Soil allelochemical residue effects of nemafric-BL and nemarioc-AL phytonematicides on soil health, growth of sweet sorghum and Meloidogyne species

Abstract

A field trial was initiated to investigate the post-treatment effects of soil allelochemical residue (SAR) of nemafric-BL and nemarioc-AL phytonematicides on soil health, growth of sweet sorghum (Sorghum bicolor) and population densities of Meloidogyne species. SAR conditions were created in tomato (Solanum lycopersicum) trials, with treatments comprising untreated control, nemafric-BL 3%, nemafric-BL 6%, nemarioc-AL 3% and nemarioc-AL 6%, which were applied at empirically established intervals for a 56-day crop cycle. Soil preparation was followed by a 30-day fallow to allow for microbial decomposition of root remnants. Sweet sorghum seeds were sown on spots where tomato plants grew and soil samples were collected for determining the soil health status at two-leaf stage. At 80 days after sowing, SAR effects improved soil health and contributed 8% in total treatment variation (TTV) of chlorophyll and sugar contents each in sweet sorghum, with nemarioc-AL 3 and 6% phytonematicides stimulating improvement of the two variables. Nemafric-BL SAR effects had no effect on growth of sweet sorghum. In contrast, SAR effects contributed 76 and 39% in TTV of nematode population densities in root and soil, respectively. SAR effects of nemafric-BL and nemarioc-AL inhibited nematode numbers by 67–97% and 64–80%, respectively. In conclusion, SAR effects on soil health, plant growth and nematode population densities were desirable, suggesting that the two products were each still active in the soil.