Establishing uniform stands of no-till corn is difficult for some folks. At least, that's the take from Extension meetings where I talk about these kinds of things. Invariably, I can be in a room full of no-tillers who love their no-till drilled soybean crops, but complain about the hardships of getting a good stand of no-till corn, even when following last year's soybean crop. What's the deal here?
What's Unique About No-Till? Why are no-till environments often less friendly to stand establishment than conventional tillage? The answers are trash, trash, and trash! Let's remember that TRASH includes stover, stubble, and other plant materials left from previous crops or weeds that can create nightmares for germination, emergence, and seedling growth of corn. RESIDUE includes stover, stubble, and other plant materials left from previous crops or weeds that conserve soil moisture and improve soil tilth, benefiting the corn crop later in its development.
Cold, Wet Soils. Trash delays soil drying and warmup, which consequently delays or causes uneven germination and hinders early root and shoot growth. During the first five weeks of growth, no-till soils can easily average three to four fewer heat units per day than full-width tillage. Given that corn's growing point remains below the soil surface until about the six leaf collar stage, the plant's development is literally slowed compared to that of full-width tillage because of the cooler soils. The problem with slow germination or growth early in the season is that it increases the plants' exposure time to damaging soil-borne pathogens and insects, delays the roots' encounter with soil nutrients, and decreases the effective length of the available growing season for the corn crop.
Planter Problems. Trash can hinder the operation of the planter, especially when soils are on the wet side to begin with. Pieces of trash can be 'hairpinned' into the planter slot instead of being cut cleanly by the coulters (remember, seed-to-trash contact is not good!). Uneven distribution of the trash across the field and/or excessive planting speeds can cause the planter to falter in seeding depth uniformity. Surface trash and wet soils can decrease the effectiveness of the planter's closing wheels, resulting in 1) open planter slots if the down pressure is insufficient or 2) compacted planter slots if down pressure is excessive.
Troublesome Pests. Remember the importance of pest-free conditions to ensure uniform germination, emergence, and initial seedling growth? Surface trash can harbor disease inoculum that can cause seedling blights, leaf diseases, or root and stalk rots. Surface trash also provides favorable habitat for certain pesky critters such as slugs, seedcorn maggots, common stalk borers, and brown stinkbugs.
Nutrient Uptake. Nutrient management is often more difficult in no-till fields. The inability to mechanically incorporate nutrients can result in nutrient stratification. There are more opportunities for nitrogen loss from fertilizer applications from volatilization and denitrification. Slow root growth, caused by cold wet soils, delays their encounter with soil nutrients.
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The Corn Growers Guidebook , a WWW resource for corn management systems in Indiana and the eastern CornBelt.
Purdue University Agronomy Extension WWW Home Page.
Purdue Agronomy On-Line! , Purdue's Agronomy Department WWW Home Page.