Document Type : Research Article
Authors
1
Soil and Water Research Department, Safiabad Agricultural Research and Education and Natural Resources Center, Agricultural Research, Education and Extension Organization, AERRO, Dezful
2
Agricultural Engineering Research Department, Safiabad Agricultural Research and Education and Natural Resources Center, Agricultural Research, Education and Extension Organization, AERRO, Dezful
3
Soil and Water Research Institute, Agricultural Research, Education and Extension Organization, AERRO, Karaj
Abstract
Introduction: Phosphorus is the third most important nutrient in crop production after nitrogen and potassium. It is involved in all biochemical processes, energetic compounds, and energy transfer mechanisms. Phosphorus participates in the cellular proteins and cell membrane and nucleic acids. In addition, this element is essential for seed formation and root development. Also, this element recovery in the first year of application estimates to be 8 to 30%, and after 30 years rarely reaches to 50% and its rest is stabilized in the soil and accumulates inaccessibly for most plants. Therefore, in the last two decades, scientists have used various methods to improve the efficiency of phosphorus, including the selection and genetic modification of plants and the adopting agricultural practices such as determining the optimal amount of phosphorus, the right time and method of application and the right fertilizer source. In addition, due to the growing trend of vegetable oil consumption and the high cost of supplying the required oil through imports, the purpose of this study was to determine the optimal rate of phosphorus and selecting the appropriate efficient cultivar in order to extend oilseed crops cultivation.
Materials and Methods: In order to study the response of safflower cultivars (Carthamus tinctorius L.), to phosphorus rates and their efficiency indices, a factorial experiment was conducted in a randomized complete block design with three replications during 2012-13 and 2014-15 at Safiabad Agricultural Research Center of Dezful, Khuzestan, Iran. The first factor included five phosphorus levels (0, 50,100, 150 and 200 kg ha-1 as Triple Super Phosphate "TSP"), and the second factor included two cultivars (Goldasht and Soffeh). Safflower seeds were planted by setting up a sugar beet planter, in a row with a distance of 50 cm between rows and a distance of 5 cm between plants. Urea and potassium sulfate were uses at 300 and 100 kg ha-1, respectively. One-third of nitrogen and all phosphorus and potassium were used pre planting. The rest of urea fertilizer was applied as top dressing in two equal splitting rates (beginning of stem and early flowering stages). Before harvesting in each replication, the number of fertile heads per square meter (in three boxes of one square meter per plot), and the number of full grains (counting full grains in 20 heads), and after harvesting the weight of 1000 seeds (with three times counts were calculated in three random groups of 1000 seeds per plot). Finally, number of fertile heads per square meter, number of seeds per heads, 1000-seed weight, seed and oil yields, seed phosphorus uptake, and phosphorus efficiency indices were measured.
Results and Discussion: The results showed that the interaction of treatments was significant on the number of fertile heads per square meter and number of seeds per head. In both cultivars, with increasing phosphorus application, the mentioned traits increased significantly. The highest number of fertile heads (252 pieces), and the number of seeds per head (23.17 pieces), were obtained at the level of 150 kg phosphorus ha-1. The interaction between year and phosphorus on 1000-seed weight and seed yield and the interaction between year and cultivar on 1000-seed weight were significant. The highest 1000-seed weight (42.41 g), and seed yield (2184 kg ha-1), were obtained by application of 100 kg phosphorus ha-1. Seed and oil yields of Soffeh cultivar (1979 and 599 kg ha-1, respectively), was superior to Goldasht cultivar. Also, the results showed that Goldasht cultivar had higher utilization efficiency (248 kg kg-1), compared to Soffeh cultivar (218 kg kg-1). Phosphorus application significantly reduced use and uptake efficiency indices (69% and 85%, respectively). So that the treatment without phosphorus application had the highest use and uptake efficiency (1 kg kg-1). The difference between use and uptake efficiency at the level of 50 kg phosphorus ha-1 with other phosphorus levels was about 19% and 25%, respectively.
Conclusions: In general, due to the highest benefit-to-cost ratio (35.51) and use and uptake efficiency indices (0.69 and 0.7 kg .kg-1, respectively), application of 50 kg ha-1 of phosphorus fertilizer and Soffeh cultivar is recommended.
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