Soil nitrous oxide emissions from sugarcane field affected by nitrogen fertilizer rate and inhibitors of urea hydrolysis and nitrification process

Reducing the use of nitrogen (N) fertilizer and inhibitors of urea hydrolysis and the nitrification process (UIs and NIs, respectively) could be the key to the successful mitigation of soil nitrous oxide (N 2 O) emissions, such information is limited for non-Annex I countries. This study focused on sugarcane ( Saccharum officinarum L.) and bare soil fields to evaluate the growth potential of the fertilizer rate with UIs, NIs and their combinations (UINIs) on soil N 2 O emissions. The N fertilizer rates applied were based on standard farmer practice (F) and soil analysis (S). The synthetic UI and NI used in this study were N-(n-butyl) thiophosphoric triamide (NBPT) and dimethylpyrazole phosphate (DMPP), the UIs and NIs from plants were garlic ( Allium sativum L.) and ground neem seed ( Azadirachta indica A. Juss. var. siamensis Valeton), and praxelis ( Praxelis clematidea (Griseb.) R.M. King & H. Rob). The results showed that compared to F, reducing the N fertilizer rate and adding NIs in the sugarcane field decreased soil N 2 O emissions by up to 19.1%, followed by UINIs and UIs (17.0 and 15.9%, respectively), while there was 18.9% N 2 O reduction with praxelis. When applying the dressing, all inhibitors seem to have potential to inhibit microbial activity but there was an inconsistent significant difference on mitigated cumulative N 2 O. The use of inhibitors decreased soil N 2 O emission factor (EF) values in the sugarcane plots by 1.1–1.6%, compared to 1.8% for S treatment. Notably, F had a lower soil N 2 O EF (0.6%), possibly due to the relatively high N fertilizer rate applied in this study. The findings suggested that reducing N fertilizer use and applying UIs, NIs and UINIs had great potential to minimize greenhouse gas (GHG) emissions from the soil. These results regarding the use of soil N 2 O EFs in a sugarcane field could provide supporting data for the national GHG inventory and be adopted for mitigation measures in Thailand.