Influence of vesicular-arbuscular mycorrhizal fungi sources and levels of phosphorus on the growth of oat forage

Abstract

The effects of vesicular-arbuscular mycorrhizae (VAM), sources (Triple superphosphate and Patos de minas rock phosphate) and phosphorus levels (0, 30 and 60 kg of P₂O₅/ha), on dry matter yield, concentration and P uptake by oat forage species (black oat - Avena strigosa Schereb. cv . Comum and yellow oat - A. byzantina Koch. cv. Coronado) - were evaluated in a greenhouse trial at Faculty of Agronomy - UFRGS -, utilizing a Hydromorphic Lateritic soil, sterilized at 110°C for one hour for three days, and reinoculated with a soil microbial suspension free of mycorrhizal fungi spores. An additional treatment with nonsterilized soil and without phosphate fertilization and mycorrhizal inoculation was used. The inoculation of VAM promoved a significative increment (P<0.05) on the DM yield, concentration and P uptake by oat species. The mycorrhizal effects were improved by the phosphate fertilization. The best results were observed with the application of triple superphosphate on the level 60 kg of P₂O₅/ha. G. macrocarpum was more efficient than native VAM fungi. The yellow oat showed the greatest RMD, independently of P source. The root colonization and the number of spores were increased by the VAM inoculation, mainly with yellow oat cultivation. The P application affected negatively these parameters, at the highest level (60kg of P₂O₅/ha). The inverse was observed with application of rock phosphate.