Growth and Yield of Shallot (Allium cepa L. Aggregatum Group) with Application of Amino Acid Biostimulant Dosages

Intensive shallot cultivation needs high application rates of inorganic fertilizers that can cause environmental problems. Therefore, it is essential to lessen the rate of inorganic fertilizers by environmentally friendlier approaches, such as the application of biostimulants like amino acids. The present study determined the most effective dosage and application method of amino acid biostimulant to increase shallot yield and growth while using only half the amount of inorganic fertilizers. The research was arranged in a randomized complete block design with two factors and four blocks as replications. The first factor was the dose of amino acids biostimulant (0, 0.5, 1, and 2 L/ha), and the second factor was the application method (through leaves and soil). Data were observed on nitrogen (N), phosphorus (P), potassium (K), manganese (Mn), boron (B), indole acetic acid (IAA), gibberellin, zeatin, kinetin, nitrate reductase activity (NRA), chlorophyll as well as the growth and yield of shallot. The results showed that the application of amino acids biostimulants increased IAA, gibberellin, and kinetin content in both application methods. Amino acids biostimulants increased N, P, K, B, Mn, and chlorophyll. Amino acids biostimulant 1 L/ha was the best dosage to increase leaf diameter, leaf dry weight, total dry weight, number of bulbs (5.63 per plant; 44%), and productivity (16.46 tons/ha; 33.77%). The application through the leaves improved NRA, leaf area, and crop growth rate. It was indicated that amino acid biostimulant through leaves provides a useful instrument for plant growth, allowing the reduction of inorganic fertilizer without compromising crop yields.