Regulating Effects Of Water And Light On Coffea Arabica Under The Shade Cultivation Of Banana Trees In Dry-hot Region

The yield and quality of Coffea arabica cannot be guaranteed due to irrational irrigation and light management in Yunnan Dry-hot Region.In order to investigate the best coupling mode of irrigation and shade cultivation of Coffea arabica in dry-hot region,a field experiment was carried out under different irrigation levels and shade cultivation modes.Different density banana trees were cultivated in coffee plantation,and banana trees provide shade environment for Coffea arabica.The complete combination design was adopted with three levels of irrigation,namely,full irrigation?FI?,light deficit irrigation?DI_L?and severe deficit irrigation?DI_S?,and four modes of shade cultivation,namely,no shade cultivation?the cultivation of Coffea arabica alone,S₀?,light shade cultivation?intercropping four lines of Coffea arabica with a line of banana,S_L?,moderate shade cultivation?intercropping three lines of Coffea arabica with a line of banana,S_M?and severe shade cultivation?intercropping two lines of Coffea arabica with a line of banana,S_S?were designed to study the effects of deficit irrigation on growth,leaf photosynthetic characteristics,water-radiation use,yield,quality,and root soil moisture content of Coffea arabica under banana shade cultivation.In this experiment,the main results are as follows:?1?The plant height,stem diameter,crown width and new shoot length of Coffea arabica increased with the increase of irrigation amount and shade degree.The opening,gap fraction,average leaf dip angle,direct fixed-point factor,indirect fixed-point factor,total fixed-point factor,direct radiation of the crown,indirect radiation of the crown,total radiation of the crown,transmittance and extinction coefficient of Coffea arabica canopy all decreased with the increase of irrigation amount and shade degree,Leaf area index increased with the increase of irrigation amount and shade degree.?2?The net photosynthetic rate?Pn?,transpiration rate?Tr?,stomatal conductance?Gs?,leaf water use efficiency?LWUE?and apparent light energy utilization efficiency of leaves?LRUE?increased with the increase of irrigation amount,while intercellular CO₂ concentration?Ci?and vapor pressure deficit?Vpd?decreased with the increase of irrigation amount.Pn,Tr,Gs,and LWUE tended to increase first and then decrease with the increase of shadow degree,and S_M was the maximum;Ci and Vpd decreased first and then increased with the increase of shade degree,and S_M was the smallest.Apparent light energy utilization efficiency of leaves and photosynthetically active radiation showed a significant negative exponential relationship or accorded with the change of Logistic curve.?3?Compared with the treatment of DI_SS₀,the two-year average yield of dry beans of the other treatments increased by 8.92%⁹6.22%,of which the average yield of FIS_M was the largest.The contents of total sugar,protein,fat,chlorogenic acid and water extracts of Coffea arabica increased with the increase of irrigation amount and shade degree,the contents of caffeine and crude fiber of Coffea arabica decreased with the increase of irrigation amount and shade degree.Principal component analysis and TOPSIS method showed that the comprehensive quality was optimal of Coffea arabica was full irrigation under severe shade cultivation?FIS_S?,next came was full irrigation under moderate shade cultivation?FIS_M?,and the comprehensive quality was poorest of Coffea arabica was severe deficit irrigation under natural light?DI_SS₀?.In conclusion,full irrigation?FI?was the most beneficial to the growth and nutritional quality is the best of Coffea arabica under severe shade cultivation?S_S?,and which could optimize the photosynthetic characteristics of Coffea arabica under moderate shade cultivation?S_M?.In 2016,the yield of FIS_M treatment was the largest.In 2017,the yield of FIS_L and FIS_M treatment were greater.Therefore,considering the comprehensive benefit of high production and superior quality,the suitable combina-tion of irrigation treatment and banana shade cultivation mode for Coffea arabica was full irrigation under moderate shade cultivation?FIS_M?.