Effects Of Different Spacing On Soil Aggregates And Nutrients In Alfalfa Intercropping System Of Jujube

Fruit-grass intercropping is beneficial to improve soil structure,optimize the distribution of soil aggregates of different grain sizes,and increase crop yield.However,the effects of fruit-grass intercropping on soil aggregates and nutrients in soil aggregates are still controversial.To explore the soil aggregate under different fruit grass interplanting configuration and its change rule of the nutrients are in jujube orchard soil as the research object,this study gardening experimental station in 2019 ～ 2020 in tarim university,jujube/alfalfa experiment set of three methods for spacing configuration,M1(0.5 m),respectively,the M2(1 m),the M3(1.5 m),at the s CK1 e time in Chinese alfalfa was(CK1)and Jujube monoculture(CK2)as the control.In order to reveal the change characteristics and response mechanism of soil aggregates and nutrients under jujube/alfalfa intercropping conditions.The results are as follows:1.With the increase of soil depth,the content of large aggregates with mechanical stability in each treatment showed a changing law of "first decreasing and then increasing",while the content of large aggregates with water stability showed a trend of "gradually decreasing" with the increase of soil depth.Compared with jujube monocropping,both fruit-grass intercropping and alfalfa monocropping could increase the contents of soil macroaggregates with mechanical stability/water stability.Therefore,alfalfa mulching could effectively increase the contents of soil macroaggregates using three-year-old alfalfa as the base.M2 has the strongest ability to improve mechanically stable aggregates,and the content of mechanically stable large aggregates is the highest.M1 has the highest content of water-stable aggregates and the lowest failure rate of aggregates,indicating that compared with mechanically stable aggregates,water-stable aggregates have a greater influence on the structural stability of soil aggregates.2.Soil organic carbon was mainly concentrated in <0.25 mm,025-1mm and >2mm aggregates,of which <0.25 mm aggregates accounted for the highest organic carbon content,and1-2mm aggregates accounted for the lowest organic carbon content.The organic carbon content of soil aggregates under different treatments showed that M1>M2>CK1>M3>CK2 in the order.Compared with the first crop,the organic carbon content of 0.25-1mm aggregates in the second crop was increased to different degrees in each of the grass treatments,and M1>M2>CK1>M3>CK2 respectively.Data of the two crops showed that M1 had the highest comprehensive organic carbon content in soil aggregates,so M1 was the most conducive to the increase of soil aggregate organic carbon content.3.The soil water content of all treatments showed a change pattern of "first rising,then falling and then rising".The soil moisture content of M1 was the highest and that of M3 was the lowest on May 15.The soil water content of all treatments reached the peak on July 30.The soil water content on August 15 was the lowest CK1 ong the four periods,and there was no significant difference between M1,M2 and jujube monoculture,while M3 and alfalfa monoculture decreased significantly.On October 30,the soil water content of all the treatments showed a rising trend,and all the grass treatments were higher than that of jujube monoculture,while M3 was at the lowest level in the grass treatment for a long time.The average soil water content of each treatment was14.68%(M1),14.25%(M2),10.85%(M3),12.7%(CK1)and 11.15%(CK2),respectively.Therefore,in general,the soil water content of M1 was the highest.The soil bulk density of each treatment reached the highest on May 15 and the lowest on October 30.The soil bulk density of M1 was the lowest on May 15.On July 30,soil bulk density under grass treatment decreased significantly,but there was no significant change in jujube monocropping.Soil bulk density under all grass treatments was significantly lower than that under jujube monocropping.The soil bulk density of grass treatment on August 15 increased slightly,and the M2 soil bulk density was the lowest.Soil bulk density decreased on October 30,all grass treatments were significantly lower than jujube monoculture,and soil bulk density of M1 was the lowest and significantly lower than that of M3 and clear tillage.M1 had the lowest soil bulk density in three periods,and was second only to M2 on August 15,indicating that M1 had the best effect on improving soil porosity.4.This study showed that M2 fresh grass yield was the highest and significantly higher than other treatments.M3 is the lowest yield.Compared with jujube monoculture,all grass treatments could effectively improve the structure of soil aggregates and enhance soil fertility.M2 significantly increased the content of mechanical stability/water stability large aggregates(>0.25mm),decreased the content of micro aggregates(<0.25mm),increased the contents of organic carbon,total nitrogen,total phosphorus and total potassium in aggregates of each grain size,and significantly increased soil water content.Although the improvement range of M2 on soil water stability large aggregate content and aggregate organic carbon content was slightly lower than that of M1,the alfalfa yield of M2 was significantly higher than that of M1.M2 reached the balance between optimizing soil structure and ensuring crop yield,so M2 was the most appropriate allocation of alfalfa spacing.