Highwire Project

(HDC Project PC273)

BACKGROUND:

UK  cucumber growers use the ‘cordon’ growing system where the main stem is trained up a vertical string that is tied to a horizontal support wire positioned about 2 m above the ground.  The side shoots are removed until the main stem reaches the support wire. Three strong lateral shoot are then selected and the main growing point is removed. The side shoots are allowed to cascade downwards to a length of about 1 m with their growing points removed to encourage sub-lateral shoot development.

HDC project PC 201 on All Year Round Cucumbers incorporated a high wire crop training system that was novel to UK growers.  The training system simplified the evaluation of crop performance and crop management decisions in comparison to the cordon system.  It improved light penetration to the fruit, had good air circulation; fruit picking was easier and of better quality with reduced waste. There was also a much reduced incidence of foliar pests and diseases.

THE PROJECT:

The technical and economic viability of using high wire crop training systems in cucumbers was investigated. Single stems of cucumber were trained up a vertical string to a horizontal support wire positioned about 3.8 – 4.2 m above ground.  As the plants approached the wire they were layered so that only the most recent 2.8 – 3.2 m of growth was vertical with the younger most productive leaves continually positioned to maximise light interception.

THE FACILITY:

Previous work in small glasshouse units had illustrated the importance of assessing labour inputs on a relevant scale. This work was done in two similar modern commercial glasshouses (each of 0.5ha), which were owned and managed by a leading CGA grower member. One glasshouse was fitted with the equipment required to grow high wire trained crops, while the other provided a comparison with best current conventional practice. The overall strategy was fine tuned as required during the growing season to maintain output in response to crop growth, water use and environmental conditions.

RESULTS:

High wire growing regimes were not economically viable compared to the conventional cordon system.   The system increased yields by up to 7% but this did not offset the higher costs of labour, consumables and energy. Labour was required to remove side shoots, unwanted fruit, old leavers and to layer the plants.   Energy costs also went up by 2.6%. In addition difficulties with the biological control of the two-spotted spider mites (TSSM) were encountered because TSSM move to the highest points of the crop in summer whereas the biocontrol agent, Phytoseiulus prefer more shaded positions.  The growing points were always at the highest position in a high wire crop so they suffered the most concentrated and sustained attacks from TSSM.

The project was supported financially by the Horticultural Development Council.