Precision Manure Injection On Nitrogen Use and N2 O Emissions in Corn.

Closed slot injection is a proven way to reduce emission of ammonia from slurry manure and hence can increase crop N use efficiency. A recent study has shown that dairy slurry injected precisely near corn rows provides starter and season-long P for corn. However, injecting manure may result in enhanced greenhouse gas emissions due to anaerobic conditions. Here we report on the first two years of a multi-year study designed to evaluate the effect of precision-injection dairy slurry on growth and N uptake by silage corn, and on emissions of nitrous oxide (N₂O). The study was conducted on silty loam in a maritime climate in south coastal BC. The slurry was injected in 15-cm deep furrows spaced 75cm apart, or broadcast and quickly incorporated, at 160 kg N ha^-1. The corn was planted a few days later at 75 cm spacing, 5-10 cm from the injection furrow. The corn receiving injected manure had about 2 t ha^-1 higher yield and 20 kg ha^-1 greater N uptake than corn with broadcast manure. However, annual N₂O emission was 1.7% of applied N for injected manure compared to 0.5% for broadcast slurry. Emissions of N₂O for all treatments spiked sharply shortly after the manure was applied with very low rates observed the rest of the year. Hence the loss of N₂O early in the season, likely from denitrification, was not associated with reduced efficiency of N use by the corn. This suggests that N lost by denitrification in the injection treatment was less than N lost by ammonia volatilization from the broadcast manure. Techniques to abate N₂O emissions are needed for injected manure.