Abstract:

To help address the problem of purple soil erosion on sloping land in Chongqing city, an experiment has been undertaken to investigate the effects of different crop-mulberry intercropping systems on soil nutrients. Four treatments were designed: crops were planted along transverse slopes (CT), crops were planted along transverse slopes with mulberry trees on the upper and lower slopes (T₁), crops were planted along transverse slopes with mulberry trees on the upper, middle and lower slopes (T₂); and crops were planted along transverse slopes with mulberry trees on the middle slope and on the four sides of the slope (T₃). The results showed that soil available nitrogen, available phosphorus, potassium and organic matter contents were significantly improved with mulberry intercropping. The sequence of improvement was T₂>T₃>T₁>CT. The ratios of carbon/nitrogen and carbon/phosphorus changed from 7 to 20 and from 10 to 27 respectively for the four treatments. The carbon/nitrogen and carbon/phosphorus ratios were largest in the T₂ treatment for every slope level. Soil organic matter, nitrogen, potassium, carbon/nitrogen ratio, carbon/phosphorus ratio and crop output were all significantly positively correlated. In conclusion, crop-mulberry intercropping in hillside fields improved and maintained soil nutrients and to some extent decreased the ratios of carbon/nitrogen and carbon/phosphorus in uphill soils. These results can be used to guide the choice of water and soil conservation cropping modes in the Three Gorges Reservoir Area.