Trophic Group Dynamics of Free-Living Nematodes in Organically Fertilized Soils with and without the Addition of Local Effective Microorganisms.

Up to 50% of nutrients applied to agricultural fields can go unused by crops. Increasing nutrient use efficiency in crop systems is vital to addressing sustainability. Farmers in parts of the developing world have pioneered the use of Local Effective Microorganisms (LEM) to enhance microbial richness of agricultural soils and improve soil health. LEM is a concentrated solution of locally derived microorganisms produced using partially decomposed leaf litter mixed with carbohydrate-rich substrates. Despite its extensive use in some parts of the world, scientific data on the effect of LEM on soil biodiversity and crop productivity are lacking. Three treatments consisting of: swine effluent mixed with LEM; swine effluent mixed with false LEM (FLEM); and a control treatment of swine effluent were applied to annual ryegrass arranged in a randomized complete block design with four treatment replicates. Data were collected for two growing seasons. Free-living nematode abundance and community structure were used as a biological indicator of LEM’s effect on soil health and productivity in this study. Additionally, forage yield, quality and nutrient content were determined. Nematodes were extracted through centrifugal flotation, counted and identified to trophic group. The objectives of this study were to compare nematode trophic structure between agricultural soils receiving swine effluent with and without the addition of LEM and to determine if there is a relationship between crop performance plant parasitic and grazing nematode populations. We found that changes in nematode community structure, including bacterial: fungal and microbial grazing: plant parasitic ratios were indicated post application of swine effluent, LEM, and FLEM.  As indicated by multivariate analysis of variance (repeated measures) populations of plant parasitic nematodes were significantly higher in LEM treated plots both years. This increased abundance in plant parasite populations did not, however, result in any significant differences in forage yield or quality.