Response of maize to foliar vs. soil application of nitrogen-phosphorus-potassium fertilizers

Foliar fertilization is a widely used practice to correct nutritional deficiencies in plants caused by improper supply of nutrients to roots. The aim of the present study was to determine the efficiency of different forms of nitrogen-phosphorus-potassium (NPK) fertilizers applied to maize (Zea mays L.), either to the soil or to the leaves. Two sweet corn plants (CV Jubilee) were grown in plastic bags with 10.5 kg silt loam desert soil (Typic Haplocalcid). Before planting, the soil was mixed with zero (control), half or full dose of 0.6 g N, 0.4 g P, and 0.3 g K per pot as mineral forms, or as the Global-Green (GG) foliar fertilizer. Three forms of foliar fertilization were applied once a week in equivalent concentrations of N, P, and K (0.12gN, 0.08gP, and 0.06gK/L): Mineral forms (NPK), GG, and Fertilizers & Chemicals (F&C) foliar fertilizers; plain water acted as the control. The plants were harvested after 55 days. The roots were washed from the soil and length measured. The shoots were measured for leaf area, fresh and dry wt, and leaf contents of chlorophyll, N, P, and K. All indices increased in response to all forms of foliar fertilization (FF), but no significant difference was obtained between the different forms. Global-Green was less effective as a soil fertilizer (SF) than NPK. The effectiveness of FF appeared to be limited by the holding capacity of leaf surface area for the liquid fertilizer. It was concluded that FF may partially compensate for insufficient uptake by the roots, but requires sufficient leaf area to become effective.