بررسی روند تغییرات جمعیت قارچ‌های Aspergillus section Flavi در خاک باغ پسته با پوشش مالچ پلاستیکی

Using of mulch in agriculture has been considered for a long time. Mulches improve plant growth and reduce the population and activity of soil microorganisms, including Aspergillus, by reducing erosion and maintaining soil moisture, altering mineral solubility and soil temperature, controlling weeds, pests and diseases. In this study, the effect of two types of white and dark plastic mulches with a thickness of 45 µm was investigated on the population of Aspergillus section Flavi in pistachio orchard soil with surface drip irrigation system. The study was performed as a randomized complete block design with three replications (including without mulch, white plastic mulch and black plastic mulch). The population of Aspergillus section Flavi fungi in soil was measured monthly by preparation of serial dilution and using sucrose-peptone-dichlorane agar medium. The results showed that the using of black and white plastic mulch in pistachio orchards reduced the population density of Aspergillus section Flavi in all sampling months except December, compared with the control. This decrease in fungal population compared to control was significantly greater during the months of June to August, As far as that in August the fungal population in white and black mulch , respectively , decreased by 46 and 64 % compared to control. During the experiment, the effect of dark mulch on reduction the population of Aspergillus section Flavi was greater than that of white mulch. Overall, the results showed that using of plastic mulch, especially the dark type, can significantly reduce the population of Aspergillus section Flavi in the warm months of the year in the soil of pistachio orchards. Increasing soil temperature under plastic cover can be one of the most important reasons for the reduction of fungal population in the warmer months of the year compared to the control. Due to the fact that the highest rate of infection of pistachio nuts with spores of Aspergillus section Flavi occurs in the warm months, so reducing the population of the fungi by using mulch in the warm months has a great effect on reduction of contamination of pistachio nuts with Aspergillus and aflatoxin.