Researchers 111 Years Apart Agree, Manure Restores Soil Health

( Anna-Lisa Laca )

By Jen Sorenson, Iowa Select Farms

What Soil Scientists Said in 1907: Ways in which manure is beneficial 

One of the most valuable assets of a farm is the manure produced upon it. It represents fertility which has been drawn from the soil by crops and must be returned to it, if productiveness is to be maintained. It not only adds to the store of plant food in the soil by returning the nitrogen, phosphoric acid and potash removed by the crops, but it also renders the native plant food of the soil more available. 

Some of the more important ways in which manure benefits the soil may be briefly stated, as follows: 
1. It increases the supply of humus 
2. It adds plant food 
3. It acts upon the soil in such a manner as to render the plant food of the soil more available 
4. It makes the soil warmer 
5. It enables the soil to receive and retain more water, and to give it up gradually to growing crops 
6. It improves soil ventilation 
7. It aids in the development of bacteria 
8. It helps to prevent the denuding effect of washing and heavy wind storms 
- A.H. Snyder, Soils Specialist, Iowa State College Agricultural Extension – October, 1907

What Researchers Say Today: Precision agriculture tools drive continuous manure management improvement 
“The value of animal manure as a crop fertilizer has been known to farmers for centuries,” says Dr. Dan Andersen, assistant professor in agricultural and biosystems engineering at Iowa State University. “But with only 25% of Iowa cropland being fertilized with manure, the nutrients found in manure are needed now more than ever.”

Andersen says current research tends to focus on the use of technology to better store and utilize the nutrients found in manure. “Many of these new technologies are quite sophisticated and mean that farmers today manage manure better than ever. After all, tractors and the equipment they control are nothing more than computers with wheels!”

He cites the following technologies that ensure farmers are using the 4R Nutrient Stewardship strategy. 
1. Mapping crop yields 
2. Matching the amount of manure applied to what the crop actually needs 
3. Data processing to match manure flow rates to fertility needs 
4. Managing cover crops to work tandem with animal manure 

Most current manure management research focuses on soil health, agricultural sustainability and improving the robustness of our soils to occurrences of drought or heavy rainfall. These subjects often have one thing in common—how to increase soil organic matter as a way to improve soil tilth and structure. 

Better Technology, Better Precision 
Today, Geographical Information System (GIS) software allows pig farmers the ability to view the manure source and the neighboring fields receiving the nutrients. Every parcel of ground is mapped into the system, including creeks, building sites, terraces or tile outlets. Aerial imagery is used as the base maps and layers are then added for contours, county tile lines, flood area, water sources and public areas. GIS technology ensures manure is applied responsibly and in compliance with all state regulations. 

“With today’s technology, including GPS location guidance, flow controllers and weigh scales on manure spreaders, it is possible to vary the rate of application on-the-go as the applicator moves through the field,” Andersen says. “The farmer can then generate maps of how many gallons per acre are applied.” 

Andersen says getting a firm grasp on issues such as manure nutrient content, variability of nutrient content during application, how accurate can farmers hit rate targets, how uniform is the application and how good is the application method will be the subject of continuing research.