Water logging in crop product
Answers
Answer:
Waterlogging in some years and some environments in the high rainfall areas of south-west Western Australia can cause significant reductions in plant growth.
We provide practical options to deal with effects of waterlogging, and to reduce the extent and persistence of waterlogging.
Why waterlogging needs to be managed
Waterlogging can lead to:
crop and pasture production loss
poor trafficability
loss of nutrients
soil structure decline.
Waterlogging plus salinity is much worse
Under saline conditions, waterlogging inhibits the ability of roots to screen out salt at the root surface. This results in large increases of salt uptake, concentration of salt in shoots, and reduced plant growth or death. More information is available on the Dryland salinity in Western Australia page. Reducing waterlogging is the first step in managing saline sites.
Management options for waterlogging
Suitable options depend on the severity, position in the landscape and land use. You can adapt crop or pasture management to the waterlogged conditions, reduce the waterlogging on-site, and reduce surface water flow to the susceptible site. We recommend a combination of these options, as part of a whole-farm water management plan.
Options include:
do nothing: just avoid waterlogged areas when seeding, spraying, and harvesting; not normally recommended
use more-tolerant crops or pastures, and use suitable agronomy
alter nitrogen management to suit the waterlogged situation
use shallow surface drainage on flat waterlogged or inundated areas
use surface water management upslope, to divert surface water flows
use raised beds on high susceptibility flats, with shallow surface drainage.
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Use tolerant crop species and adjust agronomy
Some grains are more tolerant of waterlogging than others:
Most grain legumes and canola are more susceptible to waterlogging than cereals and faba beans.
Grain legumes, in decreasing order of tolerance are: faba bean, yellow lupin, grass pea, narrow-leafed lupin, chickpea, lentil, field pea.
Oats tends to recover better from waterlogging than wheat and barley.
Wheat and barley varieties have a large genetic range of waterlogging tolerance.
Adjust seeding
Options to reduce crop damage from waterlogging:
seed crops early
use long-season varieties
plant waterlogging-susceptible paddocks first and early – crop damage is particularly severe if plants are waterlogged between germination and emergence
resow the crop if waterlogging delays emergence and reduces cereal plant density to fewer than 50 plants per square metre, if accessible and if waterlogging has ended
increase sowing rates in areas susceptible to waterlogging – waterlogging depresses tillering (and the number of seed heads); higher sowing rates increase the number of heads and improves crop competition with weeds that take advantage of stressed crops.
Manage weeds
Weed density affects a crop's ability to recover from waterlogging. Weeds compete for water and the small amount of remaining nitrogen. Waterlogged parts of a paddock are often weedy.
Spray the weedy areas with a post-emergent herbicide – if herbicide resistance is not a problem – when the paddock is dry enough to allow access and provided the crop is at an appropriate growth stage. Aerial spraying is an alternative when ground-based sprays cannot be used.
Control root diseases
Diseases, particularly take-all, of wheat and barley are often more severe in waterlogged crops, because the pathogens tolerate waterlogging and low oxygen levels better than the crops.
Reduce the severity of take-all in well-drained and waterlogged areas by eliminating grasses from the preceding crops or pastures. Leaf diseases are likely to be more severe in waterlogged crops, because the crop is already stressed. Spraying may be an option after the site has dried, but only in crops with a high yield potential. See Crop diseases: forecasts and management for detailed recommendations
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Alter nitrogen management
Crops tolerate waterlogging better with good nitrogen status before waterlogging occurs. Waterlogging usually results in nitrogen being leached beyond the root zone, and crops may be nitrogen deficient after waterlogging.