Straw mulching is used widely to improve soil fertility in the black soil region of northeastern China, but there have been few evaluations of its effects on soil water content, N use by crops, and crop growth. Field experiments were conducted during two growing seasons in Jilin Province, to study the effects of straw mulching on maize yield, evapotranspiration (ET), water use efficiency (WUE), and nitrogen use efficiency (NUE) under rainfed conditions. Measurements were conducted in a treatment with maize straw mulch on the soil surface (SM) and a control treatment with no mulch (NM). The SM treatment caused a significant decline of soil temperature and increase of soil moisture in the early growing season, compared to the NM treatment. However, the use of mulching reduced maize yields by 18% in 2011 and 26% in 2012. It also decreased WUE by 16% in 2011 and 21% in 2012, and decreased NUE by 27% in 2012, though it had no effect on total ET. Therefore, the use of mulch is not recommended as an approach for improving water and N use and maize yields, in the semi-humid black soil region of northeastern China, when the water content of soil is sufficient for maize growth.
