Soil biosolarization (SBS) is a soil disinfestation technology that combines solar heating and the accumulation of fermentative organic acids (OAs) from organic amendments to remediate infested soils. Soil microorganisms under anaerobic conditions consume available carbon from organic amendments, such as almond byproducts, accumulating OAs under tarped soil. Additionally, SBS offsets the environmental, health, and safety risks of conventional soil fumigant application. The objectives of the study were: 1) to assess the ability of almond processing byproducts—almond hulls (ALH) and a mixture of hulls and shells (ALMix)—to induce microbial fermentation and OA accumulation; 2) to monitor soil temperature during SBS; 3) to assess the nematicidal effect of the treatment; and 4) to assess the impact on soil fertility. SBS was applied during the preplant phase of a commercial almond orchard field infested with root lesion nematodes (<i>Pratylenchus neglectus</i>). OAs produced in the soil and nematode mortality were quantified across different treatments (control, solarized non-amended, solarized with ALH, and solarized with ALMix) and soil depths throughout the duration of the field trial. Soil macro-phytonutrients (N, P, K) were also monitored. ALH-biosolarized soil, with higher OA levels, outperformed ALMix-amended and non-amended solarized plots, resulting in complete nematode inactivation after ten days of treatment. Nematode inactivation in the non-amended plots indicated that cumulative heating likely played a significant role in nematode deactivation. Following the treatment period, mineralization of N, P, K was observed in solarized plots. In the months following treatment, the conversion of ammonium to nitrate was observed in ALH- and ALMix-biosolarized soil. These results demonstrated that biosolarization using almond industry byproducts could effectively deactivate orchard soil pests on a commercial scale. Further studies are needed to monitor soil nematode reinfestation and the additional benefits of the organic amendment on the orchard performance.

Using biosolarization with almond byproduct amendments to disinfest almond orchard soil during pre-plant processing and improve soil quality

256th National Meeting (2018)

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