Modelling nitrogen, phosphorus, potassium, calcium and magnesium uptake, and uptake concentration, of greenhouse tomato with the VegSyst model

Abstract

The existing version of the VegSyst model (V2) simulates daily dry matter production (DMP), crop evapotranspiration (ETc) and crop N uptake of tomato and other vegetable crops grown in greenhouse in SE Spain. In this study with greenhouse tomato, (i) the VegSyst model was adapted to simulate daily values of seasonal (i.e. throughout the crop) uptake of K, P, Ca and Mg, (ii) the simulation of seasonal N, K, P, Ca and Mg uptake was validated, and (iii) the simulation of seasonal uptake concentration (UC) of N, K, P, Ca and Mg was validated. For K, P, Ca and Mg, dilution curves (i.e. relationship of crop content of the nutrient (%) to DMP) were obtained from pooled data of six treatments from two greenhouse tomato crops. These relationships were all described by power equations with R2 values of 0.72–0.92 for all nutrients, except Mg that had a R2 of 0.40. For the simulation of tomato crop N uptake, the dilution curve previously used in V2 was replaced by the critical N curve for tomato of Padilla et al. (2015). The simulation of uptake of N, K, P, Ca and Mg was validated with a spring, soil-grown, long-life type, tomato crop (Tomato-11) and two long season soilless cherry tomato crops (Cherry-16 and Cherry-17). Seasonal uptake of N, K, P and Ca was adequately simulated in the three validation crops, with best performance (Relative Error (RE) ≤0.2) in the Cherry-17 crop. In the three validation crops, modelling of Mg uptake had poor performance. For simulation of UC in the two cherry tomato crops, there was good performance for N, K, P and Ca in Cherry-17, and reasonable to good performance in Cherry-16. The simulation of the UC for Mg was poor. The revised VegSyst model, identified as V3, will be incorporated into a decision support system (DSS) to provide recommendations for nutrient solution composition for soil-grown and soilless tomato crops grown in greenhouses.