Abstract: In order to find out the effects of different mulching models on soil temperatures in the 5-25cm soil layer and grain yield in a semiarid rainfed area of northwestern China， the field experiments with different mulching material and time were conducted from October in 2011 to August in 2012. The field experiments was comprised of the following 7 treatments: mulching plastic film applied in summer and soil placed on the top of the film at 1cm deep （T11）， similar to T11 but plastic film applied in autumn （T12）， reused the old film mulching after the first harvest of winter wheat （T13）， the combination of T11 to field returned wheat straw（T14）， mulching 5cm long of wheat straw to the field in summer （T21）， mulching whole wheat straw in summer （T22）， and an unmulched control （CK）. The results showed that:（1）compared to CK， both plastic mulching and straw mulching increased soil temperatures before the jointing stage of wheat but decreased soil temperatures after the jointing stage（P＜0.05）. The increasing magnitude of soil temperature plastic film mulching was greater than straw mulching， whereas the decreasing magnitude of soil temperature was just contrary. Among the mulching treatments evaluated in the study， T13 treatment increased soil temperatures most and higher than CK 0.24℃， whereas T21 decreased most and lower than CK 0.68℃ in 5-25cm soil layer during the whole growth period of winter wheat.（2）Soil warming effects due to mulching mainly appeared in the morning， but cooling effects were mostly at the noon and at dusk.（3）Compared to CK， any of mulching treatments increased the grain yield（5.0%-29.0%，P＜0.05）， but the yield of plastic film mulching increased  higher than that of straw mulching， Yield of winter wheat increased was mainly caused by being increased spike numbers and 1000grain weight. In conclusion， both plastic film mulching and straw mulching could regulate soil temperature and enhance the grain yield in the whole growth period of winter wheat， but T11 has the most crop productivity in a semiarid rainfed area of northwestern China.

Key words: Rainfed area in northwest China, Plastic film mulching, Straw mulching, Soil temperature, Winter wheat