Urease, invertase, dehydrogenase and polyphenoloxidase activities in paddy soil influenced by allelopathic rice variety

Allelopathic rice variety can release allelochemicals from roots to soil in which interfere with neighboring plant and microbial species, but little is currently known about their effect on enzyme activities of paddy soils. This study showed that enzyme activities and concentrations of allelochemicals in paddy field varied with rice varieties, growth stages and moisture regime. Allelopathic rice variety PI312777 paddy fields had higher levels of soil urease, invertase, dehydrogenase and polyphenoloxidase activities when compared to non-allelopathic rice variety Liaojing-9. Furthermore, allelopathic PI312777 released much higher concentrations of allelochemical 5,7,4′-trihydroxy-3′,5′-dimethoxyflavone than non-allelopathic Liaojing-9 during the whole growth stages. Both rice root exudates and the flavone changed soil enzyme activities, but their effects could be distinguished by allelopathic PI312777 and non-allelopathic Liaojing-9 varieties tested. There was a correlation with concentrations of the flavone and enzyme activities in rice soil. The flavone increased enzyme activities, but all test enzyme activities were less responsive to the flavone in flooded soil than in non-flooded soil. The flavone given the short half-life easily degraded in rice soil, but the flavone was more resistant toward degradation in non-flooded soil. These results suggest that the urease, invertase, dehydrogenase and polyphenoloxidase activities of paddy soils may be positively influenced by allelopathic rice variety through the release of allelochemicals.