Author(s)

P. Sampanpanish, S. Ruangkhum & C. Tongcumpou

Abstract

The effects of phosphorus in commercial fertilizers on concentrations of total cadmium (Cd) and zinc (Zn), plant-available Cd and Zn and sugarcane uptake of Cd and Zn were studied. A single rate (312.5 kg/ ha) of 16-16-8 NPK fertilizer was applied on three levels (0-3, 3-20 and >20 mg) of Cd contaminated sugarcane cultivated field in Mae Sot district, Tak province. In order to investigate the effects of different rates of fertilizer application, 16-16-8 NPK fertilizer at the rate of 312.5, 625 and 1,250 kg fertilizer/ ha was applied to soils in a pot experiment and planted with a piece of mature cane stem. The pot experiment was conducted in a randomized block design with three replications. Repeat applications of fertilizer were made at the same rate in the fifth month of the cultivation for both field and pot experiments. Soil and sugarcane samples were collected at the end of the second and the sixth month respectively. After harvesting, sugarcanes were divided into five components: underground stems, roots, bagasses, juice and leaves. Chemical analysis of the field experiments showed that total Cd and Zn in sugarcane increased with Cd concentration in cultivated field and found that Cd and Zn mostly accumulated in roots. Longterm effects of fertilizer application was expected to be a concern although there was no higher Cd and Zn concentrations in soil after repeat fertilization in the fifth month of the cultivation. For the pot experiment, the results showed that higher P can make more Cd available and ease take up and accumulation in different parts of the sugarcane. Moderate P application rate reduced phytoavailability of Zn at the end of the second month because of the P-Zn mineral precipitation. However, the ability of sugarcane to uptake Zn increased again at the end of the sixth month of the cultivation at which time total P in the soil decreased. Total Cd and Zn in sugarcane were significantly increased with increasing 16-16-8 NPK fertilizer application rates and we found that Cd and Zn accumulated in sugarcane according to the following sequence: roots> underground stems (setts)> bagasses> leaves> juice. Keywords: phosphorus, fertilizers, cadmium, zinc, phytoavailability, sugarcane.

Keywords

phosphorus, fertilizers, cadmium, zinc, phytoavailability, sugarcane.