Effects of nutrient solution on growth and quality of short-term cultivation tomatoes grown in rockwool

Abstract: In order to achieve high efficiency and standardized management of the nutrient supplement, tomatoes of short-term cultivation (Solanum lycopersicom L.; Brilliance 101) were grown in the greenhouse to explore a kind of nutrient solution irrigation condition to guarantee both yields and fruit quality. In this study, tomato plants were grown in an open rockwool system and the plants were irrigated with Yamazaki recipes nutrient solution to determine the responses of plant morphology, fruit weight and fruit quality to 2 factors including electrical conductivity (EC) and irrigation rates of nutrient solution from March to June. A suitable combination of EC and irrigation rates of nutrient solution was further obtained by using comprehensive evaluation method. The experiments were designed with 3 EC levels (E1, E2 and E3 represented the EC of nutrient solution at 2, 4 and 6 dS/m, respectively) and 3 irrigation rate levels (R1, R2 and R3 represented the irrigation rates of nutrient solution at one time/d, 3 times/d and 5 times/d, respectively). The regulation of EC values of each treatment level was realized by diluting the mother liquor of the major elements with different proportions while the amount of microelements was remained. Because of the difference of the plant growth and the weather, average daily irrigation volume for each plant was controlled within 0.8-1.3 L, which was divided into several equal parts according to the irrigation rates. And the nutrient solution was applied at the following times: R1 at 12:00, R2 at 8:00, 10:00 and 12:00, R3 at 8:00, 10:00, 12:00, 14:00 and 16:00. The plants were pinched to 3 trusses and single pole trained. Results showed that EC values of the nutrient solution and irrigation rates affected plant height, stem diameter, leaf number, leaf area, leaf shape index, ratio of root area of tomato plants to bottom surface area of rockwool, average fruit weight, soluble solids content (SSC) and fruit shape index of the fruits. EC value of the nutrient solution had a significant effect on the average fruit quality (P<0.05); EC value of the nutrient solution and irrigation rates had an extremely significant influence on both leaf area and average fruit quality (P<0.01); interaction of the experimental factors had an extremely significant effect on stem diameter and shape index (P<0.01); and the interaction significantly influenced SSC (P<0.05). In terms of the greenhouse tomatoes of short-term cultivation grown in rockwool, the combination of 4 dS/m EC and 5 times/d irrigation rate was obtained by using comprehensive evaluation method, which could ensure the production and the fruit quality well. Based on the optimal irrigation condition, leaf area was significantly positively correlated with average fruit weight (P<0.05); SSC was extremely significantly negatively correlated with average fruit quality (P<0.01), and significantly positively correlated with fruit shape index (P<0.05). It could be concluded that tomato plants with larger leaf area tended to generate heavier fruits which approximated to ellipsoid type with lower SSC, while smaller fruits tended to be spherical, with better quality. This study provides a guidance basis for practical scientific management of nutrient solution in short-term cultivation of greenhouse tomato grown in rockwool.