Tomato Fruit and Soil Response to Polyhalite Fertilizer on Sandy Loam Soils in the Mid-Atlantic Region, USA.

Tomatoes are the most important vegetable crop globally, making up about 15% of total vegetable production. Virginia is one of the largest producers of fresh market tomatoes in the United States with the main production region located in eastern Virginia. On average, Virginia farmers produce 1200 to 2500 ha of tomatoes annually that are worth 50 to 100 million dollars ($US). Tomatoes are produced on sandy loam and loamy sand coastal plain soils where potassium (K) and sulfur (S) deficiencies are known to occur. The objective of this study was to evaluate fresh market tomato response to K, S, magnesium (Mg), and calcium (Ca) from polyhalite in granule form (POLY4) compared to muriate of potash blend (MOP) alone and with MOP fortified with S and Ca additions (MOP+) on sandy loam soils. We applied each fertilizer source at 0, 40, 80, 160, and 240 kg K2O ha-1. The experimental design was a factorial arrangement of 3 sources (POLY, MOP, and MOP+) × 5 rates = 15 treatments arranged in a randomized complete block design with four replications. Leaf tissue, SPAD meter, yield, and residual soil nutrient concentrations were measured. Fertilizers fortified with S and Ca (MOP+ and POLY4) consistently had highest yields, while it appeared that no Mg deficiency was expressed since POLY4 parameters were statistically similar to MOP+. Leaf tissue concentrations indicated higher S concentrations for POLY4 and MOP+ treatments as compared to MOP and the no-fertilizer control, which correlated with visual yellowing and lower SPAD readings in plots receiving no S fertilizer. In conclusion, POLY4 fertilizer holds promise for providing ample fertility for necessary nutrients for optimal vegetable production in sandy loam soils in the Mid-Atlantic Region, USA.