Injecting Manure May Reduce Phosphorus Runoff Compared to Broadcast Application in No-till Corn Fields.

Most dairy farms in the northeastern USA have six month manure storage capacity and therefore must spread manure in the spring prior to crop planting or in the fall following harvest. In no-till fields, manure is most often surface applied and can result in Phosphorus (P) runoff and cause water quality impairment. Alternatively, injecting manure with a shallow disk injector has the potential to conserve nutrients in the soil and reduce run-off loss.   

Therefore, an experiment was conducted to evaluate how sub-surface and overland losses of manure P differed between manure application methods over multiple years. The experiment was conducted at the Russel E. Larson experimental farm in Rock Springs, PA, from 2012 to 2015 in a no-till cereal rye-corn rotation system. Broadcast and injection manure application methods were replicated 6 times in 12 field lysimeter plots. Manure was either injected with a shallow disk injector or broadcast in fall prior to planting a winter annual or in spring prior to corn. The concentration of P in overland and subsurface flow was captured from hydrologically isolated field plots (14 m x 28 m) with earthen berms to capture overland flow and tile drains placed just above limestone bedrock to capture subsurface flow. Data were analyzed using Proc Mixed procedure of SAS with repeated measures. Manure application method and precipitation events were considered as fixed effects whereas blocks were random. Results indicated that the P load was higher in the overland flow when manure was broadcasted (1.2 kg/ha/yr) compared to the injection method (0.6 kg/ha/yr). Also, after heavy rainfall events, higher load of P was recorded as the overland flow in the broadcast method compared with the injection.