Here is a link to PSU chloryphyll early season test: http://cropsoil.psu.edu/Extension/Facts/agfact53.pdf The test is supposed to be callibrated to work on all corn, but, there is definitely some concern that various hybrids and conditions result in bad results. The test basically measures "greeness" of the leaf and many things can influence it. Additionally, the test is not considered accurate if you are using more than 15-20#/ac of N prior to planting. The test is really meant for manure applied fields and other high organic situations. Here is link to PSU late season corn stalk test: http://www.aasl.psu.edu/Corn%20stalk%20nitrate%20sampling_web.pdf Hope these help! | 
Powdery stalks---- what are your guesses as to causes??
