Effects Of Shading And Fertilization On Nutrient,Microbial Biomass Carbon In Root Zone And Yield Of Coffee Arabica In Dry-hot Region

Coffea Arabica is mainly planted in the humid tropical areas and dry-hot valleys of Yunnan.As one of the special economic crops in Yunnan,the planting area and total yield account for more than 99%of the country.The yield of Coffea Arabica is not guaranteed for excessive light,lack of nutrition and extensive fertilization management in the process of production.In order to explore shading and fertilization management mode of fertilizer saving and high yield,this paper focuses on the effects of different shade levels and fertilization levels on the growth,photosynthetic characteristics,canopy structure,nitrogen,phosphorus and potassium content in root area,microbial biomass carbon and yield of Coffea Arabica.Thus optimizing the shading level and fertilizer amount,the theory of high efficiency utilization of Coffea Arabica shading and fertilization was further enriched.This study took Coffea Arabica as test materials,adopted field experiment which was conducted in Lujiangba,Baoshan,Yunnan.Four shading levels:no shade S₀?control,100%natural light?,mild shade S_L?75%natural light?,moderate shade S_M?60%natural light?and severe shade S_H?45%natural light?,and four fertilizer levels:no fertilizer F₀?control,0g/plant?,low fertilizer F_L?200g/plant?,medium fertilizer F_M?300g/plant,local conventional fertilization amount?and high fertilizer F_H?400g/plant?were designed to study the effects of different shade levels and fertilization levels on the growth index,photosynthetic characteristics,canopy structure,nitrogen,phosphorus and potassium content in root area,microbial biomass carbon and yield of Coffea Arabica.The main results of this study as follows:?1?Under the same fertilization conditions,compared with S₀,increasing shade level improved the increasment of plant height,stem diameter,crown width,and new shoot length by 20.71%⁴0.36%,10.60%³3.60%,17.41%³7.65%and 6.67%²1.72%.The plant height,stem diameter,crown width and new shoot length of Coffea Arabica increased first and then decreased with the increase of fertilizer amount,and reached the maximum in the medium fertilizer treatment.The plant height,crown width and new shoot length of S_HF_M were the highest,and the stem diameter was only less than S_HF_H.?2?As shade level and fertilization level increased,the leaf area index of Coffea Arabica increased,but the total radiation of the gap fraction,opening degree and the total fixed-point factor and total radiation under canopy decreased.The leaf area index of the S_HF_H treatment was the largest.?3?The diurnal changes of net photosynthetic rate,transpiration rate,stomatal conductance and intercellular CO₂ concentration showed a“single peak curve”under different fertilization levels and shade conditions.Compared with S0,the net photosynthetic rate,transpiration rate,and stomatal conductance of Coffea Arabica leaves increased with the increase of shading levels,while S_H significantly decreased;Increasing shading levels reducedintercellular CO₂ concentration.With the increase of fertilization level,the net photosynthetic rate,transpiration rate and stomatal conductance of Coffea Arabica leaves increased,while the intercellular CO₂concentration decreased.?4?With the increase of shade level,the contents of nitrate nitrogen,available phosphorus and available potassium in the root zone of Coffea Arabica decreased by9.50%²2.77%,6.91%¹0.82%and 5.25%¹4.33%,respectively.Compared with F₀,increasing the fertilizer amount increased the content of nitrate nitrogen,available phosphorus and available potassium by 69.68%¹82.53%,129.40%²30.45%and119.59%²96.90%.The contents of nitrate nitrogen,available phosphorus and available potassium of S₀F_H were the largest.?5?Compared with S₀,Increasing shade level reduced soil microbial biomass carbon by 5.97%⁹.42%.Compared with F₀,F_L,F_M,F_H increased soil microbial biomass carbon by 23.11%?45.73%and 36.69%.The S₀F_M obtained a maximum microbial biomass carbon.?6?Compared with S₀,S_L and S_M improved fresh beans yield of Coffea Arabica by 19.20%and 13.92%,while S_H decreased by 7.93%;S_L and S_M improved dry beans yield of Coffea Arabica by 18.42%and 10.75%,while S_H decreased by 12.25%.Compared with F₀,F_L,F_M and F_H increased fresh beans yield and dry beans yield by17.25%,26.25%,30.90%and 18.29%,28.13%,29.98%.The fresh beans yield?25169.50 kg/hm²?and dry beans yield?5990.34 kg/hm²?of S_LF_H were the highest.From the view of high yield and fertilizer saving,the optimum coupling model of shade and fertilizer for Coffea Arabica in dry-hot areas was mild shade and medium fertilizer combination?S_LF_M?.