There is an on-going question in my mind that has not been
answered to date. Over the long term, is zero till canola
production on stubble as profitable as on conventional
summerfallow? If one were to ask a canola producer in the moist
dark brown region of Saskatchewan you would get a mixed reaction
that would end up favoring summerfallow production as the clear
winner. I would like to challenge this bias and try to present
the pros and cons of the two systems.
Conventional Summerfallow
On June 3, a small area received a heavy rain shower just after the canola had emerged. On June 6, a strong NE wind developed and the pulverized soil began to blow. By June 7 the canola will have to be reseeded because of severe wind shear and to stop the soil erosion. To complicate matters, the land will be exposed to wind erosion for an additional two to three weeks. Fortunately this is an isolated incident covering a small but not an uncommon sight over the years. A dry loose seedbed on summerfallow in 1995 will go down as a much bigger problem for sure. Many producers have gone to the spread and till approach and there are many complaints of poor emergence as of June 10 with some areas receiving no rain yet this spring. Poor wild oat control on trifluralin treated soil has also plagued our area for the last three years. There appears to be no clear answer to this one other than cold soil conditions in the spring. This is somewhat ironic since black summerfallow is supposed to warm up early to activate trifluralin. High stinkweed populations are always a threat as this weed prefers a firm moist seedbed similar to canola.
The most disturbing trend that I have witnessed is the call for high rates of nitrogen from soil samples. This spring, I viewed one rest result called for 70 lb. of N for normal growing precipitation. I will admit that this is the worst one that I have seen in some time but 30 to 50 lb. is common. Depletion of soil organic matter and leaching of soil nutrients during the fallow period appear to be taking their toll and will continue to do so in the future.
To conclude the summerfallow picture, I must be mention that
the risk from spring water erosion is an on-going degradation
factor that will not go away. Canola does like a low residue,
warm, moist seedbed and will do very well with the extra subsoil
moisture that summerfallow provides on a dry year. Most producers
seem willing to risk summerfallow cropping in order to achieve
that "magazine cover" canola crop that we in the dark brown soil
zone don't often enjoy.
Zero Till Stubble
Straw management, in my opinion, is the most crucial management tool that needs to be performed for good canola emergence. Harvest is the time to perform an even spread of straw and chaff or you will pay dearly next spring. Weed control in zero till may not be as big a problem as previously thought since the concept of surface applied trifluralin and ethalfluralin. This is working very well in my own case in 1995. Perennial weed control can be achieved from a preharvest application of roundup. Winter annuals are controlled in the late fall. It appears that the stinkweed population in the zero till fields are much smaller and generally not a problem.
Fertilizer must be applied by fall banding or side banding during spring seeding with specialized equipment. If you are not totally confident of seed to fertilizer separation at seeding, stick to fall banding with a narrow knife. Seedbed moisture is usually very good but cool soils can pose problems in germination especially with the polish varieties. You may also be more susceptible to spring frosts as the straw covered furrow will freeze first. Overall, if the straw has been managed well you can expect a moist firm seedbed to get the crop off to a good start. However, in a dry year, moisture stress will limit yield. From a soil conservation perspective, over the long term you will not experience the soil degradation problems related to fallow cropping systems.
I have not made a lot of progress outlining the economic comparisons of the two systems but I do hope to continue this discussion in the next issue of the Prairie Steward. I will stick my neck out on the line and share with you my results with the 1995 canola crop. At this point in time our canola crops are off to a great start and we trust that there will be adequate moisture to sustain the crop. Good luck with your '95 crops and I hope they will be bountiful.