Optimization of tailor-made fertilizer formulation and experimental validation for eggplant and tomato

Abstract

Population growth in Malaysia has led to continuous demand for food as well as fertilizer production. It has become a consistent challenge to increase plant production with high profitability to sustain plant growth and yield. Chemical fertilizers are preferable to provide optimal nutrient balance. Its consistent nutrient demand for growing healthy plants is needed to avoid nutrient deficiency and toxicity. Thus, a proper fertilizer formulation for tropical plants needs to be developed for efficient fertilizer use, cost effectiveness and reduce environmental pollutions. Therefore, a systematic methodology to design fertilizer formulation for tropical plant is developed and reported in this study using computer aided approach that included three specific objectives. Objective 1 is to establish the plant nutrient requirement and fertilizer component databases. The databases comprised of 18 plants and 20 fertilizers data documented in Microsoft excel that included the plant requirements by different types of plants, fertilizer market prices, fertilizer nutrient contents, fertilizer dosage by growth stages and irrigation scheduling. Objective 2 was to develop a systematic methodology to design a fertilizer using computer-aided approach. The fertilizer design was formulated as a linear optimization problem with objective function to minimize fertilizer cost subjected to plant nutrient requirements. The optimization problem was translated into mathematical models that comprised of a linear objective function and constraints and solved using linear programming with MATLAB®. The fertilizer design methodology was applied for one case study only, which was the formulation of fertilizer for eggplant. The obtained fertilizer formulation was verified using manual calculation with aid of Microsoft excel to ensure the models were valid. The results from MATLAB® gave similar fertilizer cost that fulfilled the plant requirements as compared to the manual calculation using Microsoft excel. Objective 3 was to verify the performance of the designed fertilizer formulations obtained from objective 2 by analyzing the growth and yield of plants. However, due to time constraints, only eggplants and tomatoes were selected to be tested. The experimental procedure included the preparation of seeds, medium, automated irrigation system, fertilizer, seedling transplant, data collection and plant growth observation. The measurement recorded were number of flowers, height of plant, number and weight of fruits. For eggplant, the formulated fertilizer (FF) cost was 16% cheaper than the commercial fertilizer (CF) with higher cumulative number of eggplant flowers, higher average height of plant stem and higher cumulative number of eggplants. In tomato experiment, the cost of formulated fertilizer was 4.6% lower than the CF with insignificant change in soil pH, higher height of tomato plant until the 4th week after transplanting and slightly lower cumulative yield of tomato plants. Overall, the FF formulation presents better performance and plant growth with high yield and cost effective as compared to the CF formulation.