628 PB 478 Trees, Crops and Soil Microbes Interact In Alley Cropping Systems

Abstract

Red alder (Alnus rubra Bong) and black locust (Robina pseudoacacia L.) were intercropped in different planting patterns with sweet corn (Zea mays L.) in Corvallis, Oregon. In both years, sweet corn yield in alley cropping systems was significantly reduced when trees occupied more than 20 % of the total area. In the first year, higher yield were harvested in corn rows adjacent to the trees which compensated for reduced cropping area in the alley cropping systems. Low sweet corn yield coincided with high pruning biomass production. Red alder pruning biomass was small in the first year but equivalent to black locust in the following year. In the second year, soil microbial counts at planting time showed that bacterial and fungal activity in the tree rows was significantly higher compared to corn rows. At corn harvest, fungal activity was higher in tree rows and in corn rows adjacent to trees compared to corn rows more distant to the trees or corn rows in monocropping systems. It might be that higher sweet corn yield in rows next to the trees not only are the result of an increase in the amount of intercepted light but that below ground effects such as nitrogen mineralization from increased microbial activity or nitrogen transfer from the trees to the crop play an important role.