Apply your Nitrogen Stamp – Assess Losses and Sufficiency for Your Crop

Submitted by John Heard, Crop Nutrition Specialist, Manitoba Agriculture

With the excessive rainfall and standing water in some Manitoba fields, some agronomists may be asked to assess possible N losses. If applied N had already converted to nitrate (NO3) form it is subject to leaching on sandy soils and denitrification on poorly drained and heavier textured soils.

In many cases it is not too late to apply your “Nitrogen Rich Strip” or N Stamp” that can serve as a reference when one wants to assess potential losses and yield penalties. Nitrogen Rich Strips are usually applied with field equipment and run across the field to encompass a range of soil types, drainage, etc. Simple differences in colour and growth between the field and this strip usually indicate a lack of N for field yield potential. When applied before or at seeding such strips should be 150-200% of the base field N rate. A number of devices and sensors (like chlorophyll sensors, NDVI or GreenSeeker) can be used to quantify such a difference and estimate in-season N applications for a variety of crops.

Nitrogen Ramp Calibration Strips or N Stamps can be simply applied by hand after seeding into fields. Details on applying the N Ramp Calibration Strip are available at: http://www.gov.mb.ca/agriculture/crops/soil-fertility/nitrogen-ramp-calibration-strips-in-manitoba.html

N Stamps are simpler – generally 30, 60 and 90 lb N/ac hand applied within a 20ft x 20ft (6m x 6m) cells. We are applying these in several wheat fields to test the abilities of UAVs or drones to detect N differences in fields. To try this out simply weigh 258, 517 and 775 g of urea into bags and hand apply to the 20’ x 20’ plot. We treat our urea with NBPT to minimize losses to volatilization. Observe differences in colour and growth. If none are seen mid-season, then the applied N was likely sufficient for yield.

 

20’

20 ‘

 20’ 0 N check

 

30lb N/ac          =  258 g urea

 20’

60lb N/ac            = 517 g urea

90lb N/ac          = 775 g urea

 

 

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