AgriGuide

Tomatoes

Tomatoes (Lycopersicon esculentum Mill.) belong to the Solanaceae family and are related to egg plants, paprika, and potatoes.

Suitable varieties for organic production

Most traders, retailers and supermarkets prefer especially firm durable varieties to minimize losses due to all the handling along the logistic chain from the field to the shop. Traditional types of tomatoes have a durability of approximately one week. There are new varieties for which traditional breeding (semi-longlife or longlife) and genetic engineering (“flavour savour”) have increased durability by four weeks. In organic agriculture, genetically manipulated tomatoes are not allowed. For organic growers, disease-resistance or tolerance is in many cases more important than other factors, such as durability. For example, “Peretti” tomatoes are more susceptible to rotten flowering than round tomatoes. Furthermore, local markets decide which varieties are in demand. Market demands, disease resistance, suitability to cropping systems and life storage period are factors that influence the selection of varieties in organic tomato production.

Two different growth forms of tomatoes can be found: plants with determinate growth (bush) and tomatoes with an indeterminate growth (vining). Tomatoes with determinate growth are still found in bush tomatoes and in the early varieties used for short period growing.

Design of rotation

Organic tomatoes are planted in a rotational system. Continuous production of tomatoes can be changed in the same year by producing lettuce, cucumber, leek, cauliflower, paprika or incorporating a cover crop. For farmers that dispose of only small vegetable plots, long rotations may be impractical. In such cases, soil building practices (green manure, compost) that improve soil microflora are important to promote natural disease suppressing conditions. Pastures and small grain crops that are grown in rotations to increase soil structure and organic matter should be ploughed down several months ahead of planting (problems of cutworm and wireworm).

Organic growers have had very good experiences with planting leguminous cover crops before the tomatoes, such as hairy vetch (Vicia villosa) and fields beans (Vicia faba). Tomatoes are planted in the field when the first flowers open. Different plant densities are used; for strong growing varieties, a plant density of 2-2.2 plants per sqm; for slow growing varieties, plant to a density of 2.7-3 plants per sqm. Organic growers prefer lower density to guarantee ventilation and reduce disease infections.

Pest and disease management

Tomatoes are susceptible to physiological disturbances, diseases and pests. Priorities in organic tomato production have all the management methods to prevent such pests and diseases:

• Optimal site selection;
• Selection of pest and disease resistant varieties;
• Wide rotation (in case of soil borne diseases four years should be free of tomato-production);
• Creation of semi-natural habitats and ecological compensation areas;
• Improvement of soil fertility and activation of soil microbial life;
• Balanced nutrient supply.

With such measures, non parasitic damages and physiological disturbances, as well as nutrient deficiencies can be reduced. In addition, organic preparations are applied; however, they often are less effective than synthetic products and therefore only a combination of preventive and curative methods leads to successful organic tomato production.

Harvest and post-harvest handling

Handling

Harvesting tomatoes is labour intensive. For storage and shipping, the tomatoes can be picked at the initial stage of maturity- when the blossom end turns pink. Tomatoes can be harvested 2-3 times per week, preferably in the morning. Temperature-management is critical to maintain quality. The tomatoes should be stored at 10-13°C. The flavour will be reduced if tomatoes are stored at low temperatures, while high temperatures accelerate fruit ripening. In comparison to conventional production of tomatoes, the yield of organic grown tomatoes is comparable if all measures were managed correctly during the growing period.