Effects of Low-disturbance Manure Application Methods On Corn Silage Yields, Plant and Soil N, and Gaseous N Emissions.

Incorporation of manure by tillage can conserve manure N by reducing ammonia volatilization losses, but tillage also incorporates crop residue, which increases erosion potential. This study compared several low-disturbance manure application methods, designed to incorporate manure while still maintaining crop residue for erosion control, to conventional broadcast application in a silage corn/winter rye cover crop system. Treatments included low-disturbance sweep injection, sweep injection ridged with paired disks (strip-till), coulter injection, aerator-band, and broadcast with and without disk harrow incorporation (all fall-applied), plus pre-plant fertilizer N rates ranging from 0 to 200 kg/ha in separate non-manured plots. There were small differences in plant N concentrations (earleaf and silage harvest) and N uptake among injected/incorporated manure treatments, but all were greater than surface-applied manure, which was equal to or slightly greater than no-manure control. PSNT results were consistent with those of plant N. Ammonia emission was greatest from surface-applied manure, with reductions of 85% or more from injected manure and more modest reductions (30 to 55%) from aerator/band and disk incorporation. Residue cover of 30-40% pre-manure was reduced by manure application depending on intensity of injection or tillage action. These results indicate that low-disturbance manure application methods can reduce ammonia-N loss and improve manure N availability compared to surface application and maintain residue cover better than disk incorporation of manure.