Effects Of Irrigation Amount On Growth And Soil Microecological Environment Of Coffea Arabica Young Tree Under The Shade Of Castor

Coffea arabica is one of the special economic crops in Yunnan Province.Its planting area and production account for more than 99%of the whole country,but it is often affected by seasonal drought and soil water deficit.At the same time,Coffea arabica has the growth habit of shading,and moderate shade cultivation can provide a suitable growth and development environment for Coffea arabica.The object was to explore suitable mode of water and shade cultivation for Coffea arabica,using four levels of water,i.e.,sufficient irrigation?I₀,1.2Ep?,high water?I₁,1.0Ep?,medium water?I₂,0.8Ep?,and low water?I₃,0.6Ep?,respectively,and three shade cultivation modes,i.e.,no shade cultivation?S₀,only coffee?,light shade cultivation?S₁,a row of coffee intercropping a line castor?and severe shade cultivation?S₂,a row of coffee intercropping two lines castor?.The effects of different amount on growth,photosynthetic characteristics,canopy structure,soil moisture,temperature,nutrient and soil microbial quantity of Coffea arabica were studied by plot experiment.The main results of this study as follows:?1?Increasing irrigation amount could significantly increase plant height,stem diameter,crown width,number of leaves and dry matter quality of Coffea arabica;light shade cultivation mode promoted the growth and dry matter accumulation of Coffea arabica,and severe shade cultivation mode inhibited growth.High water and light shade cultivation mode coupling promoted growth and increased dry matter accumulation,and at the same time.?2?Leaf area index improved by 16.62%²7.70%with the increase of irrigation amount,while gap fraction,openness,the total fixed-point factor and total radiation decreased by 8.53%¹4.85%,8.86%¹6.10%,13.85%²5.16%and 17.44%²5.53%.Leaf area index increased first and then decreased with the increase of shading degree,S₁ increased by 10.17%,S₂ decreased by 5.00%.?3?Under the same shade cultivation mode,increasing irrigation enhanced daily net photosynthetic rate?Pn?,transpiration rate?Tr?,stomatal conductance?Ci?,water use efficiency?LWUE?and radiation use efficiency?LLUE?of Coffea arabica leaf by 7.62%¹7.39%,4.19%¹5.04%,17.89%⁴8.49%,0.42%⁵.20%and 10.57%¹5.06%.Under the same irrigation level,light shade cultivation mode increased coffee leaf daily Pn,Tr,Ci and LWUE by 11.34%,8.01%,11.99%and 2.17%,respectively,while severe shade cultivation decreased by 10.21%,6.13%,6.37%and 4.49%,respectively.Leaf radiation use efficiency increased by 60.44%and 89.43%with the increase of shade degree.Considering the interaction of irrigation and shade cultivation,daily Pn?Tr?Ci and LWUE of I₁S₁ were the maximum.Compared with I₃S₀,I₁S₁increased leaf water use efficiency by 6.07%.?4?Under the same shade cultivation mode,increasing irrigation amount increased bacteria,fungi,actinomyces of Coffea arabica root zone soil of spring,summer and autumn by 26.84%⁷6.03%,23.37%⁵0.60%,6.74%²1.56%and65.28%⁷5.98%,43.83%⁷9.19%,20.72%³6.15%and 107.79%¹95.40%,13.08%³8.31%,24.23%⁴0.93%.Compared with S₀,bacteria,fungi,actinomycetes of S₁increased by 7.24%²3.19%,13.40%³0.77%,4.68%¹5.12%,while bacteria and actinomycetes of S₂ reduced 3.09%²0.17%and 10.55%¹6.60%respectively,and fungi increased by 26.66%⁶3.99%.Compared with I₃S₀,the soil microbial quantity of I₁S₁ significantly increased.Through the test,the effects of different irrigation amount on growth characteristics,canopy structure,photosynthetic characteristics,soil microecological environment of Coffea arabica under shade cultivation mode was analysed,it proved the optimal irrigation amount and shade cultivation mode for Coffea arabica young tree was the combination of high water and light shade cultivation?I₁S₁?.