SOIL HUMIDITY, NITROGEN AND EDIBLE ECTOMYCORRHIZAL FUNGI ON PINE GROWTH

Abstract

The effect of soil moisture and nitrogen fertilization on plants inoculated with ectomycorrhizal fungi has received limited attention, despite the ecological significance and sensitivity of these fungi to environmental factors. In this study the influence of two soil moisture regimes [80 to 100 and 40 to 60 % of the maximum capacity of water retention by the substrate (MCWRS)], the addition of three doses of mineral nitrogen (140, 70 and 0 kg of N ha^-1) and the inoculation with three edible ectomycorrhizal fungi (Hebeloma spp., Laccaria spp. and Clavulina aff. cinerea) on the growth of two species of pine (Pinus patula Schl. et Cham and Pinus hartwegii Lindl), was evaluated under greenhouse conditions. Shoot height and diameter at 90, 180 and 310 d after sowing, number of short roots, shoot and root dry weights, and ectomycorrhizal colonization were evaluated. Relevant effects (P ≤ 0.05) on plants were originated by soil moisture and inoculation with ectomycorrhizal fungi. The significant interactions (P ≤ 0.05) were those established between soil moisture and pine species, soil moisture and inoculation with ectomycorrhizal fungi, and pine species and inoculation. Plant height and dry weight increased as a result of inoculation with Hebeloma spp. and Laccaria spp. In P. patula inoculated with Hebeloma spp. the soil moisture regime from 80 to 100 % produced higher dry weight (46 %) and height (25 %), than the soil moisture regime from 40 to 60 %. In P. patula inoculated with Hebeloma spp. and fertilized with 140 kg N ha^-1 there was an increase in foliage dry weight (29 %) compared to the control without nitrogen fertilizer. The growth of P. patula y P. hartwegii was differentially affected in the evaluated humidity regimes, depending on the inoculated ectomycorrhizal fungi.