The Effects of Zeolite-Based Slow-Release Nitrogen Fertilizer and Sulfur on the Dynamics of N,P,K, and S Soil Nutrients, Growth and Yield of Shallot (Allium cepa L.)

—Shallot or red onion is one of the horticultural commodities that has good economic value as it is needed for almost every cuisine. The aims of the research were to determine 1) the effect of nitrogen slow-release zeolite-based NZEO-SR fertilizer and elemental Sulfur on the dynamics of soil main nutrients N, P, K, and S, and their uptake the red onion plants 2) the effect of slow-release N fertilizer on the growth and yield of shallots; 4). the effect of S fertilizer on the growth and yield of red onion and 5) the interaction of slow-release N fertilizer and S soil nutrient dynamics and the growth and yield of shallots. The research was conducted in a greenhouse using Inceptisols. soil analysis was carried out in the the Land Resource Laboratory, Faculty of Agriculture, Jenderal Soedirman University, Indonesia. The design of this study was a Completely Randomized Block Design (CRBD) with two factors i.e. slow-release nitrogen fertilizer NZEO-SR and elemental sulfur. The test plant used was shallot Bauji variety. The slow release nitrogen fertilizer were applied at 0 , 100 , , 200, dan 300 kg.ha -1 , while the rates of S fertilizer were 0, 25, 50 and 75 g.ha -1 . The variables observed consisted of selected soil chemical properties, available N, P, K, and S, N and S uptake, growth and yield of shallots. The results showed that the nitrogen slow release fertilizer applications increased soil available N and S, N uptake, the number of tubers, the weight of fresh shallot bulbs but decreased the soil available P. The applications of S increased soil electrical conductivity and available N and S but decreased the soil pH, available soil P, S and N uptake, and number of bulbs. The applications of S at the highest rate (75kg.ha -1 ) decreased the bulbs fresh and dry weight. The combination of 200 kg.ha -1 NZEO-SR and 75 kg.ha -1 S gave the best results in available soil N. The applications NZEO-SR and S generated negative interaction on the soil available P.