Effects Of Drip Fertigation Combined With Coffee Peel On Soil Environment,Yield,Quality And Volatile Of Coffee

Arabica coffee is vital for the economy of Yunnan Province.However,the lack of soil nutrients in dry-hot valley and long-term unreasonable fertilization lead to low yield and unstable nutritional quality and volatile compounds.In this study,5-year-old Arabica coffee was used as the materials for 2 consecutive years of field experiment.Based on the annual fertilization of 750 kg·hm^-2,variable fertilization(low fertilizer:150 kg·hm^-2,medium fertilizer:250 kg·hm^-2 and high fertilizer:350kg·hm^-2)was carried out in three stages:early flowering（F_I）,fruit expansion(F_II)and fruit maturity(F_III).Taking single chemical fertilizer treatments（T1:FI150FII250FIII350,T2:FI150FII350FIII250,T3:FI250FII150FIII350,T4:FI250FII350FIII150）as control,other treatments were applied with 70%chemical fertilizer+30%coffee peel(3000 kg·hm^-2)（T5:70%T1+30%coffee peel,T6:70%T2+30%coffee peel,T7:70%T3+30%coffee peel,T8:70%T4+30%coffee peel）.Coffee peel was applied as base fertilizer in the early flowering.The response of soil environment,leaf gas exchange,yield,nutrients,coffee volatile compounds and cup quality to drip fertigation combined with coffee peel was explored.The main results are as follows:（1）Compared with the single application of chemical fertilizer,the treatments of chemical fertilizer combined with coffee peel increased soil nutrient contents（nitrate nitrogen,available phosphorus,available potassium,organic matter）,soil microbial quantity（bacteria,fungi,actinomyces）and soil enzyme activity（urease,phosphatase,catalase）in two years,T7 and T8 treatments increased soil microbial community diversity.Among them,T8 treatment obtained the highest mean values of organic matter content,bacteria,fungi and actinomyces quantity,soil urease and catalase activity.（2）Among the single application of chemical fertilizer,the relative chlorophyll content（SPAD value）,net photosynthetic rate,transpiration rate,stomatal conductance and carboxylation efficiency of T4 treatment were the highest in two-year average.Compared with the single application of chemical fertilizer,the treatments of chemical fertilizer combined with coffee peel treatments increased SPAD value,net photosynthetic rate,transpiration rate,stomatal conductance and carboxylation efficiency by 5.56～26.43%,7.80～9.39%,4.24～8.15%,6.33～7.28%and 21.90～29.94%,respectively,while the intercellular CO₂ concentration decreased by 11.60～16.89%.（3）In the single application of chemical fertilizer treatments,T4 treatment had the highest bean yield,water use efficiency,partial factor productivity of fertilizer,ash,total sugar,protein,caffeine and chlorogenic acid contents.Compared with single application of chemical fertilizer,the yield,water use efficiency,partial factor productivity of fertilizer,total sugar,fat and chlorogenic acid contents increased by4.54～8.25%,5.26～7.84%,4.57～8.31%,5.85～7.00%,7.12～8.52%and 4.09～5.62%,respectively.The contents of ash,protein and caffeine were reduced by 6.93～8.89%,7.16～8.85%and 1.79～3.88%,respectively.TOPSIS indicated that T8 treatment was the optimal fertilization mode.（4）The relative contents of furans,pyrazines and ketones in medium roasted coffee were 31.60～35.00%,14.50～21.00%and 16.00～20.00%,and in dark roasted coffee were 30.10～36.10%,16.10～20.00%and 13.70～16.10%respectively.T1～T4treatments and T5～T8 treatments were completely separated by hierarchical cluster analysis.The relative content of pyrazines under medium roasting in T2,T4 and T8was higher than under dark roasting,furans and ketones had high content in T4treatment,while the phenols were increased in dark roasted coffee under different treatments.T4 treatment under medium roasting had the highest total score,T6 and T8treatment decreased total score.In dark roasted coffee,chemical fertilizer combined with coffee peel increased the total cup score,and T8 treatment had the highest total score.Considering the yield,nutrients,volatile compounds and cups of Arabica coffee,it is suggested that T8 treatment is the best fertilization mode for Arabica coffee planting in this experiment.