Leaf Area‐Leaf Weight Relationships in the Soybean Canopy1

Leaf area (A) and leaf dry weight (LW) were determined throughout the growing season for lower, middle, and upper main stem segments and branches of a field soybean [Glycine max (L.) Merrill] community. The A/LW ratios were regressed on number of days after planting, using polynomial regression models. For the middle main‐stem segment, A was also regressed on LW. Mean seasonal A/LW decreased from the base to the top of the canopy. Mean A/LW of branches was higher than that of any main‐stem segment. The A/LW ralio of each main‐stem segment continually declined until just prior to leaf senescence. The trend subsequently reversed and A/LW increased rapidly during leaf abscission. The trend in A/LW of the branches differed in that there was an initial increase in A/LW, followed by a decline and then a second increase during leaf abscission. Due to time related changes in A/LW, models for the prediction of soybean leaf area from leaf weight should also include time as a variable if observations are made at different growth stages.