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. Thats 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 producers 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.
* See PM-1714 (pdf-file),
Fertilizer Recommendations for Corn in Iowa, 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 firstname.lastname@example.org or email@example.com.
© 1997-2004, Iowa State University. All rights reserved.
Page last updated October 5, 2004
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