Optimal fertigation for high yield and fruit quality of greenhouse strawberry

Nitrogen (N), phosphorus (P), potassium (K), and water are four crucial factors that have significant effects on strawberry yield and fruit quality. A quadratic regression orthogonal rotation combination experiment that involved 36 treatments with five levels of the four variables (N, P, and K fertilizers and water) was executed to optimize the fertilization and water combination for high yield and quality. SSC/TA ratio (the ratio of soluble solid content to titratable acid) was selected as the index of quality. Results showed that the N fertilizer was the most important factor, followed by water and P fertilizer, and the N fertilizer had a significant effect on yield and SSC/TA ratio. By contrast, the K fertilizer had a significant effect only on yield. N×K fertilizer interaction had a significant effect on yield, whereas the other interactions among the four factors had no significant effects on yield and SSC/TA ratio. The effects of the four factors on the yield and SSC/TA ratio were ranked as N fertilizer > water > K fertilizer > P fertilizer and N fertilizer > P fertilizer > water > K fertilizer, respectively. The yield and SSC/TA ratio increased and then decreased when NPK fertilizer and water increased. The optimal fertilizer and water combination was 22.28–24.61 g/plant Ca (NO3)2⋅4H2O, 1.75–2.03 g/plant NaH2PO4, 12.41–13.91 g/plant K2SO4, and 12.00– 13.05 L/plant water for yields of more than 110 g/plant and optimal SSC/TA ratio of 8.5–14.