Odor and Nutrient Management Newsletter

Spring 1998

Northeast Iowa demonstration project

by Gina Hanson, NEIDP manure management specialist and Charles Wittman, NEIDP communications specialist

Nearly 90 % of farms in northeast Iowa raise some type of livestock. The manure produced on these farms can become a potential threat to water quality if not managed properly. That’s because Allamakee, Clayton, Fayette and Winneshiek counties are home to steep hills and coldwater trout streams underlain by creviced limestone, a landscape known as karst topography that makes the water resources vulnerable to contamination from activities that take place on the soil surface.

The Northeast Iowa Demonstration Project (NEIDP) is an interagency project that assists producers who are adopting new management methods to protect water resources. A major priority for the project is to provide information and to demonstrate the value of manure to meet crop nutrient needs. Managing manure for crop nutrient needs reduces the commercial fertilizer required for crop production, saving producers money.

In 17 on-farm demonstrations between 1994 and 1997, project staff worked with producers to identify the contributions of manure nitrogen for corn production. Producers were asked to identify fields in a corn-corn rotation for the demonstration that had not received manure for the past two years. Farmers were asked to apply manure at their normal rates, leaving a check area with no manure. Project staff calibrated manure spreaders and took manure samples for nutrient analysis to determine first-year manure nitrogen contributions. Because manure was surface-applied on all farms, volatilization of ammonia N was also taken into consideration. The average first year manure nitrogen contribution was 124 pounds per acre.

In addition to the manure applications, project staff hand-applied 3 treatment rates of ammonium nitrate at 0, 50 and 100 pounds of nitrogen per acre. Each treatment was replicated 3 times on each producer’s farm.

The late spring nitrate test (LSNT) was used to determine if adequate N was available to the crop during the growing season. The results of the LSNT indicate that with no manure and no nitrogen applied there was not enough N available for the crop, with the manure application there was optimal N available for the crop, and with the two fertilizer applications the amount of N available exceeded the needs of the crop.

To evaluate N management at the end of the season the cornstalk nitrate test was used.

Cornstalk nitrate nitrogen levels less than 700 part per million (ppm) indicate that applying additional N would likely increase yields. Levels between 700 and 2,000 ppm nitrate nitrogen indicate that adequate N is available to maximize yields. Nitrate levels over 2,000 ppm indicate a high probability that more N is available than needed.

These demonstrations indicate that manure can supply the necessary nitrogen needed for a corn crop and maximize profits. Results from the other two treatments in which commercial fertilizer was applied in addition to the manure indicated that excess nitrogen was available to the crop throughout the growing season. The addition of either the 50 or 100 pounds of fertilizer added a production cost of $10 to $20 per acre at a nitrogen cost of 20 cents per pound with no significant increase in yield. See results in Table 1.

Table 1. Corn yields, late spring nitrate values, and cornstalk nitrate results from 17 manure management demonstrations, 1994-1997.
Treatment Yield
Cornstalk NO3N*
No manure, no N 123 20 516 Marginal
Manure, no N 134 25 2,242 Excessive
Manure, 50 lbs./A N 135 32 2,772 Excessive
Manure, 100 lbs./A N 134 38 4,173 Excessive

* See PM-1714 (pdf-file), Nitrogen Fertilizer Recommendations for Corn in Iowa, for more details
** See PM-1584 (pdf-file), Cornstalk Testing to Evaluate Nitrogen Management, for more details

Each year new NEIDP demonstrations are established so farmers in many communities can observe the results. Three demonstrations were conducted in 1997. The local media and meetings were used to inform producers of these studies.

Eleven demonstrations on 9 farms are scheduled for 1998. The demonstrations will include commercial nitrogen plots, manure applications on corn following soybeans, manure applications on corn following alfalfa, and manure application on corn-following-corn. Results of these demonstrations are published in the Water Watch newsletter.

For more information regarding the newsletter or the demonstrations contact the Northeast Iowa Demonstration Project at 111 W. Greene, Box 417, Postville, IA 52162; phone (319) 864-3999; E-mail x1spring@exnet.iastate.edu or neiademo@netins.net.

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Iowa Manure Matters: Odor and Nutrient Management is published by Iowa State University Extension, with funding support from the USDA Natural Resource Conservation Service through Cooperative Agreement No. 74-6114-8-22. To subscribe or change the address of a current subscription, write to Angela Rieck-Hinz, 2104 Agronomy Hall, Iowa State University, Ames, Iowa, 50011-1010 or call 515-294-9590, fax 515-294-9985 or email: amrieck@iastate.edu. Please indicate you are inquiring about the Odor and Nutrient Management Newsletter. The newsletter's coordinators are Angela Rieck-Hinz, extension program specialist, Department of Agronomy, Wendy Powers, environmental extension specialist, Department of Animal Science, and Robert Burns, Department of Agricultural and Biosystems Engineering; the editor is Jean McGuire, the subscription manager is Rachel Klein, the production designer is Beth Kroeschell, and the web page designer is Liisa Jarvinen.

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