Reduction of Inorganic N Fertilizer with Slow Release Fertilizer Based on Activated Bentonite in Shallot Cultivation in Coastal Area

Abstract

Coastal saline soils present significant challenges for crop production due to their high porosity, so urea fertilizers must be given in high doses. This study aims to reduce the use of inorganic nitrogen (N) fertilizers in shallot cultivation in coastal saline land with slow-release fertilizers with activated bentonite matrix. The design used was a Completely Randomized Design (CRD) with a combination of urea (U) and slow-release fertilizers (SRF) with a dose of 195.5 kg ha-1 N in different proportions, namely: (100% recommended Urea), (80% U + 20% SRF), (60% U + 40% SRF), (40% U + 60% SRF), (20% U + 80% SRF) and (100% SRF). The results showed that shallots planted with SRF showed growth performance (plant height, number of leaves, leaf greenness, fresh root weight and dry root weight) and yield (number of tillers, bulb weight per clump, dry bulb weight per clump, weight per bulb, number of bulbs per clump and bulb diameter) equal to those planted with recommended dose of urea fertilizer. Plant height and number of leaves at 6 MST had average values ​​according to the variety description, i.e. 25-44 cm for plant height and 14-50 for number of leaves. Furthermore, slow release fertilizer (SRF) with activated bentonite matrix in this study can be used to reduce the dose of Urea given by up to 100%.