Abstract: Field experiments were conducted in a solar-heated greenhouse to investigate the effects of drip fertigation strategies and frequencies on yield, quality and root growth of tomato. Three fertigation strategies that varied the order in which water and nutrient were applied and three fertigation frequencies of weekly, fortnightly and once every four weeks were tested. Photosynthetic rate was measured during the growing season. At harvest root length density and yield were measured. The experimental results show that fertigation frequencies influence the tomato yield significantly. Yield increased significantly with the increase of fertigation frequency (P=0.012). Yield declined as the fertigation time was transferred towards the end of an irrigation cycle. Both fertigation strategies and frequencies did not influence the quality of tomato significantly. Root length density varied with fertigation frequencies, and the ratio of root length density in different soil layers varied with fertigation strategies. Effect of strategies and frequencies on photosynthetic rate were investigated. Accumulation of photosynthetic rate in the whole growing season were calculated for analyzing the relationship between yield and photosynthesis. The results demonstrated that the yield was highly correlated to accumulation of photosynthetic rate. For the sake of improving yield and quality of tomato, fertigation weekly and the strategy of applying fertilizer as early as possible in the whole irrigation schedule were recommended.

Key words: Drip fertigation, Fertigation strategies, Fertigation frequencies, Tomato, Yield, Quality, Root length density