Abstract
Direct root-zone irrigation (DRZ) is a novel subsurface irrigation strategy initially tested in vineyards for economizing water and securing grape production in arid regions with unstable climatic patterns. However, studies are lacking on the responses of grapevine leaf carbon assimilation and deep rooting patterns to the novel irrigation strategy, which are essential for optimizing grapevine growth and alleviating extreme water stress during periods of heat and drought. Thus, a two-year field study was conducted in a commercial vineyard of Cabernet Sauvignon (Vitis vinifera L.) under a semi-arid climate in Washington, USA to compare the differences in leaf gas exchange and root distribution along the 0-160 cm soil profile, combined with measurements of specific leaf area and total carbon and nitrogen content in leaves and shoots to compare DRZ and traditional surface drip irrigation (SD) under three watering regimes. Compared to SD, significantly higher rates of net CO2 assimilation, stomatal conductance and transpiration in leaves, which positively correlated to midday stem water potential, were found in grapevines irrigated through DRZ in both years. Meanwhile, DRZ reduced total root number by 50-60% and root length density (RLD) by 30-40% in the upper 60 cm soil at high (0.75-0.80 crop evapotranspiration) and moderate (0.60-0.65 crop evapotranspiration) irrigation rates, but no significant differences were found at low (0.45-0.50 crop evapotranspiration) irrigation rate between DRZ and SD. Higher root number and RLD were detected under DRZ within 60-160 cm soil depths, accompanied by a decreased ratio of total carbon to nitrogen content in leaves with slightly increased specific leaf area. Decreased rainfall and increased temperature in 2018 possibly amplified the positive effects of DRZ. Our study indicates that grapevines under DRZ could develop deeper roots for water uptake, which helps ameliorate water stress and improve the photosynthetic rate as well as enhance grapevine adaptation to semi-arid climates.
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Claims 10
Claim · model-written summary
DRZ increased leaf net CO2 assimilation, stomatal conductance and transpiration relative to SD in both years.
- Treatment
- DRZe0
- Outcome
- net CO2 assimilation, stomatal conductance and transpiratione0
- Direction
- highere0
- Comparator
- SDe0
VitisOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compared to SD, significantly higher rates of net CO2 assimilation, stomatal conductance and transpiration in leaves, which positively correlated to midday stem water potential, were found in grapevines irrigated through DRZ in both years.”
Claim · model-written summary
Leaf gas exchange was positively correlated with midday stem water potential.
- Treatment
- DRZe0
- Outcome
- stomatal conductance and transpiratione0
- Direction
- positively correlatede0
- Qualifier
- midday stem water potentiale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomatal conductance and transpiration in leaves, which positively correlated to midday stem water potential, were found in grapevines irrigated through DRZ in both years.”
Claim · model-written summary
DRZ reduced upper-soil root number by 50-60% at high and moderate irrigation rates.
- Treatment
- DRZe0
- Outcome
- total root numbere0
- Direction
- reducede0
- Value
- 50-60%e0
- Qualifier
- upper 60 cm soile0
- Comparator
- SDe0
Not reportedTaxon
Verbatim
e0“DRZ reduced total root number by 50-60% and root length density (RLD) by 30-40% in the upper 60 cm soil at high (0.75-0.80 crop evapotranspiration) and moderate (0.60-0.65 crop evapotranspiration) irrigation rates, but no significant differences were found at low (0.45-0.50 crop evapotranspiration) irrigation rate between DRZ and SD.”
Claim · model-written summary
DRZ reduced upper-soil root length density by 30-40% at high and moderate irrigation rates.
- Treatment
- DRZe0
- Outcome
- root length densitye0
- Direction
- reducede0
- Value
- 30-40%e0
- Qualifier
- upper 60 cm soile0
- Comparator
- SDe0
Not reportedTaxon
Verbatim
e0“DRZ reduced total root number by 50-60% and root length density (RLD) by 30-40% in the upper 60 cm soil at high (0.75-0.80 crop evapotranspiration) and moderate (0.60-0.65 crop evapotranspiration) irrigation rates, but no significant differences were found at low (0.45-0.50 crop evapotranspiration) irrigation rate between DRZ and SD.”
Claim · model-written summary
At the low irrigation rate, DRZ and SD did not differ significantly in upper-soil root traits.
- Treatment
- DRZe0
- Outcome
- differencese0
- Qualifier
- low (0.45-0.50 crop evapotranspiration) irrigation ratee0
- Comparator
- SDe0
Not reportedTaxonDirection
Verbatim
e0“no significant differences were found at low (0.45-0.50 crop evapotranspiration) irrigation rate between DRZ and SD.”
Claim · model-written summary
DRZ increased root number and root length density at 60-160 cm depth.
Not reportedTaxonComparator
Verbatim
e0“Higher root number and RLD were detected under DRZ within 60-160 cm soil depths”
Claim · model-written summary
DRZ decreased the leaf carbon-to-nitrogen ratio.
Not reportedTaxonComparator
Verbatim
e0“Higher root number and RLD were detected under DRZ within 60-160 cm soil depths, accompanied by a decreased ratio of total carbon to nitrogen content in leaves with slightly increased specific leaf area.”
Claim · model-written summary
DRZ slightly increased specific leaf area.
Not reportedTaxonComparator
Verbatim
e0“Higher root number and RLD were detected under DRZ within 60-160 cm soil depths, accompanied by a decreased ratio of total carbon to nitrogen content in leaves with slightly increased specific leaf area.”
Claim · model-written summary
Lower rainfall and higher temperature in 2018 may have amplified DRZ benefits.
Not reportedTaxon
Verbatim
e0“Decreased rainfall and increased temperature in 2018 possibly amplified the positive effects of DRZ.”
Claim · model-written summary
The authors infer that deeper DRZ roots could improve water uptake, stress relief, photosynthesis and adaptation.
- Treatment
- DRZe0
- Outcome
- photosynthetic ratee0
- Direction
- improvee0
- Qualifier
- deeper roots for water uptakee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“grapevines under DRZ could develop deeper roots for water uptake, which helps ameliorate water stress and improve the photosynthetic rate as well as enhance grapevine adaptation to semi-arid climates.”
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See all 42 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.