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Lesson Outline Biological Fixation of Nitrogen Forms of Nitrogen in the Soil Nitrogen Ferilizer Management Nitrogen Accounting and Credits Crop Rotations Monitoring Crops for Nitrogen Deficiency Summary References

Soils - Part 5: Nitrogen as a Nutrient Rate Me 1 2 3 4 5 Monitoring Crops for Nitrogen Deficiency Nitrogen deficiency is fairly easy to diagnose because of the unique symptoms expressed in plants: initial lower leaf yellowing with the leaf tip and mid-rib affected first. However, by the time such deficiency symptoms become evident, yield reduction may have occurred, depending on the growth stage. The chlorophyll meter is a relatively new tool for nitrogen management which can detect developing nitrogen deficiencies before they are visible, and before they can significantly reduce yield. Current UNL recommendations for the use of the chlorophyll meter for corn suggest the application of 20-40 lb. nitrogen per acre if meter readings from the field are more than 5 percent below readings from adequately fertilized reference strips. Other recent methods for detecting nitrogen stress are the lower stalk nitrate test (which indicates after the season if the nitrogen supply to the crop has been adequate or limiting), and remote sensing imaging (which can detect developing nitrogen stress similar to the chlorophyll meter). The producer may be able to use a chlorophyll meter or remote sensing to detect nitrogen stress in time to correct a deficiency during a growing season, either with high clearance applicators or via fertigation through center pivot irrigation systems. Comments Be the first to write a comment... Add Comment

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This project was supported in part by the National Research Initiative Competitive Grants CAP project 2011-68002-30029 from the USDA National Institute of Food and Agriculture, adminstered by the University of California-Davis and by the National Science Foundation (NSF), Division of Undergraduate Education, National SMETE Digital Library Program, Award #0938034, administered by the University of Nebraska. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the USDA or NSF.
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