Camilo,

I don't know of any convenient non-destructive method to determine
physiological maturity for maize.  The only method I know, is to physically
sample a few of the kernels (cut them out with a knife).  In your case, I
would certainly not start sampling too early, i.e., I would wait to begin
looking, only after silks are dry and the ear covering material begins to
lose green color or dry.  Once you have the kernels removed, you can see
black layer in the pedicel.  Also, the starch line or "milk line" moves
from top of kernel toward pedicel region, as another indicator that
maturity is progressing toward black layer, but is not there yet.

Ken Boote

At 10:19 AM 5/28/02 -0300, you wrote:
>Dear Members,
>
>I am helping a coleague in a trial on which he is screening maize =
>varieties for drought tolerance. The plots (parcels?) for each maize =
>material are only two rows 5 meter long. I would like to get data to =
>adjust the genetic coeficients for some of the varieties. I am keeping =
>track of soil initial conditions as water content, fertility, number of =
>leaves, silking and tasselling date and I can get weather data, but I =
>can not damage some kernels to check on the physiological maturity (by =
>checking the black layer) since the number of plants is small. Is there =
>any other way to get maize physiological maturity date without having to =
>check on the grains? He harvest all varieties at the same day when all =
>plants are no longer green and, according to him, grain umidity varies a =
>lot between varieties since their cycle are quite different.
>Any advice?
>
>Regards,
>
>Camilo L. T. Andrade
>Embrapa Maize and Sorghum
>Rod. MG 424, Km 65, PO Box 151
>35701.970, Sete Lagoas, MG
>Brazil
>Phone: +55 21 31 3779 1235
>Fax: +55 21 31 3779 1088