LEAF-AREA OF STRIP-INTERCROPPED CORN IN DRY AND NORMAL GROWING SEASONS

Crop growth models need to be adapted for cropping systems other than monoculture. This study was conducted (i) to determine the effect of row position on leaf area of corn (Zea mays L.) strip-intercropped with soybean [Glycine max (L.) Merr.] and a small grain crop (oat, Avena sativa L., in 1991; barley, Hordeum vulgare L., in 1992) and (ii) to determine whether an established leaf area model developed from monoculture corn data fits the strip-intercropping data. Corn, soybean, and small grain were planted in north-south rows on a mixed, mesic Typic Endoaquoll in Nepean, ON. There was 55.1 rainfall from emergence of Leaf 5 to silking in 1991 and 210.6 mm in 1992. Total green leaf area at grain filling varied with row position each year. The corn row next to the small grain had less leaf area than the middle row in 1991 and more leaf area than the middle row in 1992. These variable results were due to differences in weather in the two years. Dry conditions in 1991 resulted in slow expansion of leaves and in small individual leaf area. As thermal time to full expansion of the largest leaf on the plant was similar in both years, the largest leaf in 1991 occurred at an earlier developmental stage than in 1992 (Leaf 10.5 vs. Leaf 12). An existing leaf area model was found to fit the data, provided that adjustments for row position and for the timing of the development of the largest leaf were included.