Docstoc

Water saving in rice-wheat systems

Document Sample
Water saving in rice-wheat systems Powered By Docstoc
					   Water saving in rice-wheat systems
Liz Humphreys     CSIRO     Craig Meisner       CIMMYT
Raj Gupta         CIMMYT    Jagadish Timsina    CSIRO
Geoff Beecher     NSW DPI   Tang Yong Lu        SAAS
Yadvinder Singh   PAU       Mustaque Gill       PARC
Ilyas Masih       IWMI      Zheng Jia Guo       SAAS
John Thompson     NSW DPI

                               Rice-Wheat Consortium
                                                           Rice-Wheat
                                                   40o N   Cropping
                                                           Systems
Pakistan
2 Mha               Nepal
                    0.5 Mha                       30o N



                                      China 3.5 Mha
                         Bangladesh              20o N
                         0.5 Mha                 20o S
           India
           10 Mha


                 Australia 0.1 Mha
                 Soils 45-65% clay       30o S
                 400 mm rain
                 evenly spread

 Timsina & Connor 2001                   40o S
                 Projected Water Scarcity in 2025




Degree of
water scarcity
Physical
Economic
Little or none                         Countries that will import
N/A
                                       > 10% total consumption
metres
         The World Bank (2003)


 6




12
                    Australia
• moratorium on installation of bores in many
regions (licensed)
• groundwater sharing plans
• reduction in allocations
Declining river irrigation water allocation
   “share of the water in the system”
  in Murrumbidgee Valley, Australia

                          Cap on extraction introduced
% 160                     • for environment
                          • to increase certainty of
  120                     supply for existing irrigators

 Pre-cap mean
   80
     120%
                                Post-cap mean
   40                                89%


    0
        89/90   92/93   95/96    98/99   01/02
“Resource Conservation Technologies”
        RCTs for RW systems

   e.g.
   • laser levelling
   • AWD in rice – Alternate Wetting & Drying
   • beds
   • time of sowing
   • zero tillage
   • mulching

           Do they save water ?
               How much ?
                    Fate of water             Transpiration
                                          X
  Rain               in RW fields



Irrigation                                               Runoff
                    X Soil / floodwater evaporation          X

                                              Maximum root depth
             Deep
         drainage
                    X    Capillary             – wheat up to 2 m
                          upflow                Watertable

                    Groundwater
                    inflow / outflow
 Reducing deep drainage does not “save water” if the gw can be reused
             somewhere in the system e.g. gw pumping
It does, however
• reduce irrigation amount & saves $ for the farmer
                                 (pumping costs or water charges, labour)
• reduce energy consumption
• reduce air pollution
• reduce groundwater pollution
                                        On-farm recycling system - Australia




   Reducing surface runoff does not “save water” if the water can be
          reused by the farmer or captured “down stream”

It does, however
• reduce irrigation amount & pumping costs or water charges for the farmer
• reduce surface water pollution
    Water-seeded rice


                                                                AWD on flat



40% of total ET
from floodwater




         Reducing
                                          Furrow irrigated rice on beds
    irrig. water & soil
        evaporation
Sub-surface drip irrigated rice on beds
Water-seeded rice


                    Reducing irrigation water &
                    soil evaporation can be a real
                    water saving

                    Is there a microclimate
                    compensating effect
                    on transpiration ?



                     Sub-surface drip irrigated rice on beds
        Decrease in SWC
     from sowing to harvest
         wheat after rice
      -20
      20
mm




      60
     100
     140                                    Pumping

Fallow      Early-mid wheat   Late wheat


      Impact of “water saving” technologies needs to be considered
        - over entire cropping system (crops, fallows)
        - over space (catchment)

 to determine the REAL water saving (and impacts on water quality)
Potential Water Saving Technologies
           for RW systems

 1.   laser levelling
 2.   soil selection for continuously flooded (CF) rice
 3.   puddling for rice
 4.   AWD in rice – Alternate Wetting & Drying
 5.   time of sowing
 6.   beds
 7.   direct drilling
 8.   mulching
Pakistan
               1. Laser levelling




