稻麦秸秆集中沟埋还田对麦田土壤物理性状的影响

Effects of rice and wheat straw ditch-buried returns on the soil physical properties of wheat fields

通过5.5a的大田定位试验,将上季秸秆全量沟埋还田,设置秸秆沟埋还田深度为20、40 cm以及免耕秸秆不还田(对照)3个处理。研究秸秆沟埋还田对麦田土壤水势、温度的影响以及长期秸秆沟埋还田方式下,沟埋还田20 cm处理各埋草沟土壤容重、总孔隙度的变化。结果表明:秸秆沟埋还田具有降低土壤容重,增加土壤总孔隙度的作用,随着还田时间的增加,这种作用逐渐降低。当降雨量较大(26.6 mm)时,沟埋还田各处理水势值在短时间内上升的较快,而对照则相对较慢;当降雨量较小(10 mm)时,沟埋还田40 cm处理水势值上升速度大于沟埋还田20 cm,对照处理最慢;降雨过后的12d内,沟埋还田各处理水势值下降速度较对照更快;连续40d各处理土壤水势日均值大小为对照>沟埋还田40 cm>沟埋还田20 cm。土壤0—15 cm温度日较差大小为沟埋还田20 cm>对照>沟埋还田40 cm,土壤20 cm处日较差对照最大;沟埋还田20 cm处理0—15 cm以及沟埋还田40 cm处理0—20 cm土壤日均温高于对照,沟埋还田20 cm处理20 cm处土壤日均温与对照较为接近。在沿江稻麦轮作地区,秸秆集中沟埋还田具有较好的改善土壤物理性质的作用。

Straw usually refers to the aboveground part of crops after grain harvesting and is the main byproduct of crop production. Straw return is considered an effective way of recycling crop straw residues. In this study,a 5. 5-year field experiment was conducted to evaluate different total straw returning methods using the following treatments： ditch-buried return at 20 cm and at 40 cm soil depths and the control treatment of conventional tillage with no straw return. The amount of rice and wheat straw returned was 2 kg / m^2 and 1 kg / m^2,respectively. This study investigated the soil water potential and soil temperature at the different ditch-buried return depths,as well as the effect of long-term ditch-buried returns to a depth of 20 cm on the bulk density and total porosity of soils. Our results suggested that a ditch-buried return to a depth of 20 cm could reduce soil bulk density and increase total porosity compared with the control treatment. The beneficial effects on soil structure were present even after 4.5 years. The effect gradually declined as the length of time after straw return increased.In the 0—7 cm soil layer,the bulk density and total porosity of ditch-buried return at 20 cm and 40 cm depth graduallybecame closer to the control treatment. However,there were significant differences between both ditch-buried straw return depths and the control treatment in the 7—14 cm soil layer. When rainfall was high（ 26.6 mm）,the variation in soil water potentials of the ditch-buried return to depths of 20 cm and 40 cm were 15.7 k Pa and 14.8 k Pa,respectively,within two hours,whereas the change in the soil water potential of control treatment was 2. 2 k Pa. This indicates that the soil water potentials of ditch-buried return to depths of 20 cm and 40 cm show a faster increase than the control treatment. When rainfall was low（ 10 mm）,the water potential of ditch-buried return to a depth of 40 cm showed a faster increase than that of ditch-buried return to a depth of 20 cm,which was faster than the control treatment. It was found that the water potentials of ditch-buried return to depths of 20 cm and 40 cm decreased rapidly and were lower than the control treatment 12 days after rainfall. The changes in soil water potentials for both ditch-buried straw returns and the control treatment were 187.62 k Pa,141.38 k Pa,and 104.48 k Pa,respectively. The soil water potential of each treatment over 40 consecutive days was control treatment 〉ditch-buried return 40 cm〉 ditch-buried return 20 cm. On average,the soil water potentials of ditchburied return to depths of 20 cm and 40 cm were significantly lower than those of the control treatment（ P〈0.05）. The soil diurnal temperature range was ditch-buried return 20 cm〉 control treatment〉 ditch-buried return 40 cm,when measured at a soil depth of between 0 and 15 cm. However,it was highest for the control treatment at 20 cm soil depth. In addition,ditch-buried straw return to a depth of 20 cm increased the mean daily temperature in the 0—15 cm soil layer,and ditchburied straw return to a depth of 40 cm increased mean daily temperature in the 0—20 cm soil layer. The mean daily temperature at 20 cm soil depth of ditch-buried return to a depth of 20 cm was close to that of the control treatment. In summary,ditch-buried straw return improves soil physical properties in a rice-wheat rotation system in the Yangtze River delta agricultural regions.