Articles
PEAR TRANSPIRATION AND BASAL CROP COEFFICIENTS ESTIMATED BY SAP FLOW
Article number
951_22
Pages
183 – 190
Language
English
Abstract
The crop water requirements for micro-irrigated pear orchards in the Goulburn Valley of SE Australia are currently based on generic crop coefficients.
Orchard specific basal crop coefficients (Kcb) are needed to improve our calculations of actual tree water use and thereby improve irrigation efficiency.
The objective of this study was to investigate seasonal changes in tree transpiration (T), Kcb and intercepted photosynthetically active radiation (fPAR) in a commercial pear orchard.
T was determined from sap flow measurements using the compensation heat-pulse method.
The measurements started four weeks after full bloom.
Two Williams Bon Chrétien pear (Pyrus communis L.) trees were instrumented at eight sites within the block.
Two probe sets were placed into each tree trunk, with the sensors measuring heat-pulse velocity at four radial depths.
The probes were located at approximately 0.30 m above the soil surface, and covered in foil to reduce the influence of changes in ambient temperature.
Reference crop evapotranspiration (ETo) was calculated from local weather data measured at the orchard site. fPAR was estimated using an array of 24 light sensors positioned on the orchard floor.
The correlation in sap flow between individual probe sets was very high (R>0.93). Mean orchard T varied from 1 to 52 L/tree/day during the measurement period and was largely attributed to changes in weather conditions.
The mean value of orchard Kcb was 0.55 (s.e. = 0.012) but varied from 0 to 0.87. The value of orchard fPAR remained constant at 0.61 (s.e. = 0.027).
Orchard specific basal crop coefficients (Kcb) are needed to improve our calculations of actual tree water use and thereby improve irrigation efficiency.
The objective of this study was to investigate seasonal changes in tree transpiration (T), Kcb and intercepted photosynthetically active radiation (fPAR) in a commercial pear orchard.
T was determined from sap flow measurements using the compensation heat-pulse method.
The measurements started four weeks after full bloom.
Two Williams Bon Chrétien pear (Pyrus communis L.) trees were instrumented at eight sites within the block.
Two probe sets were placed into each tree trunk, with the sensors measuring heat-pulse velocity at four radial depths.
The probes were located at approximately 0.30 m above the soil surface, and covered in foil to reduce the influence of changes in ambient temperature.
Reference crop evapotranspiration (ETo) was calculated from local weather data measured at the orchard site. fPAR was estimated using an array of 24 light sensors positioned on the orchard floor.
The correlation in sap flow between individual probe sets was very high (R>0.93). Mean orchard T varied from 1 to 52 L/tree/day during the measurement period and was largely attributed to changes in weather conditions.
The mean value of orchard Kcb was 0.55 (s.e. = 0.012) but varied from 0 to 0.87. The value of orchard fPAR remained constant at 0.61 (s.e. = 0.027).
Publication
Authors
I. Goodwin , D. Cornwall, S.R. Green
Keywords
PAR interception, Pyrus communis, compensation heatpulse, irrigation
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