Effects of maize straw mulch on spatiotemporal variation of soil profile moisture and temperature during freeze-thaw period

Abstract: Straw mulch has not only a positive effect, but also some negative effects during the seasonal freeze-thaw period. Straw mulch weakens the heat and moisture transfer between the soil and air, and it will go against the crop if the soil temperature rises slowly in the spring. With the aim of revealing the temporal and spatial variation of the soil profile moisture and temperature under different maize straw mulch thicknesses during the seasonal freeze-thaw period, a field experiment was conducted from November in 2005 to March in 2006 at Taigu Water Balance Experimental Field, Bureau of Hydrology and Water Resources Survey of Shanxi Province. Maize straw at rates of 2 100 kg/hm2 (mulching thickness was 5 cm), 4 300 kg/hm2 (mulching thickness was 10 cm), 6 500 kg/hm2 (mulching thickness was 15 cm), 8 600 kg/hm2 (mulching thickness was 20 cm) and 12900 kg/hm2 (mulching thickness was 30 cm) was placed on field plots (JD05 JD10, JD15, JD20, JD30). The soil profile moisture and temperature contours of the bare plot (LD) and five kinds of maize straw mulching thickness plots were compared. The temporal and spatial variation of the soil profile moisture and temperature were analyzed according to a statistical analysis. The results showed that the maximum frozen depth of LD was 52 cm, and the soil profile moisture and temperature of LD varied more dramatically during the seasonal freeze-thaw period and the depth of 0 to 40 cm was an active layer of water and temperature variation (ALWT) and the higher moisture zone (HMZ) appeared at the depth of 20 to 45 cm. However, the maximum frozen depth of JD05 and JD10 was 23 and 10 cm respectively that lagged from LD by about 15 days. For JD05, the depth of 0 to 20 cm was ALWT and HMZ (maximum soil moisture content was 22.5%) appeared at the depth of 15 to 25 cm. For JD10, the depth of 0 to 10 cm was ALWT and HMZ (maximum soil moisture content was 21.3%) appeared at the depth of 5 to 10 cm. Influenced by soil freezing-thawing and maize straw mulching, the effect of soil moisture conservation was best when maize straw mulching thickness was 5 cm, and the soil moisture content of the cultivated layer (from 0 to 20 cm) was 18% to 21 %, which was higher than that of other plots. When maize straw mulching thickness was up to 15 cm, the variation of the soil profile moisture and temperature was small and it had the best effect of heat preservation, the soil profile temperature changed relatively stably and the minimum temperature reached 1.1℃. When maize straw mulching thickness exceeded 15 cm, the effect of soil moisture conservation and heat preservation was less obvious with the increasing of maize straw mulching thickness. Therefore, to aim at prevention of frost damage and conservation of soil moisture, the best maize straw mulching thickness is 10 to 15 cm. The research results tend to provide a reference for scientific maize straw mulching on farmland in a seasonal freeze-thaw area during winter and spring.