Simulation of greenhouse management for the cultivation of tomato in the high altitude tropics

The second version of the modified TOMGRO model was used to simulate the production of a tomato crop in 8 hypothetical greenhouse adaptations in the Bogota Plateau; near to the equator and at 2650 m above sea level. An inflatable polyethylene tube, a thermal screen, heating and CO2 fertilisation were evaluated. With these strategies a range of average temperatures between 14.7 and 20.0 degrees C was calculated, using some basic assumptions that were deduced from literature and from previous experiments. The maximum productivity and gross income increased as the average greenhouse temperature increased, despite small decreases in greenhouse transmissivity due to the installation of a PE tube or climate screen. The maximum productivity without CO2 fertilisation was obtained in a treatment heated to maintain a minimum temperature of 18 degrees C, resulting in a fruit yield of 41.7 kg center dot m(-2) for a 300-day growth period. For each climate treatment, a combination of planting density and fruit pruning can be selected to obtain the desired average fruit weight in a range of nearly 25 g, without affecting gross income. Only a small effect of CO2 fertilisation was detected, due to the opening of the greenhouse during most of the day. The simulation model showed reasonable results, in accordance to data from the growers, and can thus be used for calculating other hypothetical climate adaptation strategies and evaluate micro-climates in the high altitude tropics.