Thu Jun 30, 2011 03:35 PM CDT
Dr. Dan Talks Agronomy 06/30 15:29 Early Season Corn Scouting Offers Many Benefits Scout everything from seed placement, plant stand, growing conditions, weeds and fertility concerns. By Daniel Davidson DTN Contributing Agronomist OMAHA (DTN) -- With our nation's holiday only a week away, it's hard to imagine that most of the corn will only be knee-high by the Fourth of July. And it varies greatly, from seed that has been in the ground for only a few weeks (such as in Ohio), compared to seed that hit the ground two months ago for much of the Western Corn Belt. With the end of June almost here, post herbicides are being applied and growers should be finishing up sidedressing nitrogen by next week. Despite this late spring, make sure you take time to scout corn. It is a vitally important activity in order to judge how planting went, what weed pressure is occurring and if the crop is off to a good start or not. When I'm out walking my fields, here are some key things I like to do. First: Record the crop leaf stage and note how it is similar or different from last year. Recording the growth stage is easy during June because you can still see the remnants of the first plumule leaf and first true leaf. From there, you simply count the number of collared leaves up from the bottom of the plant. Come July, the first two leaves have usually fallen off. So to get a true leaf stage you have to split the base of the plant and count leaf nodes (see helpful link at bottom of story). The V growth stage is important because when you get out to V8, it is too late to apply most postemergence herbicides, other than perhaps glyphosate. Second: Look at plant stands. This is a crucial observation in early corn scouting. Is emergence consistent and is the population near your target? If gaps exist, first look for seed. Was there an operator error, or mechanical error that caused seed not to be planted? Check your planter condition now while it's fresh on your mind, and make plans for repairs before next spring. If seed drop was consistent, then it was probably something else. Did the seed germinate? Cold, wet conditions are the primary causes of seed death during imbibition. Did the seed rot? Seed fungicides protect the seed and seedlings for about 30-40 days after planting, but can be overwhelmed by the pathogen if prolonged soil conditions are cool and wet. Are insects feeding? Seed corn maggot and wireworm are insects usually associated with corn emergence failures. Or are wireworms or cutworms clipping off the seedling? Third: Check planting depth. You should do this at planting and after crop establishment. Dig up a few seedlings. The growing point will be three-quarters of an inch below the soil surface. To calculate planting depth, measure the length of the mesocotyl (the stem structure between the seed and the growing point). Its length flexes, so the growing point is set at three-quarters of an inch deep. Then add the two values together (three-quarters of an inch plus length of the mesocotyl) and you have planting depth. Did you hit your target depth? Shallower-planted corn (less than 1 inch) may emerge later due to drier soil surfaces and greater temperature fluctuations. Plant too deep and emergence will be inconsistent. Make sure root tips are pointed down and shoots up and not wrapped up or unfurled. If roots seem trapped and growing laterally in the furrow, it's likely you have sidewall compaction of the furrow. Fourth: Note weed species and height. While weed pressure is important and it will be variable across a field, most growers are going to spray to take out those weeds and keep the weed seed bank count low. If you want to prevent competition and maximize weed control, knock weeds down when they average around four inches in height. I know there is a tendency to delay spring glyphosate application until the weeds are taller and more of them are present. However, this is a risk to both control and competition to the crop. Fifth: Look for early season nutrient deficiencies like nitrogen (yellow), phosphorus (reddish), or zinc, manganese or iron (yellow striations on leaves). The crop is still small enough that you can remediate the problem with either a soil or foliar application. Corn growth stages Early season cold stress Daniel Davidson can be reached at (KL/AG) Copyright 2011 DTN/The Progressive Farmer, A Telvent Brand. All rights reserved.