Can agriculturally damaging nematodes be controlled by use of green energy from onion crop residues and solar heating?

Introduction: Soil solarization (Sol) and biosolarization (BioS) are hydrothermal, organically acceptable alternatives to agricultural soil fumigation with synthetic chemical toxicants. Returning on- or off-site crop residues to decompose in soil as amendments in BioS can aid in promoting a circular agroeconomy. Materials and methods: Onion crop residue amendment and soil temperature/covering regimens were evaluated in a feasibility study for their effects on survival and activity of phytoparasitic root-knot (Meloidogyne incognita = RK) and root-lesion (Pratylenchus neglectus = LN) nematodes, and their impact on winter squash (Cucurbita moschata cv. Waltham Butternut). Results: In laboratory microcosms, residue-amended (2% w/w) and irrigated soil reduced RK survival at diurnally maximum soil temperatures of 25 and 39 °C. In an on-farm trial, 35 days of Sol, but not exposure to onion amendment, reduced RK and LN numbers to near-undetectable levels, which persisted at least 23 days after setting squash transplants. However, following crop harvest, no differences in RK and LN numbers remained. Post-harvest plant ratings showed that both Sol and onion BioS provided reductions in RK root galling up to 76% (p < 0.05). Regardless of treatments or nematode presence, squash harvest was relatively robust, with extrapolated fresh yields of ~20 t/ha. Number of marketable fruits ranged from 27 (control) to 39 per plot (Sol). Conclusions: These tests indicated that both Sol and BioS using onion are feasible soil pest control and circular agroeconomy measures, and further studies are encouraged. Yield data agreed with previous reports that C. moschata squash may have some natural tolerance to phytoparasitic nematodes.