###### Abstract  
The ridge-furrow rainwater harvesting (RFRH) planting mode is widely used in arid and semi-arid areas to solve the problems of agricultural water shortage and low productivity. However, the impact of film mulching on the stability of soil carbon pools makes this planting mode vulnerable to the risk of increased soil carbon emissions and carbon pool losses. In order to clarify the relationship between soil carbon emissions and hydrothermal factors, as well as the regulatory effect of biochar application on soil carbon sequestration and reduced emissions under this planting mode, we set up a biochar application experiment. The effects of the biochar application (at 10 Mg ha\({}^{-1}\) biochar and 20 Mg ha\({}^{-1}\) biochar) on the soil water dynamics, soil temperature changes, CO\({}_{2}\)-C and CH\({}_{4}\)-C flux dynamics, grain yield, carbon emission efficiency, and the net ecosystem carbon budget in wheat fields under the RFRH planting mode were investigated, with no biochar application as the control. The results showed that applying biochar increased the soil water content, soil average temperature, cumulative CH\({}_{4}\)-C uptake, wheat grain yield, and carbon emission efficiency by 3.10-12.23%, 0.98-3.53%, 59.27-106.65%, 3.51-16.42%, and 18.52-61.17%, respectively; reduced the cumulative CO\({}_{2}\)-C emissions by 7.51-31.07%; and increased the net ecosystem carbon budget by 2.91 Mg C ha\({}^{-1}\) to 6.06 Mg C ha\({}^{-1}\). The results obtained by equation fitting showed that in wheat fields under RFRH, the CO\({}_{2}\)-C emission fluxes had negative and positive exponential relationships with the soil water content and soil temperature, respectively, while the CH\({}_{4}\)-C uptake fluxes had no significant correlation with the soil water content and had an inverse U-shaped quadratic function relationship with soil temperature. Overall, these results suggest that the application of biochar to wheat fields under RFRH can improve grain yield, farmland carbon emission efficiency, and the net ecosystem carbon budget, and change wheat fields from a carbon source to a carbon sink. These results can provide a theoretical basis and technical support for efficient, green, and sustainable production in farmland in arid and semi-arid areas. CO\({}_{2}\) and CH\({}_{4}\); equation fitting: net ecosystem carbon budget; soil temperature; soil water content +
Footnote †: journal: Applicandand Applicstudies have indicated that there is great potential for improving the productivity of land in these areas [3]. For many years, the main factor that has restricted agricultural production in arid and semi-arid areas is a shortage of water [5]. In order to address this issue, some technical approaches for improved water utilization have been developed. In particular, the ridge-furrow rainwater harvesting (RFRH) planting technique has gradually become an important planting mode for crops in arid and semi-arid areas because it can improve the soil moisture status in the crop root zone, and promote crop growth and yield formation by collecting precipitation via film covering on the ridge [6; 7; 8; 9]. Film mulching regulates the soil hydrothermal environment and also changes the stability of the soil carbon pool [10]. Many studies have shown that film mulching promotes the mineralization and decomposition of soil organic carbon and increases losses from the soil organic carbon pool [11; 12; 13; 14; 15], thereby affecting the quality of farmland soil and leading to the gradual degradation of farmland [16; 17]. In addition, the soil carbon pool is closely related to the atmospheric carbon pool [18; 19], so the increased soil carbon emissions under film mulching will increase the atmospheric carbon concentration and exacerbate global warming [20; 21; 22; 23; 24; 25]. Therefore, there is an urgent need to sequester carbon and reduce emissions under the RFRH planting mode. Soil carbon sequestration and carbon emissions are affected by soil hydrothermal factors [26; 27; 28].