                                    past…


   Australia
                                    present….
            Pakistan   Laser levelling
                       ● 25% reduced irrigation water
                       ● othercomponents of water
                        balance unknown ?
                        - reduced deep drainage ??
                        (a real saving where dd can’t
                        be recaptured e.g. saline gw)
                       ● many   other advantages
                        - + 20-35% wheat yield
Australia                  in Pakistan
                        -          Australia
                              efficiency (time) of
                          machinery operations
                        - improved crop uniformity
                        (NOT always !! – deep cuts)
                 2. Soil selection
             POLICY for rice in Australia
Objective
- control watertables & salinisation
- reduce irrigation water use

Target
- deep drainage from rice < 1-2 mm / day (total 200-300 mm per rice crop)

cf. north west IGP “deep drainage losses ~900-1,500 mm”
Methods
1. Rice water use policy (Irrigation < ETo-rain+400 mm)


2. Rice “soil suitability” policy
- previously soil survey 1 site / ha , 100 m x 100 m grid
        2-3 m continuous med. to heavy clay (>45% clay) in 0-4 m
- now EM31 survey to determine soil variability & target sampling
       + soil sodicity to determine permeability
Survey using ElectroMagnetic Induction
          (EM31) with dGPS


                                       + 21
                                + 64

                                + 94
                                   + 54
                3. Puddling
             NOT required for high
             yields
             e.g.
             Australia avg > 9 t/ha
             California, USA
  China
                       NW India




Bangladesh
                         Puddling – reduces infiltration rate
                           Infiltration rate on sandy loam soil
mm/day                               (water use in closed pvc cylinders)


                                                                                                                     suprisingly few reports
         25.0


                                                                                  T3 PTR-CF
                                                                                  T6 DSRB-CF (furrows)
                                                                                                                        – especially with
20       20.0


                                                 Unpuddled ~12 mm/d                                                     same water mgt
         15.0
mm/day




10       10.0




          5.0




0         0.0
          05-Jun-03   25-Jun-03   15-Jul-03          04-Aug-03             24-Aug-03        13-Sep-03    03-Oct-03



                                              Date

Puddled ~4 mm/d - total infiltr ~400 mm
much less than “typical” percolation
losses of 900-1,500 mm
Puddling
• does not necessarily total water use
(due to high losses during soaking & puddling phase)
• only 1 study from RW systems Singh et al. (2001) where:
− irrigation water measured pre puddling…harvest
− same water mgt (5 cm) in puddled & non-puddled
− irrigation water saving 75 mm / 1,537 mm with puddling

+ High cost (diesel, labour, tractor)
+ Adverse affect on non-rice crops (not always)

BUT…
where water supply unreliable (limitation of canal system,
unreliable electricity supply) puddling enables storage of
water on the field during the growth of the crop - INSURANCE
Water deficit stress in Haryana due to
     failure of electricity supply




         Direct seeding/transplanting into
         non-puddled soil
         -less cracking during severe water
         deficit & less irrigation water to refill
         - is it a real water saving ?
Challenges for Direct Seeded Rice – WEEDS, Fe deficiency, nematodes
4. Water management – AWD – alternate wetting & drying

Many studies in NW IGP comparing
- Continuous Flooding CF with irrig 1, 2, 3….7 days after
floodwater has disappeared    huge water savings

cf. Cabangon et al. 2001, Belder et al. 2003 very small
water saving
– shallow watertable
- clay soils
- considerable precautions to avoid seepage/edge effects

Unreliable water / electricity supplies are a serious
constraint to adoption of AWD
                  Australia




Intermittent irrigation to ~10 days before PI

   • irrigation water ~15%     (heavy clay)
   • yield maintained, WUE
   • but more work / difficult
         Effect of water management (AWD)
 on rice yield & irrigation water use on sandy loam
               6                                           2000



                                                           1600

               4
                                                           1200

Yield (t/ha)                                                      Irrigation (mm)
                                                           800
               2

                                                           400



               0                                           0
                   CF     1-d     2-d      3-d      5-d
                           Water management

