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March 27, 2013

Nitrogen carryover questions continue from the 2012 drought and low crop yields. Significant number of nitrate soil test analyzed by Solum’s No-Wait-Nitrate process last fall showed wide ranges of carryover soil nitrates remaining in fields. Two questions remain on decisions for carryover N credits for 2013 crops.

Question 1: Which fields have significant carryover?
Use the nitrate soil test to determine. Soil testing for nitrates in the Corn Belt has not been a common tool used. This spring of 2013 may be the year to use this tool to measure carryover nitrate levels. Solum has developed technology to measure nitrates with field-moist technology that delivers accuracy, speed and efficiency in getting results.

Question 2: Will carryover N be available?
Watch rainfall patterns and amounts in your regions this spring and early summer. Significant precipitation will be needed to recharge soil moisture levels before free water will be leaving fields in tile. Most medium to fine textured soil can hold 2 plus inches of available water per foot of soil. Leaching loss will be low until enough water is received to recharge the soil profile. One caution is that nitrates in the upper layers of soil could move down during the recharge period and are not lost for plant uptake, but are positioned unavailable for early plant uptake. This positioning effect of nitrogen may require spring applications of nitrogen to carry the crop until roots reach deeper soil nitrate levels.
Nitrate Testing Procedures

  1. Timing of sampling – timing of nitrate sampling for 2013 could include a preplant sampling before spring nitrogen applications and a pre-sidedress sample when corn is 6-12 inches tall.
  2. Sample depths – since nitrates are mobile in soils, nitrate soil samples are taken deeper than regular soil samples. If sampling equipment allows, one option is a 0-24 inch sample. Divide this depth into 3 zones (0-6, 6-12, 12-24). The second option of a pre-sidedress sample is usually taken at a 0-12 inch depth (0-6, 6-12).
  3.  Sample Locations – typically, large variations exist in field nitrate levels. Sampling methods could include sampling by 2-4 management zones or sampling for a field average. Note, that areas of the field subject to leaching and denitrification losses (light textured and heavy textured poorly drained soil) should be sampled separately.

About Solum™

Solum’s™ mission is to develop software and measurement technology that makes the business of Agriculture simpler and more productive. Our advanced soil nutrient and fertilizer response models are developed by Solum's™ industry leading soil measurement laboratory in Ames, Iowa.

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Ames, IA 50010
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