Stubble steals nitrogen
SASKATOON (Staff) – Chemical fallow may steal nitrogen from the soil during seeding, says a soil specialist.
With chemical fallow, crop stubble is not worked into the soil until seeding the next year. Over the winter the composition of the straw changes and may tie up some of the soil nitrogen, Ronald Gares of the University of Saskatchewan told a recent conference.
“There is a potential for immobilization once the straw is worked into the soil at seeding time,” Gares said.
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In order for straw to break down there must be a combination of carbon and nitrogen. Leaving the stubble undisturbed in the fall and winter changes the carbon and nitrogen ratio.
“The nutrient status of the straw may change.”
Once the straw is worked into the ground at seeding time it ties up some of the nitrogen already in the soil. Farmers should compensate by increasing the amount of nitrogen during seeding. The nitrogen tied up by the straw will eventually be released, but not when it’s needed during spring seeding, he said.
Best in strip farming
SASKATOON (Staff) – A combination of chemical fallow and tillage is the most effective way to reduce erosion and get the highest yields from strip-farming, says an Agriculture Canada soil scientist.
Strip-farming, which pairs summerfallow and seeded land side by side, is still the most predominant cropping practice in southern Alberta.
“It’s a classic zone for strip cropping,” Adrian Johnston said during a recent soils conference. Farmers want to preserve the most moisture and decrease the swings in yield from continuous cropping.
In the southern Alberta study researchers compared a one-way disc, chemical fallow, heavy duty cultivator, wide-blade cultivator and chemical fallow with a fall wide-blade.
There was very little difference in yield in any of the treatments. The chemical-alone treatment preserved the most soil moisture, but was susceptible to erosion because of a changed soil structure.
Soil worked with the one-way disc was the most subject to erosion. The wide-blade maintained adequate surface residue for wind erosion.
The combination of chemical fallow and a single pass with the wide-blade reduced the most weeds and eliminated the possibility of soil erosion. Chemical fallow leads to nitrogen loss.
