My six-foot-tall father standing in our tallest corn on July 3rd.
Knee-high by the Fourth of July is a common saying in the midwest. It refers to the height of corn. I guess that used to be a decent target for corn in the old days. Corn is planted earlier now.
This is a corn plant showing potassium deficiency. Yellowing on the outside of the lower leaves is the telltale sign. This plant is alongside a gravel road so it probably has more to do with soil compaction and the inability of the corn roots to search out available potassium than an actual potassium deficiency in the soil. The corn looks fine a few rows in.
It’s enlightening that corn shows it’s deficiencies so readily. What if our personal deficiencies were as visible?
Curiousfarmer 
I see the remnants of old corn plants on the soil around the new ones. Were those from last season? I am guessing we can still see them as you “no till” planted the corn instead of plowing the old stalks under.
Do you plant corn back to back seasonally? I always heard that corn took so much out of the soil that you had to rotate it with other crops. Or do you test the soil to see how much nitrogen is available before planting?
This field is what we call 2nd year corn. Good eye to see last year’s corn stalk.
We grazed the cows on the stalks last fall. This spring we covered the field in cattle manure and then chisel plowed and disced the manure in. We then planted corn.
We have a feel for available nitrogen based on the amount of manure we apply. If we guess wrong, nitrogen deficiency shows up as yellow streaking in the center of the leaf and/or completely yellowish plants. Look at a corn field where it has flooded and you might see these symptoms.