Are Sap Flow Measurements Useful for Determining Water Use of Fruit Orchards, When Absolute Values Are Important?

Taylor, N. J.; Ibraimo, NA; Annandale, J. G.; Everson, C. S.; Vahrmeijer, JT; Gush, Mark B

doi:10.17660/actahortic.2013.991.9

Cited by 6 publications

(3 citation statements)

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“…Sap flow measurements were performed using the heat ratio method as described by Burgess et al (2001) on six trees and calibrated as described by Taylor et al (2013). These probe sets were inserted above the rootstock in the scion and below the first branch, with the probes being equally spaced around the trunk and randomly arranged, taking care to avoid any abnormalities in the trunk.…”

Section: Methodsmentioning

confidence: 99%

Modelling water use of subtropical fruit crops: the challenges

Taylor¹,

Annandale²,

Vahrmeijer³

et al. 2017

Acta Hortic.

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Subtropical fruit crops form an important part of the fruit industry in many countries. Many of these crops are grown in semi-arid regions or subtropical regions where rainfall is seasonal and as a result the vast majority of these perennial, evergreen orchards are under irrigation. This represents a significant irrigation requirement and with more emphasis being placed on the conservation of water and orchard profitability, it is becoming increasingly important to accurately estimate water use of these crops and schedule irrigation accordingly. The FAO-56 procedure is a simple, convenient and reproducible method for estimating water use. However, the transferability of crop coefficients between different orchards and growing regions is not always readily achieved, due largely to differences in canopy size and management practices. In addition, as subtropical crops tend to exhibit a higher degree of stomatal control over transpiration than most other agricultural crops, some measure of canopy or leaf resistance must be taken into account when using models based on atmospheric demand. The challenge is therefore to provide reliable and dynamic estimates of canopy resistance from relatively simple parameters which can be of use to irrigation consultants and farmers for determining the water requirements of these crops. The challenge remains to ensure that these dynamic estimates are realistic and readily applicable to a number of growing regions. The derivation of transpiration crop coefficients, based on canopy cover and height and a dynamic estimate of leaf resistance, provided reasonable estimates of transpiration in three orchards in contrasting climates, suggesting that this approach could prove useful in future for subtropical crops.

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Section: Methodsmentioning

confidence: 99%

Modelling water use of subtropical fruit crops: the challenges

Taylor¹,

Annandale²,

Vahrmeijer³

et al. 2017

Acta Hortic.

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“…The sap flow measurements were calibrated against T estimated as the residual of simultaneous measurements of ET and E s conducted in the pecan orchard at Cullinan in February 2012, using a wound effect correction coefficient of 7.2 mm. Similar calibrations of sap flow measurements have been performed by Taylor et al (2013Taylor et al ( , 2015.…”

Section: Field Measurementsmentioning

confidence: 81%

Are simple empirical crop coefficient approaches for determining pecan water use readily transferrable across a wide range of conditions?

Taylor¹,

Annandale²,

Ibraimo³

et al. 2017

Acta Hortic.

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The accurate estimation of evapotranspiration (ET) of orchard crops is critical for judicious irrigation water management and planning. However, it is impossible to measure ET under all possible combinations of climate and management practices, which necessitates the use of ET models. Although empirical models are more likely to be adopted by consultants and growers, due to easier parameterization and the requirements for fewer, more easily measured input parameters, they may not always be transferable across a wide range of conditions. As a result these models may not always give acceptably accurate ET values outside of the area in which they were calibrated. This study therefore aimed to evaluate empirical crop coefficient models for pecans in two different orchards which differ in climate and/or fractional canopy cover from where the models were developed. When testing the FAO-56 approach it was found that pecans should not be grouped under stone fruit and that a six stage crop growth should be considered, instead of the traditional four stage curve. Improved accuracy in estimating ET of pecans could, however, be achieved by using a pecan specific reference crop coefficients for a mature orchard and scaling this with fractional canopy cover for different orchards, provided that an adjustment was made for the influence of climate on canopy development. This was achieved by using a published growing degree (GDD) day crop coefficient relationship, provided seasonal accumulated thermal time is below 1600 GDD and that crop coefficients do not exceed 1.1.

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“…The accurate calibration of absolute sap flow using heat pulse techniques involves several technical calibrations, including measuring sapwood density, sapwood moisture content, area of conducting tissue, correcting needle misalignment, and determining the thermal diffusivity of the sapwood ( Taylor et al., 2013 ). However, these complex calibrations present significant challenges to the adoption of sap flow as an irrigation tool in commercial orchards where equipment and expertise may not be available.…”

Section: Discussionmentioning

confidence: 99%

Assessing water stress in a high-density apple orchard using trunk circumference variation, sap flow index and stem water potential

2023

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IntroductionAutomated plant-based measurements of water stress have the potential to advance precision irrigation in orchard crops. Previous studies have shown correlations between sap flow, line variable differential transform (LVDT) dendrometers and fruit tree drought response. Here we report season-long automated measurement of maximum daily change in trunk diameter using band dendrometers and heated needles to measure a simplified sap flow index (SFI).MethodsMeasurements were made on two apple cultivars that were stressed at 7 to 12 day intervals by withholding irrigation until the average stem water potential (ΨStem) dropped below -1.5 MPa, after which irrigation was restored and the drought cycle repeated.ResultsDendrometer measurements of maximum daily trunk shrinkage (MDS) were highly correlated (r² = 0.85) with pressure chamber measurements of stem water potential. The SFI measurements were less correlated with stem water potential but were highly correlated with evaporative demand (r² = 0.82) as determined by the Penman-Monteith equation (ETr).DiscussionThe high correlation of SFI to ETr suggests that high-density orchards resemble a continuous surface, unlike orchards with widely spaced trees. The correlations of MDS and SFI to ΨStem were higher during the early season than the late season growth. Band dendrometers are less labor intensive to install than LVDT dendrometers and are non-invasive so are well suited to commercialization.

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Are Sap Flow Measurements Useful for Determining Water Use of Fruit Orchards, When Absolute Values Are Important?

Cited by 6 publications

References 0 publications

Modelling water use of subtropical fruit crops: the challenges

Modelling water use of subtropical fruit crops: the challenges

Are simple empirical crop coefficient approaches for determining pecan water use readily transferrable across a wide range of conditions?

Assessing water stress in a high-density apple orchard using trunk circumference variation, sap flow index and stem water potential

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