Effect of Water Hyacinth Compost and Nitrogen, Phosphorus, Potassium, Sulfur Fertilizers on S-Availability, S-Uptake, and Quality and Yield of Onion (Allium ascalonicum L.) on Inceptisols of Jatinangor

Shallots are have a high potential in Indonesian agricultural land. Soil in Indonesia is dominated by Inceptisols, which is low in soil fertility. This can be managed by adding nutrients to soil to increase its fertility, which can have a good effect on quality and crop yields. This experiment's purpose was to find the dosage of water hyacinth compost and N, P, K, S fertilizers that can give the best results for available S, S uptake, quality,and the yield of Batu Ijo variety of shallots in Inceptisols of Jatinangor and were carried out in the Soil Chemistry Laboratory, Plant Nutrition Experimental Garden, Faculty of Agriculture, Padjadjaran University, Jatinangor, Sumedang, West Java, Indonesia from June to September 2020. The experiment used a Randomized Completely Block Design (RCBD) with seven treatments and four replications, namely: control; Recommended N, P, K, S; ¾ Recommendations of N, P, K, S; ½ compost + ¾ dose of N, P, K, S; compost + ¾ dose of N, P, K, S; 1½ compost + ¾ dose of N, P, K, S; and compost + N, P, K, S at dosage of 25 t ha-1 water hyacinth compost, 200 kg urea, 500 kg Ammonium Sulphate, 300 kg SP-36, 200 kg KCl. The results showed that ½ compost + ¾ dose of N, P, K, S gave the best result by increasing S-avallability, S-uptake, aroma, color, number of bulbs, fresh weight, and dry weight of shallots bulbs on Inceptisols of Jatinangor.