high Cd:Zn, this Cd is highly bioavailable and a risk to the food-chain. Growing crops which accumulate only low levels of Cd has been the best management for these soils. Fuller understanding of food-chain transfer and risk of Cd indicates that addition of Zn fertilizer may substantially reduce Cd accumulation by the crop, and that the crop Cd would have much lower bioavailability. Further, while seeking to identify byproducts which could be beneficially used in agriculture, it became evident that ground rubber may provide Zn for such soil remediation at much lower cost than purchase of commercial Zn fertilizers. Further, ground rubber is rich in Zn from highly purified Zn, so the ground rubber used in this experiment contained 13,400 mg Zn and 0.2 mg Cd/kg dry weight. Zn from ZnSO4 or ground rubber was applied to Lockwood soil (9.0 mg Cd and 56 mg Zn/kg) at 0–200 mg Zn/kg and spinach was grown to harvest stage. Concentration of Cd and Cd:Zn ratio in the crop were greatly reduced by the Zn treatments. Ground rubber was somewhat less effective than ZnSO4 in lowering spinach Cd, but much less expensive. Ground rubber is a valuable byproduct soil amendment to reduce risk of Cd in soils with high Cd and Cd:Zn ratio.
Document Type: Research Article
Publication date: January 1, 2007
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