The Effect Of Eucalyptus Bark As Seedling Substrate

Compared with soil,cultivation using organic substrate could increase crop yield,optimize quality,reduce diseases and insect pests,save water and fertilizer,and save labor and cost.The peat,which is currently the most popular organic substrate in the market,is a natural non-renewable resource,and its formation requires special wetland conditions and a long historical process.Correspondingly,wood processing wastes such as barks are cheap,easily-obtained and stable in physical and chemical properties,which can be used as alternative materials for mass production of organic nursery substrate.Eucalyptus urophylla × E.grandis is a hybrid of Eucalyptus grandis and Eucalyptus urophylla.It is native to Australia and Oceania.It is an evergreen tree with the characteristics of strong adaptability,fast growth and high economic value.Because of its straight trunk and short rotation period,it has become the main cultivated tree species in the key forest region,and the important commercial timber forest base and forest products industrial base of Yunnan Province.Every year,wood processing produces a large amount of residues represented by barks and sawdust.The traditional treatment method is centralized burning,which not only produces environmental burdens but also wastes potential bark resources.In order to improve the utilization value of Eucalyptus bark in an environmentally friendly way,microorganisms are used to decompose it and degrade the endogenous inhibitors,in order to make it an organic substrate with physical and chemical properties similar to peat.This study explored the nursery effect of Eucalyptus bark as raw material for substrate by cultivating economic plants Moringa oleifera,broccoli,lettuce,tomato,tobacco and lithops in the greenhouse,and cultivating economic trees Pinus kesiya var.langbianensis in the field.The least significant difference method(LSD)was used for the significance test.The main research results are as follows:1.The main inhibitor Eucalyptus phenol in the Eucalyptus bark of three different decomposition levels were extracted by water extraction method.Separation and analysis using high performance liquid chromatograph(HPLC)found that the Eucalyptus phenol contents were 0.005mg/g,0.413mg/g and 0.114mg/g in the raw Eucalyptus bark,40-day-decomposed Eucalyptus bark and 60-day-decomposed Eucalyptus bark,respectively.The germination test of tomato,lettuce and tobacco seeds with 0ppm,25 ppm,50ppm,100 ppm and 200 ppm of Eucalyptus phenol showed that a low concentration of 50 ppm of Eucalyptus phenol can inhibit87% of tobacco seeds germinated,and 100 ppm of Eucalyptus phenol can inhibit 32% of tomato seeds and 53% of lettuce seeds germinated.2.Through the determination of the main nutrients contents in the Eucalyptus bark of three different decomposition levels and peat,it was found that for the raw Eucalyptus bark decomposed 40 days and then decomposed to 60 days,the main internal nutrients were gradually and effectively released slowly first and then faster.Comprehensive contents of organic matter,humic acid,nitrogen,phosphorus and potassium can prove that the main nutrients contents in 60-day-decomposed Eucalyptus bark is equivalent to that of peat,and it has the potential as a substitute for traditional non-renewable resources of peat.3.The effect of three different decomposition levels Eucalyptus bark compounded with different proportions of perlite(10%,20%,30%)on the cultivation of six economic plants of broccoli,lettuce,tomato,M.oleifera,tobacco and lithops in the greenhouse showed that the nursery effects of 60-day-decomposed Eucalyptus bark on tomato,broccoli and lettuce were significantly better than peat.Among them,60-day-decomposed Eucalyptus bark compounded with 30% perlite was the best,which also indicated that these three plants are tolerant to the concentration of 0.114 mg/g of Eucalyptus phenol.But for M.oleifera and tobacco,due to the influence of the endogenous inhibitors of Eucalyptus bark,60-day-decomposed Eucalyptus bark cannot reach the nursery effect of peat.For such economic plants with low tolerance to endogenous inhibitors of Eucalyptus bark,the content of endogenous inhibitors,mainly Eucalyptus phenol,should be further reduced by optimizing the fermentation and decaying process.For lithops,the nursery effect of 60-day-decomposed Eucalyptus bark is slightly less than that of peat.The cost of the two can be compared to determine which substrate to use.Therefore,it is determined that the 60-day-decomposed Eucalyptus bark can be used as the main material of the substrate to grow seedlings of some high tolerance plants.4.The nursery effect of 25 treatments compounded with rotten Eucalyptus bark,red soil and perlite on P.kesiya var.langbianensis in the field showed that No.12(rotten Eucalyptus bark:perlite: red soil=3:0:7),No.13(rotten Eucalyptus bark: perlite: red soil=2:2:6),No.15(rotten Eucalyptus bark: perlite: red soil=2:1:7),No.17(rotten Eucalyptus bark: perlite: red soil=3:2:5),No.18(rotten Eucalyptus bark: perlite: red soil=3:1:6),No.21(rotten Eucalyptus bark: perlite:red soil=1:5:4)and No.22(rotten Eucalyptus bark: perlite: red soil=1:3:6)compound substrates on the germination rate and the growth of height,crown diameter and ground diameter at the seedling stage of P.kesiya var.langbianensis are significantly better than that of red soil(No.16),and the nursery effect is not significantly different from that of No.26 treatment with compound fertilizer.Among them,No.22 treatment compounded with 10% rotten Eucalyptus bark and 30% perlite has the best nursery effect.For the growth of P.kesiya var.langbianensis after field planting,the experimental field on the tailo is significantly better than the experimental field on the schattenseite.Among them,the No.17 and No.18 treatments compounded with 30% rotten Eucalyptus bark and 10% or 20% perlite are significantly better than No.16 treatment,and the nursery effect is not significantly different from that of No.26 treatment with compound fertilizer.Therefore,the use of No.17 and No.18 treatment substrates can achieve the dual effects of reducing the use of fertilizers to protect the environment and improving the quality of seedlings.