| With the improvement of agricultural mechanization level,the increased use of large machinery results in a widespread soil compaction,seriously jeopardizing the sustainable agricultural production.Crop rotation including cover crops with strong tap root systems has been considered as an effective method to alleviate soil compaction.However,the adaptability of different cover crop root systems to soil compaction varies with different climate conditions and soil properties.In order to reasonably arrange farming methods,alleviate soil compaction,curb soil degradation,inhibit soil erosion and improve soil productivity.A field experiment including two treatments different in soil compactness(not compacted vs compacted)and four cover crop treatments(Fallow,Alfalfa,Oil Rape,Radish + Hairy Vetch intercropped)was conducted in the Shajiang black soil.We aimed to investigate the response of the cover crop root systems to soil compaction,the effect of the cover crop on the soil physical and chemical properties,and the effect of the cover crop on growth of the subsequent maize.The results are as follows:(1)In the compacted treatment,soil bulk density in the 0 ? 30 cm soil layers and soil penetration resistance in the 0 ? 27.5 cm and 37.5 ? 45 cm soil layers were significantly higher,and soil shrinkage behavior in the 0 ? 20 cm soil layer was significantly altered,relative to those in the non-compacted treatment.In the first year of cover cropping(2018),the root dry weight density of Alfalfa,Oil Rape,Radish + Hairy Vetch significantly reduced in 0 ? 50 cm soil layer,and the root specific surface area of Alfalfa,Oil Rape,Radish + Hairy Vetch increased in the compacted treatment compared with the non-compacted treatment.In the second year of planting cover crops(2019),soil compaction reduced the root dry weight density in each layer of Alfalfa,Oil Rape,Radish + Hairy Vetch in 30 ? 70 cm soil layer,20 ? 40 cm soil layer and 0 ? 40 cm soil layer,respectively.In 2018,the above ground coverage,the biomass of above shoot and root biomass of Radish + Hairy Vetch were all much less affected by soil compaction than the other two cover crops,indicating its ability to adapt to compaction soil is stronger.However,in 2019,the Alfalfa roots performed much better than the Oil Rape and Radish + Hairy Vetch in penetrating the compacted soil.(2)Compared with the Fallow,planting of cover crops increased stable infiltration rate and soil air permeability,and reduced soil water content and soil bulk density,but had no significant effect on soil penetration resistance.The soil water content of Alfalfa and Oil Rape in 0 ? 40 cm soil layer was higher than that of Radish + Hairy Vetch in the compacted treatment.Cultivation of cover crops increases the stable soil infiltration rate,and with the increase in the length of planting,the gap between the stable soil infiltration rates under the two compaction treatment methods continues to decrease.Compaction significantly reduced the saturated hydraulic conductivity of Alfalfa and Oil Rape in 20 ? 30 cm soil layer(laboratory soil core method).Compaction has no significant effect on soil bulk density under different planting models.The air permeability of the Alfalfa,Oil Rape,Radish + Hairy Vetch treatment was the highest at the water pressure heads of-60 hPa,-10 h Pa and-20 hPa,respectively.(3)Compared with the Fallow,the soil organic carbon in the soil layer of 0 ? 10 cm was significantly increased in the three cover crops in the non-compacted treatment.In the compacted treatment,only Radish + Hairy Vetch significantly increased soil organic carbon in the 10 ? 20 cm soil layer compared with the Fallow.Compared with non-compacted treatment,the compacted treatment significantly reduced the soil organic carbon in each soil layer of 10 ? 40 cm in the Fallow treatment.In the compacted treatment,the total nitrogen in the soil layer of 10 ? 20 cm was significantly higher in the Radish + Hairy Vetch treatment than that of Fallow treatment.Compared with the non-compacted treatment,the compacted treatment significantly reduced the total nitrogen in the soil layers of 10 ? 30 cm in the Fallow treatment.In the compacted treatment,the total potassium in each soil layer of 20 ? 40 cm of the three cover crop treatments was significantly higher than that of the Fallow treatment.In the non-compacted treatment,the total phosphorus content in the 30 ? 40 cm soil layer of the three cover crop treatments was significantly lower than that in the Fallow treatment.In the compacted treatment,the total phosphorus content in 30 ? 40 cm soil layer of the Alfalfa treatment was significantly lower than that in the Fallow treatment.The difference in the content of alkaline nitrogen and available potassium was not significant among the Fallow and cover crop treatments.Regardless of the compacted or non-compacted condition,the content of available phosphorus was significantly reduced by the three cover crop treatments compared with the Fallow treatments.Compared with the non-compacted treatment,the compacted treatment significantly reduced soil alkaline nitrogen in the 10 ? 30 cm soil layers and soil available potassium in the 10 ? 20 cm soil layer of the Fallow treatment,and soil available phosphorus in the 20 ? 30 cm soil layer of the Fallow and Radish + Hairy Vetch treatments.(4)The maize plant height and stem diameter were significantly lower in the compacted treatment than the non-compacted treatment.The Oil Rape treatment presented significantly higher plant height than the Fallow treatment for the compacted treatment,while the Radish + Hairy Vetch treatment had significantly higher stem diameter than the Fallow treatment for the non-compacted treatment.For the compacted treatment,after the first year of planting cover crops(2018),the dry weight density of maize roots in Alfalfa,Oil Rape,Radish + Hairy Vetch treatments was higher than the Fallow treatment in the 0 ? 40 cm,0 ? 60 cm and 0 ? 30 cm soil layers,respectively.In the second year(2019),compared with the Fallow treatment,Radish + Hairy Vetch treatment presented higher dry weight density of maize roots in 0 ? 80 cm soil layers,while Alfalfa and Oil Rape treatments only presented higher dry weight density of maize roots in 10 ? 50 cm soil layers.Compared with the non-compacted treatment,the compacted treatment reduced by 70.5 %,9.2 % and 11.3 % of maize root biomass for the Alfalfa,Oil Rape,Radish + Hairy Vetch treatments,respectively,in the first year(2018).In 2019,the compacted treatment increased the root biomass of maize for the cover crop treatments compared with the non-compacted treatment.In 2018,the yield of maize in the Alfalfa and Radish + Hairy Vetch treatments was significantly higher than that in the Fallow treatment for the compacted treatment.In 2019,the yield of maize in the Oil Rape treatment was significantly higher than that of other treatments for the compacted treatment. |
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