Antje Fiebig Effects of over-irrigation on plant growth and. hormone balance

Transcription

1 Antje Fiebig Effects of over-irrigation on plant growth and hormone balance

2 Perfect storm scenario by 2030 the world will need to produce around 50 % more food and energy, together with 30 % more fresh water, whilst adapting to climate change. (John Beddington, 2009) Agriculture accounts for 70 % of the increased fresh water demand Challenge for global agriculture Managing and balancing supply and demand for water Grow more food on not much more land Use less water, fertiliser and pesticides Use low-cost and efficient drip irrigation systems

3 Soil moisture based irrigation PC/software Data logger Irrigation Water supply Soil moisture sensors

4 Irrigation control Soil moisture threshold to activate irrigation Soil moisture threshold to deactivate irrigation How often is soil moisture checked?

5 Practical application

6 Soil moisture sensors in a typical nursery over-irrigated well-watered water-stressed

7 PhD project Aims Study effects of over-irrigation on tomato plant growth and physiology Understand what acts as a key signal Ameliorate possible growth inhibition

8 PhD research project Materials and Methods Irrigated tomato plants according to soil moisture threshold (drained capacity after 24 h) over-irrigated plants receive 150 % Parameters: fresh weight, total leaf area, evapotranspiration, leaf water potential, gas exchange, plant hormones abscisic acid and ethylene, foliar nutrient concentrations

9 Soil moisture controlled by automatic irrigation scheduling 0.7 Soil moisture (m3 m-3) over-irrigation 1 over-irrigation 2 ontrol 1 control Time (h) control: 2 drippers over-irrigation: 3 drippers Watering threshold (drained capacity after 24 h)

10 Comparison of manual and automatic irrigation Manual Volumetric soil water content (m 3 m -3 ) plant 1 plant 2 plant Time (h) Automatic Volumetric soil water content (m 3 m -3 ) control plant 1 control plant 2 control plant Time (h) Coefficient of variation Manual: 24.9 % Automatic: 12.7 %

11 Effect of over-irrigation on tomato plant growth Significantly decreased growth after 4 weeks of over-irrigation in wild type tomato ( Ailsa Craig [AC]) control over-irrigation p-value < Leaf water potential (MPa) [a] g s (mmol m -2 s -1 ) [b] p-value control over-irrigation p-value control over-irrigation No significant differences in leaf water potential [a] or stomatal conductance [b]

12 Plant hormones abscisic acid (ABA) and ethylene 3000 [a] p-value [b] p-value < ABA in leaves (ng/gdwt) Ethylene (nmol g -1 FW hr -1 ) * 0 control over-irrigation 0.0 control over-irrigation No significant change in foliar ABA concentration [a] Significantly increased foliar ethylene emission [b]

13 Root-zone ethylene measurements Time of watering 5 [a] Rootzone ethylene (per g root dwt) surrounding air over-irrigation control dark period Time (h) Rootzone ethylene (per g root dwt) 5 [b] Soil moisture does not impact on root-zone ethylene Volumetric soil water content (m 3 m -3 )

14 Macronutrients Nutrient concentration (mg/kg) [a] control over-irrigation [b] Leaf N (%) [c] p < 0.01 ** 0 Ca Mg Na P S 0 K 0 WT con WT OI No significant change in leaf nutrient status [a, b] But significantly lower nitrogen [c]

15 Ca(NO 3 ) 2 supplementation 40 [a] 4 [b] a Shoot fresh weight (g) a a ab b Leaf N (%) a a a 0 OI 5mM 10mM control 0 OI 5mM 10mM control 10 mm calcium nitrate supplementation restores shoot fresh weight [a] and leaf nitrogen concentration [b] to control plant levels

16 Ca(NO 3 ) 2 supplementation Ethylene (nmol g -1 FW hr -1 ) [a] b b a a OI 5mM 10mM control Shoot fresh weight (g) [b] Nr OI Nr control WT OI WT control WT p Leaf N (%) P value Genotype Treatment nitrogen G*N Nr p mm calcium nitrate supplementation restores foliar ethylene emission [a] But ethylene unlikely to be key growth regulator during over-irrigation [b] Instead, over-irrigation might change nitrogen availability or uptake

17 Effects of over-irrigation on tomato plants Decreases shoot fresh weight and total leaf area No changes in leaf, g s, foliar ABA But: increase in leaf ethylene emission No significant differences in root-zone ethylene production Leaf nutrient status does not change, but significantly lower leaf nitrogen Ca(NO 3 ) 2 supplementation restores shoot fresh weight and leaf nitrogen concentration Over-irrigation might change N availability and uptake, inducing growth retardation

18 Where to from here (future projects)? What impact does overirrigation have on other species or when other substrates are used? Use of commercially used substrates (rockwool) Use of plants grown in pots: ornamentals, strawberries, herbs

19 Where to from here (future projects)? How can the automatic irrigation control be of advantage for growers (especially in the containerised area)? Embed soil moisture system in commercial greenhouses Use as an irrigation control, but also as advanced warning before water stress is harmful Enhance crop quality, save water Interact directly with growers

20 IHC Brisbane (17 th -22 nd August) Oral presentation Feedback regulation of irrigation via soil moisture monitoring and its implication on plant growth and physiology'

21 Thank you very much for your attention This research is part of the HDC-funded studentship CP 81