Optimal Combination of Organic-Inorganic Fertilizer of Coffea arabicain Southwest China Based on Soil Nutrients, Photosynthesis, Bean Yield and Nutritional Quality

[Purpose] Unreasonable fertilization practices result in soil nutrient depletion, restrict the growth of Coffea arabica, and ultimately reduce both yield and quality. To identify an optimal fertilization strategy that combines inorganic and organic fertilizer to regulate soil nutrients, enhance photosynthetic efficiency, and consequently improve coffee bean yield and quality, a two-year field experiment (2020–2022) was conducted on Coffea arabica(CIFC7963) in southwest China. [Methods] A two-factor completely randomized design was used in this study. The inorganic fertilizer allocation (IFA) treatments involved of dividing the total amount of 750 kg ha⁻¹ inorganic fertilizer into 3 different fertilizer amounts across three growth stages. They were as follows: T1(150, 250, 350 kg ha⁻¹), T2(150, 350, 250 kg ha⁻¹), T3(250, 150, 350 kg ha⁻¹), and T4(250, 350, 150 kg ha⁻¹). Additionally, organic fertilizer substitution (OFS) treatments were implemented, where 30% of the inorganic fertilizer was replaced with organic fertilizer (3000 kg ha⁻¹) at the flowering and fruiting stage, based on the IFA treatments. The OFS treatments included T5(105 + 3000, 175, 245 kg ha⁻¹), T6(105 + 3000, 245, 175 kg ha⁻¹), T7(175 + 3000, 105, 245 kg ha⁻¹), and T8(175 + 3000, 245, 105 kg ha⁻¹). [Results] Results indicated that highest transpiration rates, bean yield, and water use efficiency were recorded in T4. Compared with T4, T8increased soil nutrients, photosynthetic rate, and bean yield by 19.6–31.2%, 6.44–21.97%, and 15.48%, respectively. The least significant difference results indicated that coupling IFA and OFS significantly affected soil nutrients, photosynthetic rate, bean yield and nutritional quality. Structural equation model results indicated that the soil nutrients affected the photosynthetic characteristics, thereby indirectly affecting coffee bean yield and nutritional quality. CRITIC-TOPSIS comprehensive evaluation results signaled that T8effectively enhanced soil nutrients, photosynthetic rate, bean yield, and nutritional quality. [Conclusion] T8was identified as the optimal fertilization strategy for improving the soil nutrient, bean yield and quality of Coffea arabicain the dry-hot valley.