2019 ASHS Annual Conference

Yield and quality of fruiting crops such as melons (Cucumis melo L.) require high potassium (K) supply rates. Under field conditions, K availability is limited by numerous plant, soil and climatic conditions/processes, thus necessitating supplemental K fertilization. In this field study, muskmelon (cantaloupe cv ‘Primo’) fruit yield and quality responses to two potassium fertilizer sources namely, polysulfate (PS; a minimally-processed, low-salt index, low-chloride, multi-nutrient organic fertilizer; 14% K₂O, 17% CaO, 6% MgO and 48% SO₄) and potassium chloride (muriate of potash or MOP; 60% K₂O; a common K fertilizer source) were investigated. The two fertilizer sources and their 50:50 blend were applied at three rates (50, 100, and 150 kg K₂O·ha^-1) at planting on raised beds (2.2 m-wide) with subsurface drip irrigation and white plastic mulch. Fruit yields ranged from 25 – 32 Mg·ha^-1 and were generally higher in fields receiving the higher rates (100 and 150 kg K₂O·ha^-1). Blend treatments elicited yield and quality responses that were slightly better than, but statistically similar to responses to PS treatments. Fruit fresh mass, dry matter content, mesocarp firmness and color were significantly increased by fertilizer applications at the 100 and 150 kg K₂O·ha^-1. Yield and quality responses to MOP alone were similar to PS effects but generally inferior to responses to blends. The prolonged nutrient release pattern of PS (either applied as a straight or combined with other fertilizers) may explain the observed benefits of the multi-nutrient fertilizer source.