Effects Of Irrigation And Fertilization Methods On Soil Properties And Tea Tree Growth

Water and fertilizer integration is currently the fastest developing new irrigation and fertilization method,in which sprinkler irrigation and drip irrigation are the main methods,with nutrients are supplied with water,which can precisely regulate water and nutrient supply,so as to achieve the purpose of water and fertilizer saving.At present,there are many studies on the distribution characteristics,mobility and spatial variability of nitrogen,phosphorus and potassium in soil by drip and sprinkler irrigation fertilization methods,while there are few comparative studies on different fertilization methods of drip and sprinkler irrigation,and few studies on the effect of irrigation fertilization methods on tea tree growth.Therefore,it is of great theoretical value and practical significance to study the effects of drip and sprinkler irrigation on soil properties and the root growth of tea seedlings.In this study,soil culture experiment was combined with pot experiment,and three fertilization methods of soil application,spray application and drip application were used to investigate the spatial variation of soil nutrient content,enzyme activity and microbial biomass in response to drip and sprinkler irrigation fertilization methods,so as to explore the spatial differences of soil nutrients between drip and sprinkler irrigation fertilization methods and provide a theoretical basis for the selection of different fertilization methods for drip and sprinkler irrigation.The pot experiment of tea seedings was set up to further investigate the effects of soil application,spray application and drip application on the electrical conductivity,total nitrogen,ammonium nitrogen,nitrate nitrogen and root growth of tea seedlings under the condition of planting tea seedlings,in order to provide scientific and theoretical basis for the selection of fertilization methods and the growth and development of tea trees.The results of the experiment are as follows:(1)The soil culture experiment was carried out with three treatments: soil application(SA),spray application(FA)and drip application(DA),and the soil was divided into three zones,5 cm/0-10 cm(5 H,10 V),5 cm/10-20 cm(5 H,20 V)and 10cm/0-10 cm(10 H,10 V),according to the horizontal and vertical distance from the center of the surface of the soil culture.The samples were taken after 15 d,30d,45 d and60 d of incubation to observe p H,conductivity,nutrients and biological properties in three zones.The results showed that there were no significant differences in the spatial parameters of each soil layer between FA and SA with increasing incubation time and fertilizer accumulation in the different soil zones.Compared with FA,DA significantly increased the soil conductivity,p H,alkali-hydrolyzable nitrogen,available potassium and available phosphorus contents by 35.6%,30.7%,40.6%,34.3% and 74.8%,respectively(P<0.05),in the range of 0～10 cm horizontal from the center point and 5 cm vertical from the center point.Compared with FA,bacteria,fungi and actinomycete of DA also increased by 174.6%,167.0% and 289.0%,respectively(P<0.05).A high value area of microdomain nutrient aggregation was formed in this area,but compared with FA,the urease,acid phosphatase activity and microbial C and N contents DA decreased by42.5%,31.4%,77.5%,and 27.8% after incubation for 60 d.This indicates that drip irrigation fertilization could rapidly increase soil nutrient content in the microdomain region,but the increase of nutrient content also decreased urease,acid phosphatase activity and microbial C and N content.(2)The root growth and morphology of tea seedlings were observed in pot experiment,which included two nitrogen application levels of high nitrogen and low nitrogen,and three fertilization methods of soil application,spray application and drip application.The results showed that there was no significant difference between SA and FA treatment in different nitrogen application levels and fertilization methods.Compared with FA,DA had significant effects on soil conductivity,total nitrogen,ammonium nitrogen and nitrate nitrogen in different fertilization methods after the second topdressing and cultivation for 180 d(P<0.05).Under high nitrogen level,the conductivity,total nitrogen,ammonium nitrogen and nitrate nitrogen contents of DA increased 122.7%,19.6%,49.2% and 100.7% compared with FA,respectively.Under low nitrogen level,the conductivity,total nitrogen,ammonium nitrogen and nitrate nitrogen contents of DA increased by 95.6%,15.8%,45.6% and 69.1% compared with FA,respectively.The effects of different nitrogen application levels on soil parameters were higher at high nitrogen level than at low nitrogen level.The effect of fertilization on root growth of tea tree was obvious(P<0.05).The overall root growth was FA > SA >DA.Compared with DA,FA increased the fresh weight,total length,root volume,root tip number,branch number and crossover number by 140.0%,290.6%,295.6%,249.3%,382.7% and 154.1%,respectively.Under the conditions of low nitrogen level,the fresh weight of roots,total root length,root volume,number of root tips,number of branches and number of crosses of tea seedlings with FA increased by 173.0%,196.1%,263.3%,180.2 %,163.7% and 156.5%,respectively,compared with DA.There was no significant effect of different nitrogen levels on the root growth and morphology of tea seedlings.In conclusion,fertilization methods had significant effects on soil nutrient spatial distribution,soil biological characteristics and root growth of tea seedlings.Compared with SA and FA,DA treatment significantly increased the conductivity,nutrient content and microbial population in the microdomain area(5 H,10 V)of the central point of the drip head of(P<0.05),and there was a significant microdomain clustering effect,but the urease and acid phosphatase activities decreased significantly(P<0.05).DA significantly inhibited the root growth of tea seedlings compared to FA and SA(P<0.05),FA did not significantly increase the nutrient content of the soil,but significantly promoted the root growth and morphological establishment of tea seedlings(P<0.05);DA and FA need to match reasonable irrigation and fertilization system to strengthen their effects of water-saving,fertilizer-saving and quality improvement.