Controlling water imbalances to reduce tomato losses

The research

Tomato growers in the Isle of Wight and Yorkshire hope to considerably reduce waste from splitting and blossom end rot, which can cause yield losses of up to 10%. These are physiological issues affected by water, temperature, light and ventilation, which affect the uptake of water in the plants. Water balance sensors have been developed by industry to give insights into how plants respond to these growing conditions, but the technology has rarely been tested in UK glasshouses. The plan was to use this information to adapt the glasshouse environment to reduce stress on the plant with the hope that this will reduce fruit disease.

In this field lab, growers installed these sensors in non-organic beef and cherry tomatoes and organic piccolo tomatoes, with the plan to build a continuous picture of stem diameter and sap flow within the plants. It is hoped the findings can be applied to many other protected crops including peppers, cucumbers, and soft fruit, as well as with outdoor annual and perennial crops.

The benefits

Blossom end rot is caused by insufficient calcium reaching tomato tissue. Incorrect water balance together with suboptimal light, ventilation and humidity can lead to a shortfall of calcium in the plant, particularly at the end of the fruit, making it unmarketable. 

Similarly, sudden fluxes in temperature and irrigation can cause tomatoes to split, particularly when combined with a period of unstable light conditions, affecting transpiration. By using the data generated by the sensors, farmers can adjust greenhouse conditions and irrigation to reduce stress.

Trial Design

Three sets of sensors will be installed after an initial proof of concept trial and testing of equipment in the following 3 tomato cropping situations at 3 sites (6 farmers);

1. Speciality beef tomato crop grown on the Isle of Wight: The crop will be grown in coco husk (coir) media and ‘conventional’ fertigation used. The sensor will first be deployed into a crop grown under lights, which historically has suffered badly with BER.
2. Piccolo cherry tomato grown at a tomato production site in the Alderley Edge (Cheshire) which is prone to fruit splitting. The crop would be grown in rockwool (a basalt growing media) and conventional fertigation used.
3. Piccolo cherry tomato grown on the Isle of Wight with significant fruit splitting issues as the above. This is a soil grown organic crop presenting greater challenges when considering the optimisation of water supply. 

Although it may not be possible to have a meaningful control within the working crops during the trials work, the figures for crop losses stated are relatively stable year on year. Thus, comparison with previous years data regarding fruit splitting and BER will be used as the best and most meaningful comparison we can use. 

Data from the novel water sensors will be collected continuously to include sap flow and stem diameter provided by the 2Grow system and also measurements of moisture content, humidity deficit, vapour pressure deficit, leaf surface temperature, air temperature, heating pipe temperature, air exchange, vent position and other parameters collected by our existing environmental computers