Implication of soil grid sampling on lime, phosphorus, and potassium management of corn

Abstract

Grid-based soil sampling captures within-field fertility variability, enabling site-specific lime and fertilizer management but at a high cost. This study grid-sampled 20 corn (Zea mays L.) fields in New York to (1) document spatial variability in soil series, pH, soil test phosphorus (P), and potassium (K); (2) assess the impact of grid size (0.2, 0.4, 1.0 ha/grid) on field-based lime, P, and K recommendations compared to whole-field sampling for corn with and without alfalfa (Medicago sativa L.) in the rotation; and (3) derive guidance for soil sampling beyond the initial grid-based sampling event. Soil pH was measured using a 1:1 soil-to-water mixture, while P and K were extracted or converted to Morgan equivalents. Soil pH ranged from 6.2 to 7.4, while P and K varied from 3 to 177 mg P/kg and 22 to 213 mg K/kg, respectively. Grid-based management led to higher recommended lime rates, especially for fields in alfalfa rotations. For P, grid-based decision-making increased the recommended amount of fertilizer for many fields. For K, several fields showed potential fertilizer savings. In most fields requiring lime applications, the amount recommended increased with grid size, whereas for P and K, smaller grid sizes resulted in higher recommendations. Grid-based soil measurements were converted to soil test-based management zones, providing both a transition from regular grid sampling in the initial year to more cost-effective zone-based sampling in future years, and a means to homogenize the field with targeted lime and fertilizer management.