Optimizing the combination of Ca and Mg and water levels in cherry tomato production using comprehensive evaluation model

Objectives The efficiency of Ca and Mg fertilizer is affected by application rate of fertilizer as well as the irrigation levels. We attempted using a comprehensive evaluation model to optimize the combination of multiple factors, including Ca and Mg, for high yield, quality, and profitability of cherry tomato.

Methods A microplot experiment of five-element quadratic orthogonal rotation combination design (1/2 implementation) was carried out in a greenhouse in Yangling City, Shaanxi Province, cherry tomato cultivar ‘Fenmei 1’ as test material. The five factors were irrigation, N, K, Ca, and Mg fertilizer, and each factor had levels of –2, –1, 0, +1, and +2, composing 36 combination treatments. Total of 21 indicators involved in growth, yield, quality, and water and fertilizer utilization of cherry tomato were investigated. 14 indicators were screened out according to their importance using Pearson correlation analysis, and the differences caused by the indictors were comprehensively evaluated using a combined evaluation method. Finally, the regulation model of water and fertilizer coupling of cherry tomato was developed.

Results The final weight of individual index was calculated using the combination weighting method, yield gained the largest weight (0.2324) and the net photosynthetic rate gained the smallest weight (0.0183), indicating the yield was the most sensitive indicator to the change of tested factors. The comprehensive score of cherry tomatoes, calculated using the overall difference combination method, showed a parabolic relationship with the increase in irrigation and N fertilizer level, and the change span among irrigation levels was significantly greater than that among N fertilizer rates; and the overall score showed a very gentle downward parabolic shape with the increase of Ca application, while no parabolic shape was formed with the increased in K and Mg fertilizer levels. We used dimensionality reduction analysis, when irrigation, N and K were at level 0 (appropriate level), the composite score of cherry tomato was highest when Ca and Mg were around 0. Considering the interaction of 5 factors together, the overall difference combination comprehensive evaluation value had the optimal range: irrigation 56.26−59.03 L/plant, N 6.05−7.03 g/plant, K₂O 5.97−6.50 g/plant, CaO 2.92−3.30 g/plant, and MgO 0.58−0.64 g/plant.

Conclusions The comprehensive evaluation model can take into account the growth, yield, quality, and resource utilization, and propose the optimal combination scheme of water and fertilizer. The suitable fertilization interval of cherry tomato proposed in this experiment verifies the feasibility of this method.