What Emerson means by his last paragraph is that yield is simply the product of ears per acre, kernels per ear, and weight per kernel. Kernel weight is not identical to test weight. It is only one component of test weight; the other being how many kernels fit into a volume bushel. Low weight kernels do not automatically guarantee low test weight because those low weight kernels may also be physically smaller and so more of them fit into a volume bushel. In other words, a volume bushel that contains a lot of small lightweight kernels may weigh as much as a volume bushel that contains fewer but heavier kernels.

Our nitrogen rate trials always result in a wide range of yields between low and high rates of N, but test weight rarely is correlated with the wide range of yields for any given hybrid in those trials.

 For another take on test weight similar in thought to Emerson's article; see my recent article online at

http://www.kingcorn.org/news/timeless/TestWeight.html