Abstract

Rice straw compost (RSC) and rice straw vermicompost (RSVC) were prepared and four weeks after maturity used for plant growth studies using sorghum as host plant under glasshouse conditions. Both RSC and RSVC were applied at different concentrations with and without arbascular mycorrhizae (AM) (Glomus spp.) as additional inoculants for plant growth and mycorrhzial colonization in roots. RSC or RSVC applied at 2.5 t ha^-1 showed significant improvement in shoot length (1-12%), leaf area (20-34%), plant biomass (9-27%), root volume and mycorrhizal colonization. When RSC or RSVC were applied at concentrations of 5 t ha^-1, there was decrease in plant biomass with RSC+AM and RSVC+AM, when compared to the application of RSC and RSVC alone. Similar observation was found even when they were applied at 10 t ha^-1. However, application of RSC or RSVC along with AM at 5 and 10 t ha^-1 did not show any inhibitory effect on mycorrhizal colonization but did decrease the dry matter of plant. The study shows that the application of microbial inoculants along with higher concentrations of composts may not be synergistic for plant growth.

Key words: Composts, vermicomposts, arbascular mycorrhizae, sorghum, root colonization.