A two-year experiment was conducted in Karacadag rangeland, Sanliurfa, Turkey to evaluate Nitrogen (N) and Phosphorus (P) fertilization on forage quality and plant species composition and to determine their economic impact on animal production. Treatments were 0, 50, 100, 150 and 200 ka ha(-1) of N and 0, 50, 100, and 150 kg ha(-1) of P fertilizer doses. Nitrogen and Phosphorus fertilization significantly influenced the composition of plants. Botanical composition of experimental fields was recorded as 25 legume, 22 grass and 27 species from other families. The results showed large interaction between P and N due largely to the fact that legume species are relatively abundant fertilization reduced legume proportions however, P fertilizer increased the proportion of legume in vegetation. Adverse effect of N on growth of legume resulted in significantly crude protein decrease in forage. In both years, overall mean dry matter yield increased with increase in N and P applications. The highest dry matter yield production was 3407 kg ha(-1) 150 kg ha(-1) P and 200 kg ha(-1) of N as compared to control treatment which had a 1152 kg ha(-1). Average mean crude protein concentration was 110 g kg-l for control plots, while it decreased to 106, 102, 104 and 103 kg(-1) for 50, 100, 150 and 200 kg ha-1 N applications, respectively. Crude protein concentrations were significantly enhanced with increasing P fertilizer amounts. Maximum crude protein concentration was 140 g kg(-1) and obtained from P-150+N-0 treatments. The average crude protein yield was 126.7 kg ha(-1) in control plots and maximum crude protein yield was 464.1 kg ha(-1) from P-150+N-200 treatment. Overall results indicated that, the most profitable treatment was P-150+N-200 and average calculated benefit was 644 E per hectare.
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