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How To Manage Those Knolls

Most people not from the Prairies think our region is a tabletop from Winnipeg to Edmonton and all points in between. Yes, we have many level lacustrine (glacial lake) plains like the Red River Valley in Manitoba, the Regina and Rosetown plains of Saskatchewan, and the Edmonton area in Alberta. But we also have uplands and glacial till plains that make up millions of acres of moderately to strongly rolling land with great variations in soil in any given quarter section. Variable rate fertilizer applications have great potential on such quarters, but not all variable rate programs will be a success.

One of the main disappointments on such rolling land for most crops is how the yield monitor drops as the combine works its way over bald, eroded knolls. We all know that snow blows off those knolls and heavy rains run off. And even before cultivation they did not have as much topsoil as mid-and lower slopes. But the wind and water erosion and cultivation over the years have taken the topsoil to almost nothing and soil fertility is a big limiting factor. That is particularly true for phosphorus because the bald knolls now have free lime right to the soil surface and P availability is greatly compromised.

Assert FL

If a source of manure is available, experiments have shown great yield response on the knolls. But for the vast majority, that is not an option so an extra dose of fertilizer P is one way to smarten up the yield on those bald knolls. I know that soil fertility is limiting on my bald knolls. Soil probing in the fall always shows some moisture left over, so the limited fertility does not make use of all the water. If a prescription were written to double the P rate over the knolls in a zero-till program, a gradual improvement should be noted. In my situation I will likely be forced to broadcast any extra dose of P.

Zero till and accurate band placement of P near or with the seed is an improvement in itself. If P is placed with the seed, there are limits — especially with canola and pulse crops. With narrow knife openers and spacings of nine inches or more with canola, a rate of 20 pounds of P2O5 per acre is about the limit on most soils.


With peas, the normal relation of yield to slope position can go out the window. On my 47-bushels-per-acre pea crop in 2009, the yield monitor showed clearly that most of the peas came from the higher portions in the landscape. The lower land had tremendous growth, but disease limited the yield in the end. A prescribed dose of fungicide on the lush lower land would have paid a large dividend. The photo shows my pea crop in a slough I pumped out in April. I walked through that and licked my lips at the potential yield all summer. The vegetation was enough to give a 70+ bushel crop, but come harvest the peas actually came from the higher land.

Incidentally, I use no fertilizer on my peas — inoculant for sure, but no fertilizer. In a future article I will tell you about another lesson I learned in my pea crop this summer.

J. L. (Les) Henry is a former professor and extension specialist at the University of Saskatchewan. He farms near Dundurn, Sask.

About the author


Les Henry

J.L.(Les) Henry is a former professor and extension specialist at the University of Saskatchewan. He farms at Dundurn, Sask. He recently finished a second printing of “Henry’s Handbook of Soil and Water,” a book that mixes the basics and practical aspects of soil, fertilizer and farming. Les will cover the shipping and GST for “Grainews” readers. Simply send a cheque for $50 to Henry Perspectives, 143 Tucker Cres., Saskatoon, Sask., S7H 3H7, and he will dispatch a signed book.



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