Pulse School: Dry year? Check residual nitrate levels


Pulse crops, for the most part, prefer drier conditions; however, the level of drought in some areas of the Prairies over the past few years has been too much for even them.

Following multiple years of drought, it becomes more important for farmers to conduct soil tests ahead of planting pulse crops, such as lentils and peas, which can be picky crops to grow, to say the least.

Lara de Moissac, precision agronomist with SWAT Maps, joins our latest episode of the Pulse School to discuss why residual nitrate levels could be high after such dry conditions, which could negatively impact nodulation and nitrogen fixation next year.

Proper nodulation is very key for pulses to exchange carbohydrates for usable nitrogen from rhizobia bacteria in root nodules, says de Moissac. Too much residual nitrate in the soil will stop the pulses from singling rhizobia to initiate the nodulation process.

Soil testing in the fall will allow farmers to determine these residual nitrate levels, allowing time to potentially change field selection to set the crop off  with the best possible chance for success.

“If you think of the brown soil zone, they barely had any snowpack last year, and most areas are surviving with less than three inches of precipitation this year. So the nitrogen levels could be really really high,” she explains.

Check out the full conversation between de Moissac and RealAgriculture’s Kara Oosterhuis, below:

When soil sampling, de Moissac says it’s best to separate samples by zone, based on factors such as topography, texture, and organic matter that influence nutrient response. Hilltops as well may have very high residual levels, while low-lying areas could be even higher.

“You also want to make sure you’re going deep enough in case there was any nitrogen movement, since it is a mobile nutrient. So test at least down to 16 inches. I know a lot of people would recommend down to 24. With the amount — or lack thereof — precipitation we’ve had, I think 16 years this year would suffice. So you do want to make sure you’re getting that complete picture.”

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