覆盖作物多样性对橘园土壤理化性质的影响及综合评价

Effects of Cover Crop Diversity on Soil Physicochemical Properties in Citrus Orchards and a Comprehensive Evaluation

选择当地生产最常用的6种覆盖作物剪股颖、高羊茅、白三叶、红三叶、菊苣和车前草,在柑橘园中按照1、2、3、4、6物种梯度和1、2、3功能群梯度,构建不同多样性水平的覆盖作物群落,测定建植1年后0~20 cm土层土壤水分、温度、全氮、碱解氮、有效磷、速效钾和有机质等土壤理化指标,分析覆盖作物多样性对土壤理化性质的影响,并采用灰色关联度分析法进行综合评价。结果表明:(1)与清耕相比,覆盖作物可以使夏季的土壤温度平均降低2.51℃,冬季的土壤温度平均提高0.26℃,土壤水分平均提高4.59%;(2)与清耕处理相比,覆盖作物处理下,土壤全氮、碱解氮、有效磷、速效钾和有机质含量平均分别提高了11.20%、17.86%、6.48%、7.53%和6.31%;(3)随着物种丰富度的增加,土壤养分大致呈先增加后减少的趋势,与单一种植相比,不同功能群的覆盖作物混合种植使土壤全氮提高7.08%,土壤碱解氮、有效磷和速效钾分别提高16.20%、7.09%、3.54%;(4)相关性分析表明,物种丰富度与土壤全氮、碱解氮和有效磷显著正相关(P<0.05),功能群丰富度与土壤全氮和碱解氮存在极显著相关(P<0.01),功能群丰富度与土壤养分之间的相关性要高于物种丰富度;(5)灰色关联度分析的综合评价表明,当覆盖作物物种丰富度为4、功能群丰富度为3时的关联度最大,是较理想的柑橘园覆盖作物混播模式。本研究中最优的混播处理为剪股颖+高羊茅+菊苣+车前草和高羊茅+白三叶+菊苣。

The study established cover crop communities with different diversity levels in citrus orchards by incorporating 1,2,3,4,6 species to achieve 1,2,or 3 functional group richness using Agrostis clavate,Festuca elata,Trifolium repens,Trifolium pratense,Cichorium intybus and Plantago depressa.Following one year of cover crop cultivation,soil samples were collected from 0~20 cm soil layer to assess moisture content,temperature,electrical conductivity,total nitrogen concentration,alkaline hydrolyzed nitrogen concentration,available phosphorus content,available potassium content,and organic matter.The effects of cover crop diversity on soil physicochemical properties were compared and analyzed,followed a comprehensive multivariate evaluation using grey interconnect degree analysis.The results showed that:(1)In comparison to the clean tillage treatment,cover crops led to a reduction of soil temperature by 2.51℃during summer and an increased by 0.26℃during winter,along with a 4.59%rise in soil water content.(2)Relative to soil tillage,various cover crop treatments resulted in an elevation of soil total nitrogen,alkaline hydrolyzed nitrogen,available phosphorus,available potassium,and organic matter by 11.20%,17.86%,6.48%,7.53%,and 6.31%,respectively.(3)Soil nutrient levels initially increased and then declined with the rise in species richness.When compared to monoculture treatments,mixed cover crop cultures categorized into functional groups amplified the concentrations of soil total nitrogen,alkaline hydrolyzed nitrogen,available phosphorus,and available potassium by 7.08%,16.20%,7.09%,and 3.54%,respectively.(4)Correlation analysis between cover crop species richness and soil physicochemical properties revealed a significant correlation between species richness and the concentrations of soil total nitrogen,alkaline hydrolyzed nitrogen,and available phosphorus(P<0.05).Moreover,functional group richness of cover crops exhibited a significant correlation with the concentrations of soil total nitrogen and alkaline hydrolyzed nitrogen(P<0.01).This demonstrated that the correlation between functional group richness and soil nutrients was higher than that of species richness.(5)Integrated evaluation using grey interconnect degree analysis between cover crop diversity and soil physicochemical properties indicated that the greatest associations were observed with a combination of four species richness types and three functional group richness types of cover crops.This configuration represents an ideal mixed culture pattern for citrus orchard.The recommended mixed cover crop treatments from this study are A.cla⁃vata+F.elata+C.intybus+P.depressa and F.elata+T.repens+C.intybus.