Corn Emergence Assessment in Crusted Soils


and we’re out in a field up in the central part of the state that was planted about three weeks ago and in a good year you would hope that three weeks after planting we’d be able to look out across this landscape and very easily see the young corn plants but today you got to look pretty hard in some places to see anything emerging and it’s been a result of a combination of cold weather over the past three weeks and maybe more so an awful lot of rain and frequent rains that have come over the last three weeks since planting this field was planted maybe only a couple of days before all that rain started so it didn’t get much of a chance at germination before the soils likely became saturated throughout most of this field and so the farmer rotary hoed this field yesterday and we’re here today to help assess what the recovery options are and so I want to talk a little bit about what we’re seeing some of the kinds of factors that play into this decision on whether this farmer keeps the field or whether he decides to replant some or all of it. This area of the row really didn’t get a lot of action from the rotary hoe it threw a few clouds up but it mostly just sort of left big pock marks in this area of row and that’s certainly a reflective of the fact that this surface crust really set up in a in a serious way and and so there are other areas of the field where the rotary hoe did a lot more was a lot more effective but even here we see a few seedlings that I’m guessing were probably barely emerged yesterday when they ran the field and I think or the course of the another day or two is going to be become a lot more evident what kind of effective population that they have in the field is a fairly healthy seedling. The mesocotyl between the crown and the seed is nice and white the coleoptile on the first leaf are reasonably healthy the kernel itself is is firm it’s not mushy like it sometimes gets as it begins to decompose the one thing that does show on this seedling though is the radical root which is right there has simply stopped developing it doesn’t look like insect injury I don’t believe it’s disease what I suspect is that it’s probably some combination of excessive soil moisture in other words saturated soils and the cold soil temperatures that this field experienced over the last three weeks this much development of the side roots or adventitious roots is simply not normal on a seedling of this age and they developed because the primary the root tip or the growing point of the radical root was damaged by something and I suspect again it’s a combination of too much soil moisture and cold the crown of the seedling as well as the mesocotyl right below the crown is a little a little fatter that it ought to be it’s it’s swollen and that’s often a symptom of coleoptile that’s been impeded by a dense surface crust as it’s trying to elongate to the surface good example of what we call a cold shock injury to the developing seedling and it may be a little hard to see but right near the crown at the the beginning of what’s supposed to be the coleoptile that tissue is simply dead it’s not diseased and it’s not the result of insect feeding but I think this is simply indicative of not lethal cold temperatures but cold temperatures enough that it shocks the metabolic system of this young seedling and simply just stops it in its place so while technically that seedling is alive it’s certainly not going to mount to anything the other thing I worry about or the next week or so is fields like this that have been in the ground for three weeks some of them approaching four the fungicidal seed treatment is beginning to deteriorate and in fact may be totally deteriorated by now and there are still opportunities then on these young seedlings to be infected by seedling blights diseases and so a field that emerges fine say over the next couple of days under these conditions and maybe it looks good at that point there’s still a chance in another week that seedling diseases could really take a big toll and eliminate a lot of these young plants that have survived well we’ve been out in this field now for probably an hour or so and you know my initial thoughts were from the area the field we were walking was that it maybe didn’t deserve replanting as I’ve walked more this way in the field I’m simply seeing more and more areas that are not yet emerging the seedlings are looking a little rough some the radical roots are seem to be either dead or dying the dilemma that the farmer faces is you see parts of the field that are coming up just fine and so you really don’t want to replant those and then as you walk farther and farther out you you just sort of realize that well this this is much more extensive than you thought so it’s a bit of a risk to come in here and replant but given what I’m seeing now over more the field I’m thinking that may well in fact become the decision for this particular grower

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