Studies on growth, flowering, mineral composition of leaves and yield and quality of fruit of greenhouse tomatoes (Lycopersicon esculentum) in relation to level of N and K fertilization in the area of Crete.

The effect of 6 levels of N and 3 levels of K on plant growth, flowering, number of attached fruits, yield, leaf mineral composition and certain quality attributes of fruits were studied in glasshouse tomatoes (Lycopercicon esculentum Mill. cv. Caruso). Plant height, number of nodes and the numbers of attached fruits showed no positive response to N and K application. Plant height increased slightly with increasing N supply to a maximum of 4.72m at N1 level. N1 also increased the number of nodes by 8.5 and significantly increased the number of flowers per plant. K ferilizer had little effect on flowering. The highest yield of class A fruits and total yield/plant was recorded at N1 treatment. Raising N above this level decreased the Class A and total yield. Other studies concerned the mineral composition of the leaves in relation to N and K fertilization were done. Leaf N and P contents were highest in the first sampling, decreasing significantly in Nov and Dec months, and increasing significantly in Nov and Dec months, and increasing during late winter-early spring. Leaf K was low in the early samplings, and higher in late winter-early spring. Ca, Mg and B showed comparable seasonal changes, and were highest in December. Increased N markedly increased leaf N, P and K contents, but K did not. The highest concentration of P was recorded at N1 treatment and N and K at N4. Leaf Ca, Mg and B decreased significantly with increasing levels of both N and K application. A comparative study on the mineral composition of the new and old leaves was carried out. Concentrations of N, P and K were highest in old leaves; Ca, Mg, B were highest in new leaves. Vitaminn C, TSS, sugars and pH of fruit showed significant changes, especially in response to N. Acidity increased with increasing N to a peak at N5 but K fertilizer did not affect it. Lowest acidity was at N1. Vitamin C decreased with increasing N to a minimum at N3. Nitrogen at 1500g/ha (N4) give the highest juice pH. No significant changes in sugar contents occurred with the application of both N and K fertilizer. Also sugars increased slightly but not significantly from the immature to the ripe stage.