Effect of nitrogen application on concentration of cadmium and nutrient ions in soil solution and in durum wheat

A growth chamber experiment was conducted to study the effect of nitrogen f ertilizer on the chemical composition of the soil solution over time, and t o determine Cd uptake as a function of rates of nitrogen fertilizer applica tion and transpiration. Sceptre durum wheat was grown in a fine sandy loam soil, in pots with treatments of 0, 50, 100, 200, 400, and 800 mu g N g(-1) as urea. The soil solution was removed by water displacement and analyzed for Cd and other nutrient ions at time of seeding, 10, 20, 30, and 40 d aft er seeding, and at the time of crop maturity. Soil samples were analyzed at each sampling time, and aboveground plant material was also harvested at t hese times and analyzed for Cd and other nutrient ions. Behaviour of Cd was compared to that of the nutrient ions to gain a better understanding of pa tterns of ion behaviour. Conductivity measurements were taken as estimators of ionic strength. Both solution Cd concentration and DTPA-extractable soi l Cd increased significantly with increasing nitrogen rate. The increases i n Cd concentration with N fertilization were greatest immediately after fer tilization and appeared to be related to an increase in soil and solution c onductivity, with pH also having an influence on DTPA-extractable Cd. The s oil solution concentration of all nutrients, with the exception of phosphat e, increased with N rate. The effects of N fertilization on the amounts of extractable nutrients in the soil were more variable. Plant Cd concentratio ns increased with increasing N application rate to 800 mu g g(-1), but dry matter yield and transpiration only increased with N rate to 200 mu g g(-1) . Cadmium was the element most affected by increasing the N rate, and there were minor changes in uptake of other elements such as N, P, K, Ca, Mg, Mn , Zn, and Cu with N application rate and time. This study clearly illustrat ed the effect of nitrogen fertilization on the concentration of Cd in the s oil solution and its uptake by durum wheat.