          1-d = irrigated 1 day after floodwater disappeared etc.     Sandhu et al. 1980
                                                                 PTR-2d


      DSRB-2d                                PTR-CF


 Input water      PTR-CF   PTR-2d   TRB-2d   DSRB-2d   DSRB-CF
(irrig. + rain)
     mm
        4000



        2000

   Large “apparent” input water savings irrigating 2 days (2d) after
    Large “apparent” input water savings irrigating 2 days (2d) after
   floodwater gone
    floodwater gone
          0
   compared with continuous flooding (CF)
                  sandy loam 1
    compared with continuous flooding (CF)             loam P
 Huge EDGE EFFECTS in small plots on sandy loam PTR-CF
      (plot water use minus open microplot water use)
mm
 2500




 2000




 1500

                                                  Past findings on “water savings”
                                                   Past findings on “water savings”
 1000                                             from small plot studies in RW
                                                   from small plot studies in RW
                                                  may be confounded by edge
                                                   may be confounded by edge
                                                  effects
                                                   effects
  500                                             --underbund seepage
                                                     underbund seepage
                                                  --lateral seepage
                                                     lateral seepage
                                                  --advection
                                                     advection
    0                                             ⇒Need for water balance studies
                                                   ⇒Need for water balance studies
   05-Jun-03 25-Jun-03   15-Jul-03   04-Aug-03       in farmer fields with real edge
                                                 24-Aug-03 13-Sep-03 03-Oct-03
                                                      in farmer fields with real edge
                                                     effects
                                                      effects
                     Pressurised irrigation
Overhead sprinkler
                     Australia
                     - large irrigation water
                     savings in rice
                     BUT larger yield decline
                     - 25% irrigation water
                     saving in barley, similar
                     yield
                     - total water saving ???
                        Sub-surface drip
        5. Time of rice planting in NW India
ET rice (Epan)                                      Yield (t/ha)
     (mm)

 800                                                         8


 600                                                         6


 400                                                         4


 200                                                         2


   0                                                         0
       1-May     17-May   24-May   3-Jun   17-Jun   30-Jun




20% rice area transplanted in May in Punjab
1. labour shortages      2. long duration var. (Pusa)
3. water avail.          4. pests & diseases             Hira 1994
     6.                      Australia
    Beds
      -
    wheat
           India
            wheat on beds in Bangladesh




Pakistan




                                     Bangladesh
Lots of studies in IGP showing:
- irrigation times &/or amounts, typically   ~30%
for wheat & other upland crops on beds; yield ≈
- farmer fields
Other components of the water balance ???
-   deep drainage losses ??
- real water saving only if g.w. can’t be recaptured

Beds have many other potential benefits e.g.
- soil structure (controlled traffic)
- improved surface drainage (reduced waterlogging)
- interrow culture, fertilizer placement (controlled traffic)
- crop diversification
- perm. beds opportunity for double cropping (better
drainage; faster turnaround)
Challenge – mgt of permanent beds in RW to maintain yields
                  e.g. sandy loam Feb 04
    Light interception 86% - 3.8 t/ha   Light interception 81% - 3.6 t/ha




          Conventional PTR-CTW                     PTR-DDW


    Light interception 82% - 4.1 t/ha   Light interception 61% - 3.1 t/ha




           Fresh beds after PTR
                                             Perm. beds after DSRB
TRB - Bangladesh   Many reports of
                   irrigation water savings
                   with rice on beds
                   – BUT compared with
                   what ?
                   PTR-CF ? what depth ?
                   PTR-2d ?
                   PTR-?? ?


