No-till farming is considered a kind of conservation tillage system and is sometimes called zero tillage. It is a way of growing crops from year to year without disturbing the soil through tillage. Once called chemical farming, the terminology was changed in order to promote the idea of no-till farming being more natural. It is becoming more common as researchers study its effects and farmers uncover its economic benefits.
Producing crops usually involves regular tilling that agitates the soil in various ways, usually with tractor-drawn implements. Tilling is used to remove weeds, mix in soil amendments like fertilizers, shape the soil into rows for crop plants and furrows for irrigation, and prepare the surface for seeding. This can lead to unfavorable effects, like soil compaction; loss of organic matter; degradation of soil aggregates; death or disruption of soil microbes, arthropods, and earthworms; and soil erosion where topsoil is blown or washed away. No-till farming thus avoids these unfavorable effects by reducing or excluding the use of conventional tillage.
There is evidence that repeated tillage is destroying the soil resource base and causing adverse environmental impacts. Tillage degrades the fertility of soils, causes air and water pollution, intensifies drought stress, consumes fuel, and contributes to global warming. Today, farmers are expected to produce food in ever greater quantities. This is becoming more difficult to do in view of declining soil quality, which can be caused by soil tillage. It is becoming well known that no-till is an effective technique to reduce the degradation of soil. With this way of farming, crop residues or other organic amenities are retained on the soil surface and sowing/fertilizing is done with minimal soil disturbance. A major obstacle that farmers often face with change to continuous no-till is overcoming yield-limiting factors during the transition years, that is, the first years of no-till following a history of intensive conventional tillage. These factors are often poorly understood and may be biologically-driven. Some of the problems involve residue management and increased weed and disease infestations. Farmer experience seems to indicate that many problems during the transition are temporary and become less important as the no-till system matures and equilibriates. The judicious use of crop rotations, cover crops and same soil disturbance may help reduce agronomic risks during the transition years. Farmers switching to continuous no-till must often seek new knowledge and develop new skills and techniques in order to achieve success with this different way of farming. Answers to these questions are urgently needed to provide strategies for promoting no-till as a way to enhance agricultural sustainability for future generations.
The benefit currently receiving much scientific attention is the potential for carbon sequestration in the soil of crop fields and reducing energy input. When soil is tilled with machinery, the soil layers are inverted, air is mixed in, and, ultimately, soil microbial activity increases greatly over their natural levels. The result is that soil organic matter is broken down much more rapidly and carbon is lost from the soil into the atmosphere. This, in addition to the emissions from the farm equipment itself, increases carbon dioxide levels in the atmosphere. Carbon sequestration, in soil or elsewhere, is a proposed method of reducing these greenhouse gases. Cropland soil is an ideal carbon sink, since in most areas it has been depleted of carbon. Traditional farming practices that rely on tillage have removed carbon from the soil ecosystem by removing crop residues such as left over corn stalks, and the above mentioned effects on soil microbes. By reducing tillage, leaving crop residues to decompose where they lie, and growing winter cover crops such as grains, alfalfa, or crimson clover, a farmer can slow or even reverse carbon loss from a field. However, newer research shows that no-till may not improve carbon sequestration, as preliminary research did not sample soil deep enough to measure the soil carbon flux completely.
Yields are often immediately impacted negatively by inexperienced no-till farmers. A combination of technique, equipment, pesticides, crop rotation, fertilization, and irrigation has to be found which is optimal for the particular native conditions. However, dropping the need to till, and organize the soil into rows and drainage ditches is often cited as increasing profit by reducing costs and labor, even with an initial diminished yield.
Certain crops, like corn, do not tolerate the increased competition in early life well, and are not suitable for complete no-till agriculture. These types of plants are currently grown most successfully in a hybrid fashion by cultivating 7-inch-wide strips of fertilized bare soil spaced out with no-till mowed areas. This combines most of the environmental and labor benefits of no-till agriculture with very close to conventional corn cultivation.
Another problem that growers face is that in the spring the soil will take longer to warm and dry, which may stall planting to a less ideal future date. One reason why the soil is slower to dry is that the field absorbs less solar energy as the residue covering the soil is a much lighter colour than the black soil which would be exposed in conventional tillage.
The primary disadvantage of no-till farming is the need for specialized seeding equipment designed to plant seeds into undisturbed soil and crop residues. Often, the combination of machinery has to be custom-tailored to the condition of the native soil. However, today many types of no-till seeding equipment are readily available.
One of the purposes of tilling is to remove weeds. No-till farming does change weed composition drastically. Faster growing weeds may no longer be a problem in the face of increased competition, but shrubs and trees may begin to grow eventually.
Some farmers attack this problem with a “burn-down” herbicide such as Glyphosate in lieu of tillage for seedbed preparation, and because of this, no-till is often associated with increased chemical use in comparison to traditional tillage based methods of crop production.
In reality, attacking hardy weeds individually while mowing sporadically in between crops is a suitable substitute for that type of practice in most cases, and mixed with certain elements of a conventional herbicide regime can often serve to reduce herbicide load as well as soil fatigue from herbicide toxicity since it's directly applied, instead of mixed throughout the soil. Likewise, fertilizer use is drastically reduced as it is directly applied to the seed hole, usually in liquid form.
Crop rotation is also more important in no-till farming, as soil conditions change, and some no-till farmers utilize a wide variety of crop cycles to exploit their particular soil condition at the time and their weed situation at the time for maximum yields.
Long-term erosion is sometimes considered a problem - while much less soil is displaced, drainage gulleys that do form get deeper every year instead of disappearing. This may necessitate either sod drainways or permanent drainways in extreme circumstances. Because there is often a slight increase in soil bulk density associated with no-till farming there is a misconception that periodic tillage is necessary to “fluff” the soil back up. There are millions of acres of land that have been no-tilled for over 20 years where water infiltration, biologic activity, soil aggregate stability, and productivity have all increased well beyond nearby traditionally tilled land. No-till farming mimics the natural conditions under which most soils formed more so than any other method of farming in that the soil is left undisturbed except to place seeds in a position to germinate.
Prior to no-till farming's rise in popularity, the annual tilling of the soil often exposed arrowheads and other artifacts. Other artifacts include Civil War era bullets, medals, and buttons, coins and other metal items from destroyed houses and barns.