Rolling pulses paid in 2004
By Lorne McClinton
Timing is important, but do the spraying first!
Rolling pulse crops paid big dividends to producers in 2004 even though wet
harvest conditions made combining pulse crops a nightmare across the prairies.
Peas were a particular problem. Weeks of rain in September, followed by snow,
left pea crops flat on the ground. It was common for harvest of unrolled fields
to be delayed until the weather conditions improved in October.
"All pea crops should be rolled because we don't know what the weather
will be like in the fall," says Ken Lopetinsky, pulse research agronomist
with Alberta Agriculture's Crop Diversification Centre North in Barrhead. "Most
new pea varieties have good standability under relatively dry conditions so
producers were starting to cheat and not roll. It caught up with some producers
Rolling pulses pushes some of the small stones and dirt lumps into the ground,
reducing the odds these will pass over the cutterbar and enter the combine.
This speeds up harvest and eliminates costly rock damage repairs to the combine.
It is easier to adjust lifter fingers and improve cutting performance when the
field has a smoother soil surface. Conversely, if lifter fingers are always
crossing furrows and ridges, they tend to ball up with dirt when the soil is
wet or throw dirt over the cutterbar and into the combine.
Timing is important
Pre-emergence rolling is the only safe time to roll crops like dry beans and
chickpeas. If producers wait until the crop comes out of the ground to roll,
they risk stressing the crop and damaging the stems. It can also spread disease.
"Ascochyta can be spread through chickpea crops by rolling," Lopetinsky
says. "Bruising a plant with a roller is like cutting your finger. A wound
makes it easier for an infection to set in."
Even though crops like peas and lentils can be safely rolled after emergence,
Lopetinsky recommends rolling pulse crops before they come out of the ground.
"Usually the best time to roll pulse crops is immediately after seeding,
as soon as the soil surface is dry," he says. "We have had instances
where it starts raining and doesn't seem to want to stop and the fields never
did get rolled because they were too wet for a whole month and the peas were
in the six to eight node stage."
Rolling rarely causes crop problems when done correctly, though it can lead
to wind and water erosion in some areas. Rolling breaks up lumps on the soil
surface. If it turns dry in a wind zone or if there is a sudden two or three
inch rain on an extreme slope, serious erosion can occur. Erosion-prone fields
should be rolled after crop emergence.
"Compaction isn't a problem with an empty roller," Lopetinsky says.
"We did some work adding water ballast and we saw differences starting
to show up. I understand that, because of some disturbance with direct seeding
systems, people were starting to roll with ballast to smooth out fields. I'm
not sure that is a good idea."
Care should be taken to avoid double rolling since tractor tires can cause
excessive packing and plant damage. One option is to roll 'round and round'
the field instead of back and forth. This eliminates double rolling the headlands
but leaves some areas of the field unrolled. If you have to roll back and forth,
slow down for the turns.
Post-emergence rolling possible
Peas can be safely rolled up to the third node stage without a reduction in
yield. Lentils can be rolled up to between the fifth and seventh node stage
depending on variety.
"Lentils can be rolled a bit later than peas," Lopetinsky says, "but
I would say that earlier is better. I wouldn't roll anything after the fifth
node. By this time, you are building up such a volume of material you can't
help but bruise plants."
Rolling in the early morning, when plants look lush and are wet with dew, can
cause trouble too. Stems are firmer and more subject to damage and small plants
can be pulled out of the ground. Producers can avoid trouble by waiting until
the afternoon when the plants have dried off and become more wilted before rolling.
"On a good day, you can roll and come back the next morning and the plants
will all be standing up again as if nothing happened," Lopetinsky says.
"The second to third node stage is the ideal time for post-emergence rolling,
but it is also the ideal time for herbicide application."
Trying to juggle rolling and spraying demands is often the biggest issue with
post-emergence rolling. "Pulse crops are poor competitors with weeds,"
Lopetinsky says. "If you have to choose between rolling and spraying, spray
first. The more severe the weed competition, the more urgent it is to control
them before rolling because weeds will affect your yield, rolling won't."
Agriculture and Agri-Food Canada researchers in Lacombe and Lethbridge found
that field pea yields declined every week that spraying was delayed after emergence.
Waiting four weeks after emergence to spray reduced yields by 25 percent.
"Take care not to apply two stresses to the crop at the same time."
Lopetinsky concludes. "Leave enough time between rolling and spraying operations
to allow the crop to recover. Don't roll and then turn around and spray the
next day." -30-
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