Variations in nitrous oxide emissions as manipulated by plastic film mulching and fertilization over three successive years in a hot pepper-radish rotated vegetable production system

Abstract

Plastic film mulching (FM) is widely applied in agro-ecosystems to improve soil hydrothermal conditions for better crop productivities. However, effects of such FM practices on nitrous oxide (N2O) emissions are not well known in high nitrogen (N) input vegetable fields. Using static chambers under no-mulching (NM) and FM with four N application rates N2O emissions were monitored in a hot pepper (Capsicum annuum)-radish (Raphanus sativus) rotation in southwest China over three years (Cycle 1, 2 and 3) from May 2014 to February 2017. These four N application rates for each vegetable crop were 0, 150, 300 and 450 kg N ha−1 and 0, 100, 200 and 300 kg N ha-1 in the respective hot pepper and radish seasons. Compared to NM, FM insignificantly reduced N2O emissions in the hot pepper season owing to lower soil moisture, while significantly increased N2O emissions in the radish season owing to higher soil NH4++NO3− and temperature. Additionally, FM had no remarkable effects on N2O EFs or crop yields of hot pepper or radish. N application exerted stronger effects on N2O emissions under FM and NM in Cycle 1 than in other two cycles during the hot pepper season owing to higher temperature and rainfall, resulting in very high N2O EFs (2.56 %–7.43 %). The average seasonal EF was 1.52 % (0.15 %–7.43 %), while the average annual EF was 1.74 % (0.16 %–5.32 %), which was comparable to the 2006 IPCC defaulted of 1.00 %. Yield-scaled N2O emissions under FM were significantly increased in the radish season, but not in the hot pepper season. Additionally, N application remarkably increased N2O emissions and crop yields in the hot pepper season, with a bigger effect on N2O emissions than on crop yields, leading to increased yield-scaled N2O emissions with increasing N application between 0 and 450 kg N ha-1. Moreover, the stimulation effect of N application on crop yield was strongest under 150 kg N ha-1 with lower yield-scaled emissions. In addition, N application remarkably increased N2O emissions and crop yields, but were more prominent on crop yields than N2O emissions during the radish season, resulting in insignificant increase of yield-scaled N2O emissions between 0 and 300 kg N ha-1. Our results demonstrated that no-mulching with 150 or 300 kg N ha-1 fertilization in the hot pepper or radish season is a more suitable agronomic practice to simultaneously mitigate N2O emissions while increasing crop yields in subtropical vegetable fields.