| Coffee arabica is semi-shaded crops with liking cool and humid environment,and too high solar radiation can cause light inhibition.As the tropical dominant agricultural products in Yunnan Province,the planting area and yield accounts for over 90%of the country,but the yield and quality are not guaranteed for soil drought,lack of nutrition and excessive light.Based on the above background,this study took coffee arabica as test materials,adopted two complete combination test.Test one(pot experiment)was set three nitrogen levels of no nitrogen N0,medium nitrogen Ni,high nitrogen N2 and three shade levels of no shade S0,moderate shade S1,heavy shade S2.Test two(plot experiment)was designed as three irrigation levels of low water W0,medium water W1,high water W2 and three shade levels of no shade SC0,moderate shade SC1,heavy shade SC2.This study concentrated on the effect of irrigation and nitrogen on growth and photosynthetic characteristics under shade condition by setting different nitrogen treatments and irrigation levels.The main results of this study as follows:(1)Increasing the amount of nitrogen could significantly promote the growth of the morphological indexes(plant height,stem diameter,leaf number,branch number,crown width and new branch length)of coffee arabica.Plant height and crown width increased with the increase of shade degree.Compared with N0S0,N2S2 increased plant height and crown width by 31.88%and 29.08%,respectively.(2)The total amount of.chlorophyll and carotenoid increased with the increase ofnitrogen application rate.The increase of shade degree significantly increased total amount of chlorophyll and carotenoid,and S2 could increase chlorophyll content significantly.Compared with N0S0,the other treatments increased the total chlorophyll content by 28.22%?597.71%.The total amount of chlorophyll of N2S2 was the largest.(3)Daily main net photosynthetic rate,transpiration rate,stomatal conductance and water use efficiency increased by 11.85%?25.84%,7.32%?18.76%,22.14%?50.38%and 12.75%?21.22%with the increase of shade degree under the same nitrogen treatment,respectively.Daily main net photosynthetic rate and transpiration rate increased by 1.4%?11.3 1%and 6.79%?12.20%with the increase of nitrogen amount under the same shade degree,respectively.The daily mean Pn,Tr and WUE of N2S2 were the highest considering the interaction between nitrogen and shade,and compared with N0S0,N2S2 increased the water use efficiency by 65.48%.It was found that adequate nitrogen could make efficient use of low light environment through the study of light response,and shade treatment could improve the ability to use weak light of coffee arabica leaf under the higher soil nitrogen content.(4)Total dry matter mass increased by 25.45%?32.21%and root-shoot ratio first decreased then increased with the increase of nitrogen amount under the same shade level.Total dry matter mass first increased then decreased and root-shoot ratio decreased with the increase of shade degree under the same nitrogen.The total dry matter mass of S1 was the highest,which was 22.22%higher than that of S0.Compared with N0S0,N2S1 increased total dry matter mass by 76.87%.(5)Compared with SC0,SC2 increased net photosynthetic rate and stomatal conductance by 46.47%and 9.54%under the same irrigation level.Compared with WOSC0,W2SC2 increased water use efficiency by 61.56%.Plant height and stem diameter of coffee arabica increased by 5.42%?9.18%and 15.01%?18.60%under the same shade cultivation.Plant height and stem diameter of SC1 were the largest,a moderate increase of shade cultivation density could significantly increase the main plant height and stem diameter,but excessive shade have no significant increase of plant height.The plant height and stem diameter of W2SC1 of coffee arabica were the highest.The optimal light nitrogen supply pattern is N2S1 considering the dry matter accumulation.of coffee arabica,.and the optimal water light combination of coffeearabica is W2SC2 based on the photosynthetic characteristics and leaf water use efficiency. |
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