A decision model for hydroponic greenhouse tomato production

A decision model for hydroponic tomato production (HYTODMOD) was developed for achieving high yield, high quality fruit. The model was based on five key tests during each of five growth stages. The five growth stages were germination and early growth, seedling, vegetative, early fruiting, and mature fruiting. The five key tests included hydrogen ion concentration of the feeding solution, electrical conductivity of the feeding solution, root temperature, greenhouse air temperature, and air relative humidity. Optimum ranges for the five tests were developed for HYTODMOD and utility theory was used to prioritize actions needed to correct unacceptable test levels. Thirteen Growth Response Functions (GRFs) were necessary to represent the potential influence of key test variables on the growth of the tomato plant throughout the entire production period. HYTODMOD was validated by comparing the model recommendations with four experts who were each given 25 hypothetical and random production situations.