During the later stages of growth it is particularly important to ensure that environmental and growth constraints do not limit quality potential. For example, the resultant color, aroma, flavor and texture are all established at this stage of development.
Maintaining steady growth of fruit at all times will ensure good quality criteria are met.
Reducing glasshouse temperatures can slow ripening. A fruit ripening agent can be applied a couple of weeks prior to harvest in processed tomatoes to ensure even maturity. It can also be promoted by treating harvested green fruit with ethylene or ethephon.
Control of pests and diseases, and maintenance of a controlled irrigation regime throughout fruit fill, will help maintain skin and internal fruit texture with minimal disorders.
The minimization of fruit disorders will also ensure good crop quality:
- Blossom End Rot (BER) will be minimized by avoiding large fluctuations in water deficits. Mulching to conserve moisture in field tomato crops can help.
- Similarly, in a greenhouse environment, maintaining a steady transpiration rate through night and day humidity control can help reduce the incidence of BER.
- Blotchy ripening is more common under low light or heavy vegetative growth due to low temperatures, excess of water, or low salinity. It can be minimized by changing the irrigation regime (amount and EC) and by leaf pruning.
- Sunscald can be reduced by increasing leaf shading of the fruit by careful water and crop protection management techniques. Increased planting density and variety choice can also help.
- Cracking and russeting of the fruit is made worse by fluctuations in water supply.
- Puffiness is associated with low light and low temperature conditions. Thinning, and preventing prolific vegetative growth or shading can minimize this disorder.
Crop nutrition is essential. Fertilizer programs starting early during establishment and vegetative growth are needed to ensure nutrients don’t limit fruit quality:
- High potassium supply decreases puffiness. Too much nitrogen increases the disorder and can slow ripening.
- Maintaining high potassium and nitrogen levels in the fruit will minimize blotchiness and greenback problems in fruit.
- Potassium and nitrogen are important for aroma. Too much ammonium-N adversely affects taste.
- Potassium is the main nutrient affecting the quality of the tomato, improving the uniformity of ripening, shape, acidity and taste of the fruit.
- High levels of calcium are important in maintaining firmness and preventing damages due to disorders or during handling and transportation.
- Maintaining high levels of calcium in the root zone and throughout the plant, minimizing the impact of competing cations such as ammonium, will reduce BER incidence.
- Low levels of boron can lead to corkiness of the fruit and poor marketable quality.
- Zinc also has a role to play in maintaining fruit quality.