Effect of nitrate addition on the efficient use of ammonium sulfate fertilizer on corn under saline conditions . II. field experiment

two field experiments during two consecutive seasons, were conducted on corn (Zea mays L. var. Ghota-82), grown on a saline soil under flood irrigation system at ACSAD research station located at the Euphrates valley, Deir-Ez-zor district, east of Syria. The objective was to study the effect of applying different ratios of mixed NO3-N and NH4-N fertilizers on the biomass yield of corn. Five rates of nitrogen (0, 50, 100, 150 and 200 kg N/ha) were applied either in a single or in combination of two forms of 15N labelled nitrogen fertilizers (15NH4)2 SO4 and Ca(15NO3)2. Total N, 15N, nitrogen use efficiency (N recovery) and dry matter yield were the parameters investigated. The results showed that: (1) The high concentrations of NH4-N reduced dry matter yield; (2) NO3-N was more effective in increasing total N content of plant tissues than the same concentration of NH4-N; (3) Combination treatments always induced both higher yields and N content of plant tissues than single treatments of NH4-N; (4) NH4-N form increased the NO3-N uptake, and the NO3-N form had an effect on the absorption of NH4-N; (5) the recovery of NO3-N form was much higher than NH4-N form under saline soil conditions. (author)