Effects of sodium and sulphur fertilisers on the concentrations of nitrate and potentially toxic elements (PTEs) in water leached from permanent pasture

Abstract

AbstractThe concentrations of nitrate and potentially toxic elements (PTEs) are reported in water leached from a perennial ryegrass pasture to which isonitrogenous quantities of sodium nitrate, ammonium nitrate or ammonium sulphate fertilisers had been applied in an experiment lasting 2 years. The experimental design allowed a comparison of the immediate effects of sodium nitrate in the grazing season in which the fertiliser was applied with the residual effects of applying it in the previous year. Leachate composition was monitored from December of the first year to August of the second year. Sodium fertiliser reduced the concentrations of cadmium in soil and leachate, but it increased lead concentration in soil and reduced it in leachate. Sulphur fertiliser had no effect on any PTE. Nitrate concentration in leachate increased towards the end of the winter to almost reach the EU legal limit in water and then declined during the spring and summer. Sodium fertiliser applied in either but not both years reduced nitrate concentration. Sulphur fertiliser had varied effects on nitrate concentration in leachate depending on the timing of sodium fertiliser application. When applied at the same time as sodium fertiliser, sulphur fertiliser decreased nitrate concentration, but when applied to areas that had received sodium fertiliser in the previous year, it increased nitrate concentration. It is suggested that sodium fertiliser residues may have long‐term effects on leachate nitrate concentration that determine the impact of sulphur fertilisers. It is concluded that sodium fertilisers may reduce the concentrations of at least two PTEs, cadmium and lead, in ground water and that the effects of sulphur fertilisers are dependent on the sodium status of the soil.© 2002 Society of Chemical Industry