Ascertaining the Functions of Soil Nematodes in a Wheat Agro-Ecosystem.

Nematodes are the most abundant soil metazoans, occupying all trophic levels with multiple ecological functions. The functions of nematodes in an ecosystem could be categorized as a service or disservice. In order to determine the functions of soil nematodes in wheat plots, we collected soil samples preplant (MPS), midseason (MMS), and at harvest (MHS), and extracted the nematodes according to standard methods. Nematodes were identified  using morpho-anatomical features and the data was analyzed using analysis of variance (ANOVA), Nematode Faunal Analysis/Diagrams, and the Nematode Indicator Joint Analysis (NINJA): The results of our investigation reveal that the herbivorous or plant-parasitic nematodes were the dominant feeding group, that utilized the most soil carbon and also was the source of the most loss of soil carbon during respiration as CO₂; Among the free-living nematodes the bacterivorous and fungivorous nematodes dominated. Previously, these nematode feeding groups have been associated with the mineralization and release of N into the soil; Our data also reveal an inverse relationship between the regulatory/suppressive nematodes and the pest/target species nematodes;  An inverse relationship between the Maturity Index (MI-all free-living nematodes) and the Plant-Parasite Index (PPI-all herbivorous nematodes) was also recorded as well as a PPI/MI-ratio less favorable for nutrient uptake by the wheat plants; The nematode composition revealed that the soil conditions in the wheat plots investigated changed from basal (MPS), to enriched (MMS), and then to a semblance of maturing (MHS), with the overall soil conditions being described as stressed soils. Overall the data of our investigation revealed an abundance of plant-parasitic nematodes in the wheat plots (disservice) and the use of nematodes as biomonitors of soil conditions and indicators of soil nutrient state (service). Based on our data, the wheat plots sampled are underproductive stressed soils, teeming with plant parasitic nematodes that may interfere with nutrient uptake.