<p class="MsoNormal" style="margin-bottom: 12.0pt; text-align: left; mso-line-height-alt: 14.0pt; layout-grid-mode: char; mso-layout-grid-align: none;" align="left">Soil Cover Influences the Effectiveness of Microbial Biofertilisers on the Growth and Yield of Papaya (<em>Carica papaya</em> L.)

In a field experiment with papaya (Carica papaya L.), the effects of three soil cover types (bare soil, living cover of Canavalia ensiformis, and senescent cover) and three microbial biofertilisers (Bacillus subtilis, Pseudomonas putida, and Trichoderma viride) on crop growth and yield were evaluated. Vegetative and reproductive variables were monitored over 187 days, and the data were analysed using generalised linear mixed models (GLMMs) and generalised linear models (GLMs). The results indicated that soil cover was the dominant factor, explaining the largest proportion of variation in plant growth and final yield (p &lt; 0.001), whereas biofertilisers did not exhibit significant main effects when applied independently. However, significant interactions between soil cover and biofertiliser were detected (p &lt; 0.05), demonstrating that inoculant efficacy was strongly context-dependent. Trichoderma viride increased stem diameter by approximately 7% under living cover only, while Pseudomonas putida showed a comparative advantage under bare soil conditions, increasing final fruit weight by approximately 32%. Principal component analysis (PCA) further confirmed that treatment groupings were primarily driven by soil cover type. These findings provide field-based evidence that the efficiency of microbial biofertilisers in promoting papaya growth depends on edaphic conditions shaped by soil cover management. A hierarchical management strategy is therefore proposed, in which establishing a favourable soil habitat through plant cover is a prerequisite for maximising the benefits of microbial inoculants in tropical fruit production systems.