| Reducing chemical N and increasing fertilizer efficiency are the primary issues of pineapple orchard,ensuring the healthy and sustainable soil ecosystem in Hainan Province.The purpose of the study is to clarify the suitable cultivation model of pineapple,including continuous cropping years and fertilizer application in Hainan Province.Therefore,the test is divided into two major aspects:First,after soil sampling with different continuous cropping years（4,6,8,10,12）in pineapple orchard,the careful analysis of microbial community structure and physiochemical properties were worked.These results reflected the changes of soil nutrient indexes and microbial community during pineapple continuous cropping,which build a theoretical basis for further elucidating the relationship between microbial community and soil nutrients,and practical rational fertilization as well.Then,in the orchard of continuous pineapple planting for 8 years,‘No.17’species was selected to evaluate the effect of different fertilization patterns,based on the pineapple yield and quality,soil physicochemical characters and microbial community structure.The experimental models were set as follows:CK,blank control;T1,conventional fertilization of planters;T2,optimized fertilization;T3,organic nitrogen instead of 20%inorganic nitrogen in T2,to find the appropriate fertilization techniques.The main results are as follows:（1）The contents of Soil Organic Matter,Soil Alkaline Nitrogen and Quick-acting Potassium decreased with the extension of continuous cropping years,in the contrast the Effective Phosphorus enriched.Interestingly,Soil p H varied from 4.35 to 5.44,which first increased and then decreased.（2）With the increasing years of pineapple planting,the population quantity of soil bacteria and actinomycetes gradually reduced,but fungi gradually increased,thus the soil ecosystem changed from"bacterial"into"fungal".（3）In the continuous pineapple orchard,the abundance of some beneficial microbial communities markedly changed.The community richness and diversity of soil bacteria and fungi in continuous cropping for 6 years were higher than those in other treatments.At the phylum level,the dominant phyla of Proteobacteria and Actinobacteria were the highest in the soil for 4 and 6 years of continuous cropping.The biocontrol species Penicillium,Chaetomium,and Nitrospirae related to N cycle showed a decreasing trend with long-term continuous cropping.Notedly,the common plant pathogen,Fusarium was significantly enriched in the soil planted for 8 years.（4）In the field experiment,the optimal fertilization mode reduced soil phosphorus accumulation,nitrogen loss,and alleviated soil acidification.The highest yield was53.25 t·hm-2 in T3 with organic fertilizer was applied to replace part of chemical fertilizer as base fertilizer,which increased 19.53%compared with T1.Secondly,optimized fertilization T2 model 50.85 t·hm-2.The fertilizer utilization rate of T2 and T3 treatment was significantly higher than that of T1 treatment,and the fertilizer contribution rate of T2 treatment was significantly higher than that of T1 treatment.T3treatment increased fruit sugar content,decreased titratable acid content,and increased fruit length,fruit width,fruit weight and other external qualities.（5）High throughput sequencing results indicated,Proteobacteria,Actinobacteria,Acidobacteria,Firmicutes,Verrucomicrobia is the highest 5 phyla of bacteria,and Ascomycota and Basidiomycota reached the highest abundance in fungi.T3 treatment significantly improved the abundance and diversity of beneficial bacterial groups in the rhizosphere,such as Actinobacteria,Firmicutes,Streptomyces,Ktedonobacter and Burkholderia,which promote plant growth and nutrient cycling.Further clustering diagram analysis showed that less chemical fertilizing measures（T2,T3）can obviously change the bacteria,fungi community structure.Redundancy analysis illustrates that the abundance of fungus bacteria genera was influenced by the relativity between Quick-acting Potassium and Effective Phosphorus.In RDA diagram,the collaborative relationship existed in environmental factors of Organic Matter,Soil Alkaline Nitrogen,Quick-acting Potassium,intuitively showing the critical equilibrium ratio of nutrient abundance for the diversity of soil microorganism（bacteria,fungi）. |
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