三峡库区紫色土旱坡地农桑配置模式对土壤养分的影响

Effects of different crop-mulberry intercropping systems on nutrients in arid purple soils in the Three Gorges Reservoir Area

针对三峡库区紫色土流失严重和土壤肥力低的现状,本试验利用水土保育模式--农桑间作试验,研究横坡农作（CT）、双边桑树＋横坡农作（T1）、等高桑树＋ 双边桑树＋ 横坡农作（T2）及四边桑树＋ 等高桑树＋ 横坡农作（T3）4个处理对土壤养分的影响.结果表明,桑树布局小区内的土壤碱解氮、速效磷、速效钾和有机质含量均有极显著提高,且土壤碱解氮、速效磷、速效钾和有机质含量平均值大小均表现为：等高桑树＋ 双边桑树＋ 横坡农作（T2）〉四边桑树＋等高桑树＋横坡农作（T3）〉双边桑树＋横坡农作（T1）〉横坡农作（CT）.4个处理的土壤碳氮比和碳磷比变化幅度分别在7～20和10～27之间,其中等高桑树＋双边桑树＋ 横坡农作（T2）小区各个坡长的土壤碳氮比和碳磷比最大.土壤有机质、碱解氮、速效钾、碳磷比与玉米和榨菜产量具有极显著的正相关关系.可见,旱坡地农桑配置模式在一定程度上可以提高和维持土壤养分,降低上坡段土壤碳氮比和碳磷比,从而为三峡库区水土保育模式优选提供理论依据.

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 nutri-ents.Four treatments were designed:crops were planted along transverse slopes (CT),crops were planted a-long transverse slopes with mulberry trees on the upper and lower slopes (T1 ),crops were planted along trans-verse 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 signifi-cantly 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 slopelevel.Soil organic matter,nitrogen,potassium,carbon/nitrogen ratio,carbon/phosphorus ratio and crop out-put were all significantly positively correlated.In conclusion,crop-mulberry intercropping in hillside fields im-proved 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.