Composts From Chinese Chestnut Residues And Their Mechanism On Chestnut Seedling Growth And Fruit Yield And Quality Improvement

With the rapid development of Chinese chestnut industry,Chinese chestnut residues increased sharply.Based on the goal of resource utilization and the increasing of the fruit quality and yield,mixed litter of chestnut leaves and hulls(B),corn stalks(Y),edible fungi residues(Z),and chicken manure(F)were used as raw materials,according to different ratios of BYZ(B:Y:Z:F=2:2:4,the proportion of chestnut residue was 40%),BZ1(B:Z:F=4:2:4,the proportion of chestnut residue was 60%),BZ2(B:Z:F=6:2:2,the proportion of chestnut residue was 80%),ZF(Z:F=6:4,the proportion of chestnut residue was 60%)and with EM,VT or their mixture EM+VT addition as in-situ composting microbial agents.The bottleneck of the low proportion of chestnut residues in the past was broken through,and the composts were returned to field through deep application in situ and used for seedling cultivation.The effects of different compost on the chestnut seedlings growth,photosynthetic characteristics,chestnut fruit yield and quality,and the activation of soil phosphorus were studied,in order to screen optimum technological conditions of chestnut residues composting,compost application type and proportion,and reveal the mechanism of the composts on chestnut seedlings growth and fruit quality and yield improvement.Theses could provide guidance for realizing Chinese chestnut residue utilization,building an environment-friendly and high-yield management technology system for chestnut industry and increasing farmers' income and wealth.The main conclusions were as follows:(1)Compared with the composting process without adding microbial agents,only adding EM or VT microbial agents,EM+VT amendment can improve BYZ composting process,increase the number of bacteria,fungi and actinomycetes in high temperature period significantly and promote the rapid heating of compost.The compost C/N ratio dropped the most(by 57.58%).BZ1 had the fastest warming rate and both BZ1 and BZ2 showed fungal attraction in high temperature period under the same bacterial agent EM+VT treatment.BZ1 compost had the highest content of nitrogen,phosphorus and potassium,and BZ2 compost had the highest content of organic matter.ZF compost showed the characteristics of low organic matter and low content of nitrogen,phosphorus and potassium.The order of total porosity was BZ2>BZ1>BYZ>ZF.It could be seen that a higher proportion of leaf and hull mixtures(B)could improve the physical and chemical properties of compost.(2)The growth index of chestnut seedlings varied with the type and proportion of compost added to cultivation medium.When ZF was added in 1/8 ratio and BZ2 in 1/8 ratio,the promotive effect on root length,root surface area and root volume,especially the root<2mm in diameter were the best,and the total biomass accumulated by seedlings was the largest,and the net photosynthetic rate and transpiration rate increased significantly.Addition of ZF in 1/8 rario could induce the formation of mycorrhiza of chestnut seedlings,which could be used as a recommended formula for chestnut seedlings cultivation.(3)The results of compost application on fruit trees test showed that deep application of BZ1 could not only improve soil organic matter content and available nutrient content,but also improve soil structure,water content and water potential,and reduce C/N,C/P and C/K of fine root.Moreover,it had the most significant effect on increasing fruit yield of chestnut.The average fruit yield order of different compost treatment was as follows:BZ1>BYZ>ZF=BZ2.BZ1 was a good choice for aerobic composting raw material system and deep application in given area.(4)There were significant differences in phosphorus form characteristics and soil phosphorus activation among the four composts.Total phosphorus content was highest in BZ1 and lowest in BZ2.Inorganic phosphorus in compost was dominant form(accounting for 62.88%?73.62%).The proportion of H2O-Pi in total phosphorus was the highest in BZ1 and BZ2,and the water-soluble phosphorus content in BZ1 was also the highest.The field test with equivalent phosphorus amendment showed that compost application treatments showed a strong effect on soil phosphorus activation.Fertilization increased the contents of active H2O-Pi,NaHCO3-Pi and moderately active NaOH-Pi significantly.BZ1 was the best treatment for phosphorus activation coefficient.The distribution of active inorganic phosphorus or moderately active inorganic phosphorus in different soil horizons correlated significantly with the changes of organic matter,soil aggregate structure and soil water caused by different fertilization treatments.The results of seedling cultivation test showed that compared with CK,the content of acid phosphatase and available inorganic phosphorus of ZF treatment with 1/8 ratio in the rhizosphere soil increased significantly,and the increase of total phosphorus in roots,stems and leaves was the largest.ZF treatment with 1/8 ratio promoted the transport of phosphorus to the aboveground,which was related to the formation of larger fine root absorption area and higher acid phosphatase content.Compared with pure culture medium,the proportion of soil organic phosphorus decreased with the presence of seedlings,especially HCl-Po in total phosphorus.The biggest drop of HCl-Po proportion in total phosphorus was found in ZF treatment with 1/8 ratio.(5)The interaction between chemical fertilizer and organic compost varied with application ratios of chemical and organic fertilizers.The increased nitrogen and phosphorus efficiency by 50%inorganic fertilizer and 50%BZ1 compost treatment(F0.5M0.5)was found on the condition that equal N,P and K nutrients were supplied,which was an important reason for its best yield(4104.77 kg·hm-2),net income(73.3 thousand yuan·hm-2)and quality,and F0.5M0.5 was a good choice for the combined application of organic and inorganic fertilizers in given area.