Regulating strawberry growth by combining root-zone temperature and fertilizer concentration

This study aims to clarify the influence of various root zone temperatures and fertilizer concentrations on the strawberry growth. The parameters were collected from the Jiangsu Province from 2021 to 2023. Nine hierarchy indices were applied to conduct analytic hierarchy process (AHP) and Criteria importance using intercriteria correlation (CRITIC). A combined hierarchy of indices was closely related to strawberry growth. These indices included the firmness, sugar acid ratio, soluble solid, single fruit weight, yield, fertilizer partial productivity (PFP), and water utilization rate (WUE). Technique for order preference by similarity to ideal solution (TOPSIS) was also used to evaluate the comprehensive growth evaluation system for strawberry. The result showed that the root zone heating shared a positive effect on the growth of facility strawberries. There was the more significant behavior, as the heating time increased. In the first crop, the highest content of soluble solid was observed under T1 treatment. Nevertheless, the low fertilizer concentrations (0.5 g/L) led to the highest single fruit weight among all three-temperature treatments. While the high fertilizer concentrations resulted in the smallest single fruit weight. The highest PFP was observed in the T8 treatment, indicating the significantly higher than the rest. In the second crop, the highest single fruit weight was observed under the low fertilizer concentrations, whereas the lowest was found under the high fertilizer concentrations. The highest yield and PFP were achieved under the T5 treatment, which was the higher than the rest. The highest WUE was also found under T5 treatment, which was significantly higher than that under T1, T2, T3, T4, T6, and T7 treatment. There was no significant difference, compared with the T8 and T9 treatments. In the third crop, the highest yield was achieved under the T5 treatment, which was significantly higher than that under T1 and T7 treatment. As such, the better performance was found in the medium fertilizer concentration at medium temperature. The single-factor effect analysis of root zone temperature and fertilizer concentration showed that the highest single fruit weight, PFP and WUE were found at a fertilizer concentration of 1.5 g/L. Therefore, the moderate concentration of fertilizer was optimized for the WUE and economic benefits. The highest yield, PFP and WUE were obtained at a root zone temperature of 16 ℃, followed by 22 ℃, and lowest under 8 ℃ (without heating). The moderate heating of root zone was effectively enhanced the root absorption capacity, while the excessively high temperatures of root zone presented an inhibitory effect. The multi-objective evaluation was obtained to optimize the quality, yield, PFP, and WUE in the strawberry production. The AHP and CRITIC were used to define the subjective and objective weights, in order to evaluate strawberry production, respectively. The weight was calculated and then ranked in the descending order of the yield, fruit weight, sugar acid ratio, PFP, soluble solid, WUE, and hardness. The TOPSIS indicated that the T5 (16 ℃, 1.5 g/L) shared the highest score among all treatments, followed by the T8 (16 ℃, 0.5 g/L) and T3 (2 ℃, 2.5 g/L). The lowest score was found under the T7 (8 ℃, 0.5 g/L). A binary quadratic regression equation was also constructed for the growth control of facility strawberries, according to the root zone temperature and fertilizer concentration. Additionally, the equation was statistically significant at the significance level of 0.05. The bivariate quadratic regression equation was converted into a contour map of the comprehensive score of strawberry by root zone temperature and fertilizer concentration. Dividing the optimal closed loop interval of root zone temperature and fertilizer concentration coupling based on a comprehensive evaluation of more than 82%, the root zone temperature amount of 13.10-18.47 ℃ and the fertilizer concentration amount of 1.43-1.87 g/L were the most beneficial to strawberry growth. The findings can provide the theoretical reference to evaluate the relationship between root zone temperature and fertilizer, particularly for the precision management in strawberry production.