Optimum Doses of N, P, and K Fertilizers for Samosir Shallot Varieties in the Plains of the Lake Toba Region

Abstract

The surrounding plain of Lake Toba is well known as a shallot producing area in North Sumatra Province. Samosir variety is the mainstay variety of shallot farmers in this area. One of the efforts to increase the productivity of shallot variety Samosir is the application of fertilizer. Nitrogen (N), phosphorus (P) and potassium (K) are nutrients in fertilizers that are needed by plants in large quantities. The amount of N, P and K nutrients given to the Samosir variety shallot plants must be appropriate. If less will inhibit plant growth and development. If excessive, it can cause plant poisoning, increase production costs and can pollute the environment. This study aims to obtain the optimum dose of N, P and K fertilizers in the cultivation of shallot varieties Samosir planted in the rainy season in the plains around Lake Toba. This study consisted of 3 parallel experiments to determine the optimum N, P, K fertilization with a non-factorial randomized group design (RAK). P₂O₅ and K₂O fertilizers were applied 100% in the N rate experiment, N and K₂O fertilizers were applied 100% in the P rate experiment, and N and P₂O₅ fertilizers were applied 100% in the K rate experiment. Each experiment consisted of 5 levels, namely 0, 50, 100, 150, and 200% of the reference dose and each treatment was repeated 3 times so that there were 45 experimental plots. Parameters were: fresh weight of tubers and crowns at the end of the vegetative period, crown weight and wind-dried harvest tubers. Data were processed with SPSS v.27. If the results of the analysis of variance showed a significant/very significant effect, then continued with the polynomial regression test. If the results of the test show a quadratic response, then proceed to find the optimum point of the treatment. The results obtained the optimum dose of N and P fertilizer recommendations are 154.22 kg N ha-1 and 126.62 kg P₂O₅ ha-1. For K fertilization does not give a quadratic response pattern so there is no optimum dose.