Document Type : Research Paper
Authors
1
MSc student; Associate Professor
2
Professor
3
Department of Soil Science, Tarbiat Modarres University, respectively.
Abstract
The optimum use of fertilizers under saline conditions is essential for maximum crop production. several studies have shown that salinity level and fertilizer rates interact to affect yields. This effect may be related to the nutrients status of plant tissues. The objective of this study was to investigate the interactive effects of salinity and nitrogen fertilizer on growth, yield and the concentration of nutrients in sorghum (Sorghum bicolor L. Moench). Consequently, a randomized complete block factorial experiment with 3 replications was conducted. Ten sorghum seeds were sown at 3cm depth in each pot. The applied irrigation water was 50 percent more than the consumptive use of plants to achieve the target leaching fraction. Irrigation waters consisted of C0, C1, C2, C3 and C4, corresponding to 0.6, 6, 8, 10 and 12 dSm-1, respectively. The fertilizer treatments consisted of F0 (no fertilizer), N0 (control: just triple superphosphate as a base fertilizer without any N- fertilizers), U1(114 Kg/h urea N-), U2 (137 Kg/h N-urea), U3 (160 Kg/h urea N-), A1 (114 Kg/h ammonium nitrate), A2 (137 Kg/h N-ammonium nitrate) and A3 (160 Kg/h ammonium nitrate- N). All the fertilizers were applied on two plants. The plants that received water with ECs of 10 and 12 dSm-1 were eliminated from the experiment after 7 and 9 weeks, respectively, due to chloride toxicity. The remaining plants were harvested during the flowering stage, 77 days after seeding. The plant height, fresh weight, dry weight and the leaf area were measured as the growth indices and nitrogen, potassium, calcium, magnesium, sodium and chloride contents of whole plants were measured. The results indicated that both the emergence and growth rates decreased significantly by increasing salinity. The plant response to N fertilizers appeared to be different at each salinity level. The maximum production at C0 salinity level was obtained for N-3, while at C1 and C2 treatments, the maximum production were obtained with N-2 and N-1 treatments, respectively. In C1 to C4, There was no significant difference between the two applied N-sources. The concentrations of N, Ca, Mg, Na and Cl in plant tissues increased by increasing soil salinity. While K concentration and the uptake of N, K, Ca and Mg decreased. Nitrogen fertilization in treatments with saline water caused decrease in the concentration of sodium and chloride and increase in the concentration and uptake of potassium in plant tissues.
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