Tomato Nutritional Quality Indexes under Various Biogas Slurry and Irrigation Schemes

Abstract

The tomato (Lycopersicum esculantum Mill.) comprehensive nutritional quality evaluation index was evaluated in present study with biogas slurry irrigation along with the analysis of its response to the supply of water and fertilizer. Three crop-pan coefficients (0.6, 0.8 and 1.0, respectively) and four biogas slurry concentrations (volume percentages of 0, 12, 15 and 20%, respectively) were used under field conditions. Six single nutritional quality indexes including soluble solids, soluble total sugar, titrate acid, the sugar acid ratio, vitamin C and soluble protein were monitored. On the basis of analytic hierarchy process and the variation coefficient method, the combination weighing method of game theory was adopted to obtain weight of each tomato single nutritional quality. Results showed in the descending order of vitamin C>soluble protein>the sugar acid ratio>soluble sugar>soluble solids>titrate acid. Tomato comprehensive nutritional quality indexes were obtained by technique for order preference by similarity to ideal solution. On this basis, mathematical models were established by stepwise regression analysis to analyze the response to different water and fertilizer factors. Results showed that the response of tomato comprehensive nutritional quality to each water and fertilizer factor was in a descending order of the irrigation amount>nitrogen rate> phosphorus rate> potassium rate. When other factors were at the intermediate level, the changing between tomato comprehensive nutritional quality and P, N and K rates and the irrigation water amount were all fitted in quadratic curves. According to the optimum solution of the established equation, the P, K and N rates of 2.24, 6.05 and 5.78 g and water amount of 25 L irrigated can reach the best comprehensive nutritional quality of tomato. In conclusion, application of biogas slurry concentration (20%) and irrigation amount of 0.8AEp was the treatment most close to the optimum among all observed treatments.