Leaf Azimuth in Strip‐Intercropped Corn

In strip‐intercropping conditions where rows of corn ( Zea mays L.) are subjected to widely different levels of radiation interception and of water and nutrient competition, leaf azimuthal direction may be an important determinant of yield. Observations of ear leaf direction were made on two outside rows and one middle row of a corn strip grown with small‐grain cereal and soybean [ Glycine max (L.) Merr.] stripintercrops in four trials with north‐south rows in Ontario and Michigan. The objectives were to assess if row position within the strip and seed orientation at planting affect leaf azimuth and to find out if ear leaf azimuth and yield are related. In only one of the four trials was there a correlation between yield and the frequency of ears from ear leaves pointing in a specific direction (west). In both locations, row position affected the proportion of ear leaves in a direction perpendicular to the row and toward the inside of the strip rather than toward the outside in the case of border rows. When seed orientation at planting was controlled, 60 to 74% of ear leaves (leaves 11 or 12) developed in the same direction as the embryo orientation or opposite this orientation. Random orientation of the seed resulted in random ear leaf azimuths, except in a very dry growing season, when leaf azimuthal directions were mostly parallel to row direction, minimizing interception of radiation. This suggests that leaf azimuth could be an indicator of water deficit.