Effect Of Phosphorus Supply Level And Method On Pitaya Root Morphology And Nutrient Absorption

Pitaya（Hylocereus polyrhizus）is a shallow root crop with high nutritional value and commercial value.In recent years,the pitaya planting area has increased year by year,but excessive application of phosphate fertilizer is common in the planting process.This project uses research and pot/root box simulation research methods,study on the effect of phosphorus supply level(0 mg kg^-1,25 mg kg^-1,50 mg kg^-1,100 mg kg^-1,200 mg kg^-1)and supply method（localized phosphorus supply and uniform phosphorus supply）on the root morphology and nutrient absorption of“Ruan Zhi”pitaya.Provide basis for scientific application of phosphate fertilizer in pitaya production.The main results were as follows:1.The results of the survey of 38 pitaya planting enterprises show that:37%of planting companies have pitaya planting density between 1.5 and 2.25 million plants hm^-2;79%of growers planting“red 2”pitaya varieties;Changes in the magnitude of pitaya garden soil p H value of 4.02～7.53,mean 6.19;The soil organic matter content varies from 4.03～46.69 g kg^-1,with an average value of 15.57 g kg^-1;Soil available nitrogen content variation in soil nitrogen content in the range of 14.20～124.07 mg kg^-1,71.1%of the pitaya orchards have a lack of soil alkaline nitrogen content;The soil available phosphorus content varies from58.73～457.57 mg kg^-1,with an average value of 252.92 mg kg^-1,available phosphorus content is 6.3 times greater than the abundance level,the content of available phosphorus in the soil of all pitaya plantations exceeds the abundance level.The soil available potassium content varied from 56.72～694.61 mg kg^-1,with an average value of 240.88 mg kg^-1.2.38 pitaya plantation companies to fertilize an investigation on display that the application rate of pitaya organic fertilizer was 45～75 t ha^-1,applied twice in march to april and september to october each year.The average fertilizer application amount N is 550～750kg ha^-1,P₂O₅ is 1000～1200 kg ha^-1,and K₂O is 1200～1400 kg ha^-1,apply water and fertilizer together every 5～7 days.There is little difference in the amount and method of fertilizer application in each plantation.The application rate of phosphate fertilizer is much higher than that of nitrogen,which is basically the same as that of potassium fertilizer.The input amount of pure phosphorus in the production of pitaya is 8～26 times and 5～23 times higher than the recommended amount of pure phosphorus for food crops and cash crops,respectively.3.During the growth period of pitaya,when the phosphorus supply level reaches 200mg kg^-1,the growth and development of the root system is inhibited.In the seedling stage,the phosphorus supply level is 25～50 mg kg^-1,and the total root length of pitaya root system is the largest and fine roots（<0.3 mm）account for the largest proportion,it is 1068.8～1069.6cm.It shows that the appropriate level of phosphorus has a great influence on the root morphology of pitaya.4.Phosphorus supply level has little effect on the phosphorus uptake of the aboveground part of pitaya seedlings,but after the pitaya enters the vegetative growth period（I and II）,phosphorus uptake in the ground increases firstly and then stabilizes with the increase of phosphorus supply level;Phosphate levels only 25～50 mg kg^-1 promotes the absorption of nitrogen on pitaya seedling,nitrogen uptake is 365.6～375.4 mg plant^-1.If the phosphorus level is too low or too high,it is not conducive to the absorption of nitrogen by pitaya.During the whole test period,the phosphorus supply level had no effect on the potassium uptake of pitaya above ground.5.Root box simulation test shows that local phosphorus supply（soil layer 8～16 cm）increases the total root length,root surface area,total root volume,root mass ratio,root shoot ratio and fine root（<0.3 mm）ratio of pitaya seedlings compared with uniform phosphorus supply（uniform application across the entire soil layer）.The total root length,root surface area,and total root volume of the local phosphorus supply are 887.3 cm,186.7 cm²,and 3.1m³,respectively.By relevance show that different phosphorus supply methods mainly affect the total root length and root surface area of pitaya seedlings,and then affect the pitaya absorption of nitrogen,phosphorus,and potassium,thereby affecting plant biomass.It shows that concentrated root layer application of phosphate fertilizer can significantly promote the development of pitaya root system and nutrient absorptionIn summary,different phosphorus levels significantly affected the total root length,root surface area and the proportion of different root diameters of pitaya seedlings,and indirectly affected the nitrogen absorption of pitaya.Among them,when the phosphorus supply level is 25～50 mg kg^-1,the growth and development of the root system of pitaya seedlings is the best,which can increase the absorption and accumulation of nitrogen and increase the biomass;When the phosphorus supply level is greater than 200 mg kg^-1,pitaya root system development is inhibited.Local supply of phosphorus can promote pitaya root growth,increase the total root length and root surface area of pitaya seedlings,optimize root growth and distribution,and improve the ability of pitaya seedlings to obtain heterogeneous phosphorus nutrients.