One thing I like to evaluate while doing yield checks is the health of the corn plant. The easiest, and most common, deficiency to check for is Nitrogen deficiency. Nitrogen deficiency will show up as yellowing on the lowest leaves of the plant first, and then work its way up the plant if it is more severe. Nitrogen deficiency starts on the tip of the leaf and works towards the stalk. Wide spread nitrogen deficiency can mean a couple of things. First, in good growing conditions it may simply be a sign that yield is outpacing the yield goal and amount of fertilizer applied. Second, if yield goal and estimated yield are approximate, some nitrogen may have been lost somewhere in the growing season. A good remedy for both situations is to consider split applying your nitrogen next season.