Non-native with biological nitrification inhibition capacity stimulates grassland NO emissions.

INTRODUCTION

, a tropical grass, could release root exudates with biological nitrification inhibition (BNI) capacity and reduce soil nitrous oxide (NO) emissions from grasslands. However, evidence of the reduction effect in tropical grasslands in China is lacking.

METHODS

To evaluate the potential effects of . on soil NO emissions, a 2-year (2015-2017) field experiment was established in a Latosol and included eight treatments, consisting of two pastures, non-native . and a native grass, , with four nitrogen (N) application rates. The annual urea application rates were 0, 150, 300, and 450 kg N ha.

RESULTS

The average 2-year . biomass with and without N fertilization were 9.07-11.45 and 7.34 t ha, respectively, and corresponding values for . increased to 31.97-39.07 and 29.54 t ha, respectively. The N-use efficiencies under . and . cultivation were 9.3-12.0 and 35.5-39.4%, respectively. Annual NO emissions in the . and . fields were 1.37 and 2.83 kg NO-N ha, respectively, under no N fertilization, and 1.54-3.46 and 4.30-7.19 kg NO-N ha, respectively, under N fertilization.

DISCUSSIONS

According to the results, . cultivation increased soil NO emissions, especially under N fertilization. This is because . exhibited the more effective stimulation effect on NO production denitrification primarily due to increased soil organic carbon and exudates than the inhibition effect on NO production autotrophic nitrification. Annual yield-scaled NO emissions in the . treatment were 93.02-183.12 mg NO-N kg biomass, which were significantly lower than those in the . treatment. Overall, our results suggest that cultivation of the non-native grass, . with BNI capacity, increased soil NO emissions, while decreasing yield-scaled NO emissions, when compared with native grass cultivation.