Determine Nitrogen Levels In Sweet Corn With Presidedress Nitrate Test

Crop Focus chart

Editor’s Note: This article was excerpted from The Sweet Corn Nutrient Management Guide, Oregon State University. For more inforomation, go to http://extension.oregonstate.edu/catalog and type “Sweet Corn Nutrient Management Guide” in the search box.

Two approaches have been evaluated inOregonfor postharvest nitrogen (N) testing in sweet corn: stalk nitrate-N and soil nitrate-N testing. Both tests are designed to assess whether the overall plant-available N supply for the crop (from organic inputs, fertilizer, irrigation water, and N mineralized from soil organic matter) was excessive. Of the two end-of-season tests, the postharvest soil nitrate test, which will be discussed in this article, is the most useful and reliable.

Postharvest tests will not indicate whether N supply was deficient or adequate. When building an N monitoring program, start with the presidedress nitrate test (PSNT). In westernOregon, using the PSNT when sweet corn has five or six leaves is an excellent indicator of the need for additional N.

Postharvest testing has the most value where organic inputs supply N because accurate predictions of the timing and amount of plant-available N supply are difficult with these materials.

Directions For Taking The PSNT

Interested in performing the presidedress nitrate test (PSNT)? Follow these seven steps.

  1. Sample soil when the corn has five collared leaves or at least a week before planned sidedressing. This usually coincides with a plant height of about 12 inches at the center of the whorl.
  2. Collect the soil sample between rows, away from fertilizer bands. Avoid irregular areas, such as low areas or field entrances.
  3. Sample soil to a depth of 12 inches.
  4. Collect a composite sample of 15 to 20 cores. The more cores you collect, the better your chance of getting an accurate measurement.
  5. Mix the sample in a clean container. Fill a soil sample bag with a subsample of the mixed soil.
  6. Send the sample to a soil testing laboratory to be analyzed for nitrate-N (NO3-N). Deliver the sample immediately. To avoid shipping delays over the weekend, do not mail samples on Thursday or Friday. Changes in results are likely to occur when the soil is warmed.
  7. Request results in pounds per acre.

Determine Excess Nitrogen
The postharvest nitrate test is used to diagnose accumulation of excess N at the end of the season. Excess N accumulates when plant-available N supplied from all sources exceeds crop capacity for N uptake.

Begin by collecting soil (0- to 12-inch depth) immediately following harvest. When rainfall follows harvest and substantial crop residue decomposition occurs, soluble N may move from decomposing leaves into soil. This soluble N may add nitrate-N not present at harvest time, confounding test interpretation.

The effect of N fertilizer application rate on postharvest nitrate-N has been measured in a number of on-farm and experiment station field trials. Based on these trials, when a NO3-N (nitrate-N) test for the top foot of soil is above 50 pounds per acre, N supply from all sources was probably greater than needed for maximum ear yield.

An example of the relationship between N fertilizer rate, crop N uptake, and postharvest soil nitrate is shown in the chart below. Maximum ear yields occurred with 100 to 200 pounds of N per acre in these trials. At N fertilizer rates of 0 to 150 pounds of N per acre, sweet corn was efficient in N uptake, and postharvest nitrate-N was less than 50 pounds N per acre.

At the highest N fertilizer rate (200 pounds per acre), postharvest nitrate-N averaged 75 pounds per acre and had the most variability (range of 43 to 123 pounds per acre). Although a relationship has been shown between N fertilizer rate or N supply and postharvest soil NO3-N, keep in mind that soil NO3-N is linked with irrigation practices. Low NO3-N values at harvest may be a result of excess irrigation.

