Allelopathic potential of barnyard grass on rice and soil microbes in paddy

Abstract

Allelopathic potentials of barnyard grass (Echinochloa crus-galli) on rice (Oryza sativa) and soil microbes in paddy were investigated. In the barnyard grass infested soil, the growth of non-allelopathic rice variety Liaojing-9 was considerably reduced than allelopathic rice variety PI 312777. Further experiments showed that barnyard grass germinating seeds exudates and their one component p-hydroxymandelic acid suppressed the germination and growth of rice. The inhibitory effects depended on concentrations, the maximum inhibition occurred at 2000 barnyard grass seeds/10 ml water per dish (barnyard grass germinating seeds exudates) and 500 mu g1/g soil of p-hydroxymandelic acid. Similarly, soil microbial populations in paddy soil varied with concentrations of barnyard grass germinating seeds exudates and p-hydroxymandelic acid. Actinomycetes and fungi were less sensitive than bacteria to the exogenous application of barnyard grass germinating seeds exudates, but fungi were more sensitive to p-hydroxymandelic acid. These results suggested that allelopathic interference could occur from barnyard grass on rice growth and soil microbial population in paddy ecosystem.