Methane uptake in semiarid farmland subjected to different mulching and nitrogen fertilization regimes

Abstract

Methane (CH4) uptake by dryland soils is an important part in the global CH4 budget and is sensitive to the management practice. This research measured the annual CH4 flux over 2 years at the rain-fed maize fields in semiarid northwestern China using the static chamber technique. Methane uptake was measured under three mulching practices with the same nitrogen (N) application: no mulching (NM), gravel mulching (GM), and plastic film mulching (FM). In addition, methane uptake was also measured under film mulching management and three different N fertilizer rates: 0 (N0), 250 (N250), and 380 (N380) kg N ha−1. The results showed that the rain-fed maize fields acted as a sink for CH4, with the annual mean uptake rate of 21.3–40.8 μg CH4-C m−2 h−1. The soil CH4 uptake was positively correlated with soil temperature, but negatively correlated with soil moisture; these two factors together explained 35.5–50.9 % of the variance in CH4 uptake. Compared to the NM treatment, the mulching treatments markedly increased the topsoil temperature, but the annual CH4 uptake was significantly reduced by 5.2–6.7 % in the GM treatment and by 26.3 % in the FM treatment, most likely because the increased soil moisture restricted CH4 oxidation and diffusion. The CH4 uptake showed an increasing tendency with the N rate, probably because N fertilization decreased soil moisture and increased soil NO3 − content. These results help in understanding the effects of agricultural managements on CH4 uptake and to properly assess the role of dryland soils in the global CH4 budget.