Manure Mineralization Rates in Lab Study

 In-situ nitrogen mineralization of manure amended soils

The objectives of this research were to develop predictive relationships of nitrogen mineralization (Nmin) on manure amended soils and to use this information to improve manure management practices in cooperation with producers. To accomplish these objectives, we first conducted an in-field study of manures from different livestock sources (beef, chicken, hog, and turkey). Then we compared how different management practices influenced Nmin of one beef manure.

Results:

• The carbon/nitrogen ratio, total nitrogen, acid detergent fiber were significantly correlated with total Nmin with r values of -0.24, 0.38, and -0.33, respectively.
• Percent nitrogen mineralized in relation to total nitrogen applied averaged 15% at 45 weeks.
• Fall application of manure in the dryland had greater Nmin than the spring application at V6 (corn vegetative stage).
• In the irrigated plots, there were no significant differences between the fall and spring applications.
• Incorporating manure increased Nmin at V6, but was not different at tassel.
• The Nmin was significantly higher for irrigated plots than the dryland plots at tassel but not at V6.
• The irrigated and dryland manure averaged a 22% Nmin rate at tassel.

Graduate Student: Bradley R. Jakubowski

Cooperators: Dr. Glen Rask, an associate professor in the College of Agricultural Sciences at Colorado State University and Dr. Merle Vigil, Research Leader and Soil Scientist at CSU Central Great Plains Research Station in Akron, CO.

Funding for this project was provided by USDA Fund for Rural America.

Manure Mineralization Rates in Lab Study

Knowing various manures’ mineralization rates and total mineralization potentials under optimal conditions is critical for development of reliable Best Management Practices for agriculturalists. Eighteen manure samples were selected from a group of 137 for laboratory incubation. Five of those were further analyzed the following year. A variety of chemical and physical assays were conducted on all manures and an incubation study was conducted to analyze mineralized nitrogen (N) and carbon (C).

The secondary objective centered on a field experiment conducted to assay the effects of varying amounts of feedlot manure and sidedress N surface applications on three soil parameters (chemical parameters, earthworm populations, and microbial biomass C and N) in order to quantify changes in the soil quality.

Results:

• The incubation study indicated that with known manure N and C content it is feasible to predict manure C mineralization (R 2=0.84).
• To a lesser extent, manure N mineralization can be predicted (R 2=0.59).
• The regression model showed that soluble N and soluble C are as important as non-soluble components for predicting mineralization.
• This study was not able to draw conclusions about short-term effects on earthworms from manure or nitrogen additions due to a low number of earthworms found.
• Microbial samplings showed a consistent pattern of decrease in C, N, or active C from early to later in the field season.
• No consistent significant relationships between manure or commercial inorganic N and microbial populations were found.

Graduate student: Gregory M. Smith

Project collaborators: Dr. Kenneth Doxtader, Retired Professor, Colorado State University Department of Soil and Crop Sciences, Dr. Merle Vigil, Research Leader and Soil Scientist with the CSU Central Great Plains Research Station in Akron, CO.

Funding provided by USDA- Sustainable Agriculture Research Education (SARE) grant.

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