Plant and Soil 126. 79-83 (1990). © Kluwer Academic Publishers. Printed in the Netherlands. PLSO 7669 Effects of nitrogen sources and copper levels on yield, nitrogen and copper contents of wheat (Triticum aestivum L.) VINOD KUMAR, D.V. YADAV and D.S. YADAV Department of Soil Science, Haryana Agricultural University, Hisar-125 004, India Received 26 January 1988. Revised March 1990 Key words: Cu levels, N sources, wheat Abstract A pot experiment was conducted, in a greenhouse, at Hisar, India, using a sandy soil deficient in nitrogen and copper, to study the effects of various levels of N and Cu on the dry matter yield and the N and Cu contents of wheat (Triticum aestivum L.). The sources of nitrogen used were Ca(NO3)2, NH4C1 and NH4NO 3 applied in amounts necessary to establish 120ppm of soil nitrogen and using a control (0ppm N). Copper was applied, as copper chloride, to give soil Cu levels of 0, 5, 10 and 20ppm. In general, dry matter yields, N and Cu concentrations in shoots and roots and available soil-N after harvest of the plants, followed the order Ca(NO3) > NH4NO 3 > NH4CI. Up to a level of 5 ppm Cu, the dry matter yields of shoots and roots increased, but decreased at higher levels of Cu. Increasing Cu levels significantly decreased the available soil-nitrogen after harvest and also the concentration of N in the plants. At the same time the concentration of Cu in shoots and roots and available Cu in the soil was increased. Nitrogen and copper were found to have a mutually antagonistic effect on each other's concentration in the plants. The antagonism was greater with NH4 + sources than with NO 3- compounds. Introduction Heavy applications of nitrogenous fertilizers may induce or accentuate Cu deficiency symptoms in wheat (Hooper and Davis, 1968). Gilbert, (1951), suggested that N induced Cu deficiency by inhibiting the transport of Cu from plant roots to tops. Likewise, the N content of plants may be decreased by heavy applications of Cu. Dif- ferent sources of nitrogen have been reported to behave differently in affecting wheat yields and the superiority of nitrate over ammonium, as a source of N for maize and wheat, has been reported by several workers (Cox and Reisenauer, 1973; Hargrove et al., 1988). On the contrary, Singh and Singh (1975) have reported that different sources of N behaved similarly in their effect on wheat yields. Since N is applied as fertilisers containing nitrate, ammonium, and both nitrate and ammonium combined, these forms of N are supposed to behave differently as far as their effects on crop yields and contents of N and Cu are concerned. There is limited infor- mation regarding the effects of different nitro- genous fertilizers on the uptake and utilization of Cu by wheat. The present investigation was, therefore, undertaken to ascertain the effects of ammonium and nitrate sources of N, at various Cu levels, on the dry matter yield, concentration and uptake of N and Cu by the wheat plant. Materials and methods The experiment was conducted in 25-cm diam- eter clay pots lined with polyethelene sheet. The