Micorrizas arbusculares em sistemas agroflorestais em duas comunidades rurais do Amazonas

Abstract

The deforested areas in the Amazonia occupy more than 70 million hectares, the majority in advanced stage of degradation. Allied to this, the majority of the soils present high acidity and high aluminum saturation, which limits its uses in the regional agriculture. An efficient alternative for soil utilization is the use of soil microorganisms aiming at a better exploitation of the nutrients for the plants. The arbuscular mycorrhizal fungi (AMF) increase the capacity of the plant to absorb water and nutrients of the soil favoring its nutrition. The Agroforestry Systems have for base, to approach the structure and dynamics of a natural forest. The objective of this study was to evaluate the mycorrhizal interactions in the plant rhizosphere of two Agroforestry Systems. The interactions among chemical and physical characteristics of the soil and leaves nutrients with the mycorrhizal variable in component species of two Agroforestry Systems (AFs) were analyzed at distinct times and localities. Roots colonization by arbuscular mycorrhizae fungi ranged from 6.8 to 99.6% on plants of AFS in the Brasileirinho community and 0.4 to 52.4% in the AFS in the São Miguel community. Hyphae predominated in the roots of all the species, with 80 to 100% of the observed fungal structures, in both the AFs. The arbuscules, in the Agroforestry System of the Brasileirinho, were the mycorrhizal structure that more was correlated with rhizospheric and leaves nutrients cntents. The rhizospheric pH, in both the AFs, was the component of the soil that more influenced the mycorrhiza variables, correlating in such a way positively as negative with the mycorrhizal structures. The Fe in the rhizospheric soil, in both the AFSs, was the element that more influenced the nutrients-mycorrhiza relations in all the species. The leaves nutrients that were more related with the AMF were the Mg and K in the AF of the Brasileirinho and P and Ca in the AFS of São Miguel