Organic amendments divergently shape thrips communities in barley: maize compost is associated with higher diversity, maize green manure with pest dominance

The Green Revolution of the 1960s led to the widespread adoption of synthetic fertilizers, which, despite boosting crop yields, introduced significant ecological concerns such as groundwater contamination and biodiversity loss. In response, sustainable alternatives like organic amendments have gained attention for their potential to mitigate pest pressures while supporting agroecosystem health. This study assessed the effects of different soil management practices, including maize stubble, maize compost, and maize green manure applied as well as synthetic fertilization and an untreated control, on thrips (Thysanoptera) communities in barley fields. Through the use of integrated molecular (mtCOI barcoding) and morphological identification methods, a total of 16 thrips species were recorded across different applications. Haplothrips tritici was the dominant species, particularly under maize stubble (645 individuals) and maize green manure (530 individuals) applications. Maize compost plots exhibited the highest species diversity (Shannon H = 0.82), although they also showed a slight increase in the pest Frankliniella occidentalis (13 individuals). In contrast, maize green manure led to the lowest diversity (H = 0.15) and evenness (Pielou J = 0.077), suggesting conditions favorable for the dominance of a single pest species. Interestingly, the synthetic fertilizer and control plots harbored the highest number of predatory thrips (7 individuals each), which may be associated with factors other than soil disturbance, such as vegetation structure or prey availability. Overall, the findings demonstrate that organic applications exert divergent effects on thrips communities: maize compost promotes thrips diversity, whereas maize green manure may increase pest risk. These outcomes underscore the importance of context-specific organic management strategies in sustainable agriculture.