Effect of Organic Matter, Potassium and Calcium on Yield, Chemical Composition and Blossom-End Rot of Watermelon in a Sandy Soil

Iran stands 2nd in the world in watermelon production and export. Kerman province, in southeast of Iran, ranks 1st in the country, but in the recent decade, some factors including drought, soil physical and chemical properties, low quality of irrigation water and lack of optimum and balanced nutrient use has resulted in reduction of quantity and quality as well as blossom end rot (BER) rise in this product. Therefore, an experiment was conducted to assess simultaneous effects of organic matter, potassium and calcium on yield, chemical composition and BER severity of watermelon that is a new study in the region. The experiment was accomplished as factorial in a Randomized Complete Block Design (RCBD) in one of the southeast towns of Iran. Experimental treatments were comprised of organic matter in two levels (0 and 20 ton ha-1 of farmyard manure), potassium sulfate fertilizer in three levels (0, 250 and 350 kg ha-1) and foliar spray of calcium chelate in two levels (0 and 4 g l-1). The results showed that organic matter application and foliar spray of calcium chelate increased yield, calcium, iron and zinc concentration of plants, whereas the severity of BER was declined. Potassium sulfate application caused yield increase, but the rates more than 250 kg ha-1 resulted in reduction of plant calcium, zinc and iron concentration and higher rate of BER.