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Soil N trend surprising

A dry summer could have left a nice bonus for you in your fields

Manitoba postal code map.

AGVISE Laboratories says the trend this fall is towards higher levels of residual nitrogen in Manitoba soils.

The Northwood, North Dakota company says an early harvest has allowed producers to get a jump on fall soil testing, and its accumulated data from more than 3,000 wheat fields already.

That’s been surprising to many producers who enjoyed good yields this season and were expecting their residual nitrate-N to be depleted, the company said in a recent news release.

The company says there are several reasons growers are finding these surprising results:

  • Dry growing conditions could have stranded N near the soil surface because lack of moisture made it unavailable for crop uptake. Crops then sent roots deeper seeking moisture and they found nitrogen in the subsoil below the 24-inch depth, allowing higher yields.
  • The warm temperatures may have increased N mineralization during the early summer, when there was significantly more heat than usual. The warmer temperatures increased mineralization from soil organic matter. If a field had five per cent organic matter, that could have meant as much as an extra 30 pounds of N.
  • There may have been areas that experienced none of the regular losses through denitrification or leaching. There were significant areas of the province that simply didn’t get wet enough to enable the typical losses farmers might be used to after more than 20 years of wet soils.

The accompanying graphic below displays the number of wheat fields that tested in each nitrogen range in several postal code areas in Manitoba. This year, 14-20 per cent of wheat fields have more than 80 lbs./acre nitrate-N remaining in the 0- to 24-inch soil profile. In most years, less than six per cent of wheat fields test more than 80 lbs./acre N (0 to 24 inch).

Depending on how dry soils were in your area, what yields you achieved, when the rain started again, and how much organic matter your soils have, you could see many wheat fields testing over 80 lbs./acre this fall.

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