Abstract: To explore the coupling mode of irrigation and shading for rapid growth and optimizing soil environment of Coffea arabica, an experiment was carried out from 2016 to 2017 under four levels of irrigation \[full irrigation (FI, 1.2Ep, Ep is water surface evaporation) and three levels of deficit irrigation (DI₁, 1.0Ep; DI₂, 0.8Ep; DI₃, 0.6Ep)\], and three modes of shading \[no shading (S₀, only coffee, control), light shading (S₁, a row of coffee intercropped with a row of castor (Ricinus communis), and severe shading (S₂, a row of coffee intercropped with two rows of castor)\]. The effects of irrigation level and shading mode on canopy structure and dry matter mass of Coffea arabica and soil microorganism abundance were investigated. The results showed that compared with FI, DI₁ significantly increased canopy area and dry matter mass by 9.53% and 10.46%, respectively (P<0.05), and non-significantly decreased total radiation under canopy by 5.51% (P>0.05), but had no significant effects on the number of soil bacteria and actinomycetes. DI₂ and DI₃ reduced the abundance of bacteria, fungi and actinomycetes by 8.94%-47.06%. Compared with S₀, S₁ significantly increased the abundance of fungi, bacteria and actinomycetes by 13.99%, 30.77% and 9.72%, respectively (P<0.05), and significantly increased leaf area index (LAI) and dry matter mass by 10.31% and 30.02%, respectively (P<0.05). The abundance of soil bacteria, fungi and actinomycetes showed the trend of first increase and then decrease with the increasing water content and temperature, which showed a quadratic relationship with water content and temperature under different irrigation and shading patterns. DI₁S₁ had the highest dry matter mass, larger LAI, and the smallest total radiation under canopy. Compared with FIS₀, DI₁S₁ significantly increased dry matter mass by 62.90% (P<0.05), while significantly decreased radiation under canopy by 21.77% (P<0.05). Therefore, DI₁S₁ treatment can improve the microenvironment of Coffea arabica growth and promote the growth of young trees, and it is thus a better combination of water and light management for Coffea arabica.

Key words: tritrophic interaction, insect-resistant genetically engineered crop, semiochemical, natural enemy, chemical communication.