                       TRB - India
 Rice – sandy loam - 2004


             TRB-2d
             4.8 t/ha    PTR-2d
            2,360 mm     7.0 t/ha
                        2,590 mm




DSRB-2d                      PTR-CF
 4.8 t/ha                    6.5 t/ha
2,880 mm                    3,190 mm
         Rice 2004 – loam – farmer’s field

         TRB-2d
                             6.6 t/ha
         6.6 t/ha            Irrigation 2,560 mm

   irrigation 2,560 mm
                                            PTR
depth 100 mm ? after irrig
                                          7.3 t/ha


                              49 irrigations 2,260 mm
                                AWD after 5 weeks
                              depth ~33 mm after irrig.
      Irrigation +                                Yield (t/ha)
       rain (mm)
     2000

                                                          12
     1600

     1200                                                 8

      800
                                                          4
      400

         0                                                0
              Flat - CF   Bed15   Bed-furrow Bed-ssdrip



Sowing on the shoulders of the beds will close the yield gap
                   7. Zero till wheat

Many reports of:
- irrigation water savings of 20-35% (90-100 mm),
        espec. 1st irrig. (faster)
- comparable or higher yields (due to more timely sowing)
- reduced costs

Other components of water balance ???
-   dd loss due to faster irrigation ?
-   soil evaporation ?    – faster turnaround after rice
                          - no cultivation
-   ET ?                  - earlier planting (crop matures
                          under lower evaporative demand
      Real water savings
 Pakistan                         India
Rice stubble burning is usually
  a prerequisite for ZT wheat
    in mechanised systems



            Australia   India
        8. Mulching may save water
        by reducing soil evaporation
• few reports (espec. with same water mgt in rice)
• reports of saving 1 irrigation in wheat in NW IGP
(or yield increase where water limiting)
• needs quantification
  Direct drilling and mulching in a single pass




         Chute




Seed    Forage            35 H.P.
drill   harvester         Massey Ferguson

                           ~6.5 t/ha rice straw
Happy Seeder
 Wheat sown Nov 2003 with Happy Seeder




Double disc
                            Inverted T
         0 t/ha 13 t/ha




0   13      11    7   t/ha rice straw
Direct seeding
   rice into
 wheat straw
Direct seeding rice into
    wheat stubble




                           • irrigation mgt ??



        no mulch           + mulch
  – Fe deficiency worse
Mungbean in wheat straw
                                Combo Happy Seeder




Fig. 1 Combo Happy Seeder                   Fig. 2 Combo Happy Seeder (During Sowing
                                            Wheat)




          Strip Tillage rotor
Laddhowal – clay soil
 Fig. 9 Crop stand at USF Ladhowal (after
 21 days)                                   Pabbian (after 35 field
                                            Farmer’s days) at Pabian
                                            Fig. 10 Crop stand at Farmer field at




                                               Combo Happy Seeder
                                               with strip till drill
Pak FMI Happy Seeder - MI




Indian Combo Happy Seeder




                            Oz-Twynam Happy Seeder
                     Conclusions
Many technologies in RW reduce irrigation water requirement
Some may also save water:
       - evaporation from soil or free water suppressed
       - drainage into unrecoverable g.w. reduced
       (e.g. too saline, non-pumpable)
       - drainage into unrecoverable surface water reduced
        (e.g. sea)
Very little quantification of components of the water balance
or total water saving
Need to account across:
       - cropping system within field (crops, fallows)
       - space
       - time
Infrastructure & policy constraints to adopting potential on-
farm water saving technologies – reliability of water supply
 Best bet water saving technologies for “RW” NOW

Reduce rice area / diversify         –      NW IGP, Aust
Rice planting time - delay NWIGP, earlier eastern India
Mulching
Zero tillage after rice – quick turn around, undisturbed soil Esoil;
                            crop maturing under lower evap. demand
Beds – appear to save irrigation water on permeable soils for
     individual crops e.g. wheat (system ?? total water ??)
     - & rice (some situations ?? which ?? compared with ?)
     - AND total system benefits of perm. beds
     ( crop diversification, intensity, yield of non-rice crops)
AWD in rice – BUT irrigation water savings may not be as
            large as thought (edge effects in small plots)
            - total water savings ??
            - reliable water (power) supply major constraint
  Wish list technologies & policies for water
             saving in RW systems


Forecasting water availability – dam supply
                           - cropping area (weather)
Water allocation system

Removal of price support for rice & wheat

Markets for alternative crops

Removal of subsidies for water & electricity
Thank you

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:6
posted:7/25/2011
language:English
pages:54