Nitrogen cycling trade-offs with broadcasting and injecting dairy manure

Abstract

Understanding the fate of nutrients in land-applied manure is key to improving the efficiency of their use in crop production. We developed nitrogen (N) budgets for 2 years of continuously cropped corn fertilized by dairy manure via broadcast application or shallow disk injection. Major pathways and pools of N loss were monitored on 12, 0.04 ha field lysimeters in central Pennsylvania, USA to estimate the impact of manure application method on N fate: gas emissions, off-site runoff (overland and subsurface flow), crop uptake, and, soil storage. The budgets illuminated trade-offs in N cycling with each management strategy. Crop removal accounted for the largest portions of manure N applied in both budgets (16–43%). Injection manure N balances were more difficult to close because balances included a large proportion of ‘unaccounted’ N (49% and 68% of applied N for two accounting periods). Even so, results point to cumulative differences in nutrient use efficiencies that can be attributed to the greater conservation of ammonia-N with manure injection. There was an apparent build-up of soil N with manure injection that was not observed with broadcast application (in pre sidedress nitrogen test measurements). However, these trends were preliminary; over the two growing seasons covered by this study, these findings did not result in significant differences in corn yield or crop N removal.