Nitrous oxide emissions in corn (Zea mays L) as affected by timing, method of application and source of dairy manure.

Abstract

Field trials were conducted during three years to evaluate the effect of timing, method of application and manure source on N2O emissions and corn grain yield at Elora, ON, Canada. A randomized block design was set up every year, evaluating two timings (fall vs. spring), three methods of manure application (surface broadcasting, incorporation and injection) and two manure sources (raw, RM vs. anaerobically digested, AD), using non steady state chambers. Three and two years of data were used to evaluate the effect of manure application timing and manure source respectively on N2O emission, considering also application methods in each experiment. A hybrid, decision tree-based flux calculation method (DTBM) was developed and chosen to calculate N2O emissions, given that it advantaged to other methods due to its ability to match each data type with the best model. Nitrous oxide emissions did not respond to timing of manure application; however, as the interaction year by manure application timing as well as application method significantly affected N2O emissions (p< 0.01 and p< 0.05, respectively). The effect of method on cumulative N2O emissions depended on manure source(p<0.01), since surface broadcast AD had the highest emission (6.4 kg N2O-N ha-1), and both injected AD and incorporated RM had the lowest values (2.6 kg and 2.8 N2O-N ha-1 , respectively). Manure source tended to affect cumulative N2O emissions (F=4.67, p<0.1), with the largest emissions for AD (4.8 kg N2O-N ha-1). Anaerobically digested manure was proven to reduce cumulative N2O emissions when it was fall injected to corn in cold climates; however, if AD is broadcasted or broadcasted and incorporated, it may result in greater N2O emissions than those produced by RM. Short (2-3 yrs.) and long term (26 yrs.) trends for cumulative N2O emissions were simulated with a process based model (DNDC-CAN). Even though no difference between predicted application timings was found at short term, spring application was detected to decrease N2O emissions in the long term. The inter-annual variability canceled the effects of method of application in the long term on predicted N2O emissions. Injection of AD showed to be a goodtechnique to mitigate predicted N2O emissions in the long term.