柏木根系分泌物对盆栽香椿土壤养分和酶活性的影响

Effects of root exudates of Cupressus funebris on soil nutrients and enzyme activities of potted Toona sinensis

为了研究柏木与香椿混交时柏木根系分泌物对土壤养分和酶活性的影响,试验采用盆栽法进行,将土培法收集的柏木根系分泌物按月施加到香椿苗盆栽土壤中,设4个处理:G1、G2、G3和G4,分别为1株、2株、4株和8株柏木根际土提取液,同时设置空白处理CK。处理1年后测定种植香椿的土壤(简称:香椿土壤)养分含量和酶活性。结果表明:柏木根系分泌物对香椿土壤全N、全P、全K含量影响不显著(P>0.05);但显著增加了土壤碱解N、有效P和速效K含量(P<0.05),且随施加浓度的增加,碱解N含量、有效P和速效K含量也增加,而G3与G4处理差异不显著(P>0.05);添加根系分泌物后,香椿土壤脲酶、磷酸酶、过氧化氢酶和蔗糖酶的活性增强,且随根系分泌物施加浓度的增加,土壤酶活性递增;相关分析显示,4种酶的活性与土壤碱解N、有效P和速效K及土壤p H值均呈极显著相关(P <0.01),但与全N、全P、全K不相关(P>0.05);4种酶相互之间存在极显著正相关(P<0.01);不同施加浓度的柏木根系分泌物均能提高碱解N、有效P、速效K含量,增强土壤脲酶、磷酸酶、过氧化氢酶和蔗糖酶的活性,从而直接或间接影响土壤养分的有效性。综合分析得出,以4株柏木根系分泌物的促进效果较好,柏木与香椿的混交比例为4∶1能较好地改善土壤环境。

We examined the effects of Cupressus funebris root exudates on soil nutrients and enzyme activities in the mixed plantation of C. funebris and Toona sinensis with a pot-culture method. The C. funebris root exudates were collected by soil culture method and added to the potted seedlings of T. sinensis every month. Four treatments of G1,G2,G3 and G4 were set up,corresponding to the treatments with rhizosphere soil extracts of 1,2,4,and 8 cypresses respectively. Meanwhile,a control was treated with distilled water. After one year,the nutrient concentrations and enzyme activities of soil in the five groups were measured. The results showed that C.funebris root exudates had no effect on the concentrations of soil total N,total P and total K( P>0.05),but significantly increased the concentrations of alkali-hydrolysable N,available P and available K( P<0.05). The concentrations of alkali-hydrolysable N,available P and available K increased with increasing concentration of the extracts,with no difference between G3 and G4( P>0.05). The activities of urease,neutral phosphatase,catalase and invertase in soil were boosted after adding root exudates,which were increased with increasing concentrations of exudates. The results of correlation analysis showed that the activities of the four enzymes were remarkably correlated with the concentrations of soil alkali-hydrolysable N,available P,available K and pH( P<0.01),but had no relationship with that of total N,total P,and total K( P>0.05).There was a positive correlation among the activities of the four enzymes( P<0.01). Our results indicated that increasing concentration of C. funebris root exudates could increase the concentrations of alkali-hydrolysable N,available P and available K,and enhance the activities of soil urease,neutral phosphatase,catalase and invertase,which would directly or indirectly affect the availability of soil nutrients. The root exudates of four cypresses had the strongest effects on soil available nutrients and soil enzyme activities. When the mixing ratio of C. funebris and T. sinensis was 4 ∶ 1,the soil environment could be much improved.