Growth and symbiosis of plants with arbuscular mycorrhizal fungi in soil submitted to biochar application.

Arbuscular mycorrhizal fungi (AMF), which is intrinsically present or may be introduced in soils by inoculation, is an example of natural and renewable resource to increase plant nutrient uptake. This kind of fungi produces structures (hyphae, arbuscles and sometimes vesicles) inside the plant root cortex. This mutualistic relationship promotes plant gains in terms of water and nutrient absorption (mainly phosphorus). Biochar can benefit plant interaction with AMF, however, it can contain potentially toxic compounds such as heavy metals and organic compounds (e.g. dioxins, furans and polycyclic aromatic hydrocarbons), depending on the feedstock and pyrolysis conditions, which may damage organisms. For these reasons, the present work will approach the impacts of biochar application on soil attributes, AMF-plant symbiosis and its responses in plant growth and phosphorus uptake. Eucalyptus biochar produced at high temperatures increases sorghum growth; symbiosis with AMF; and enhances spore germination. Enhanced plant growth in the presence of high temperature biochar and AMF is a response of root branching stimulated by an additive effect between biochar characteristics and root colonization. Biochar obtained at low temperature reduces AMF spore germination; however it does not affect plant growth and symbiosis in soil.

Growth of native trees in two agroforestry systems.

Agroforestry systems with eucalyptus prevail in Central and Southeast Brazil, and little information is available about systems using native trees. The aim of the present study was to evaluate the development of seven native tree species grown under two agroforestry systems. The experiment was conducted starting in 2007 in 12-hectare area in the municipality of São Carlos, São Paulo state, Brazil. The tree species planted in the two systems (a silvopastoral system and an agrisilvicultural system) were: 'capixingui' (Croton floribundus) and 'mutambo' (Guazuma ulmifolia) (tutors), 'jequitibá-branco' (Cariniana estrellensis), 'canafistula' (Peltophorum dubium) and 'ipê felpudo' (Zeyheria tuberculosa) (timber trees), and 'angico-branco' (Anadenanthera colubrina) and 'pau-jacaré' (Piptadenia gonoacantha) (N-fixing trees). Data were collected for 48 months. The results show differences among tree development, which was evaluated as growth in height and diameter, as well as sensitivity to insect and disease damage. The overall results show that the agrisilvicultural system allowed better tree development. The species with best performance in the two systems were capixingui, mutambo and canafístula. Ipê-felpudo and jequitibá-branco showed the worst results. The high variability among individuals of the same species indicates the possibility of high production advances with selective breeding of these species.