University of Nebraska-Lincoln Extension, Institute of Agriculture and Natural Resources

July 21, 2006

In-season application of liquid manure

In-season application of liquid manure is a common and agronomically sound practice as water and nutrients can be applied when crop demand is high. Occasionally crop damage occurs, presumably due to high salt content of the applied effluent. Various positively and negatively charged ions contribute to the salt effect of manure. Ammonium (NH4+) is often the main cation.

Salt content is easily measured by electrical conductivity (EC). Hand-held EC meters can be purchased for around $60. The units of EC measurement are typically mmhols per centimeter (mmhol/cm), deci-siemen per meter (dS/m), or milli-siemen per centimeter (mS/cm). Fortunately, these EC units are all equivalent in value.

In-season application of liquid manure should be safe for all growth stages if the EC is less than 6 dS/m, while EC of less than 10 dD/cm should be safe for soybean after R1 and corn after the seventh leaf stage. Application in the evening, at night, and in the early morning is safer than application between 9 a.m. and 3 p.m. if it’s hot and sunny.

Charles Wortmann
Extension Nutrient Management Specialist

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Copyright 2006 by the University of Nebraska Board of Regents. All rights reserved.
Published by University of Nebraska-Lincoln Extension in the Institute of Agriculture and Natural Resources Cooperating with the counties and the U.S. Department of Agriculture.
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