| Abstrakt: |
Soil water content and phosphorus availability are important factors for sunflower (Helianthus annuus L.) production especially in arid and semi-arid regions. Water deficit, low organic matter of most soils, high prices of chemical fertilizers along with their environmental negative effects have attracted attention to find effective methods for improving water use efficiency (WUE) and yield of sunflower. One of these methods is integrated application of organic and chemical fertilizers. A two-year field experiment was conducted in order to investigate the effects of triple superphosphate (TSP) at three levels (0, 100, and 200 kg ha−1) and sewage sludge (SS) at four levels (0, 14.2, 28.4, and 56.7 Mg ha−1) on sunflower yield and contents of oil and protein under optimum and limited irrigation conditions as third factor. The results showed that the seed and oil yields significantly decreased under limited irrigation, while the WUE increased as compared to the optimum irrigation. The applications of TSP and SS positively affected relative water content (RWC), WUE, seed yield, and contents of oil and protein. The highest RWC (66%), seed yield (5,163 kg ha−1), seed oil concentration (45.9%), and oil yield (2330 kg ha−1) were observed in the treatment 200 kg TSP +56.7 Mg SS ha−1 under optimum irrigation condition. The highest seed protein concentration (19.3%) in the treatment 100 kg TSP +56.7 Mg SS ha−1 in 2014, and the maximum seed protein yield (907 kg ha−1) in the treatment 56.7 Mg SS ha−1 were observed under optimum irrigation condition. The highest WUE (4.6 g L−1) was obtained by the application of 100 kg TSP and 56.7 Mg SS ha−1 under limited irrigation condition. In order to reduce the chemical fertilizers use and achieve the optimum growth of sunflower, applications of 56.7 Mg SS ha−1 under optimum irrigation and 100 kg TSP +56.7 Mg SS ha−1 under limited irrigation are recommended at similar conditions. [ABSTRACT FROM AUTHOR] |
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