| In recent years,in order to improve the comprehensive economic benefits of orchard,the cultivation mode of Alfalfa intercropping in jujube orchards has been gradually popularized and applied in southern Xinjiang.Reasonable planting spacing can not only avoid the fierce competition of water and nutrients among plants,but also improve the quality of soil,promote the growth of plants and increase the yield.Therefore,the selection of the best planting spacing could guide the management of jujube-alfalfa intercropping system and provide the basis for the standardization of jujube-alfalfa intercropping technology.The experiment was conducted in the Tarim University from 2019 to 2020.Three kinds of intercropping spacing?0.55 m,0.85 m,1.15m?were designed in this experiment.The effects of different spacing on the quantity of soil microorganism,the physical and chemical properties of soil,the biological properties and the yield of alfalfa in jujube and alfalfa intercropping system were studied.The results are as follows:1.In the intercropping system of jujube and alfalfa,the number of soil microorganisms showed a change rule of"increase first and then decrease"with the development of the period,the bacteria reached the peak on June 19,fungi and actinomycetes reached the peak on July 21.Compared with monoculture,jujube and alfalfa intercropping could significantly increase the number of soil microorganisms.And the effect of different spacing on the number of soil microorganisms reached a significant or extremely significant level.The average number of bacteria,fungi and actinomycetes was the highest when the spacing was 0.55 m.2.In the intercropping system of jujube and alfalfa,the soil chemical properties changed with the development of time.The soil pH,the content of alkali hydrolyzed nitrogen and the content of available phosphorus showed the change rule of"decrease first and then increase",and the content of available potassium showed the change rule of"increase first and then decrease".The total value of soil pH showed the change rule of intercropping<monoculture,and the content of available phosphorus and potassium in the soil showed that intercropping with jujube and alfalfa could effectively reduce soil pH and significantly increase the content of soil available phosphorus and potassium.The total content of soil alkali hydrolyzed nitrogen showed the change rule of alfalfa monoculture>intercropping>jujube monoculture,which indicated that compared with jujube monoculture,jujube and alfalfa intercropping could significantly increase the content of soil alkali hydrolyzed nitrogen,but compared with alfalfa monoculture,the content of alkali hydrolyzed nitrogen decreased.When the spacing is 0.55 m,the average value of soil pH is the lowest?7.62?,which is 2.31%and 2.06%lower than that of monoculture,and the content of soil available potassium is the highest(261.94 mg·kg-1).When the spacing is 0.85 m,the content of soil available nitrogen(90.38 mg·kg-1)and phosphorus(43.10 mg·kg-1)is the highest.3.In the intercropping system of jujube and alfalfa,the physical properties of soil change with the development of time.The average water content of soil shows the trend of"decrease,then increase,and decrease".It is the lowest value in September,and the soil bulk density shows the change rule of"increase first,then decrease".It reaches the highest value in June.Compared with the jujube monoculture,jujube and alfalfa intercropping can significantly improve the average water content of soil.When the spacing is 0.55 m,the average water content of the soil is the highest,the bulk density is the largest,and the soil condition is the best.4.In the intercropping system of jujube and alfalfa,comparing the biological characteristics of alfalfa under different spacing,the first and second stubble showed the best performance at 0.85 m spacing,and showed the potential of high yield.The average growth rate of alfalfa in the first stubble?1.56 cm/d?was higher than that in the second stubble?0.59 cm/d?.In the whole growth period,the growth rate of M3 treatment was fast,and that of M1 was slow.5.In the intercropping system,when the spacing is 0.85 m,the annual yield of alfalfa is the highest(40820.00kg·hm-2).The effect of different treatments on the yield of jujube is not significant;the land equivalent ratio?LER?of M1 and M2 is above 1,which can increase the yield when compared with monoculture.When the spacing is 0.85 m,the LER is the highest?1.32?,the yield increase rate is the highest.6.Correlation analysis showed that soil pH was negatively correlated with soil available phosphorus and potassium,and negatively correlated with soil fungi.The soil available phosphorus was positively correlated with soil fungi.The soil available potassium was positively correlated with soil water content and soil fungi number.The results showed that the Jujube and alfalfa Intercropping system could significantly increase the number of soil microorganisms,increase the content of soil moisture and nutrients,effectively reduce the soil bulk density and soil pH,and also increase the yield.When the spacing is 0.55 m,the soil was loose and soft,with good permeability and strong capacity of water storage and moisture conservation,the number of soil microorganisms was abundant,which improved the soil pH obviously.When the spacing is 0.85 m,the soil nutrient content was the highest,the biological characteristics of alfalfa was the best,and the yield was the highest. |
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