A new approach to the search for indicators of root disease suppression

Abstract

Disease suppressiveness can be viewed as one of the characteristics of a healthy soil. From an ecological point of view, soil health implies ecosystem stability, diversity, functional connectedness, and resilience in response to a disturbance or stress. Disease suppression can be viewed as a manifestation of ecosystem stability and health. Previously suggested indicators for soil health and disease suppression have mainly been lists of variables that were correlated to more or less disturbed soils (ranging from conventional and organic agricultural soils, to grassland and forest soils) or to root disease conduciveness. We suggest that indicators for soil health and disease suppression could be found by monitoring responses of the soil microbial community and nutrient availability to the application of a disturbance or stress. This approach is illustrated by wave-like responses of microbial communities, soluble carbon and nitrogen, and damping-off by Pythium spp. after incorporation of a cover crop in soil. The amplitudes of the waves were mostly wider when cover crop debris was incorporated in fallow soil than in cover cropped soil. qrthium damping-off was less severe in cover-cropped soil. These results suggest that the proposed approach to the search for indicators of soil health and disease suppression, namely measuring the amplitude of fluctuations in microbial populations and resilience to a disturbance or stress, is promising.