Comprehensive Evaluation of Soil Quality on Agroforestry Stereoscopic Management Patterns of Southern Medicine
LI Chen-Chen, ZHOU Zai-Zhi, LIANG Kun-Nan, HUANG Gui-Hua, YANG Guang
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In order to select optimum stereoscopic management patterns of southern medicine, we chose four kinds of medicinal plants which were suitable for growth in south area, using completely randomized block design to establish four agroforestry stereoscopic management patterns(SM, SMA, SMC, SMG) in 15-year old third generation Chinese fir plantation, and seven physical indexes, eleven chemical indexes and five enzyme activity indexes at 0-20 and 20-40 cm soil layers were determined. By the principal component analysis, we evaluated the effect of these patterns on soil quality. Compared to control, four patterns can significantly reduce soil bulk density and increased with increasing soil depth. In 0-20 cm soil layer, soil bulk density dropped, respectively, SM by 22.3%, SMA by 13.4%, SMG by 14.1%, and SMC by 20.8% while decreased by 7.0%-15.5% in 20-40 cm soil layer. The soil mass water content, field moisture capacity, capillary moisture capacity, capillary porosity and total porosity were significantly increased(P<0.05) and decreased with increasing soil depth. The maximum of these indexes all appeared in SM, respectively, increased by 55.0%, 88.7%, 100.1% and 88.7% than control in 0-20 cm soil layer while in 20-40 cm soil layer was SMG, respectively, increased by 61.5%, 67.6%, 69.7%, 43.4% and 44.0%. In 0-20 cm soil layer, pH dropped by 0.7%-6.2%, while in 20-40 cm soil layer it did not reach significant levels among treatments. The soil nutrient content decreased with increasing soil depth. In 0-20 cm soil layer, the contents of organic matter, total nitrogen, total phosphorus, available N, available P, available K, exchangeable calcium and magnesium, and cation exchange capacity reached maximum in model SMC, and increased by 79.7%,69.5%, 30.3%, 91.4%, 30.3%, 166.1%, 91.6%, 166.1% and 91.6%, respectively. The highest content of total potassium appeared in SMG, increased by 26.9% than control, while in 20-40 cm soil layer, most chemical indicators between models did not reach significant differences except available potassium. As to the soil enzyme activity, in 0-20 cm soil layer, the activities of soil urease, invertase, polyphenol oxidase and acid phosphatase activity among models and control had significant difference(P<0.05). The activities of urease and polyphenol oxidase of SMC were highest, 1.7 and 1.6 times higher than that of control, respectively. The activity of invertase of models were lower than control, decreased by 59.3%-69.4%. The maximum of acid phosphatase activity appeared in SMA, which was 1.38 times of the control. In 20-40 cm soil layer, only acid phosphatase activity of models and control had significant difference(P<0.05), and it reached maximum in SMA, which increased by 78.7% than control. The descending order of improvement effect of four agroforestry stereoscopic management patterns on soil quality were SMC(2.811), SMG(1.293), SMA(0.111), SM(-1.544) and CK(-2.671).