Effects Of Irrigation Amount And Shade On Growth And Physiological Characteristics Of Coffee Arabica

Coffee arabica mainly distributes in dry-hot valley and humid tropics. According with the problems of drought and water shortage, serious contradictory of water and heat, poor soil water storage and keeping moisture, agricultural production has been seriously affected. Light directly affects the activities of photosynthetic enzymes in the carbon cycle for photosynthesis and also affects plant growth environment, such as temperature, humidity which indirectly influences the plant’s physiological and biochemical processes. Based on this point, this thesis mainly studied the effects of different irrigation and shade on growth and physiological characteristics. The project seek for efficient mechanism of irrigation and shade on coffee arabica, perfected theory of efficiency use of water and light on coffee arabica.This study took coffee arabica as an example, adopted pot and plot experiment which were conducted in the plastic shed in Faculty of modern Agricultural Engineering, Kunming University of Science and Technology from April,2014 to July, 2015 and from May to December 2015, respectively. Pot experiment were set three water treatment:High water WH (65%～75%)θF, Medium water WM (55%～65%)θF, Low water WL (45%～55%)θf and three shade treatment:No shade S0 (natural light), Light shade S1 (50% of natural light), Moderate shade S2 (30% of natural light). The primary research of pot experiment concentrated on the effect of irrigation and shade on growth characteristics, physiological property, water and shade use efficiency and dry mass accumulation and distribution of coffee arabica. The plot experiment was designed as four water treatment:Sufficient water Ws (75%～85%)θF, High water WH (65%～75%)θF, Medium water WM (55%～65%)θF, Low water WL(45%～55%)θF and four shade treatment:No shade So (natural light), Light shade S1 (50% of natural light), Moderate shade S2 (30% of natural light), Heavy shade S3(18% of natural light). The primary research of plot experiment concentrated on the effect of irrigation and shade on growth characteristics, photosynthetic characteristics, leaf water potential and water use efficiency of coffee arabica. The main results of this study as follows:(1) Under natural shade treatment, increasing irrigation could increase plant growth index of coffee arabica significantly in pot and plot experiment. After shade treatment, increasing irrigation adequately could promote the growth index (plant height, stem diameter, crown width and new shoot length) of coffee arabica significantly in pot experiment, however it showed first increased then decreased by increasing irrigation under other shade treatment in plot experiment. It was not suitable to the development of various morphological index in low water treatment under no shade condition. The combination of high water and light shade treatment was beneficial to growth index of coffee arabica.(2) The effect of shade on chlorophyll and carotenoid content of coffee Arabica was greater than that of irrigation, and chlorophyll and carotenoid content with shade treatment was higher than that in no shade treatment significantly.it indicated that increasing irrigation was beneficial to synthesis of chlorophyll and carotenoids under no shade and light shade. The change law of leaf water potential in pot experiment was basically identical to that of plot experiment which had positive correlation with irrigation and shade treatment significantly.(3) The diurnal variation of net photosynthetic rate, transpiration rate and stomatal conductance all showed double peak type under different irrigation amount and shade conditions. Compared with no shade, increasing degree of shading, it increased net photosynthetic rate and stomatal conductance by 12.36%～57.74% and 4.56%～42.66%, respectively, but reduced daily transportation rate significantly. Compared with low water, increasing irrigation amount substantially increased average stomatal conductance and net photosynthetic rate. Compared with low water, increasing irrigation amount increased the maximum net photosynthetic rate by 26.61%～185.27% under no and light shade, but increasing irrigation amount, the maximum net photosynthetic rate increased firstly and then decreased under moderate shade. Compared with no shade, increasing shading degree increased the maximum net photosynthetic rate by 10.73%～103.73%.(4) Under the same soil moisture treatment,compared with no shade treatment,it increased the net photosynthetic rate with light shade treatment by 2.91%～26.02% at 10:00,0.86%～89.91% at 12:00,9.96%～71.39% at 14:00 and 0.76%～23.94% at 16:00 respectively, while under moderate and heavy shade condition, it decreased the net photosyntheti rate by 2.43%～52.65%,58%-46.75%,13.75%-33.97and 2.71%～14.08% respectively at four interval. Transportation rate significantly decreased after shade treatment, however the difference of shade treatment was not significant under other irrigation treatment.(5) Compared with the low water treatment, increasing irrigation could increase total dry mass accumulation,water consumption and water use efficiency of coffee arabica by 1.08%～21.91%,43.61%～72.37% and 3.31%～31.06%, respectively. Compared with no shade treatment, the total dry mass accumulation and water use efficiency first increased then decreased by increasing shade intensity and those with shade shade were maximum. Daily evapotranspiration of coffee arabica seedling decreased with the increase of shade significantly, while increased with the increase of irrigation significantly.After comparative analysis of plot and pot experiment, and comprehensive consideration of growth, physiological characteristics, dry mass accumulation, water use efficiency and other factors of pot and plot experiment, it proved optimal water and nitrogen supply mode of coffee arabica:High irrigation (65%～75%)θF with light shade(50% of natural shade).