A study was undertaken to evaluate the role of Trichoderma strains on 15N-uptake by maize under greenhouse and field conditions. The Trichoderma strains were isolated from different maize production systems in Guanajuato State, Central Mexico. A total of 39 Trichoderma isolates were obtained, 23 correspond to Trichoderma harzianum (Intra-Genic-Segment). Some colonized the endorhizosphere of maize better than others; however, Trichoderma diversity did not correlate with the maize production system (rainfall vs. irrigation conditions). In greenhouse conditions, biomass production and 15N-uptake were equally variable; maize plants inoculated with selected Trichoderma species (high root colonization) and fertilized with 140 mg N kg-1 soil, showed similar increase in grain yield and 15N-uptake vs. those fertilized with 280 mg N kg-1 soil. Biomass and 15N-uptake directly correlated with the capacity of Trichoderma spp. to colonize the rhizosphere. Under field conditions, the N-fertilizer use efficiency was the highest when maize cv. P30G40 was inoculated with T. harzianum T35 at a N fertilization rate of 180 kg N ha-1 (78%). All measured parameters showed positive effects of inoculation under-scoring the feasibility of inoculants with these fungi based on Trichoderma to increase the N-fertilizer use efficiency applied to maize.
Key words: Biofertilizers, N-fertilizer use efficiency, 15N isotope.
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