Soils in Poland are characterised by relatively low available water reserves. Soil mulching is one of the methods which positively influence soil moisture and structure, reduce negative effects of erosion, and help to decrease fluctuations of soil temperature. The experiment was carried out in the years 2010-2012 at the Experimental Station of the Siedlce University of Natural Sciences and Humanities as a split-block design with three replicates. The study aimed to determine the effect of plant covering (without cover, under polypropylene fibre) and soil mulching with different kinds of straw (rye, corn, rape, buckwheat) on changes in soil temperature and moisture as well as on the yield of broccoli. Soil temperature at a depth of 10 cm in covered plots was higher than in plot without cover. Soil temperature in the plots without straw, irrespective of whether a covering was used, was higher than in plots with straw. The lowest fall in temperature compared to the control plot was observed in plots mulched with buckwheat straw. This phenomenon was a result of lower intensity of light reflection of this straw which absorbed more sunlight than straw of other species. All investigated kinds of straw caused an increase of moisture in the upper (0-20 cm) and lower (20-40 cm) soil layers after cover removal and before broccoli harvest, in the cultivation without cover and under polypropylene fibre. Application of covers and simultaneous soil mulching had more favourable influence on water content in the soil than only mulching. Significantly the highest total yield of broccoli in the cultivation under cover was achieved from plots mulched with buckwheat straw. In non-covered objects slightly higher yields compared to remaining kinds of straw, but significantly higher than in control plot, were noted for soil mulching with corn straw.