Influence of arbuscular mycorrhizae on soil P dynamics, corn P nutrition and growth in a ridge-tilled commercial field

摘要

Ridge-tilled corn (Zea mays L.) could benefit from arbuscular mycorrhizal (AM) fungi. Under low soil disturbance, AM hyphal networks are preserved and can contribute to corn nutrition. A 2-yr study was conducted in the St. Lawrence Lowlands (Quebec, Canada) to test the effects of indigenous AM fungi on corn P nutrition, growth, and soil P in field cropped for 8 yr under ridge-tillage. Phosphorus treatments (0, 17, 35 kg P ha(-1)) were applied to AM-inhibited (AM(I)) (fungicide treated) and AM non-inhibited (AM(NI)) plots. Plant tissue and soil were sampled 22, 48 and 72 days after seeding (DAS). P dynamics was monitored in situ with anionic exchange membranes (PAEM) from seeding to the end of July. AM(NI) plants showed extensive AM colonization at all P rates. At 22 DAS, AM, plants had decreased growth in the absence of P inputs, while AM(NI) plants had higher dry mass (DM) and P uptake in unfertilized plots. The P-AEM was lower in the AM(NI) unfertilized soils in 1998 and at all P rates in 1999, indicating an inverse relationship between P uptake and P-AEM. At harvest, grain P content of AM(NI) plants was greater than that of AM(I) plants. In 1998, only AM(I) plants had decreased yield in the absence of P fertilization. In 1999, AM(NI) plants produced greater grain yield than AM(I) plants at all P rates. AM fungi improve the exploitation of soil P by corn thereby maintaining high yields while reducing crop reliance on P inputs in RT.