| Lolium multiflorum L is taken as the major object in this study to investigate the effect of the cement content in soil on its root growth,which could ascertain the adaptability of the root system of Lolium multiflorum L to the unfavorable soil environment with different cement content.After planting Lolium multiflorum L in soil with the cement contents of 0%to 7%,some indicators like root vitality,root morphological indicators,main enzyme activities in roots,soil fertility characteristics in root zone,community structure and diversity of rhizosphere and non-rhizosphere soil bacterial were measured during the tillering,booting and flowering stages of Lolium multiflorum.The results show that:(1)In the three measurements,the total root lengths of Lolium multiflorum L in soils with cement content of 1% to 7% were significantly lower than that of CK,and the root vitality values of Lolium multiflorum L in treatment group were significantly lower than that in CK.The characteristics of root physical growth and root vitality inhibition of Lolium multiflorum L mainly appeared at the tillering stage.At the tillering stage,the total root length with cement treatment was reduced by 10.86%(Y1),17.49%(Y2),36.95%(Y3),and10.44% compared with CK.(Y4),and the root activity decreased by 7.41%(Y1),18.35%(Y2),25.10%(Y3),28.09%(Y4)compared with CK.The inhibitory effect of soil with different cement content on the root growth and root activity of Lolium multiflorum L gradually weakened with the maturity of Lolium multiflorum L.The activities of SOD,POD and CAT in the roots with 5% cement content of Lolium multiflorum L in the tillering stage were significantly higher than other groups with cement treatment,which indicates that when the cement content is greater than 5%,the stress on the root growth of Lolium multiflorum L is greater.Therefore,5% cement content is more suitable for the growth of Lolium multiflorum L root system in the all treatments.(2)During the three growth periods of Lolium multiflorum L,the soil fertility characteristics of the Y3 group were closer to the control group.The soil available phosphorus content of the cement treatment group at the tillering stage was increased by34.17%(Y1),36.28%(Y2),16.20%(Y3),32.33%(Y4)compared with CK;the total phosphorus content of the treatment group increased by 8.89%(Y1),6.67%(Y2),2.22%(Y3),8.89%(Y4)compared with CK;the available potassium content of the treatment group increased by 93.20%(Y1),118.17%(Y2),80.49%(Y3),135.88%(Y4)compared with CK;the organic matter content of the treatment group increased by 1.09%(Y1),3.10%(Y2),0.11%(Y3),0.33%(Y4)compared with CK;the total potassium content,alkali-hydrolyzable nitrogen content and total nitrogen content were slightly lower than CK,and the soil p H value of the treatment group was higher than CK.The nutrient content in soil at the booting stage was lower than that at the tillering stage,which was due to the consumption of plant growth.The soil p H of the treatment group also showed a downtrend,which was because the soil p H was diluted by the watering and irrigation.The soil fertility characteristics at the flowering stage tended to be stable,and the change trends of soil nutrient content of the treatment group and CK were consistent with the booting stage.(3)In all treatments,the Proteobacteria,Bacteroides and Actinobacteria were dominant in the rhizosphere environment,and their relative abundances were 30%～38%,16%～17%and 11%～14% respectively.The dominant flora in the non-rhizosphere environment is Proteobacteria,Bacteroides and Actinobacteria,with relative abundances of 34%～41%,13%～16% and 12%～23%.The soil microbial community diversity is also affected by the phosphorus,potassium and p H in the soil(p<0.05).Different cement contents in the soil have an impact on the structure of the soil bacterial community,and can increase the diversity of soil bacteria,but there was no significant difference between different treatment groups.The relative abundance and soil fertility characteristics of the soil bacteria in the root zone with Y3 treatment at the phylum and class level were closer to that of the control group,which shows that rhizosphere and non-rhizosphere soil bacteria are relatively more adaptable in the treatment with 5% cement content.In summary,the cement content of about 5% has little effect on the growth of Lolium multiflorum L,soil fertility characteristics and the adaptability of bacteria in the root zone of Lolium multiflorum L. |
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