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United States Department of Agriculture

Agricultural Research Service

Title: Nitrate Distribution in Corn Stalks at Maturity

Authors
item Wilhelm, Wallace
item Varvel, Gary
item Schepers, James

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2001
Publication Date: November 1, 2001
Citation: Wilhelm, W.W., Varvel, G.E., Schepers, J.S. 2001. Nitrate distribution in corn stalks at maturity. Agronomy Abstracts #160534.

Interpretive Summary: The end-of-season corn stalk nitrate-N test was developed as a post- mortem to determine if insufficient (less than 700 mg nitrate-N/kg) or excessive (greater than 2000 mg nitrate-N/kg) N was available to the corn crop. The stalk section specified for the test is very specific (the section from 15 to 35 cm above the soil). Under field conditions, this precise stalk section may be difficult to collect. The objective was to determine how stalk nitrate concentration varied and how this variation affects interpretations of the stalk nitrate data. Stalks (from the soil to ear node) were collected and separated into phytomers. Phytomers were divided into three segments, dried, ground, and analysed for nitrate-N with a nitrate-ion specific electrode. Nitrate concentrations of segments varied from less than 50 to greater than 7000 mg nitrate-N/kg. When average stalk nitrate concentrations where less than 200 mg nitrate-N/kg, stalk nitrate did not vary over phytomers. With greater average levels of stalk nitrate, stalk nitrate concentrations increased 740 mg nitrate-N/kg per phytomer from the ear to the soil in the irrigated study; 330 mg nitrate-N/kg per phytomer in the rain fed study. If the phytomer nearest the soil is sampled, critical values may need to be increased 30% from those listed above.

Technical Abstract: The end-of-season corn stalk nitrate-N test was developed as a post- mortem to determine if insufficient (less than 700 mg nitrate-N/kg) or excessive (greater than 2000 mg nitrate-N/kg) N was available to the corn crop. The stalk section specified for the test is very specific (the section from 15 to 35 cm above the soil). Under field conditions, this precise stalk section may be difficult to collect. The objective was to determine how stalk nitrate concentration varied and how this variation affects interpretations of the stalk nitrate data. Stalks (from the soil to ear node) were collected and separated into phytomers. Phytomers were divided into three segments, dried, ground, and analysed for nitrate-N with a nitrate-ion specific electrode. Nitrate concentrations of segments varied from less than 50 to greater than 7000 mg nitrate-N/kg. When average stalk nitrate concentrations where less than 200 mg nitrate-N/kg, stalk nitrate did not vary over phytomers. With greater average levels of stalk nitrate, stalk nitrate concentrations increased 740 mg nitrate-N/kg per phytomer from the ear to the soil in the irrigated study; 330 mg nitrate-N/kg per phytomer in the rain fed study. If the phytomer nearest the soil is sampled, critical values may need to be increased 30% from those listed above.

Last Modified: 9/10/2014
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