Nitrogen ManagementIntro to Soils

Nitrogen in the Plant Part of

› Amino Acids: Building blocks of proteins› Enzymes: responsible for all biological

process› Nucleic Acids› Cholorphyll

Needed for Carbohydrate use Increases root growth

SCIENCE Magazine Excess nitrogen flowing down the

Mississippi each year is estimated to be worth $750,000,000 (Science, Malakoff, 1998)

NUE in cereal production must be improved

Raun and Johnson, Agron J. 91:357-363

N that is not used is lost

Liebig's Law of the Minimum

Growth is controlled not by the total of resources available, but by the scarcest resource. › Only by increasing the amount of the limiting

nutrient (the one most scarce in relation to "need") was the growth of a plant or crop improved.

Justus von Liebig1803 - 1873

Bray’s Nutrient Mobility Concept

Root SystemSorption Zone Root Surface

Sorption Zone

Nutrient limitation expressed as a % of potential yield, or “sufficiency”, and independentof the environment

Nutrient limitation directlyrelated to yield potential, and dependent on the environment

Mobile Nutrients Immobile Nutrients

Plants respond to the totalamount of mobile nutrientspresent

Plants respond to the concentration of immobilenutrients present

Nitrogen is mobile…..

Nitrogen is mobile…..

Yield GoalsYield Goals: average of last 5 years +20% average of the last 3 best years.Yield Goal includes, grain and forage/lbs of meat

Nebraska study showed that farmers overestimated yield by 2 Mg ha-1 (32 bu ac-1), resulting in an excess of 35 kg N ha-1 (Schepers et al., 1986)

Over-optimistic yield goals were the largest contributor to excess N applications with average yield goals exceeding actual yields by over 15%, only about 30% of the fields were within 5% of the yield goal (Daberkow et al., 2001)

N rate recommendation Nitrogen Recommendation =

Yield Goal N rate – Residual N

Residual N is› 0-6” (Top-soil) Soil Test NO3 › 6-18” (Sub-soil) Soil Test NO3› NO3 from irrigation› Cover Crop Credits.

Exp. 502, 1971-2006

0

10

20

30

40

50

60

70

80

9019

7119

7219

7419

7519

7619

7719

7819

7919

8019

8119

8219

8319

8419

8519

8619

8719

8819

8919

9019

9119

9219

9319

9419

9519

9619

9719

9819

9920

0020

0120

0220

0320

0420

0520

06

Gra

in y

ield

, bu/

ac

0-40-60

100-40-60

Long-Term Winter Wheat Grain Yields, Lahoma, OK

Ave Yld 42 bu/ac

“After the FACT” N Rate required for “MAX Yields” Ranged from 0 to 140 lbs N/ac

0

20

40

60

80

100

120

140

Opt

imum

N R

ate,

lb/a

c

Exp. 502, 1971-2006

Optimum N Rate Max YieldAvg. 49 lb N/ac +/- 39 Avg. 43 bu/ac +/- 13

4 R’s

1. Right Source2. Right Place3. Right Rate4. Right Time

IPNI: International Plant Nutrition Institute

Nitrogen sources Anhydrous Ammonia NH3 Urea Liquid UAN DAP, MAP, APP Coated N (sulfur and Polymer)

Nitrogen Placement Corn vs wheat vs forages

Application

Application

Right Rate Cereal Grains, Cotton, Sugar Beets

Malting Barley

Yield Goal Soil Testing Sensors

Right Time Pre plant and Top-dress/ Side-Dress

› Winter Wheat › Corn

Forage Systems› Spring, summer, fall

Thank you!!!

Brian Arnall373 Ag Hall405-744-1722b.arnall@okstate.eduPresentation available @ www.npk.okstate.eduTwitter: @OSU_NPKYouTube Channel: OSUNPK

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