Science into practice: improving plants with irrigation management

Testing potential for the use of regulated deficit irrigation (RDI) as a tool to manage plant quality for the hardy nursery stock sector was the aim of HDC project HNS 141.

As nursery irrigation systems become more precise and controllable, they not only save water but offer new opportunities to manage plant quality using RDI.

The sector is a major user of water and 75 per cent of grower sites are situated in regions where competition for limited water resources is increasing. Forty per cent of growers are in areas classified as "over abstracted". Improving water efficiency helps growers to comply with legislation to safeguard water resources.

RDI involves supplying only a proportion of the water a plant uses. The aim is to impose a very gradual drying of the soil or growing media that stimulates production of certain plant hormones and other chemical signals from the roots. These travel to the shoots, where they can modify growth and the behaviour of the stomata in the leaves controlling transpiration. As well as restricting water loss from the leaves, some of these signals influence plant robustness, plant habit, time of flowering and as a result, visual appeal. Six species and four rose cultivars were used to determine the effects of RDI on plant quality.

RDI use had a species-specific impact on quality, with some responding positively (Forsythia x intermedia 'Lynwood Gold' & 'Weekend', Cornus alba 'Elegantissima' and Cotinus coggygria 'RoyalPurple') and others negatively (Mahonia and Photinia). RDI can reduce stem height by 20 per cent in Hybrid T roses. In addition to producing a more compact plant with greater visual appeal, this could also reduce transport costs.

- For details on all HDC activities, visit

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