No-Till Farming Pros and Cons

Image Gallery Herbicides are often used in no-till farming to kill a cover crop before a cash crop is planted in the spring. PHOTO: U.S. DEPARTMENT OF AGRICULTURE

To many people, no-till farming appears to be a tremendous step forward for agriculture. At a time when fertile topsoil is being worn away by wind and water at rates that are figured in tons per acre per year, a drastic new soil-conservation measure is certainly in order. And as you're about to see, no-till does preserve topsoil, but this advantage doesn't come without certain trade-offs. As it's currently practiced in the U.S., no-till farming might more appropriately be called no-till/chemical agriculture.

No-Till Basics 

In conventional tillage, the earth is turned to a depth of 8 to 12 inches with a plow, most commonly one of the moldboard variety. Subsequently, the plot is disked at least twice more to prepare the seedbed before planting takes place. In no-till, however, the first three steps in conventional cultivation are dispensed with. Planting is done right through the residues of previous plantings and weeds with a device (usually a coulter) that cuts a slot a few inches wide, followed by equipment that places the seeds and closes the trench. There's much more of a difference between these two agricultural techniques than three passes over the field, though, so let's look into the rationale of each method.

Benefits of No-Till Farming  

In the first paragraph of the landmark 1943 book Plowman's Folly, Edward H. Faulkner said, "The truth is that no one has ever advanced a scientific reason for plowing." Nonetheless, 40 years after that publication cracked the foundations of agricultural science, most farmers still plow. Why?

The most obvious (or at least the most frequently claimed) reason that soil is tilled is to loosen it so oxygen and water can reach the area where roots will grow. It seems logical that friable, loose earth would allow roots to spread evenly and to proliferate, and this is indeed the case. But using a moldboard plow doesn't necessarily produce such soil. Plowing and disking a field results in a soil with broken structure lying atop a heavily compressed plow pan (the undisturbed layer that the plow doesn't reach). This broken-up soil is very prone to being compacted by rainfall. In addition, many passes must be made over the field with very heavy equipment, the wheels of which further compress the soil. Untilled ground starts off being less compacted than a heavily machine-worked field, and it stays that way. What's more, earth that has become compressed by tillage or machinery will return to a less compacted state after a few years of no-till planting.

Plowing, it is claimed, incorporates fertilizers and crop residues into the soil, making nutrients readily available to the roots of the plants. Turning organic matter under also has the benefit of preventing planters from becoming fouled with surface trash. In no-till farming, crop residues are left on the surface, where the nutrients that result from their decay can leach into the soil. This leaching process is far more thorough than you might imagine. Fertilizers—including anhydrous ammonia, phosphorus, and potassium—are at least as effective on the no-till fields where they've been dispersed as on the plowed plots. And with the right equipment, these ingredients can be placed directly into the planting trench (where they're most needed) during seeding. As for the potential problem of the planter fouling with residues, specially designed no-till planters have a device that cuts a slot through surface trash. Besides, studies have shown that the accumulation of this surface material levels off after a few seasons of no-till practice.