Mapping of interactions between soil factors and nematodes

A study was undertaken to investigate the effect of soil physical and chemical properties on nematodes associated with sugarcane. Principal component analysis (PCA) showed little or no change in the nematode community between nematicide treated and untreated plots or between sugarcane varieties. Analysis of the topsoil revealed very small differences in chemical elements between varieties. Soil of plots with the variety N16 had higher levels of Mg and Ca and lower levels of Fe. The study of soil characteristics of the topsoil and of the deeper layer revealed a heterogeneous situation alluding to the distinction of two zones over the area. However, the overall distribution of the entire nematode community, described by the factorial values of the PCA, was not related to the location of these two soil delimited zones. The coinertia analysis was then performed to identify the relationship between individual soil factors and individual species. These relationships were shown to be significant and concerned mainly the Mn level in the soil, the size of the plant–parasitic community and the abundance of Helicotylenchus dihystera and Xiphinema elongatum. All three decreased as the Mn content increased. To a lesser extent, pH and Na were positively associated with the numbers of free-living nematodes.