| Walnut(Juglans regia)is one of the four major dried fruits in the world,with a long planting history and wide distribution.Walnut is an important oil crop in China because of its delicious taste,rich nutrition high kernel and oil yield rate and health care function.At present,most walnut forests have low economic benefits and high maintenance costs in the early stage of planting.Based on the agroforestry can improve the sustainability of land resources,walnut forest with different management modes is set up in this paper,walnut without weed(NP),walnut preserving weed(HC),walnut intercropping sweet potato(HS),walnut intercropping tobacco(YC).Walnut intercropping soybean(DD)and walnut intercropping pepper(LJ)were used to compare the growth of walnut,production and revenue,soil physicochemical properties and soil microorganisms,in order to reveal and evaluate the effects of ecological and economic of different management on walnut,and to provide a basis for the sustainable management of walnut forest.The main results of this study are as follow:(1)With management pattern of walnut differences in growth.The meters diameter,leaf length,leaf width,leaf thickness,and spring tip of walnut in NP were the lowest,intercropping crops or keep weeds are conducive to the growth of walnut,including intercropping tobacco can increase walnut most annual increment,leaf thickness and water content of meters in diameter,and summer tip point suppression effect is best.Compared with NP,N,P,Mg and Mn contents of walnut leaves in other stands were increased in different degrees.The contents of P,Ca,Mg and Fe in walnut leaves were significantly increased by reserving weeds.The highest Zn and P contents in walnut leaves were YC,and the highest Ca and Cu contents were HS.LJ,due to the high yield of pepper,had more of these nutrients taken away from harvest,and the P,K,Cu and Zn contents in walnut leaves were significantly the lowest.(2)The benefits of tobacco and pepper in intercropping forest crops are considerable,among which pepper has the highest economic benefits.Keep the weeds or intercropping crops in agroforestry models are conducive to walnut production,but if not reasonable nutrition management,understory plants such as LJ due to high production consumes too much soil nutrient,is not conducive to the walnut production,weeds and lots of sweet potato biomass through litter to return part of the nutrition soil,so the HC and HS best for walnut production increases.(3)There are some differences in physical and chemical properties of soil under different management modes.The NP bulk density was significantly higher than that of the other models,and the soil total porosity and capillary porosity were significantly lower than that of t he other models.The other soil physical properties were improved in different degrees.It was found that intercropping sweet potato had the most significant improvement effect on soil physical properties of walnut stand,which was considered by bulk density,soil water content,total soil porosity and capillary porosity.The negative effects of plastic film laying on tobacco and pepper resulted in the soil physical properties being significantly worse than those of other intercropped crops because the soil could not receive rainfall in time and had poor air permeability.The contents of OM,TP,Zn,Mn,AP and AK in NP soil were the lowest,while the contents of OM,TN,TK,Zn,AK and AP in YC plot were the highest.Intercropping pepper may have a certain negative effect on soil alkali-hydrolyzable nitrogen content while the retention of weeds greatly promoted the release of available p from soil.Therefore,proper retention of wasteland in walnut forest can promote the conversion of available nutrients in walnut soil.(4)Intercropping crops or retaining weeds could improve the soil microbial diversity and increase the number of microorganisms at different classification levels,but intercropping tobacco might have negative effects.The dominant bacterial phylum in 6 stands soil include Actinobacteriota,Proteobacteria,Chloroflexi,Acidobacteriota,and the dominant soil fungal phylum include Ascomycota,Mortierellomycota,unclassified＿k＿＿Fungi and Basidiomycota.The abundance of soil microbial phylum species in both NP and YC stands was significantly different from that in other stands,and there was also a significant difference between YC and NP.Redundancy analysis showed that AP,SCP,SMC and TP were the main soil factors that significantly affected the bacterial community structure,while AP and TP were the main soil factors that significantly affected the fungal community structure.In different operating modes of stand in walnut growth,soil physical and chemical properties and structure of soil microbial diversity are differences.Weeding is not conducive to the growth of walnut production and soil environment.Agroforestry can significantly improve the growth and soil environment of walnut,among which the retention of weeds can also improve the growth and soil environment of walnut to a certain extent.Intercropping tobacco was more beneficial to walnut growth,walnut and intercrop yield and economic benefit,soil physical and chemical properties,soil microbial diversity.However,it is necessary to pay attention to the effects of tobacco disease control and plastic film laying.Comprehensive evaluation of YC is the best operation mode of the six treatments in this study,and HS and LJ are also worthy of promotion. |
