From the report «Can agriculturally damaging nematodes be controlled by use of green energy from onion crop residues and solar
heating?» from James J. Stapleton and Tarcisio S. Ruiz, published at Academia Biology.
It was evaluated whether onion crop residues, alone or combined with soil solarization, can reduce populations of two agriculturally important nematodes—Meloidogyne incognita (root‑knot) and Pratylenchus neglectus (root‑lesion). Laboratory microcosm experiments showed that finely ground onion residues at 2% (w/w), under moist conditions, reduced survival of M. incognita, especially when combined with moderate heating that simulated solarization. Biosolarization (onion plus heat) was the only treatment that achieved complete nematode mortality at some sampling times. These results confirmed earlier indications that Allium residues can release biocidal compounds, particularly under warm, anaerobic, or semi‑anaerobic conditions.
In the on‑farm field trial, however, onion amendment alone did not significantly reduce nematode populations. Solarization for 35 days lowered both nematode species to near‑undetectable levels before planting, but populations rebounded by harvest across all treatments. Even so, solarization—with or without onion—substantially reduced root galling on squash plants, suggesting a delay or suppression of early nematode colonization. Yield of ‘Waltham Butternut’ squash remained relatively stable across treatments, with solarized plots producing more marketable fruits but similar total fruit weight.
Overall, the study concludes that both solarization and biosolarization using onion residues are feasible nonchemical approaches for short‑term nematode suppression and align with circular‑economy goals. However, onion residues alone were insufficient under field conditions, likely due to coarser incorporation and less effective sealing compared to laboratory microcosms. The robust squash yields also support previous observations that Cucurbita moschata may possess partial tolerance to phytoparasitic nematodes.