Mycorrhiza and fertilization: effect on the production of Pinus engelmannii Carr. in nursery

Introduction: In the nursery, controlled-release fertilization and inoculation with mycorrhizal fungi promote the quality of plant material reproduced in containers. Objective: To evaluate the effect of two commercial mycorrhizal inoculants and one controlled-release fertilizer on the development of Pinus engelmannii Carr. in nursery. Materials and methods: Two commercial inoculants (fungi native to Mexico [1 mL·plant-1 with 1.05 x 107 spores·mL-1] and exotics [1.5 mL·plant-1 with 6.5 x 106 spores·mL-1]), two doses of a controlled-release fertilizer (11-28-11 NPK [3 and 6 g·L-1]) and a control were evaluated; in total, nine treatments were used. The variables analyzed were: survival, stem height, root collar diameter, wet and dry biomass, ratio of dry biomass of the aerial part/dry biomass of the root part, lignification index, Dickson’s quality index and mycorrhizal colonization. Results and discussion: Survival (80 to 96 %) was similar between treatments. Eight months after sowing, seedlings showed significant differences (P ≤ 0.05) in morphological variables; combined treatments gave better results. Plants with commercial inoculum of native fungi (1 mL·plant-1 [Amanita rubescens Pers., Amanita sp., Lactarius indigo [Schwein] Fr., Ramaria sp. and Boletus sp.]) and fertilization of 3 g·L-1 had higher Dickson quality index. It was observed that the higher the fertilization dose, the lower the percentage of mycorrhizal colonization. Conclusion: The combination of ectomycorrhizal inoculum of native fungi and low-dose fertilization showed that both components are complementary in the plant development of P. engelmannii.