Average versus individual height can differ due to variability, but are the same in principle. Usually productivity is depending on pod production relative to % absorbed light, Q%. If so plant height is a covariate of leaf number and shape but Q% is measured with light sensors, or by leaf dry weight and pod number per unit area; both can be measured by parcel sampling in a given square frame that is moved at random in the plot, at different intervals from plantation. This last procedure is destructive. Main variables are plant density and soil condition for a given variety.

Might I add that if you like instrumentation or not-so-remote sensing for precision agriculture there is a CIGR explicative reference with several applications on cotton and soybean http://www.cigrjournal.org/index.php/Ejounral/article/view/1115/1171

Hi,

I pretty much agree with Guido's answer about the difference between individual (plant) and crop (canopy) height values. Canopy height is usually an average( or maximum) in situ measurement of above- ground parts. There can be a large difference between plant height and canopy height when crops senesce or lodge; plant height ( as measured on a ruler when unfolded) is then large, whereas canopy height is low.