Comparative Study On The Effects Of Different Forms Of Nitrogen Combined With Phosphorus Fertilizer On Soil Characteristics And Tea Tree Growth In Southern Shaanxi

Efficient nutrient utilization plays an important role in tea yield and quality assurance.As the world’s population continues to grow,natural resources are depleted,global warming and other major problems appear and intensify,countries have formulated the goal of "carbon peak",and green and sustainable development that respects ecological laws has become the mainstream.Although the application of a large amount of chemical fertilizer promoted the increase of tea yield in the short term,it brought many negative effects,not only caused acidification in large tea plantations in southern China,reduced fertilizer utilization rate,but also caused the increase of production costs and other problems.Stored nitrogen is an important source during the growth and development of spring tea and plays an important role in the yield and quality of spring tea.It is very important to improve the nitrogen utilization efficiency of tea plant and obtain higher yield and better quality under the limited nutrient condition in Jiangbei tea garden.It is of great significance to select the application technology of nitrogen fertilizer suitable for representative tea garden soil and tea tree varieties in southern Shaanxi province,and demonstrate "fertilization based on location and species",which is of great significance to solve the practical problems in tea production process and promote the high-quality development of tea industry.In view of the blindness of base fertilizer application,especially phosphate fertilizer,and blind nitrogen fertilizer selection in response to the "double carbon" target in autumn application in southern Shaanxi province,field test was used in this experiment.The application of two kinds of phosphate fertilizer(monoammonium phosphate and diammonium phosphate)with different acid and base properties and their combination with different forms of nitrogen fertilizer(ammonium nitrogen(NH4+-N),nitrate nitrogen(NO3--N)and amide nitrogen(urea))on the gain and improvement of soil properties and tea green quality;Combined with soil physical and chemical properties,tea tree growth and development,physiological and ecological,tea quality and resistance indexes,a comprehensive evaluation of different fertilization treatment schemes was made to obtain the best fertilization scheme,which laid the data foundation for large-scale popularization and application in the later period.The test results show that:1.The effects of different nitrogen forms on soil physicochemical properties were varied.The effect of different fertilization treatments on soil varies with different soil layers.Fertilization treatment of Y-NN(mono-ammonium nitrogen: nitrate nitrogen =3:1)and E-NN(diamonium-ammonium nitrogen: nitrate nitrogen =3:1)in 0-20 cm soil layer could significantly increase soil water content.The soil bulk density in 0-20 cm soil layer and20-40 cm soil layer was significantly increased under Y-AN(mono-ammonium nitrogen)and E-UN(diammonium-urea)fertilization treatment compared with the control.The total soil porosity of the two soil layers treated with E-UN fertilization decreased significantly.The p H of 0-20 cm and 20-40 cm soil layers was significantly decreased compared with the control,and Y-UN(monoammonium urea)was the most significant effect.Urease activity of E-UN fertilization in 0-20 cm soil layer increased significantly.Fertilization treatment can increase soil water content,decrease soil p H,and increase urease activity in shallow soil.2.Different forms of nitrogen had different effects on the growth and physiology of tea tree.Compared with the control group,fertilization treatment could significantly increase plant height,shoot length,shoot density,1 bud 3 leaf internode length,1 bud 6 leaf internode length,100 bud weight,leaf vein logarithm and total nitrogen content of tea tree,and significantly promote the growth and development of tea tree.Fertilization treatment Y-UN(monoammonium urea)had the most obvious effect on the growth and development of tea tree.Fertilization treatment could promote the synthesis of chlorophyll in leaves,but there were differences due to different leaf positions.Y-UN combined treatment could significantly increase the content of chlorophyll in leaves 2,3 and 4,and carotenoid content in leaves 3 and 4.Fertilization treatment could significantly increase leaf photosynthesis.Y-UN could increase leaf net photosynthetic rate(Pn),reduce transpiration rate,improve water use efficiency and increase photosynthetic nitrogen use efficiency in all fertilization treatments.3.Different forms of nitrogen had effects on the improvement of tea quality and resistance.Fertilization treatment increased the amino acid content of tea leaves and reduced the caffeine content of tea leaves.The effect on the tea polysaccharide content was not easy to observe,but could significantly reduce the content of tea polyphenols and increase the dry matter content of tea leaves.Fertilization treatment could significantly increase the stress resistance of tea plants.The leaf thickness,stomatal density,palisade tissue thickness and vascular bundle area of Y-UN(uni-ammonia urea)treatment increased significantly,stomatal opening decreased and electrical conductivity decreased,except for spongy tissue thickness,vein island and cell layer number did not change.Combined with the comprehensive evaluation of various indexes,the application of mono-ammonium phosphate plus urea base fertilizer and topdressing treatment has significant effects on the improvement of soil properties,growth and development of tea trees,quality and resistance of tea trees in southern Shaanxi province,and achieves the purpose of cost saving.