ISSUE 2 May 17, 2007
CONTENDING WITH CRUSTING
In parts of the state circumstances have conspired this spring to create ideal conditions for soil crusting. Soil crusting that occurs after planting and before crop emergence can prevent emergence and/or induce variability in timing of emergence. Crop establishment is currently a concern for corn fields planted the first week of May in the southeastern part of the state where heavy rains after planting followed by warm, dry weather resulted in a difficult-to-penetrate crust. Though most of the small grains were able to emerge and establish before this crust formed, corn, which takes more heat units to germinate, is just now encountering this barrier.
What can be done to prevent stand losses and improve uniformity in emergence when crusting is a problem? This question is even more important given the potential expense of replanting, both in terms of seed and planting costs as well as the potential cost to yield with a delayed planting date. The first step in determining what action is needed is to examine the extent of crusting and the stage of the germinating seedling. The coleoptile of the corn is designed to penetrate through the surface of the soil, so if you find leaves that have been force out of the side of the coleoptile before reaching the surface of the soil because of the crust, there is probably a need to help plants establish by breaking-up this crust. Timing is critical in making a decision about dealing with crusting, as older seedlings are more easily damaged by crust-breaking interventions. A range of implements have been used to break up crusts, with the rotary hoe the most commonly recommended. Harrows, culti-packers, coulter-carts, and press drills have also been used with some level of success. Whatever implement you decide to use, try it in a small area of the field first. Make sure that the benefit from breaking the crust will be greater than any losses associated with damage caused to emerged or emerging seedlings. Donít worry too much if the operation "roughens" or breaks the tip of the coleoptile, as the emerging leaves will likely be able to establish normally. If the operation leaves seedlings on the surface or excessively damages developed seedlings, then try something less aggressive. Less seedling breakage will occur when operations are done in the early morning or later in the evenings when plants are typically more pliable, but if plants are struggling and you have many acres to cover, donít be deterred by this.
Extension Agronomist for Cereal Crops