Leave a Reply

Crop Protection Stories

Crop ProtectionBioConsortia Inc. Bolsters Executive Team
August 18, 2014
Industry veterans Christina Huben and Dr. Susan Turner bring experience to plant biotechnology firm. Read More
Crop ProtectionCover Crop Solutions Offers New Three-Way Cover Crop Mix
August 13, 2014
A fast-growing cover crop mix needs 45 to 60 days of growth in warm conditions. Read More
Crop ProtectionBiopesticides Vs. Traditional Agrochemicals
August 4, 2014
To effectively control pests, understand how the products work and know the biology of insect pests. Read More
Crop ProtectionFrench Crop Protection Firm Acquires Fine Holdings Ltd.
August 4, 2014
De Sangosse group seeks to bolster its business with purchase of plant growth regulator specialist. Read More
CEU SeriesCEU Series: Gain A Deeper Understanding Of Fertilizers
August 1, 2014
It's never too late to grow your knowledge of plant nutrients. Read More
Insect & Disease UpdateBaythroid XL Receives Special Florida Label For Asian Citrus Psyllid Control
July 30, 2014
EPA approval will add another option for growers’ chemical rotations. Read More
Crop ProtectionNew York Combats Giant Weed
July 30, 2014
The state continues efforts to control this species that is harmful to humans. Read More

The Latest

Crop ProtectionBioConsortia Inc. Bolsters Executive Team
August 18, 2014
Industry veterans Christina Huben and Dr. Susan Turner bring experience to plant biotechnology firm. Read More
Crop ProtectionCover Crop Solutions Offers New Three-Way Cover Crop Mi…
August 13, 2014
A fast-growing cover crop mix needs 45 to 60 days of growth in warm conditions. Read More
Crop ProtectionBiopesticides Vs. Traditional Agrochemicals
August 4, 2014
To effectively control pests, understand how the products work and know the biology of insect pests. Read More
Crop ProtectionFrench Crop Protection Firm Acquires Fine Holdings Ltd.
August 4, 2014
De Sangosse group seeks to bolster its business with purchase of plant growth regulator specialist. Read More
CEU SeriesCEU Series: Gain A Deeper Understanding Of Fertilizers
August 1, 2014
It's never too late to grow your knowledge of plant nutrients. Read More
BerriesNew Study Finds Simple Solution To Monitoring Spotted W…
July 31, 2014
UF/IFAS researchers are using a mixture of yeast, sugar, and water to lure, trap major berry pest. Read More
Crop ProtectionNew York Combats Giant Weed
July 30, 2014
The state continues efforts to control this species that is harmful to humans. Read More
CitrusThe Exponential Rise Of Biopesticides
July 28, 2014
The first sustainable commercial success stories in the biopesticide market were seen in the 1980s and 1990s. Since then, the market has grown exponentially, and is projected to exceed $3 billion by 2016. Read More
Citrus9 Resources For All Of Your Biopesticide Questions
July 25, 2014
As the use of biopesticides continues to increase at a staggering rate, more and more resources are being made available to the public to help increase awareness of the sector. Read More
Apples & PearsAn Awakening To The Value Of Biopesticides [Opinion]
July 25, 2014
With the entry of major suppliers into the biopesticide arena, whether or not biopesticides work is no longer the question. Now, people want to understand how they work. Read More
Apples & PearsPGRs: The Overlooked Piece Of The Biopesticides Puzzle
July 25, 2014
Yield and quality can be as important to growers as crop protection. Read More
Crop ProtectionDon’t Let Your Cruciferous Crops Get Beaten By Cl…
July 23, 2014
Learn how to ID, the survival and spread, as well as management methods for this vegetable disease. Read More
Crop Protection4 Methyl Bromide Alternatives To Consider
July 22, 2014
With the phase-out of the popular soil fumigant, it's important to know you have crop protection options. Read More
Crop ProtectionFlorida Farmers Feeling Pains Of Methyl Bromide Phase-O…
July 22, 2014
Growers look for recommendations to keep fields clean in the absence of the long-used fumigant. Read More
CitrusPhytech To Bring PlantBeat Service To U.S. Farmers
July 22, 2014
After growth in Israel, Phytech’s PlantBeat comes to California. Read More
Crop Protection2014 Florida Agricultural-Environmental Leadership Awar…
July 17, 2014
Growers place an emphasis on protecting the state's fragile water resources. Read More
Crop ProtectionUnexpected Discovery Prompts Giant Snail Alert
July 15, 2014
L.A. International Airport inspectors confiscate 67 live specimens of notorious invasive pest from East Africa. Read More
Crop ProtectionUSDA Farm Service Agency Announces Tree Assistance Prog…
July 11, 2014
Growers can recuperate financial losses from natural disasters with the USDA's Tree Assistance Program. Read More