Improving Kale Yield and Freeze Tolerance after Soil Biosolarization.

Disinfecting soil can reduce or eliminate crop loss from soil-borne pathogens, parasitic nematodes and weed competition. Biosolarization creates combines biotoxic products from organic matter decomposition and heat from solarization. While biosolarization offers an organic option for soil pest control and avoids human and environmental health risks associated with chemical fumigants, it still has broad negative impacts on microbial communities. Quickly re-establishing these communities can be key in preventing resurgence in disease pressure and in maximizing nutrient use efficiency. The objective of this study was to determine the ability of several amendments to rebuild an active soil ecosystem in biosolarized soils by measuring nematode community structure, microbial biomass and C and N mineralization in soil as well as kale yield and quality. The study was conducted using potted kale grown in biosolarized soils. Treatments were bare soil, receiving no fertilization, and soils receiving two different rates of organic, composted broiler litter or a mineral fertilizer. Half of the pots in each treatment received a locally-derived microbial inoculant (LEM). Among amended soils we found no significant differences between LEM treatments in soil properties or kale yields. Between the bare soils, however, the soils that received applications of LEM mineralized more nitrogen and produced higher yields. Soils that received the highest rate of compost immobilized the highest proportion of nitrogen applied but also produced the highest yields. These soils were also the most cold tolerant. Kale that received mineral fertilization were the most sensitive to cold stress. None of the kale that received heavy mineral fertilization alone survived a hard freeze, however, the ones that received LEM applications were able to partially recover. Amendment with high rates of compost after soil biosolarization is ideal but if no compost is added, the application of LEM can improve nitrogen availability, yield and cold tolerance.