AGRONOMIC AND PARTIAL ECONOMIC PERFORMANCE OF LIMESTONE AND AGRICULTURAL GYPSUM RATES IN NO-TILL MAIZE

Soil acidity constrains maize production in tropical regions, and decisions regarding limestone and agricultural gypsum should consider both grain yield and the additional costs of these amendments. This study evaluated the agronomic response and partial economic performance of limestone and agricultural gypsum rates for no-tillage maize in Roraima, Brazil, using partial budgeting. The experiment was conducted in a randomized complete block design with a split-plot arrangement augmented by an additional control and four replications. Limestone rates corresponded to nominal base-saturation targets of 50, 60, 70, and 80%, and agricultural gypsum rates corresponded to 0, 50, 100, and 200% of the reference gypsum requirement. At the adopted maize price of R$ 66.00 per 60-kg bag, limestone applied alone at 0.55 t ha⁻¹ (T1) provided the highest partial net benefit (R$ 6,123.61 ha⁻¹). The combination of 0.55 t ha⁻¹ limestone and 1.20 t ha⁻¹ agricultural gypsum (T3) produced the highest observed grain yield (12,437.50 kg ha⁻¹) but a lower partial net benefit (R$ 5,660.48 ha⁻¹). Switching-price analysis indicated that T1 was preferred from R$ 3.05 to R$ 127.52 per bag, whereas T3 became preferable only above R$ 127.52 per bag. Thus, the rate associated with the highest observed grain yield differed from the rate that maximized partial net benefit under the adopted prices. Because only amendment acquisition costs were deducted, the estimates represent partial net benefits rather than total farm profitability.