Impact of Chemical Inputs on Arbuscular Mycorrhizal Spores in Soil

Response of AM Spores to Fertilizer and Herbicides

OLUYEMISI B. FAWOLE 1* AND ELIZABETH T. ALORI 2

1 Department of Agronomy, University of Ilorin, P.M.B. 1515, Ilorin, Kwara state, Nigeria

2 Crop and Soil Science Department, Landmark University, P.M.B. 1001, Omu Aran, Kwara state, Nigeria

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Abstract

Effects of chemical inputs on abundance of arbuscular mycorrhizal (AM) fungi spores were investigated under a maize monoculture in Southern Guinea Savanna ecological zone of Nigeria. The experimental plots received 0, 60, 120 and 180 kg N/ha of fertilizer (N.P.K. 15: 15: 15) and 0, 1, 2 and 3 kg active ingredient (a i) pre-emergence herbicide (atrazine) per hectare. AM fungal spores were isolated from the conventionally tilled, treated soils, cropped with maize by wet sieving and decanting method. Isolated AM spores were counted and spore abundance calculated. The spores were morphotyped and 13 AM fungi taxa were identified. These belong to six genera of AM fungi: Glomus, Paraglomus, Acaulospora, Enthrophospora, Gigaspora and Scutellospora. Increasing atrazine concentrations resulted in significant deduction in AMF spores while increasing N.P.K. content led to an initial significant increase in AMF spores but a later decline in spore population. Both fertilization and herbicide application resulted in a decrease in AMF spore numbers at maturity of maize crop. Application of 160kg N/ha and 3kg a.i. ha – 1 of atrazine caused a significant reduction in spore density (117g – 1 of soil as against 202 g – 1 of soil at 0 kg N ha -1 and 0kg a.i. ha -1 atrazine).

Keywords: Arbuscular Mycorrhizal Spores, Herbicide, Fertilizer, Southern Guinea Savanna

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