Unexpected high suppression of ammonia volatilization loss by plastic film mulching in Korean maize cropping system

Abstract

Plastic film mulching (PFM) as an agronomic practice was rapidly expanded to improve crop yield and quality, mainly due to improving soil water and temperature condition. PFM has been known to increase greenhouse gas (GHG) emissions, but its influence on ammonia (NH3) volatilization loss was not properly studied. To determine the impact of PFM on NH3 emission loss, PFM and no-mulching were designed as the main treatment. In addition, chemical (NPK) and organic fertilization plots as the sub-treatment were placed under the same mulching condition. In the NPK, the recommendation level (N-P2O5-K2O=186–35–74 kg ha-1) of chemical fertilizers was only applied for maize cultivation. In the organic fertilization, the mixture of barley and hairy vetch was cultivated during the fallow season and its whole biomass as green manure was incorporated for maize cultivation. PFM considerably improved average soil water and temperature regimes during cropping season by 0.02–0.05 m3 m-3 and 0.8–1.4 ℃ over no-mulching, respectively. These improved soil properties enhanced maize grain yield by around 95–270 and 80–300% in NPK and organic fertilization plots over no-mulching, respectively. The emission loss of NH3 gas which is highly water-soluble was 70–215% higher in NPK than organic fertilization under the same mulching. However, PFM significantly decreased seasonal NH3 emission loss by approximately 40–45% over no-mulching, probably due to physical trapping in water drops under the plastic film. To verify the suppression mechanism of NH3 emission loss by PFM, the emission rates of nitrous oxide (N2O) which is a water-insoluble gas were simultaneously monitored using the closed chamber method. Different from NH3 emission loss, PFM slightly increased N2O emission without a statistical difference, regardless of fertilization background. In conclusion, PFM could be a very useful cropping practice to decrease NH3 emission loss, as well as improve soil properties and crop productivity.