Change in diversity and abundance of nematode destroying fungi in land use under irrigation in selected small scale irrigation schemes in Kenya

Abstract

: Intensity of land cultivation is usually associated with increase in crop production and loss of soil biodiversity or its function. This study was conducted to determine the effect of intensity of land use under irrigation on the occurrence, abundance and diversity of nematode destroying fungi in selected small scale irrigation systems in Kenya. The study was conducted in four spatially separated irrigation schemes namely Kabaa and Kauti in Machakos and Kathiga Gacheru and Mbogooni) in Embu. The study areas were stratified according to land use, which included the irrigated land, rain-fed cultivated land and undisturbed land under fallow. The period of cultivation also differed with the oldest cultivated irrigation system, having been opened in 1960, while the youngest having been opened in 2011.Soil samples were collected from the study site for isolation of nematode destroying fungi. The soil sprinkle and culture technique was used to isolate soil nematode destroying fungi from the soil samples. A total of 216 fungal isolates were identified as nematode destroying fungi belonging to six genera namely Acrostalagmus, Arthrobotrys, Haptoglossa, Harposporium and Monacrosporium. All the isolates were identified resultingto nine species. 49.5% of all the fungi were isolated from irrigated land while, the rain-fed and the undisturbed land uses accounted for 29.7 and 20.8% of the isolates, respectively. The oldest irrigation systems had the least diversity (0.110) of nematode destroying fungi compared to the youngest which had a diversity index of 1.311.The species Arthrobotrys oligospora was the most frequently isolated fungus followed by Monacrosporium cionapagum with occurrence frequencies of 57 and 53%, respectively. The least frequently isolated species was Nematoctonus leiospora with an occurrence frequency of 2.3%. Of the total identified species, only Nematoctonus leiosporus and Arthrobotrys dactyloides were not affected by the irrigation activities.). From the study, it is evident that land use intensity under irrigation system and the duration of cultivation impacts on occurrence and diversity of nematode destroying fungi in the soil.