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More crop per - PowerPoint Presentation

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More crop per - PPT Presentation

drop Improving our knowledge on crop water requirements for irrigation scheduling Mark Gush David le Maitre Seb Dzikiti amp Nebo Jovanovic Introduction Background Food security ID: 301254

amp water crop tree water amp tree crop results agriculture data irrigation year streamflow dept drop

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Slide1

More crop per drop:Improving our knowledge on crop water requirements for irrigation scheduling

Mark Gush

David le

Maitre

,

Seb

Dzikiti

& Nebo

JovanovicSlide2

IntroductionBackground:

Food security =

water security

Increasing pressure on water resources in SA (population & economic growth, climate change, dilution capacity for water quality)Economic importance of agriculture and forestry to SA (GDP & value add / jobs)Significant water use by irrigated agriculture, forestry & invasive alien plantsVaries by crop type, irrigation vs dryland, rainfall region, tree species, riparian / uplandHow to produce more “crop-per-drop?”Measure to manageSlide3

Water use by sector

Source: Dept. Water and Sanitation, NWRS-2

.Slide4

Measuring water useTranspiration (tree)

Heartwood

SapwoodSlide5

Measuring water useTotal evaporation (forest / orchard)

3-D Sonic Anemometer (

H

)Net Radiometer (Rn)Soil Heat Flux Plates (G)IRGA (ET)Signal Collection BoxesHPM45C (T & RH

)Slide6

Use of models to simulate ET from trees & canopy surfaces – calibrated & verified with seasonally observed data

ET

P-M with Jarvis

r

s

sub-model

Priestley-Taylor

ModellingSlide7

Remote sensing &earth observationSlide8

Irrigated agricultureSlide9

Water use of fruit tree orchards

Groblersdal

Rustenburg

CullinanWhite River

Malelane

Citrusdal

Koue

Bokkeveld

/

Wolseley / EGVVSlide10

ResultsSlide11

A

14

yr

old ‘Pink Lady’ apple tree transpires:± 20-30 L water/day in summer (max 42 L)± 4000 L water/yr (680 mm / 6800 m³.haˉ¹)

±

27 L water per apple (170 L/kg apples)

ResultsSlide12

Forests & plantations

Zhang

et al

., 1999ΔEt ≈ ΔStreamflowSlide13

Streamflow reductions

Cathedral Peak (1950 – 1987):

Af

forested (treatment) vs. grassland (control).*Gush, M.B. 2010. Policy-orientated research for forests and water in South Africa. In: German, L.A., Karsenty, A. and Tiani, A., (Eds). Governing Africa’s Forests in a Globalized World. Earthscan, UK. Pp 208-211.Slide14

Results

3343

±

2102 L tree-1 year-110300 ± 2890 L tree-1 year-17994 ± 5995 L tree-1 year-17488 ± 4473 L tree-1 year-1Slide15

Invasive alien plantsSlide16

ResultsSlide17

IAPs Summary

Total condensed area 1.50 (1.3-1.7) million ha

Total

MAR reduction 1 444 (1 304-1 598) mill m³/yr (2.88% of MAR) - Equivalent to 97 mm/yrMost invasions in E Cape, KZN, MpumalangaMost affected Biome:Forest – issues of data resolutionGrasslands – greatest volumeIndian Ocean Coastal Belt – highest %Slide18

Clearing of IAPsSlide19

Streamflow gains

6-yr

increase in streamflow

= 114mm / 46.5%1ha riparian zone cleared = 3.5 ha non-RZ clearedSlide20

Where to from here?

On-going

field measurements and

modellingUse results in water allocation & irrigation schedulingImproved efficiencies & productivity (“crop per drop”)Enhanced monitoring (water meters), reduced transmission losses / leaks, more use of waste-water (grey water, rainwater harvesting etc.)Increased use of groundwater for irrigationOngoing removal of IAPs to augment water suppliesApplication of new technologies for precise monitoring of water use e.g. remote sensing (UAVs / satellites), online /

real-time irrigation scheduling

.Slide21

Conclusions

Agriculture can & must

become more efficient in its use of

waterAgricultural water allocation processes need to be enhancedRequires accurate crop and tree water use data (how much water is required, when, and where)Requires accurate data on crop areas (crop type mapping)Requires improved modelling, validated with accurate field data collected for a wide variety of trees and crops, growing in a range of conditions.Recognise full value-added benefit of agriculture to SA

Crop-per-drop”; “Jobs-per-drop”, “

Frogs*-

per-drop

*Environmental indicatorsSlide22

Acknowledgements

Funding:

Water

Research Commission Dept. Agric. Forestry & FisheriesDept. Environmental AffairsProject Teams (CSIR & external)StudentsLand Owners and ManagersSlide23

Thank you