Influence of Elevated Phosphorus Levels In Nutrient Solution On Micronutrient Uptake and Deficiency Symptom Development In Strawberry Cultured with Fertigation System

The relationship between the total amount of micronutrients absorbed by the above-ground plant part and the occurrence of visible micronutrient deficiency symptoms in strawberry (Fragaria×ananassa Duch.) as influenced by elevated phosphorus (P) levels in fertigation solution was investigated. Stolon-propagated plants of two strawberry cultivars, ‘Seonhong’ and ‘Keumhyang’, were cultured in the field and irrigated with a standard fertilizer solution containing 0, 0.5, 1, 2, 4, or 6 mM P. Dry matter yield and tissue nutrient content were determined on plants harvested 120 days after transplanting. Plant growth response to increased P levels in fertilizer solution was cubic, with the highest dry matter production occurring at 0.5, 1.0 and 2.0 mM P in ‘Keumhyang’ and at 0.5 and 1.0 mM P in ‘Seonhong’. The pattern of P accumulation in the tissues of the two cultivars as influenced by elevated nutrient solution P levels showed a quadratic response, while the total amount of P contained by the above-ground plant part decreased when P concentration in nutrient solution was higher than 4 mM in ‘Keumhyang’ and 2 mM in ‘Seonhong’. Young leaves of the plants grown with nutrient solution P levels higher than 4 mM and 2 mM, respectively, in ‘Keumhyang’ and ‘Seonhong’, developed interveinal chlorosis with pale green color. Tissue concentrations of iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn) in both cultivars, when expressed as mg·kg^-1 dry weight, did not decrease even in the treatments in which deficiency symptoms were observed. The total amount of these metallic micronutrients absorbed by the above-ground plant part decreased in the treatments in which nutrient deficiencies were observed. The total amount of absorbed micronutrients showed a cubic response to increasing P levels in nutrient solution. Result of this study indicates that total amount of micronutrients taken up by the plant, not tissue concentration, is a better indicator of P-induced micronutrient deficiency in the two cultivars of strawberry tested.