Brassica biofumigation cover crops in US agroecosystems: A systematic review of research from 2014 to 2024

Abstract Biofumigation with brassica cover crops (BCCs) is gaining momentum in the United States as an ecologically sound alternative to chemical pest suppression in agricultural systems. This review critically evaluates the impacts of Brassica species on soil health, weed suppression, disease mitigation, and control of plant‐parasitic nematodes (PPNs) across US agroecosystems over the last decade (2014–2024). Synthesizing data from over 50 peer‐reviewed studies, we found that brassicas, particularly mustard ( Brassica juncea ), radish ( Raphanus sativus ), and canola ( Brassica napus ), exert a significant biofumigation effect due to the release of allelochemicals, notably isothiocyanates, during residue decomposition. BCCs exhibit mixed effects on soil physical and chemical health, with certain species, such as turnip ( Brassica rapa ) and mustard, alleviating soil compaction and improving organic carbon under specific conditions. In contrast, others, such as canola, may reduce soil water content or microbial diversity due to high biomass demand or the release of allelochemicals. While 87.5% of the studies observed disease suppression and 60% reported nematode control, weed suppression showed variable outcomes, depending on Brassica species and management practices. Mustard was notably effective in pathogen control, while daikon radish consistently suppressed soybean cyst and reniform nematodes. However, some Brassica species acted as hosts to certain nematodes under specific conditions, highlighting the complexity of plant‐nematode interactions. Additionally, limited data exist on long‐term soil structural and chemical changes, particularly under arid or saline conditions prevalent in the western United States. This review identifies critical research gaps, including the need for integrated, multi‐functional assessments; long‐term trials; and innovative tools such as spatial‐spectral sensing, modeling approaches, and microbial functional profiling. Future research should prioritize exploring brassica performance under abiotic stress, assessing region‐specific impacts, and developing decision‐support tools to optimize biofumigation practices.