Aug. 22 2012 02:38 PM

A partial incorporation of nitrogen saw no difference in loss in a four-year study. When trying to limit N loss, injection is easily your best bet.

by Lucas Sjostrom, Hoard's Dairyman Associate Editor

Whether you are looking for tips on sand separation, thinking about using nitrification inhibitors or just looking for your next spreader, the North American Manure Expo was the place to be this morning. Attendees saw, and some even felt (due to a rogue lagoon agitation raft sending a small amount of slurry into the crowd), the many different ways to apply manure. Educational presentations shared the latest data on manure application and were well attended by the farmers, custom applicators and haulers that showed up.

This year's Manure Expo was in Prairie du Sac, Wisconsin. You can read our report from last year's proceedings in Fremont, Neb., by clicking here: Below is a short summary of just one of this year's many educational sessions.

Injecting manure makes sense for those of us who have lagoons and can hire someone to dragline the manure directly into the fields. As we've learned from years of research, manure loses much of its nitrogen in the first 48 hours after application. This is why draglining is such an advantage.

J. Mark Powell, a research soil scientist with the USDA Dairy Forage Research Center, came to the same conclusion about nitrogen (N) loss in a four-year study. But his team dug deeper to see how that loss occurs using field monitors, and compared the findings amongst surface-applied manure, tilling in the surface-applied manure (hereafter called "partial injection") and a direct injection.

The basic findings were no surprise; direct injection prevented less N loss than the other two applications. But how those losses were divided was quite interesting.

Powell's team tested three strips of land with the three different applications for four years. Surprisingly both the surface applied and partial injection strips totaled similar losses – about 27 percent N loss for surface application and 22 percent for partial injections. Of those losses, 75 percent of the surface applied N was lost as ammonia (through the air), while just 50 percent of the partial injection manure was lost in the same manner.

Meanwhile, the direct injection saw only 9.6 percent of the nitrogen lost, and too found about 50 percent of loss split between ammonia and run-off through nitrate leaching.

Powell concluded that, compared to the surface-applied manure, partial injection kept 18 percent more of the N in the land. Direct injection was an amazing 65 percent improvement to surface-applied. To Powell, there was no doubt that more injection meant more N retention.