Abstract:Arabica coffee has the habit of shading cultivation and its growth often is inhibited by soil drought stress. Shade changes micro-climate of coffee growth and further affects photosynthetic characteristics and water consumption. The object was to explore suitable management mode of water and light, using three levels of deficit irrigation, i. e., light deficit irrigation (DIL, (65%~75%) field capacity), medium deficit irrigation (DIM, (55%~65%) field capacity) and severe deficit irrigation (DIS, (45%~55%) field capacity), respectively, and three levels of shade,i.e., no shade (S0, natural light), light shade (SL, 50% natural light) and severe shade (SS, 30% natural light). The effect of deficit irrigation and shading levels on daily mean photosynthetic characteristics, growth and water—radiation use efficiency of arabica coffee was studied by pot experiments, and regression model was established under different deficit irrigation and shade levels. The results showed that compared with DIL, DIS reduced coffee leaf net photosynthetic rate, stomatal conductance and radiation use efficiency by 17.61%, 22.99% and 27.43%, respectively, and reduced the total dry mass by 6.29%, but DIM had no significant effects on leaf net photosynthetic rate, stomatal conductance, radiation use efficiency and total dry mass. Leaf radiation use efficiency of S0 was the lowest, SL was the second and SS was the highest. S0 or SS inhibited net leaf photosynthetic rate and water use efficiency, and SL increased dry mass by 11.14%. Compared with DILS0, shading under deficit irrigation reduced leaf transpiration rate but increased light use efficiency significantly. Leaf radiation use efficiency showed a significant exponential relation with photosynthetically active radiation. Irrigation water use efficiency was increased first and then decreased with the increase of water deficit level and shading degree. On the basis of high dry mass accumulation and water use efficiency, the suitable mode of water and light management of arabica coffee was the combination of light deficit irrigation and light shade (DILSL). The study results can provide scientific basis for irrigation and shade management of arabica coffee. In addition, this experiment was only focused on coffee growth, dry matter and water—radiation use, and yield, quality and flavor were not involved. Further systematic discussion of arabica coffee was needed under different irrigation and shade conditions.
