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Impact of Heavy Rains on Nitrogen

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Throughout the past 60 days, we have experienced heavy rains that have caused saturated soils and leaching conditions. The excessive rain may lead to denitrification and/or leaching. 

Denitrification is the process of converting nitrogen from a nitrate to atmospheric nitrogen, which occurs in oxygen-limiting conditions. During these oxygen-limiting conditions, anaerobic bacteria uses nitrate nitrogen in their respiration process. Depending on the soil temperatures and the length of saturation, you can lose as much as 60% of your nitrogen in as little as three days (see University of Nebraska Table 1-1 below).

Source: Ferguson, R., and T. M. Shaver (ed.). 2014. Chapter 1: Nitrogen, pp. 3–16. Nutrient Management for Agronomic Crops in Nebraska. http://www.ianrpubs.unl.edu/epublic/live/ec155/build/ec155.pdf

On average, we had soil temperatures 65 to 75 degrees across the area over the past couple of weeks. We could potentially have 25% to 60% nitrogen losses if your nitrogen has completed conversion to nitrate nitrogen. 

Another avenue for nitrogen loss is leaching. Leaching is the movement of nitrate nitrogen through the soil profile and below the root zone. The amount of lost nitrogen could be more or less — it’s hard to predict. Fields with the highest chance of leaching are those with low organic matter and low clay soils (sand to silt loam soils). Additionally, if you added tile drainage to your field, you have just increased your chances of nitrogen loss due to the water moving through the soil profile and off your field, taking the nitrogen with it. Whether you have heavy or light soils, there is a good chance you have lost some nitrogen. 

How much could 25% nitrogen loss affect your yield?

  1. 170 units of nitrogen applied (assuming 100% conversion) x 25% loss = 42 units of nitrogen
  2. 42 units of nitrogen / 1.25 (units of nitrogen to 1 bushel of corn) = 33.6 bushel potential yield loss

With those potential losses, we need to be prepared to sidedress nitrogen or find alternatives to supplement nitrogen to your corn. For additional reading on this subject, please refer to Plan for When Plants Need Nitrogen Most and Diagnose Nutrient Deficiencies in Young Corn.

In the past two years, we have seen significant advantages (30+ bushels) when sidedressing corn or flying late nitrogen into fields with high precipitation events. This year’s rain is one we’ll all remember. Nitrogen is a high-priority nutrient that farmers will need to address in-season. With first-planted corn approaching V5 to V6 stage in some areas, now is the time to look at a sidedress nitrogen application.

If you have any questions or concerns about nitrogen loss and applications, contact your local Mycogen commercial agronomist or ag retailer.

Impact of Heavy Rains on Nitrogen

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