| Citrus container seedlings have the advantages of high transplant survival rate,fast growth,and early fruit production.Producing high-quality potted citrus seedlings is crucial for achieving high yields in citrus production.However,current practices in citrus seedling cultivation commonly include the inappropriate use of nitrogen and potassium fertilizers and outdated irrigation techniques.These practices have a severe impact on the quality of container seedlings and impede the healthy development of the citrus industry.To address this,this study aimed to explore suitable nitrogen and potassium fertilization ratios and irrigation fertilization methods for cultivating potted citrus seedlings.The author of this study used two citrus varieties,Citrus sinensis Osbeck cv.Newhall and Citrus reticulata Ehime 28,as materials and conducted a potted experiment in the citrus glass greenhouse of Huazhong Agricultural University.The study investigated the effects of different nitrogen and potassium ratios on citrus growth and soil physical and chemical properties using Newhall.The study set up five nitrogen and potassium ratio treatment groups: 0.2:1(T1),0.6:1(T2),1:1(T3),1.4:1(T4),and 1.8:1(T5),and each treatment group was used as a control.The effects of five irrigation and fertilization methods,including sprinkler irrigation,drip-sprinkler dual-use,drip irrigation,and conventional broadcasting(CK),on the growth of citrus trees,soil physical and chemical properties,and soil microbial community were investigated using Ehime 28.The main research results were summarized as follows:1.Increasing the ratio of nitrogen and potassium fertilization had a positive effect on the growth of citrus trees and enhanced the EC value and soil alkali nitrogen content in potted soils,while simultaneously reducing soil acid phosphatase activity.The specific results are as follows:(1)Increasing the nitrogen and potassium fertilization ratios effectively increased the length and thickness of summer shoots,the length of autumn shoots,as well as the number of root tips in citrus plants,while reducing the number of shoots in summer.However,the impact on the length and thickness of spring shoots,the thickness of autumn shoots,the number of shoots in spring and autumn,root volume,total root length,and average root diameter was relatively small.Specifically,the length of summer shoots in each treatment was observed to be T4 > T5 > T2 > T1 > T3,and the length of summer and autumn shoots in the T4 treatment increased by 38% and 88%,respectively,compared to the T1 treatment,while the number of shoots in summer and autumn decreased by 57% and 43%,respectively.Moreover,the number of root tips of each treatment was observed to be T4 > T5 > T3 > T2 > T1,and the T4 treatment showed a 263% increase in the number of citrus root tips compared to the T1 treatment.(2)Increasing the nitrogen and potassium fertilization ratio significantly increased the EC value and alkali nitrogen content of potted soils,while reducing soil acid phosphatase activity.However,the impact on soil p H,organic matter,available phosphorus,available potassium,soil sucrase,soil urease,and soil alkaline phosphatase was relatively small.Specifically,the T5 treatment increased the EC value and alkali nitrogen content of the soil by 52% and 30%,respectively,compared to the T1 treatment,and reduced acid phosphatase activity by 29%.2.Compared to conventional broadcasting,the application of irrigation and fertiliza tion integration can enhance the growth of citrus trees and increase the EC value,soil moi sture content,soil alkali nitrogen content,soil organic matter content,and soil urease activ ity in potted soils.In contrast,the effects of watering treatments were not significant.The specific results are as follows:(1)Irrigation and fertilization integration significantly boos ted the photosynthetic rate of summer shoot leaves,the length and thickness of spring sho ots,the number of shoots in summer and autumn,total root length,root volume,and root t ips of citrus plants.Meanwhile,the effects on the number of shoots in spring,the length a nd thickness of summer and autumn shoots and the average root diameter were relatively minor.The number of autumn shoots in each treatment was ranked as sprinkler irrigation >drip irrigation > drip-sprinkler combination > conventional broadcasting > watering.The drip and sprinkler treatments increased the number of autumn shoots by 6.33 and 5.33 per plant,respectively,compared to the conventional broadcasting treatment,with an increas e in root tips of 85% and 56%,respectively.(2)Irrigation and fertilization integration sign ificantly increased the soil porosity,soil moisture content,and soil urease activity of potte d soils,while reducing soil bulk density.The impact on soil phosphatase,soil sucrase,ava ilable phosphorus and potassium was relatively minor,and the effects of watering treatme nts were not significant.Drip irrigation had the most significant effect,increasing the soil alkali nitrogen and soil organic matter content by 62% and 85%,respectively,compared t o conventional broadcasting.(3)There was no significant difference in soil microbial dive rsity among different irrigation and fertilization treatments,but the species composition of soil microorganisms varied.The relative abundance of four phyla had significant differen ces,namely Proteobacteria,Actinobacteria,Gemmatimonadetes,and Acidobacteria.Sprin kler irrigation and drip irrigation significantly increased the relative abundance of Acidob acteri-a in the soil.In summary,a nitrogen-potassium ratio of 1.4:1 was found to be effective in promoting the growth of potted citrus trees while also increasing soil nutrient content to some extent.Drip irrigation was found to be effective in promoting tree growth,improving soil physical and chemical properties,and increasing soil nutrient content.These results provided a theoretical basis for selecting appropriate fertilization and irrigation strategies for cultivating potted citrus seedlings in practical production. |
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