Development of Water Soluble NPK Fertilizer for Watermelon Cultivation Under Rain Shelter Structure

Commercial watermelon cultivation at open field depends on granular fertilizer for higher yield and quality. However, application of granular fertilizer is laborious, inefficient, inadequate nutrient uptake and can cause toxicity. Therefore, smart fertigation system as incorporated by IoT (Internet of things) appears to be the best option to improve such issues. To complete the smart fertigation system, application of water-soluble NPK fertilizer is the key tool. Therefore, an experiment was conducted to evaluate and select the optimum water soluble NPK rates used on growth, yield and fruit quality of watermelon under rain shelter structure. Watermelon seedlings were subjected to four water-soluble NPK fertilizer rates at 75%, 100% (Control - 108 kg N, 247.32 kg P and 153.6 kg K ), 125% and 150% based on common practices of NPK granular fertilizer used in watermelon at open field planting system for 65 days. Fertilizer rates induced at 150% significantly increased leaf number, leaf SPAD, total leaf area and leaf dry weight as compared to control at 14.17%, 16.22%, 21.55% and 15.06% respectively. Whereas, application of fertilizer at 125% significantly increased the leaf number, total leaf area and leaf dry weight with the respective increments of 11.5%, 17.19% and 13.08%. Based on regression trendline, application of 125% optimized the performances of the plants such as leaf number, total leaf area and fruit weight. To conclude, increasing 25% NPK standard fertilizer rate (125%) could be promising for watermelon cultivation throughout fertigation under open field planting system. Further trials in open field planting system needs to be undertaken to ensure the selected rates identified from this study could improve the whole performances of watermelon