Irrigated Wheat Best Practice Cotton WATER Pakrk
Irrigated Wheat Best Practice Cotton WATER Pakrk
Irrigated Wheat Best Practice Cotton WATER Pakrk
• Seasonal water requirement The amount of water required Figure1 shows the daily water use in
varies from 360 to 550mm to produce a wheat crop with wheat which peaks during flowering
maximum yield is not a fixed and milk development (GS60 to
• A full irrigation strategy or GS70).
value as temperature and relative
limited water irrigation strategy
humidity during the growing Moisture availability at this stage
can be used
period along with wind and soil is critical to the yield of the crop.
• The period leading up to and moisture all determine the rate Moisture stress for more than a few
including flowering is the most of evaporation from the soil and days during this period will result in
sensitive to water stress. transpiration from the plant lower grain yield and quality.
• Good agronomic practices are (evapotranspiration or ETC ). In
needed to maximise production favourable seasons the water The area of irrigated wheat to
and minimise lodging risk requirement may be as low as plant is a function of wheat price,
360 to 440 mm whereas in a available water and your planned
• Starting soil-N determines the irrigation strategy.
most appropriate nitrogen warmer dry year this requirement
strategy could be up to 480 to 550 mm to
• Durum out yields bread wheat produce maximum yields. Table 1
summarises the results of APSIM
Irrigation Strategies
and quick maturing varieties
with good lodging resistance simulations for wheat yields and
should be used evapotranspiration water use in the Full Irrigation
Northern Grains Region.
• Adjust row spacing to manage For fully-irrigated wheat (with
biomass and tillering – 30cm row The DAFF Queensland free on-line a target yield exceeding 8 t/ha)
preferred tool CropWaterUse can be used to where water is not limited, the aim
examine the seasonal variability is to maximise yield by scheduling
• Aim to establish 100-150 plants/
in crop water requirement for fully irrigations to match crop water
m2 of bed or hill area
irrigated wheat at your location (see demand and avoid crop stress
• Planting on rainfall preferred Table 2). during the entire growing season.
over pre-irrigation and watering
It shows the irrigation demand This requires the close monitoring
up which can delay planting
for 1 June planted wheat at of soil moisture once secondary root
and produce excessive biomass
three locations (Narrabri, Dalby development has been completed
respectively
and Emerald), assuming that the (normally GS31).
• Irrigate to encourage secondary crop was fully-irrigated to target
root development if needed In order to avoid crop stress, do not
maximum yield. An irrigation allow soil water to fall below 50%
• Use plant growth regulators to application efficiency of 75% and of plant available water capacity
minimise lodging a 75mm irrigation target deficit (PAWC). This is commonly referred
• Use disease resistant varieties are assumed. Results show a large to as the ‘refill point’.
and a pre-planned fungicide variation in seasonal crop water
application strategy demand, rainfall and irrigation
Table 4.1.1 Range of simulated maximum yield (t/ha) and evapotranspiration water
use for 90% of years 1, for quick maturing irrigated wheat (Kennedy) on 2m beds in the
Northern Grains Region, in the absence of lodging, disease, pest and frost damage
1
(excludes the top 5% and bottom 5% of years). Source: A. Peake
Table 4.1.2 Comparison of average water requirements for wheat planted on the 1 June
at Narrabri, Dalby and Emerald, based on historical weather data (1957 to 2008)
Figure 4.1.1 Wheat water use pattern and critical growth stages
291 WATERpak — a guide for irrigation management in cotton and grain farming systems
4.1 Irrigated wheat – best practice guide
Once below 50% of PAWC, crops use can also be reduced with surface automatically downloads daily
more energy extracting the remaining irrigation systems by increasing weather data from different locations
soil water. Plant growth and yield siphon flow rates and reducing in Queensland and New South Wales
potential will fall considerably if soils irrigation runtimes. and, using farm-specific inputs,
are allowed to dry down beyond this • Crops can only extract water conducts a daily soil water balance
threshold. from their effective root zone. and economic analysis to determine
Make sure water is available for 2 to 3 Therefore, the depth of soil when and how much to irrigate.
