RESUMO
The effect of 10% azadirachtin granules (alcoholic extract of neem seed kernel mixed with China clay) was studied on the population of bacteria, actinomycetes, fungi, Azotobacter and nitrifying bacteria; soil dehydrogenase, phosphatase and respiratory activities on 0, 15th, 30th, 60th and 90th days after application in sandy loam soil collected from the fields. It was observed that baring the Azotobacter sp., azadirachtin at all the doses exerted a suppressive effect on the rest of the microbial communities and enzyme activities in the initial 15 day period. The population of bacteria, actinomycetes besides phosphatase and respiratory activities recovered after 60th day and subsequently increased significantly. The fungi and nitrifiers were most sensitive groups as their numbers were reduced significantly throughout the studies. The two times and five times recommended dose of azadirachtin had very high biocidal effects on the soil microorganisms and its activities. However, analysis of the data by the Shannon Weaver index showed that azadirachtin reduces both the form and functional microbial diversity at all doses.
Assuntos
Azadirachta/química , Inseticidas/farmacologia , Limoninas/farmacologia , Microbiologia do Solo , Poluentes do Solo/farmacologia , Bactérias/efeitos dos fármacos , Bactérias/enzimologia , Proteínas de Bactérias/metabolismo , Proteínas Fúngicas/metabolismo , Fungos/efeitos dos fármacos , Fungos/enzimologia , Oxirredutases/metabolismo , Monoéster Fosfórico Hidrolases/metabolismoRESUMO
In an experiment, application of different levels of metalaxyl to a sandy loam soil significantly affected the nodulation and nitrogenase activity of mungbean. In both the compost amended and unamended soils, 0.5 mg kg(-1) of metalaxyl enhanced acetylene reduction activity and yield of mungbean, where as higher concentrations (1 mg and 2.5 mg kg(-1) of fungicide) inhibited the nodulation traits as well as economic traits of mungbean.