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| Titel |
Mitigation of soil water repellency improves rootzone water status and yield in precision irrigated apples |
| VerfasserIn |
S. Kostka, N. Gadd, D. Bell |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030601
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| Zusammenfassung |
| Water repellent soils are documented to impact a range of hydrological properties, yet studies
evaluating the consequences of soil water repellency (SWR) and its mitigation on crop yield
and quality are conspicuously absent. With global concerns on drought and water availability
and the projected impacts of climate change, development of novel strategies to optimize
efficient rootzone delivery of water are required. Co-formulations of alkyl polyglycoside
(APG) and ethylene oxide-propylene oxide (EO/PO) block copolymer surfactants have
been shown to improve wetting synergistically. The objectives of this study were to
determine if this surfactant technology: 1) increased soil water content and wetting front
depth in mini-sprinkler irrigated, water repellent, Goulburn Valley clay loam soils
and 2) assess the consequence of SWR mitigation on yield of Malus domestica
Borkh.
Three trials were conducted in the apple varieties ‘Pink Lady’ (2006/07 and 2007/08) and
‘Gala’ (2007/08) growing on Goulburn Valley clay loam soils in Victoria, AU. The test design
was a randomized complete block with treatments replicated 5-6 times. Plot size varied by
location. SWR was mitigated by applying surfactant at initial rates of 0, 5, or 10 L ha-1 in the
spring, then at 0, 2.5, or 5 L ha-1 monthly for up to four months and compared to an
untreated control. Treatments were applied to tree lines using a hand held small plot sprayer
(118 liters of spray solution ha-1) followed by irrigation within 1-3 days of treatment
applications. At each location, plots were irrigated by mini sprinklers and received the
same irrigation volumes and management practices. Soil volumetric water content
(VWC) was monitored at depths of 0-10 and 10-20 cm using a Theta probe (Delta-T
Devices, Cambridge, UK). At harvest, fruit number and weights were measured and
used for crop yield estimations. Data were analyzed using analysis of variance with
mean values summarized and separated using Least Significant Test at 5% level of
probability.
As surfactant rate increased, wetting front depth increased and soil VWC increased for the
surfactant treatments (p=0.05). Soil VWC was significantly lower (p=0.05) in untreated soils
than in the surfactant treatments on each measurement date throughout the growing season. In
the surfactant treatments, soil VWC at the 0-10 cm and 10-20 cm depths of the soil profile
were 2-5 percentage points higher than at the same depths in the untreated control
(p=0.05). Mean fruit size for the variety ‘Pink Lady’ was 17-33 g greater in the
surfactant treatments than in the untreated control in the 2006/07 and 2007/08 seasons,
respectively (p=0.05). Mean fruit size differences of 41 g were observed between
surfactant treatments and the untreated control in the single year of results for the
variety ‘Gala’. Due to thinning, there were no differences in fruit number. Total
yield (kg tree-1) differed significantly between the untreated and surfactant treated
plots (p=0.05), however, yields between the two surfactant treatment rates were
statistically equivalent. In the variety ‘Pink Lady’, surfactant treatment increased total
yield by approximately 20% in each of the two test seasons. Yield increases in
the surfactant treated ‘Gala’ were nearly 50% greater than the untreated control.
When examining the yield differences on a hectare basis, yield increases of 3.7 – 6.0
Mg kg ha-1 were encountered between the surfactant treatments and the control
in the two varieties tested. Mitigation of SWR resulted in increased net return of
$6,000 - $9000 ha-1 for the variety ‘Pink Lady’ and $3,600 ha-1 for the cultivar
‘Gala’.
This study demonstrates that simple innovative management strategies such as low level
surfactant treatments to water repellent soils resulted in improved infiltration, increased
rootzone water reserves, and significant increases in apple yield and quality under deficit
irrigation. |
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