Alleviating the deleterious effects of water salinity on greenhouse grown tomato

Use of saline water in greenhouse led to the gradual increase of salinity in tomato roots zone. The salinity suppresses the phosphorus (P) uptake and reduces available P, causing a decrease in growth of roots and plants. This research evaluated rapid early growth of tomato to avoid the deleterious effect of water salinity by using four NPK starter solutions (SS); SS1: without SS, SS2: 200-200-200 (1:1:1), SS3: 150-300-150 (1:2:1) and SS4: 100-400-100 (1:4:1) mg L-1 of N-P2O5-K2O and three rates of humic acid (HA); 0, 750 and 1500 mg L-1 , as well as their interactions. The vegetative growth, flowering, leaf mineral contents and fruit yield characters of tomato plants was increased significantly and successively as P concentration in starter solutions increased. Tomato plants receiving SS4 recorded maximum plant height; at 6, 8 and 10 weeks after transplanting (WAT), and leaves number; at 6 and 8 WAT, as well leaf P content. While, tomato plants receiving SS3 achieved maximum root and shoot fresh weight and highest mean values of the number of flowers per cluster, leaf NK contents and fruit yield per plant. Increasing the HA level up to 1500 mg L-1 was able to improve plant height, number of leaves, fresh weight of root and shoot, earliness, number of flowers per cluster, leaf N, P and K contents and fruit yield per plant of tomato under salinity stress compared to control treatment. The interaction between SS and HA indicated that with any SS, increasing level of HA, significantly increased plant height, the number of leaves, fresh weight of root and shoot, earliness, number of flowers per cluster, N, P and K contents of leaf and fruit yield per plant. Nonetheless, the application of SS3 with HA at 750 or 1500 mg L-1 was the most efficient treatment combination, to alleviate the deleterious impacts of salinity on tomato plants irrigated with saline water.