Articles
APPLICATION OF DEFICIT IRRIGATION TO CONTROLLING GROWTH OF HARDY NURSERY STOCK
Article number
889_51
Pages
417 – 422
Language
English
Abstract
Deficit irrigation (DI) has proved successful in saving water without severely impacting on yield for a variety of fruit-producing crops.
The potential application of DI to hardy nursery stock (HNS) crops, however, has received less attention.
Since growth control of many HNS cultivars requires substantial labour investment, the possibility of reducing labour inputs by controlling growth via irrigation scheduling is appealing to growers.
Additionally, water costs and the increasing difficulty of obtaining abstraction licences have led to grower interest in reducing water consumption.
We aimed, firstly, to determine whether DI could be applied to control growth of selected HNS cultivars without damaging quality, using a highly uniform drip irrigation system.
Secondly, we determined the extent to which the benefits of DI were affected by the non-uniformity of water uptake inherent under overhead irrigation, as a result of variation between plants in canopy size, water use, and uptake from the surface on which the pots stand.
We also investigated whether DI had different effects depending on the type of growing substrate.
Finally, we compared scheduling of DI using an evaporimeter with scheduling using soil moisture sensors.
The potential of thermal imaging for scheduling DI was also investigated.
The results show that DI successfully controlled growth without deteriorating quality, whether overhead or drip irrigation was used, and whether plants were grown in 100% peat or a peat/ bark mix.
Scheduling of a specific severity of DI was more difficult using soil moisture sensors than the evaporimeter, and thus biomass was not reduced in a relatively mild DI treatment (70% crop evapotranspiration) when soil moisture sensors were used.
On the other hand, when the evaporimeter was used, growth was significantly reduced either when this mild DI treatment was imposed over the whole growing season or when a more severe DI treatment (50% crop evapotranspiration) was imposed only after pruning in late June.
On warm, clear days, thermal images showed notably increased canopy temperatures under DI compared to control irrigation.
The potential application of DI to hardy nursery stock (HNS) crops, however, has received less attention.
Since growth control of many HNS cultivars requires substantial labour investment, the possibility of reducing labour inputs by controlling growth via irrigation scheduling is appealing to growers.
Additionally, water costs and the increasing difficulty of obtaining abstraction licences have led to grower interest in reducing water consumption.
We aimed, firstly, to determine whether DI could be applied to control growth of selected HNS cultivars without damaging quality, using a highly uniform drip irrigation system.
Secondly, we determined the extent to which the benefits of DI were affected by the non-uniformity of water uptake inherent under overhead irrigation, as a result of variation between plants in canopy size, water use, and uptake from the surface on which the pots stand.
We also investigated whether DI had different effects depending on the type of growing substrate.
Finally, we compared scheduling of DI using an evaporimeter with scheduling using soil moisture sensors.
The potential of thermal imaging for scheduling DI was also investigated.
The results show that DI successfully controlled growth without deteriorating quality, whether overhead or drip irrigation was used, and whether plants were grown in 100% peat or a peat/ bark mix.
Scheduling of a specific severity of DI was more difficult using soil moisture sensors than the evaporimeter, and thus biomass was not reduced in a relatively mild DI treatment (70% crop evapotranspiration) when soil moisture sensors were used.
On the other hand, when the evaporimeter was used, growth was significantly reduced either when this mild DI treatment was imposed over the whole growing season or when a more severe DI treatment (50% crop evapotranspiration) was imposed only after pruning in late June.
On warm, clear days, thermal images showed notably increased canopy temperatures under DI compared to control irrigation.
Authors
O.M. Grant, M.J. Davies, H. Longbottom, R. Harrison-Murray, A. Herrero
Keywords
irrigation systems, labour costs, sensors, soil moisture content, substrate, thermal imaging, water use efficiency
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