桂南茶园土壤团聚体有机碳和养分对植茶年限的响应

Responses of soil aggregate-associated organic carbon and nutrients to tea cultivation age in southern Guangxi,China

研究茶园土壤团聚体有机碳和养分对植茶年限的响应机制,可为茶园提升土壤肥力、保障土壤健康及促进土壤资源可持续利用奠定理论基础。本研究以植茶年限8、17、25和43年的桂南南山白毛茶园土壤为对象,采集0~20 cm土层原状土样,通过干筛法获得各粒径(>2、2~1、1~0.25和<0.25 mm)团聚体,并测定其中有机碳和养分含量。结果表明:不同植茶年限土壤团聚体组成以>2 mm粒径团聚体为主,其含量显著高于其他粒径团聚体,平均值为63.8%;其次是<0.25 mm粒径团聚体;而2~1和1~0.25 mm粒径团聚体含量较低,平均值分别为9.9%和7.8%。土壤团聚体稳定性指标平均重量直径(MWD)表现为植茶17年>8年>25年>43年。各植茶年限土壤团聚体有机碳、全氮含量随着粒径的增大而升高,其中>2和2~1 mm粒径团聚体较高,平均值在>2 mm粒径中分别为18.76和0.84 g·kg^-1、在2~1 mm粒径中分别为18.65和0.80 g·kg^-1;不同植茶年限土壤团聚体碱解氮、有效磷和速效钾含量在<0.25 mm粒径团聚体中最高,平均值分别为50.43、23.06和68.04 mg·kg^-1。长期植茶有助于土壤有机碳、全氮、碱解氮和有效磷的积累,但其储量的积累速率却逐年降低,不利于土壤速效钾的保持,其储量的流失速率在植茶中期(17~25年)最高。在区域茶园管理中,应重视植茶17年以后土壤团聚体稳定性降低、速效钾流失加剧等问题,以保障茶园土壤质量及促进土壤资源可持续利用。

Understanding the response mechanism of soil aggregate-associated organic carbon(OC)and nutrients to tea cultivation age can lay a theoretical foundation for improving soil fertility,ensuring soil health,and promoting sustainable utilization of soil resources in the tea plantations.In this study,concentrations of soil OC and nutrient were analyzed in>2,2-1,1-0.25,and<0.25 mm fractions(split by a dry-sieving procedure)at the 0-20 cm soil layer in four tea plantations with Baimao tea of different ages(8,17,25,and 43 a)in southern Guangxi,China.The distribution of soil aggregates showed that the dominant aggregates were>2 mm fractions with a mean value of 63.8%,followed by<0.25 mm fractions,while 2-1 and 1-0.25 mm fractions with mean values of 9.9%and 7.8%,respectively.As an indicator of soil aggregate stability,the mean weight diameter(MWD)in the tea plantations showed an order of 17 a>8 a>25 a>43 a.Regardless of tea cultivation age,soil aggregate-associated OC and total nitrogen(TN)concentrations increased with increasing aggregate size.Soil OC and TN concentrations in>2 and 2-1 mm fractions were significantly higher than those in other fractions.The mean values of soil OC and TN concentrations were 18.76 and 0.84 g·kg^-1 in the>2 mm fractions,and were 18.65 and 0.80 g·kg^-1 in the 2-1 mm fraction.Soil aggregate-associated available nitrogen(AN),available phosphorus(AP),and availa-ble potassium(AK)concentrations were highest in the<0.25 mm fractions with mean values of 50.43,23.06,and 68.04 mg·kg^-1,respectively.Long-term tea cultivation was favorable to the accumulation of soil OC,TN,AN,and AP,whereas the accumulation rates of these element stocks in the whole soil decreased with increasing tea cultivation age.In contrast,soil AK was susceptible to leaching in tea cultivation,with the loss rate of this element stock in the middle stage(from 17 to 25 a)being higher than those in the other stages.To ensure soil quality and promote the sustainable utilization of soil resources,more attention should be paid to the problems such as the decrease of soil aggregate stability and the aggravation of AK loss after 17 a of tea cultivation.