Using Manure with Growing Crops

Mr. Glen Arnold, Extension Agriculture Educator, Putnam County

Applying animal manure to a growing crop can add an additional window of time rarely utilized for manure application. Also, applying animal manure to a growing crop allows the farmer to capture more of the manure's nutrients and potentially save on purchased fertilizer. The OSU Extension has applied swine manure to growing crops on several research plots in recent years in an attempt to make maximum use of the available nitrogen.

In addition to phosphorus, potassium, and a host of micro nutrients, livestock manure contains organic nitrogen and ammonium nitrogen. More than half the nitrogen in liquid livestock manure is typically ammonium nitrogen. The ammonium nitrogen and approximately one third of the organic nitrogen in livestock manure is available to growing crops during the season of application. The OSU Extension research plots attempted to determine if the nitrogen in livestock manure could replace the purchased nitrogen normally applied to corn and wheat.

Three replicated research plots were undertaken in 2005 and 2006, comparing swine manure to 28% nitrogen as a sidedress nitrogen source to a growing corn crop. Sidedress nitrogen was applied at the agronomic rate needed by the growing crop according to pre-sidedress nitrogen testing. This was typically 150 units per acre. Manure application equipment was calibrated, as closely as possible, to match the amount of nitrogen applied as 28%. Generally, plots required 3000 to 4000 gallons per acre of manure. The manure was applied using a tanker fitted with narrow wheels and an AerWay toolbar with rolling tines that incorporated the manure.

There was no statistical yield difference between the corn plots receiving purchased 28% nitrogen and the corn plots receiving swine manure in 2005 or 2006. One of the plot replications in 2006 involved "spiking" the livestock manure with 28% nitrogen to cut the needed manure application rate in half. Approximately 16 gallons of 28% nitrogen was added to a 3500 gallon manure tank to double the acreage the manure could cover and still provide the needed nitrogen rate. Plot yields using the spiked manure were similar to the other plots.

Swine manure was also applied to a growing wheat crop in Putnam County in the spring of 2006 and compared with urea as a source of nitrogen to topdress wheat. The manure and the urea were both applied in early March and the plot was replicated four times. Approximately 100 units of nitrogen was applied as urea and approximately 3250 gallons per acre of manure was applied using an AgCo AgChem Grassland Applicator. The tool cut a narrow slot in the ground at 7.5 inch spacing using a smooth coulter. A boot located immediately behind the coulter allowed the liquid manure to flow into the slot.



The wheat top dressed with manure out yielded the wheat top dressed with urea by approximately eight bushels per acre. There was no difference in harvest moisture or test weight of the wheat in any of the replications.

These plot results indicate livestock manure is an excellent source of nitrogen for growing crops. However, the large volume of manure needed to meet the nitrogen needs of the growing corn crop makes it difficult to efficiently apply using current technology.

Research plots in 2007 will focus on applying livestock manure as a sidedress to corn after the crop is planted but prior to emergence. Depending on soil temperatures, a window of 7 to 15 days could be available to apply manure as a sidedress using a dragline system immediately following corn planting.