Understanding water requirements of Black Box: a drip irrigation study

Transcription

1 Understanding water requirements of Black Box: a drip irrigation study Tanya Doody, Susan Gehrig WATER FOR A HEALTHY COUNTRY FLAGSHIP 4 th July 2017 Goyder Water Forum

2 Background o Markaranka floodplain 25 km downstream from Waikerie o Semi-arid ~250 mm rain year o Evaporation ~ 1800 mm year o Black Box at higher elevations Treasury Wine Estates vineyards

3 Flood history o ~ 40 years since last flooded o need 60 GL day to begin flooding but for complete inundation o hence, tree heath is quite poor 145+ GL day required to flood the plot area

4 AIM 1: to determine the influence of environmental drip irrigation water on Black Box under five drip application regimes Hypothesis 1 - trees receiving drip irrigation will maintain higher transpiration rates than the control Hypothesis 2 - trees receiving higher regimes more frequently will maintain better tree condition Water addition and tree condition *Transpiration is a surrogate for tree condition Timing and magnitude and tree condition AIM 2: assess the influence of creek bank lateral recharge in response to flooding Hypothesis 3 - trees will maintain higher transpiration rates as a direct result of feeder creek flooding

5 Method o Site location Control 20 mm month mm month mm month mm month -1

6 Method Weekly instalment Monthly instalment Weekly instalments o 50 x 50 m plots

7 Method Sap flow transpiration from January 2014 o 6 trees/treatment (50 x 50 m plot) o 30 minute readings o sap flow in mm day -1 /plot o 6 weekly download Tree condition and water potential o Seasonal (3-4 times per year) Creek flooding o 10.6 ML late March o Creek was 3m deep, o No over bank inundation o Creek height was 2m below bankfull

8 Results impact of rain Jan 24 - Feb 13 - important to determine treatment effect before Feb rain Period 1 25 Jan-14 Feb Period 2 15 Feb 26 Mar Period 3 27 Mar 9 Apr Period 4 10 Apr 12 May C3-20mm C4-control T4-60mm T7-30mm T6-50mm o Minimal rainfall Dec 2013 to P1 o Control and T20 respond after P1 rain o T20 irrigation not sufficient to sustain prolonged improvement o Hot dry period from mid March led to decline in T although irrigation continued o Control response o T20 response o Rapid response to rainfall

9 Results transpiration and dripper water regimes o Hypothesis 1 confirmed irrigated trees maintain higher transpiration rates (rain does confound this though) o Control low before rain (2014) and after irrigation commence (2015) o mm month (delivered weekly) appears best in 2014 water season to sustain trees better to summer o 105 mm month, delivered weekly exceeds other treatments in 2015 o C3 received double water in 2015 but significant decline in T due to 2 month frequency

10 Results tree condition (2014/2015) October December October December February May Predawn Ψ October December February Control C3-50 2m T m T6-0 T w February May Control C3-50 2m T m T6-0 T w Midday Ψ May o October/December high stress -5ψ o Decline due to lateness of drip watering o Improve ψ for 100 and 105 mm month -1 in February o Tree condition scores alter mm month -1 improve by February; decline in control by May o Results agree with transpiration o C3-50 2m although more water, less frequent therefore decline Presentation title Presenter name Page 10

11 Results tree condition (2014/2015) o Before watering o Hypothesis 2 confirmed trees receiving higher regimes more frequently maintain better tree condition w is best timing and magnitude with very high T over summer unlike 100 1m. Both maintain lower ψ and higher canopy condition o After watering Presentation title Presenter name Page 11

12 Results tree condition (2014/2015) o River Cooba and Black Box o Very different water use strategies o Black Box transpiration was significantly higher in 2015 (P=<0.001) which was also substantially drier (little rainfall in 3 months) o Both respond rapidly to rainfall o Hypothesis 3 confirmed trees maintain higher transpiration as a result of feeder creek flooding Presentation title Presenter name Page 12

13 Summary o Water improves tree condition and transpiration! o Rainfall is especially important for maintenance of trees o Tree water use responds immediately to rainfall o Require more than 30 mm month (0.4ML) delivered weekly to provide sustained condition o 50-60mm month ( ML) delivered weekly, produces a sustained response in transpiration (but not necessarily visual health and water potential) o Require water before summer to prevent condition decline when spring and peak transpiration period arrives (trailed in 2015/2016) o Frequency, magnitude and duration, is important! C3-50 received more than double water of previous year (0.7ML) but declined as a result of 2 monthly frequency o Although health of 100 and 105mm month magnitude of water (both 1.4 ML) was similar, transpiration indicated a significant increase in 105mm due to frequency (and therefore duration) watered with 25 mm every week o Antecedent watering (0.4ML for 100 and 0.8ML for 105) is likely to have been important to the transpiration rates of 105mm month plot Before and after (60 mm moth) Presentation title Presenter name Page 13

14 Acknowledgements o South Australian Murray-Darling Basin Natural Resource Management Board s Biodiversity Fund Grant o Rebecca Turner for continued support and assistance obtaining data o Dr Sue Gehrig for her assistance and input into the development of this project and sharing of data. o Brendan Turner from Treasury Wine Estates has been of great assistance in providing a call-in person and rain monitor, thank you!

15 Thank you CSIRO Land and Water Tanya Doody t e tanya.doody@csiro.au w CSIRO LAND AND WATER FLAGSHIP