Eggplant dry matter composition fruit yield and quality as affected by phosphate and total salinity caused by potassium fertilizers in the irrigationsolution

Eggplant (Solanum melongena L.) grown under winter conditions in unheated p olyethylene covered greenhouse displays unmarketable red color fruit skin. The purpose of this work was to study the effect of potassium (K), phosphat e and total salinity levels in the irrigation solution on the quality of eg gplant fruit grown at winter and spring seasons. Eggplant was grown in cont ainers filled with basalt erupted tuff scoria. The fertigation solutions we re composed of three levels of P:18, 36, and 54 g P m(-3), using mono K pho sphate (MKP). Each level of P was applied on two levels of total K concentr ations, 475 and 920 g K m(-3) composed of K nitrate, MKP, and K chloride (K Cl). The KNO3 fertilizer was used in all treatments at 150 g N m(-3). Incre asing the KCI concentration increased the average electrical conductivity ( EC) in the irrigation solution from 2.3 to 3.9 dS m(-1), reduced class A fr uit number and weight, but had no effect on the skin color. During the cold winter period the intensity of the skin color was weaker than in the norma l hot growing period. Increasing the average phosphorus (P) concentration i n the irrigation solution throughout the growing season from 36 to 54 g m(- 3) increased the number of fruit per plant, the number of class A fruits bu t has no significant effect on total fruit yield. Increasing the total elec trical conductivity of the nutrient solutions by K fertilizers above 3.8 dS m(-1) decreased fruit yield and total dry matter in the spring growth peri od.