Abstract

This study aimed to evaluate the production costs and returns of forage maize cultivation under zinc management on a 1-rai farmer’s field in Saraburi Province, where the soil is slightly alkaline (pH 7.8). The experiment involved three soil-applied zinc fertilizer treatments in combination with macronutrients: 1) no zinc application (ZnSO₄ • H₂O), 2) application of ZnSO₄ • H₂O at 1.1 kg/rai with the second topdressing (Zn3), and 3) application of ZnSO₄ • H₂O at 1.45 kg/rai with basal fertilizer and an additional 1.45 kg/rai with the second topdressing (Zn6). Two single-cross hybrid maize varieties, Suwan 5720 and Suwan 5821, were used in the trial. The results showed that zinc application had no statistically significant effect on yield or yield components in the first year. Suwan 5720 yielded highest under the no-zinc condition (Zn0), while Suwan 5821 exhibited a positive response in kernel number per unit area, though not in overall yield. Economic analysis revealed that Zn0 had the lowest production cost and the highest net profit per rai for both maize varieties. This suggests that zinc fertilization may not be necessary in the short term for soils with sufficient zinc levels. However, longer-term studies of at least two years are recommended in areas with delayed crop response to zinc, to support evidence-based decision-making and promote efficient fertilizer use.