| The citrus industry in Zigui County is an important economic industry in the local area.However,long-term intensive planting has brought high-intensity fertilizer input,which has led to the deterioration of the soil structure,soil acidification,and decline of soil nutrients in the citrus orchard.These problems have restricted the sustainable development of the citrus planting industry.Applying organic fertilizers and amendments can improve soil acidification and increase crop yield,but there is a lack of research on the amount of organic fertilizers applied,the combination of amendments and green manure amendments applied in citrus orchards,and the management model is not clear.Therefore,this study takes the citrus orchard in Zigui County as the research object,and sets up a commercial organic fertilizer application amount experiment through field experiments.Combining four types of amendments,including biochar,calcium magnesium phosphate fertilizer,microbial inoculants,and earthworm manure,as well as a combination of green manure and amendments,the study analyzes their effects on soil properties,fruit yield,and quality,in order to provide reference for soil improvement in the citrus orchard in Zigui County.The main results of this study are as follows:(1)Compared with CK(5 kg/plant),the application of high organic fertilizer treatment can increase soil p H by 0.01～0.09.Both 10 kg/plant and 15 kg/plant treatments can reduce soil bulk density by 0.03 g/cm~3,while the 15 kg/plant treatment of organic fertilizer has the greatest increase in soil available potassium,available phosphorus,and alkaline nitrogen content.Applying high amounts of organic fertilizer can increase the proportion of dominant populations such as Actinobacteria,but it does not significantly improve microbial diversity.The fruit yield of the 15 kg/plant organic fertilizer treatment increased by 10.80%,but the fruit yield showed a downward trend under the 20 kg/plant organic fertilizer treatment.The increase in the amount of organic fertilizer applied showed an increasing trend in single fruit weight,edible rate,and solid acid ratio,but the effect on improving fruit quality was not significant.(2)Applying soil amendments can improve soil physical properties and enhance soil nutrients.Applying biochar resulted in a maximum decrease in soil bulk density of 0.05 g/cm~3 and an increase in soil moisture content of 0.99%;The microbial agent treatment in Shangba Village and the Citrus Variety Breeding Center increased soil p H and organic matter by up to 0.79 and 23.90 g/kg respectively;Applying biochar in Maoping Town can increase p H by 0.28 and organic matter content by 5.12 g/kg.The application of calcium magnesium phosphate fertilizer showed the greatest increase in total phosphorus and alkaline nitrogen content,while the application of biochar showed the greatest increase in available potassium content.Due to the short nature and improvement time of the soil,the application of amendments has a relatively small impact on the content of trace elements in the soil.The biochar treatment has the greatest improvement in microbial biomass and diversity,and has an enhancing effect on dominant populations such as Actinobacteria and Proteobacteria,as well as other phyla.The application of amendments significantly increased fruit yield,with the improvement treatment in Shangba Village increasing by 11.80-35.80 kg/plant compared to CK.However,there was no significant difference in the results of applying different amendments.The biochar treatment had the greatest effect on improving single fruit weight,juice yield,soluble solids,and solid acid ratio,but most of the improver treatments did not significantly improve fruit quality.(3)The combination application of green manure and amendments,as well as the intercropping of green manure,can improve soil properties.The combined application of green manure and biochar can reduce the bulk density by up to 0.05g/cm~3,and intercropping with rapeseed peanut green manure can increase soil moisture content by 1.97%.The combination application of green manure microbial inoculants in Shangba Village and green manure biochar in Maoping Town increased p H by 0.56 and 0.97,respectively.However,most of the green manure improver combination treatments and single intercropping of green manure did not significantly increase p H.Green manure microbial agents have the greatest effect on improving organic matter and alkaline nitrogen content.The single intercropping of green manure and the combination of green manure and modifier did not significantly improve microbial biomass and microbial diversity.The combination of green manure and modifier could significantly increase fruit yield,while the combination of green manure biochar and green manure microbial agent could improve fruit quality.However,the single intercropping of green manure did not significantly improve fruit yield and fruit quality.(4)Under the condition of hole application,the soil bulk density of 1.55 g/cm3decreased by 0.12 g/cm~3 compared to ditch application,and the soil p H increased by 0.14.It also had an increasing effect on the content of organic matter,available potassium,and other nutrients.Compared with furrow application,hole application could increase fruit yield by 8.00%,increase fruit juice yield,soluble solids and solid acid ratio,and reduce titratable acid to improve fruit quality.In summary,the application amount of organic fertilizer can promote the improvement of soil properties and fruit yield and quality.The soil nutrient content and yield are highest under the treatment of 15 kg/plant of organic fertilizer.The application of amendments and the combination of green manure and amendments have positive effects on the improvement of soil structure and the promotion of nutrients,and the effect of microbial agents and biochar is significant.The application of earthworm manure has the most significant effect on improving fruit yield and quality.Compared with ditch application,hole application has a positive impact on soil properties,fruit yield and quality. |
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