Best Management Practices for Fall Manure Application

September 5, 2012
ICM News

Here is a list of Best Management Practices (BMPs) that can be implemented by all livestock farmers and commercial manure applicators to maximize use of manure nutrients for crop production and reduce potential impacts of water quality this fall.

1. Soil and water conditions
Know and understand your soil conditions prior to land application.  Much attention has been given to dry and cracking soils and manure application. Generally speaking, cracking soils and preferential flow of manure to a tile line is not an issue in Iowa. Tillage prior to manure or fall fertilizer application may actually shatter soils such that no structure will remain and intense rainfall may cause surface crusting that reduces water infiltration and could cause runoff of nutrients. Be aware of conditions and take appropriate actions; this may include delaying manure application.

Know where tile lines and tile inlets are located.  If you think preferential flow to a tile line is possible, consider plugging the tile to prevent movement of manure to water sources or installing a flow control structure to manage drainage. If runoff conditions are present, take time to cover or block tile inlets.

If early spring rains caused erosion and formed gullies on your farm, take some time to map out these conditions so caution can be used during land application to prevent breaking axles on manure tank wagons or even possibly tipping over a tank wagon.

2. Keep an eye on the forecast for heavy rainfall events
While not 100 percent predictable, the amount and intensity of rainfall greatly affects nutrient retention. If you surface-apply manure, you could lose nutrients from runoff of nutrients on the soil surface. If you inject or incorporate manure, an intense rainfall event could increase soil erosion and possible off-site movement of nutrients due to the soil disturbance of injection or incorporation. In either case, a low intensity rainfall could benefit movement of nutrients into the soil, but a high intensity rainfall could cause loss of nutrients from runoff and erosion. Again, attempt to apply manure on fields away from water sources and keep an eye on the weather forecast.

3. Calibrate, inspect, and maintain manure application equipment
As with all farm equipment, calibration of manure application is necessary. Calibrating manure application equipment takes a little time, but helps to meet the correct application rate and make manure nutrients more effective and efficient.

Also take time to inspect and do maintenance on equipment. This will help protect employees and reduce the chances of equipment malfunction that can lead to over or under-application, cause serious damage to equipment or cause a manure spill.

4. Separation distances for land application
All animal feeding operations, regardless of size, are subject to manure application separation distances from designated areas (water sources). Get a copy of an aerial photograph of all fields to which manure is applied. Map out neighbors' houses, churches, businesses, schools, cemeteries and other public use areas, as well as all designated areas such as sinkholes, wells, including abandoned wells, cisterns, designated wetlands, water sources, high quality water resources, ag drainage wells and tile inlets to ag drainage wells. Identify all other sources of concern for manure application. Sketch out separation distances. Train your employees to read the maps and stay away from areas where manure is not allowed to be applied. Read DNR Fact Sheet 113 on separation distances for manure application.

5. Irrigation of manure sources
Irrigated manure sources often have low nutrient concentration, which allows for high application rates. These rates can sometime be in the tens of thousands of gallons per acre. When irrigating manure, be sure to understand soil infiltration rates to prevent over-application of liquid that could lead to surface runoff of manure sources. These sources of manure may need to be applied over a course of multiple application events. Check to make sure all irrigation equipment is properly calibrated and in good working order. Continuously monitor the equipment to make sure it is working properly and no runoff is occurring.

6. Savvy stockpiling and dry manure management
Be sure to follow all dry manure stockpiling rules. Information is available on the DNR's Animal Feeding Operations Web page. The goal is to make sure the stockpile is located such that runoff or leaching from the stockpile does not affect water sources.

Open feedlot producers should take advantage of the dry weather conditions to scrape manure from feedlots so if we do receive rain there are less nutrients on the feedlot to move through the settling basin. This helps reduce potential impact on water sources and provides a nutrient source that can be used for crop production next year. Producers should also consider removing manure from settling basins. Dry conditions offer a great opportunity for thorough settling basin cleaning and maintenance.

7. Develop an emergency spill response plan
Hundreds of millions of gallons are safely applied each year in Iowa, yet manure spills can occur, so plan accordingly. Train employees and family members in manure spill response. Ask commercial manure applicators if they have a plan of action in the event of a spill. If they don't have a plan, require one. Keep important phone numbers and contact information for excavators, neighbors with pumps and tractors, and local officials and emergency response units up-to-date and posted where everyone knows where to find them. Remember to contact DNR if a manure spill or release does happen. You must report any spills or releases within six hours. Call the 24-hour spill hotline at 515-281-8694.

8.  Evaluate soil temperatures
Much like avoiding fall anhydrous ammonia application until soil temperatures are 50 degrees and cooling, the same applies to liquid manure with high amounts of ammonium-nitrogen such as liquid swine manure. Producers and commercial applicators should consider delaying manure application until soil temperatures cool down to slow the rate of nitrogen conversion and the potential loss of nitrogen if conditions turn wet yet this fall or next spring. 

9.  Plan for next year
Remember to account for the nitrogen and phosphorus needs of your crop next spring. If liquid manure is applied early this fall and loss conditions occur, supplemental nutrients may need to be applied next year. Keep in mind what your manure or nutrient management plan allows for application rates. In most cases, it pays to plan ahead when using manure as a nutrient source even a year in advance.

Understand your manure storage needs through the next 12- 14 months. If you haul manure in late summer or early fall, will you have enough storage to get you through next year if the spring is wet or fall harvest is delayed the following year? Make sure you have adequate storage or land available for manure application after next year's growing season.

10. Be safe
Fall is a busy time of year for farmers and commercial manure applicators. Get plenty of rest, take breaks and slow down. Observe all laws of the road and watch out for the "other driver." They may not realize you are moving at a much slower rate of speed or how long your tractor and tank wagon are when they attempt to pass you on the road. Check "slow moving vehicle signs" and replace as needed. Check lights to make sure they are working and are visible. Install additional lights as needed to improve your visibility and to help people see you. Make sure employees and family members meet manure applicator certification requirements and are well trained to handle various situations. Take time to train new employees and refresh the memory of experienced employees.

You can read more about manure management issues by visiting the IMMAG website.


Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on September 5, 2012. The information contained within may not be the most current and accurate depending on when it is accessed.


Angie Rieck-Hinz Field Agronomist in NC Iowa

Angie Rieck-Hinz is a field agronomist in north central Iowa for Iowa State University Extension and Outreach. She has worked for ISU Extension and Outreach for over 30 years, serving in various roles on campus and now in the field.  She works closely with farmers on integrated pes...

Daniel Andersen Assistant Professor

Dr. Anderson's research interests are in the areas of manure management and water quality, which involve: mature treatment and utilization, nutrient management planning, field and farm scale soil and water quality monitoring and modeling, and economic evaluation of agricultural practice alternati...