“As irrigation water is often high in pH and bicarbonate, high tunnel soils generally climb the pH scale without precipitation to leach through the profile,” Jud Reid, Cornell Vegetable Program, told Vegetable Grower News. “The result of is lower nutrient levels in the plant foliage, ultimately decreasing vigor and yield. Manganese (Mn) deficiency is often the first sign of this problem.”
Solutions include measuring and adjusting pH of irrigation water and using sulfur to reduce soil pH prior to planting.