GROWTH, DEVELOPMENT AND YIELD OF A TOMATO CROP - PERIODIC DESTRUCTIVE MEASUREMENTS IN A GREENHOUSE

The results of 12 growth experiments with indeterminately growing tomato (Lycopersicon esculentum cultivar 'Counter') cultivated in heated greenhouses without CO2 enrichment in different seasons and 5 different years are presented, summarised and discussed. Periodic destructive measurements (fresh and dry weights of different plant organs, leaf area, number of leaves and trusses) were conducted in each experiment for a period of about 100 days after flowering of the first truss (planting date). Except for one experiment, trusses were pruned to seven fruits per truss. Crop growth rate showed a slightly saturating response to photosynthetically active radiation (PAR) inside the greenhouse, probably caused by CO2 depletion at high irradiance. Assuming a linear relationship between crop growth rate and PAR resulted in a slope (crop efficiency) of 2.5 g dry matter MJ-1 PAR. Crop growth rate varied between almost zero in winter and 20 g m-2 day-1 in summer. Truss appearance rate was linearly related to temperature (18-23-degrees-C), with a slope of 0.010 truss day-1-degree-C-1. At 20-degrees-C this rate was 0.146 truss day-1. Average crop specific leaf area (SLA) showed a sinusoidal relation with season and was 175-250 cm2 g-1 in summer and 300-400 cm2 g-1 in early spring, late autumn and winter. At 95-101 days after planting in most experiments 54-60% of cumulative dry matter was distributed to the fruits, 28-33% to the leaves and 12-13% to the stem. However, for late autumn plantings only 35-38% of dry matter was distributed to the fruits, 44-45% to the leaves and 18-21% to the stem, owing to poor fruit set. For all but one experiment the same relationship between total dry weight (TDW; g m-2) and fruit dry weight (FDW; g m-2) was observed: FDW = 0.642 (TDW - 80.0). In all experiments the ratio between produced leaf and stem dry weight was 7:3 and this ratio did not change with crop development. Fruit harvest rate showed a sinusoidal relation with season, maximum harvest rate (1 kg fresh weight m-2 week-1) was reached around mid-June. Fruit dry matter content was on average 5.6% and did not clearly depend on the season.