Land application of manure may produce unacceptable odors. Field experiments in undisturbed (no-till) soybean and corn residue were conducted to evaluate six liquid swine manure application/incorporation methods. The methods were injection with a commercial (1) chisel or (2) sweep, (3) incorporation with tandem disk harrow after broadcast application, (4) broadcast application with no incorporation, (5) injection with a narrow-profile knife, and (6) surface application behind row cleaners. The row cleaner and all injection treatments used spoke-covering wheels. Air samples over the soil surface were obtained immediately following and one day after manure application, and odor level was measured by olfactometry (i.e., the amount of air dilutions to reach odor threshold). Residue cover and yield were also measured. Incorporation techniques typically reduced odor level by a factor of three to ten as compared with a broadcast application. One day after application, odor was greatly reduced and often indistinguishable from that of untreated soil (no manure application). Residue cover differences among application methods were more pronounced in soybean residue. Application by the narrow-profile knife, row cleaner, and chisel maintained soybean residue cover better than other incorporation methods yet limited odor similar to these methods. Although cover was reduced over winter, greater soybean residue cover remained after planting with fall than with spring manure applications. Differences in odor level and residue cover among methods were less in corn than soybean residue. All incorporation techniques reduced odor levels, and chisel incorporation maintained corn residue cover after planting similar to broadcast application. For both crops, broadcast application maintained the greatest residue cover but had the highest odor level. Incorporation of manure generally reduced odor, reduced residue cover, increased corn yield, and did not affect soybean yield.
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