Abstract
Abstract Water and nutrient application using three irrigation systems, namely daily drip irrigation, pulsing drip irrigation and micro irrigation were studied with respect to photosynthetic efficiency, water use efficiency and leaf water relations in ‘Brookfield Gala’ apple trees during 2004/5 and 2005/6 in the Western Cape Province, South Africa. The amount of water used per irrigation strategy was 5254 m3 ha−1 yr−1 and 5661 m3 ha−1 yr−1 for the micro irrigation; 3429 m3 ha−1 yr−1 and 39260 m3 ha−1 yr−1 for the daily drip and 3429 m3 ha−1 yr−1 and 4047 m3 ha−1 yr−1 for the pulsing drip for 2004/5 and 2005/6 seasons respectively. Trees were budded on either M793 or M7 root-stocks and planted in blocks using a split-plot experimental design with irrigation as the main effect and root-stock as the sub-plot. Maximum light-saturated net CO2 assimilation rate (Amax) was consistently higher under pulsing drip irrigation (this system applies water several times during the day creating an even shorter frequency cycle than the normal daily drip) compared to micro irrigation (applies water once to twice a week and uses sprinklers that spray water in a circle resulting in wetting a continuous strip within the drip row) but, occasionally, significantly higher than daily drip irrigation (applies water on a daily basis creating a shorter cycle compared to micro sprinkler system). The maximum rate of electron transport (Jmax) showed similar trends to Amax during 2004/5, but not during 2005/6. Amax peaked during midmorning (10h00) with a steady decline thereafter in all treatments, but with significantly lower rates under micro irrigation. Stomatal conductance (gs) declined steadily throughout the morning, with higher gs under the drip based systems compared to the micro system. The implications are that, irrigation application should be given early in the morning to sustain stomatal conductance and maximise CO2 assimilation rates during the period between 08h00 to 12h00. Results indicate higher photosynthetic capacity and water use efficiency under both drip-based irrigation systems compared to micro irrigation. Differences in photosynthetic capacity were related to both stomatal and non-stomatal responses.
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Claims 10
Claim · model-written summary
Pulsing drip produced higher maximum net carbon assimilation than micro irrigation.
- Taxon
- apple
Malus domesticat0 - Treatment
- pulsing drip irrigatione0
- Outcome
- Maximum light-saturated net CO2 assimilation rate (Amax)e0
- Direction
- highere0
- Comparator
- micro irrigatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“Maximum light-saturated net CO2 assimilation rate (Amax) was consistently higher under pulsing drip irrigation”
e1“compared to micro irrigation (applies water once to twice a week”
Claim · model-written summary
Pulsing drip occasionally yielded significantly higher maximum assimilation than daily drip.
- Taxon
- appleMalus domesticat0
- Treatment
- pulsing drip irrigatione0
- Outcome
- Maximum light-saturated net CO2 assimilation rate (Amax)e0
- Direction
- highere1
- Qualifier
- occasionallye1
- Comparator
- daily drip irrigatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“Maximum light-saturated net CO2 assimilation rate (Amax) was consistently higher under pulsing drip irrigation”
e1“occasionally, significantly higher than daily drip irrigation”
Claim · model-written summary
Maximum electron transport showed an assimilation-like pattern in 2004/5 but not 2005/6.
- Taxon
- appleMalus domesticat0
- Outcome
- maximum rate of electron transport (Jmax)e0
- Qualifier
- during 2004/5, but not during 2005/6e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“The maximum rate of electron transport (Jmax) showed similar trends to Amax during 2004/5, but not during 2005/6”
Claim · model-written summary
Assimilation peaked at midmorning and declined thereafter.
- Taxon
- appleMalus domesticat0
- Outcome
- Amaxe0
- Direction
- peakede0
- Qualifier
- midmorning (10h00)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“Amax peaked during midmorning (10h00) with a steady decline thereafter in all treatments”
Claim · model-written summary
Micro irrigation produced significantly lower assimilation rates.
- Taxon
- appleMalus domesticat0
- Treatment
- micro irrigatione0
- Outcome
- Amaxe1
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“significantly lower rates under micro irrigation”
e1“Amax peaked during midmorning”
Claim · model-written summary
Stomatal conductance declined through the morning.
- Taxon
- appleMalus domesticat0
- Outcome
- Stomatal conductance (gs)e0
- Direction
- declinede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“Stomatal conductance (gs) declined steadily throughout the morning”
Claim · model-written summary
Drip systems had higher stomatal conductance than micro irrigation.
- Taxon
- appleMalus domesticat0
- Treatment
- drip based systemse0
- Outcome
- gse0
- Direction
- highere0
- Comparator
- micro systeme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“higher gs under the drip based systems compared to the micro system”
Claim · model-written summary
The authors recommend irrigating early in the morning to sustain conductance and assimilation.
- Taxon
- appleMalus domesticat0
- Outcome
- irrigation application should be given early in the morninge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“irrigation application should be given early in the morning to sustain stomatal conductance and maximise CO2 assimilation rates during the period between 08h00 to 12h00”
Claim · model-written summary
Drip systems had higher photosynthetic capacity and water use efficiency than micro irrigation.
- Taxon
- appleMalus domesticat0
- Treatment
- both drip-based irrigation systemse0
- Outcome
- photosynthetic capacity and water use efficiencye0
- Direction
- highere0
- Comparator
- micro irrigatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“higher photosynthetic capacity and water use efficiency under both drip-based irrigation systems compared to micro irrigation”
Claim · model-written summary
Photosynthetic capacity differences were related to stomatal and non-stomatal responses.
- Taxon
- appleMalus domesticat0
- Organ / stage
- leavest0
- Outcome
- photosynthetic capacitye0
- Qualifier
- stomatal and non-stomatal responsese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“apple leaves”
e0“Differences in photosynthetic capacity were related to both stomatal and non-stomatal responses”
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