MYCORRHIZAL DEVELOPMENT AND PHOSPHORUS ABSORPTION IN MAIZE UNDER CONVENTIONAL AND REDUCED TILLAGE

Arbuscular mycorrhizae participate in P uptake by maize (Zea mays L.). Previous studies using pot-grown plants have shown that P uptake by m aize is greater when soil is not disturbed between cropping and planti ng. This study was conducted to determine if mycorrhizal colonization and shoot P absorption in the field are higher under reduced tillage, under conditions of soil fertility and tillage management representati ve of commercial farming. Maize was sampled in 1990 and 1991 from plot s maintained under no-till (NT), and ridge tillage (RT). These were co ntrasted with maize from plots given moldboard plow (MP) tillage each year, which disturbs the soil to a greater extent. Plots were fertiliz ed at recommended rates. In the early part of both years, shoot P conc entration in NT and RT were significantly greater than under MP. These differences in shoot P did not persist after the six-leaf stage. Grea ter development of mycorrhizae in the early season was seen in the RT and NT systems relative to that in MP. There were no significant effec ts of tillage on final yield, possibly due to the relatively high soil P levels. Under NT and RT, arbuscular colonization had a maximum at 4 8 d after planting (DAP) of 55% and 60%, respectively, followed by a l inear decrease to near 10% at 166 DAP. Under MP, a plateau of 45% arbu scular colonization was sustained between 48 and 97 DAP, followed by a linear decrease similar to that in NT and RT.