One thing I have missed since the demise of provincial soil testing labs is soil test summaries. Ed Hammermeister of Western Ag labs presented a very good summary of their Saskatchewan data for 2007 and 2008. Western Ag Labs uses Plant Root Simulator probes, which measure supply rate of nutrients rather than a stated quantity. This concept is different from other soil test labs.
Ed’s data showed 2007 and 2008 data for phosphorus (P) and potassium (K) to be carbon copies, as we would expect. But the 2008 nitrogen (N) data showed markedly lower supply rates than the 2007 data. This makes sense based on the big crop many took off in 2008. The bottom line is — do not expect the same big yield in 2009 with the same N fertilizer rate. The soil reserves just aren’t there this spring.
Of course, every farm, every field, every crop and every year are different — but the soil test summary for N does provide us with a general picture. Thanks Ed and thanks Western Ag Labs for sharing that data.
BREAKING ALFALFA STANDS WITH HERBICIDE
S. S. Malhi, a research scientist with Agriculture and Agri-Food Canada (AAFC) in Melfort, Sask., reported on a study to determine the N dynamics of ending an alfalfa stand with herbicide. The study compared herbicide versus tillage and the combination of the two. It also compared various times of terminating the stand — after cut one, after cut two, or in the spring just before planting wheat.
The good news is that in year one after alfalfa, where herbicide was used to kill the alfalfa, the best wheat yield was obtained when the alfalfa was killed the same spring as the wheat was planted. Two cuts had been taken the previous year. That means no disruption in production.
The bad news is that to get that wheat yield it took 100 pounds of nitrogen fertilizer per acre. In other words, the alfalfa had no chance to make a N contribution to the wheat crop. Where a combination of herbicide and tillage was used after cut one the previous year, a 50-bushel wheat crop was grown with zero fertilizer N. In other words, the N released from the alfalfa supplied enough N for a good crop with no need for a big N bill.
In Malhi’s study, the second crop after alfalfa (canola) needed 75 pounds of fertilizer N for a top-yielding crop — although the check (with zero N fertilizer added) yield was still 30 bushels per acre. The third crop after alfalfa was wheat and linear response to N fertilizer was obtained, but yields for the unfertilized check were still 60 bushels per acre.
It was interesting to see some new and local data on alfalfa breaking and N contribution. If you read page 43 of “ Henry’s Handbook,” I say that year one after alfalfa all the N requirements will be met by soil reserves. In year two, two thirds of N will be met, and in year three, one third of N will be met. By year four, the party is over and go back to normal N rates. Malhi’s data shows N response kicking back in by year two, but check yields were also very high.
If you want more detail about Malhi’s study, give him a ring at 306-752-2776. Guess what? He answers the phone when he is in the office.
BALING WHEAT STRAW
Guy Lafond with AAFC in Indian Head, Sask., reported on a 50-year study of a fallow-wheat-wheat rotation where wheat straw had been baled and there was no negative effect on soil organic matter or total N. As it turns out, baling only removes a bit more than a third of total above ground biomass and there is still a lot more residue below ground. Since 1991, the study has run as zero-till with chemfallow.
Now, this study was on a Thick Black Indian Head soil, so do not expect to extrapolate the data to brown, sandy or grey soils. The main reason for the data is to look at possible downside to baling cereal straw for ethanol production, and only Black soils with high production would be considered for such venture anyway. The only area I have seen take a serious look at straw for ethanol is around Birch Hills, Sask., which has good black soils and high yields.
As we continue to see practical and useful information come from smaller local research facilities such as Melfort, Indian Head and Scott, we must be vigilant to make sure the decisionmakers know that these facilities are essential to the long-term health of our industry. Some of the high priced help in Ag Canada have a habit of looking for ways to cut budget and think these small places are the place to start –to save more budget for big fancy labs and even fancier computers spitting out models in big urban centres. At the Soils and Crops Conference, models of wheat production were shown and this old dirt digger was anything but impressed –—to say the least.
J. L. (Les) Henry is a former professor and extension specialist at the University of Saskatchewan. He farms near Dundurn, Sask.