| Organic fertilizer of plant origin,mainly cake manure,and organic fertilizer of animal origin,mainly chicken manure,are the main forms of organic fertilizer application in navel orange orchards in Gannan;traditional organic fertilizer application is mainly applied in solid form by trenching,and organic liquid fertilizer irrigation is applied as a new technology for efficient fertilization of organic fertilizer in navel orange orchards in hilly mountainous areas.However,there is a lack of systematic research on its effect on soil quality in terms of soil fertilization.Based on this,this study investigated the effects of inorganic liquid fertilizer,organic liquid fertilizer of animal origin alone,organic liquid fertilizer of plant origin alone,50%organic liquid fertilizer of animal origin + 50% inorganic liquid fertilizer,and 50%organic liquid fertilizer of plant origin + 50% inorganic liquid fertilizer on soil quality under the same amount of nitrogen,pure inorganic liquid fertilizer,pure organic liquid fertilizer of animal and plant origin,and 50% organic liquid fertilizer of plant origin +50% inorganic liquid fertilizer on soil quality through a combination of field experiment and indoor simulation.The effects of five fertilization methods,namely,pure inorganic liquid fertilizer,pure organic liquid fertilizer of animal and plant origin and inorganic liquid fertilizer,on soil nutrients,soil biological properties and soil active organic carbon fraction were investigated under the same N application rate.The aim is to clarify the effects of different fertilization patterns on soil biological characteristics and active organic carbon fraction in navel orange orchards,in order to provide a scientific basis for light and efficient fertilization of navel orange orchards in Gannan.The main results are as follows:1.The results of the field experiment showed that both pure animal and plant-derived organic liquid fertilizers could regulate the pH of 0-15 cm topsoil;the organic liquid fertilizer of plant origin with inorganic liquid fertilizer had the best effect in enhancing the organic matter content;the organic matter content decreased with the increase of soil depth.The fertilization treatment significantly increased the contents of soil alkaline nitrogen,available phosphorus and available potassium;in the 0-15 cm soil layer,the contents of soil alkaline nitrogen,available phosphorus and available potassium were 117.83 mg/kg,44.37 mg/kg and 168 mg/kg,respectively,in the moderate range of plant-derived organic liquid fertilizer with inorganic liquid fertilizer compared with other treatments.2.The results of the field test showed that the fertilization treatments increased the number of bacteria,fungi and actinomycetes in the soil;the plant-derived organic liquid fertilizer with inorganic liquid fertilizer enhanced the best effect compared with other treatments.The application of plant-derived organic liquid fertilizer with inorganic liquid fertilizer significantly increased soil urease,sucrase,and acid phosphatase activities.Both soil enzyme activity and microbial population decreased with the increase of soil depth.3.The results of the field experiment showed that the combination of inorganic liquid fertilizer,plant-derived organic liquid fertilizer and inorganic liquid fertilizer significantly increased the content of labile organic carbon,particulate organic carbon and microbial organic carbon in the 0-15 cm soil layer;compared with other treatments,the combination of plant-derived organic liquid fertilizer and inorganic liquid fertilizer had the best effect on the enhancement of soil microbial carbon,dissolved organic carbon and particulate organic carbon.4.The results of the field experiment showed that the application of plant-derived organic liquid fertilizer with inorganic liquid fertilizer significantly increased the alpha diversity and the number of endemic species of soil bacteria,significantly increased the richness and diversity of soil bacterial communities,and significantly increased the relative abundance of the dominant bacterial phyla,the Proteobacteria and unidentified＿Bacteria.Compared with other treatments,pure plant-derived organic liquid fertilizer had the greatest effect on soil bacterial community structure;two soil layers,15-30 and 30-60 cm,had higher similarity in soil bacterial community structure than 0-15 cm soil layer.Spearman analysis showed that soil organic matter,labile organic carbon,particulate organic carbon,and acid phosphatase were the key environmental factors driving changes in soil bacterial communities.5.The results of the field experiment showed that the fertilization treatment reduced the alpha diversity and the number of endemic species of soil fungi in the0-15 cm soil layer;the inorganic liquid fertilizer,pure animal-derived organic liquid fertilizer,and plant-derived organic liquid fertilizer with inorganic liquid fertilizer increased the alpha diversity of soil fungal communities in the 15-30 and 30-60 cm soil layers;the fertilization treatment increased the relative abundance of Ascomycota and decreased the relative abundance of Basidiomycota.Spearman’s analysis showed that soil pH,particulate organic carbon and acid phosphatase were the key environmental factors driving the changes of soil fungal communities.6.The results of indoor experiments showed that fertilization treatments increased the number of soil bacteria,fungi,and actinomycetes throughout the incubation period;plant-derived organic liquid fertilizer and its organic-inorganic mixture treatments significantly increased the number of soil microorganisms.All fertilization treatments inhibited soil acid phosphatase activity.7.The results of the indoor experiments showed that the fertilization treatments significantly increased the content of soil microbial carbon and soluble organic carbon.At 90 d of incubation,soil microbial quantity carbon was significantly higher with plant-derived organic liquid fertilizer and inorganic liquid fertilizer than with other fertilization treatments.During the whole incubation period,the treatment of plant-derived organic liquid fertilizer with inorganic liquid fertilizer had the best effect on the enhancement of soil soluble organic carbon compared with other treatments.8.The results of indoor experiments showed that fertilization treatment reduced soil bacterial α-diversity and the number of endemic species,fertilization treatment increased the relative abundance of soil Chloroflexi and Firmicutes,and the combination of plant-derived organic liquid fertilizer and inorganic liquid fertilizer increased the relative abundance of Firmicutes and unidentified＿Bacteriacompared with other treatments,and had the greatest effect on soil bacterial community structure.Inorganic liquid fertilizer and pure animal-derived organic liquid fertilizer increased soil fungal α-diversity and the number of endemic species compared with other treatments,but pure plant-derived organic liquid fertilizer and plant-derived organic liquid fertilizer with inorganic had a greater effect on the community structure of fungi.In conclusion,compared with other treatments,the application of plant-derived organic liquid fertilizer with inorganic liquid fertilizer significantly increased the contents of soil available nitrogen,available phosphorus,organic matter,microbiomass carbon Dissolved organic carbon,significantly increased the number of soil microbial number and soil enzyme activity,as well as had the best effect on improving the structural diversity of soil bacterial communities.In this study,the treatment of 50% plant-derived organic liquid fertilizer N + 50% chemical fertilizer N application pattern showed the best effect on soil fertilization in Gannan navel orange orchards. |
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