days before the crop reaches its refill wetted by irrigation needs to be Figure 4.1.2 is an example of the
point. The reproductive growth phase adjusted during the season to end of season report generated by
typically coincides with an increase respond to increases in root zone WaterSched2 for a fully irrigated
in temperature and an acceleration of depth and irrigation wetted front wheat crop at Dalby in the 2009
plant water use. Any delay in water should not go deeper than the season. This report summarises
application can cause significant yield effective crop root zone. the water, crop and economic data
losses. • The soil water deficit to trigger for the crop. It provides the WUE
The period leading up to and irrigation also depends on the indices for predicted and actual yield
including flowering is the most depth of the root zone and achieved. The graph at the bottom
sensitive to water stress. Stress at needs to be adjusted during the of the report shows the daily soil
this time will reduce the number of season. Both the ETC rate and the water depletion during the season.
heads per plant, head length, and soil water deficit change daily, During the season this report
number of grains per head. It can so irrigation frequency needs to provides the information needed by
also restrict root growth. Yield losses be adjusted in response to these the grower to decide on their most
from excessive water deficits at this changes. appropriate irrigation scheduling
time cannot be recovered by later • The desired soil water deficit strategy in response to crop water
irrigations. and the irrigation frequency requirements, likely economic
Key points to consider when also depend on the irrigation returns and whole farm water
scheduling irrigation for fully- system capacity (mm/day). This availability.
irrigated wheat are: highlights how much water the Correct timing of the last irrigation
irrigation system can apply in will ensure adequate grain fill and
• crop stress must be avoided. ETC
one day, allowing for system also reduce the risk of lodging and
is usually linearly related to crop
breakdowns or maintenance. The harvesting delays. It should be
yield. Stressing the crop at any
greater the system capacity, the applied around mid dough growth
stage of development reduces ETC
greater the soil water deficit that stage (GS80) if readily available
and yield. This yield loss cannot
can be replenished quickly. water has been used to 60 to 90cm
be recovered by irrigating at a
later time. To avoid crop stress, Irrigations can be scheduled based soil depth.
it is important to know when to on soil moisture monitoring using
irrigate and how much water to one of the commercial soil moisture
apply. Table 4.1.3 summarises monitoring tools available. This
the water management equipment can tell you the rate of
considerations for each growth crop water use and the depth of
stage of wheat. water extraction.
• The application of a fixed water This can be used to make irrigation
depth at each irrigation can lead scheduling decisions.
to deep drainage losses. It is not Irrigation can also be scheduled
necessary to refill the soil profile based on estimation of crop ETC
at each irrigation. Overhead from weather data. WaterSched2,
systems are especially suited to a free online irrigation scheduling
application of small irrigation tool developed by DAFF Queensland
depths, but application depths is now available. This tool
Table 4.1.3 Critical water management considerations by growth stage for wheat
Main stem leaf production Early weed control will conserve plant available
1 Seedling Stage is the growth stage from wheat water.
emergence until the plants begin to tiller
Booting
4 By booting each plant should have 2-3
productive tillers depending on growing
conditions and crop density.
Heading
5 The spike (also called the head or ear) is Water stress will significantly reduce yield. Soil
emerging from within the flag leaf. water depletion should not exceed 50% of PAWC.
Flowering
6 Pollen is being released and the individual
grains are being fertilized.
Grain dough stage Yield is almost set, but water stress will still reduce
8 When squeezed, the grain will still deform grain size and yield. Soil water depletion should
slightly, but no liquid is apparent. not exceed 50% of PAWC.
293 WATERpak — a guide for irrigation management in cotton and grain farming systems
4.1 Irrigated wheat – best practice guide
Figure 4.1.2 WaterSched2 End of Season Field Summary report for a fully irrigated wheat crop at Dalby in 2009
295 WATERpak — a guide for irrigation management in cotton and grain farming systems
4.1 Irrigated wheat – best practice guide
297 WATERpak — a guide for irrigation management in cotton and grain farming systems