Effect of water quality on grain yield and nutrient uptake of rice (Oryza sativa L.)

Abstract

The use of poor quality water for agriculture is now receiving major attention especially in arid and semi-arid regions. This experiment was carried out to evaluate the effects of different irrigation water qualities on the grain yield and nutrient uptake of rice and on the heavy metal concentration in the grains. Six water treatments were applied at intervals of three days, involving either fresh water (FW), drainage water (DW), mixed water (MW), fresh water followed by drainage water (1FW + 1DW), two applications of fresh water followed by one of drainage water (2FW + 1DW) or one application of fresh water followed by two of drainage water (1FW + 2DW). The rice grain yield and the uptake of nitrogen (N), phosphorus (P) and potassium (K) were determined. The grains were also analysed for the concentration of nickel (Ni), cadmium (Cd) and lead (Pb). The results showed that the grain yield, the uptake of N, P and K in the plant biomass and the concentration of heavy metals in the grains were significantly affected by the water quality. The rice grain yield exhibited a close correlation with the water quality. The highest grain yield was obtained in the FW treatment and the lowest yield in the DW treatment. The uptake of N, P and K was detrimentally affected by poor quality water. However, the uptake trend for these elements was similar across all the irrigation treatments. The concentrations of heavy metal in the grains were significantly higher in plots irrigated with poor quality water. Among the treatments the cumulative concentrations of heavy metal were in the order of: DW ≯1FW + 2DW ≯ MW ≯ 1FW + 1DW ≯ 2FW + 1DW ≯ FW. This study showed that there is a potential risk of heavy metal contamination in rice crops treated with poor quality water. The lower grain yield after irrigation with poor quality water could be due to the disturbed mineral nutrition or to relatively higher salt toxicity.