Impact of straw return on soil temperature and water during the freeze-thaw period

Generally, straw return can reduce soil freezing depth and inhibit soil evaporation in cold/dry agricultural regions. However, when crushed corn straw is returned with thoroughly mixed with the topsoil (0–20 cm), the influence on water and heat flux during soil freezing and thawing is still unclear. In this study, two years straw return experiments of total 9 treatments for 3 straw returns (1.6, 0.8 kg m−2, no return) and 3 autumn irrigation amounts (180, 135, 90 mm) were conducted in 27 lysmeters with bottomless. Spatial and temporal dynamics of water and heat within soil profiles were continuously observed for freezing and thawing period. The results showed that straw return inhibited the decrease and increase of soil temperature during the freeze-thaw period. Furthermore, straw return reduced the freezing rate and delayed the complete thawing date. Results showed that effect of straw return on soil temperature and water were affected obviously by irrigation amount. Finally, straw return can restrained soil evaporation after soil thawing completely, and the soil unfrozen water content and the total water content were higher for treatments with the straw return to topsoil. Our findings can enhance the understanding to soil temperature and water dynamics for freeze-thaw period.