Vertical till cuts or sizes crop residue and lightly tills the top 1 to 4 inches of soil. This definition eliminates any use of shanks, points and disks. Most vertical-till equipment consists of vertical coulters set between 0- and degree angles Figure Vertical till typically maintains a crop residue cover of at least 50 percent of the soil surface Figure However, a potential downside to vertical till may occur if crop residues are sized too small and become easily blown or washed away, reducing soil coverage.
Field cultivation is a common secondary tillage practice done once in the spring before planting. It pulverizes smaller soil clods remaining after primary tillage and incorporates broadcasted fertilizers Figure It leaves soybean crop residues covering 20 to 30 percent of the soil surface and tends to be a good option for medium-textured, well-drained soils Figure Field cultivation in the spring has a much lower fuel, time and labor cost requirement than deep and medium-depth tillage systems.
Tandem disking is a common secondary tillage practice used in the spring to prepare a smooth seedbed and incorporate broadcasted fertilizers. However, if used as a primary tillage tool, tandem disking can have the same potential downside as vertical tillage, as crop residue becomes prone to blowing or washing away. No-till is the complete absence of any primary or secondary tillage practices with the goal of leaving the soil undisturbed as much as possible during the entire year.
Most no-till planters have residue managers, finger coulters and double disk openers that move some residue from the row and improve seed-to-soil contact. Similarly, grain drills have a wavy coulter ahead of the seed tube to provide optimal seed placement. This is the only soil disturbance in no-tilled fields. The high amount of crop residues remaining on the soil surface helps maintain or increase soil organic matter, improve moisture retention and decrease soil erosion Figure No-till requires special fertilizer application techniques for corn, complete chemical weed control and specially equipped planters.
Due to the potential slower soil warm-up in the spring, no-till has typically been successful in regions with lower precipitation or well-drained coarse or medium-textured soils. Field activities performed under wet conditions often cause surface compaction.
Perennial crops such as alfalfa, or cover crops such as annual rye or tillage radish may help break up compacted layers. Additionally, many Minnesota soils have a high content of expanding smectite clay minerals that experience annual wetting and drying cycles. These properties shrink and swell the soil, creating deep cracks that can naturally repair compaction damage. Earthworms are another form of bio-tillage Figure They create large pores, which increase water infiltration and root growth.
Their castings improve microbial growth, nutrient availability and soil structure. Earthworms are quite active and feed by bringing organic debris residue from the surface down into their burrows.
In a well-populated Minnesota soil, earthworms can recycle 8, pounds of soil per acre per year. Full-width tillage systems, such as moldboard and chisel plowing, disrupt earthworm channels, resulting in reduced numbers in tilled fields compared to no-till or similar low-disturbance systems. Tillage equipment manufacturers have recently been developing new technological advances for tillage implements.
Companies are investing in the research and development of variable-depth or variable-intensity tillage implements that can be controlled by wireless touchscreen devices or integrated with emerging soil sensor technologies and decision-support tools, creating a fully automated tillage management system. Other features include using preset gang adjustments for different fields with differing residue levels and soil texture.
Salford, an Ontario-based company, recently introduced a variable-depth tillage implement that combines a chisel plow and a wavy coulter vertical till Figure A farmer can engage both the chisel plow and vertical till for high crop residue conditions or for clayey soils and then automatically raise up the chisel plow to only use the vertical till coulters when on slopes, sandier soils or low-residue areas.
Table 1 categorizes tillage implements based on their relative cost per acre to operate and the potential to have negative soil effects. Negative soil effects of tillage include soil crusting, soil erosion, losing soil organic matter, and poor soil structure. Lower numbers from the chart indicate that tillage systems such as no-till, strip till, and vertical tillage have less potential for soil loss by erosion, will maintain soil aggregation, can maintain or build organic matter, and are less expensive to operate.
Aggressive systems such as moldboard or chisel plowing and deep ripping have a much higher potential for destroying soil structure, creating individual soil particles that are prone to wind and water erosion, and cost the most in fuel and wear and tear on machinery.
Note that there are a variety of tillage implements that cover the spectrum of cost and soil impacts. This model is based on crop management decisions applied in a field. The NRCS assigns a numerical value to each tillage operation. STIR values range from 0 to , with lower scores indicating less soil disturbance. Soil structure is formed by the aggregation of individual soil particles clay, silt, sand, pieces of organic matter into structural units or peds.
Soil aggregation is the movement and then sticking of soil particles together Figure Microscopic bacteria and fungi in the soil as well as plant roots play a vital role for soil particles to stick and stay together as peds.
Their sticky exudates and hyphae physically hold the soil together, helping soil structure to form and persist over time. The more diverse and abundant the microbial population, the faster soil aggregation can build. Between aggregates, many large pore spaces allow roots to penetrate the soil more easily and air and water to readily pass through. All these benefits are based on building and preserving soil structure.
Tillage breaks apart soil aggregates, damaging the existing soil structure, and adds oxygen to the soil that facilitates the breakdown of organic matter by microbes. Over time, tillage reduces soil biological life. The deeper and more aggressive the tillage, the weaker the soil structure.
This leads to more fine aggregates and individual soil particles, which can clog pores and crust the soil surface, slowing water infiltration and increasing runoff Figure Smaller soil particles are also highly susceptible to being swept away by wind and water. The loss of topsoil severely diminishes a field's productivity. As the soil loses structure, it becomes denser and more susceptible to compaction, because of the loss of larger pore spaces Figure Compaction inhibits root growth and decreases water-holding capacity.
Repeated tillage operations at the same depth may cause serious compacted layers, or tillage pans, just below the depth of tillage. This process is only the beginning of the problem. Splashed particles clog soil pores, effectively sealing off the soil's surface, resulting in poor water infiltration. The amount of soil lost from Iowa farmland each year is directly related to soil structure, levels of crop residue remaining on the soil's surface, and the intensity of tillage practices.
Every growing season is different and the best managers make decisions based on frequent scouting and our knowledge of soil conservation practices. A couple years ago, drought left production short at the end of the season in some areas. Crop residue levels also fell short, or could at least be classified as insignificant. In the following season, a producer managing soil quality through tillage would have accounted for that in the choices made about tillage throughout the season.
Converting to no-till or reducing tillage or cultivation would have been 'in-season' choices made the following year based on the desire to limit the impact of tillage on soil erosion and soil physical, biological, and chemical properties. Producers who used conventional in-season tillage plans under those circumstances may have undermined soil quality on their land.
In general, frequent tillage can have the same negative impact on soil quality without the special circumstances. When producers use unnecessary tillage, more serious problems begin to occur. Without a break from tillage, a total break down of soil structure is possible.
Soil organisms can be affected, bringing microbial activity to a halt. Soil pores are closed, imposing severe limitations on infiltration and increasing runoff.
There may even be some initial loss of productivity with moderate levels of erosion. MidWest Plan Service. Iowa State University, Ames.
Easy to read and handy for reference, this book the work of more than 60 university and industry specialists explains the major benefits of conservation tillage. Supplementing descriptions are color drawings and photographs, plus 72 tables with color highlights. Twenty-nine chapters cover all aspects of conservation tillage. Appendices describe tillage implements and offer rainfall and temperature data maps. From the soil up. Green fields forever: The conservation tillage revolution in America.
Island Press, Washington, DC. Comprehensive collection of information on the art of horse-powered tillage using plows, discs, harrows, harrow carts, rollers, culti-packers, single row cultivators, and straddle row cultivators. The new American farmer: Profiles of agricultural innovation, 2nd ed. Lots of practical information about tillage systems can be found by searching the document for terms related to tillage.
Resource management: Soil. Revised ed. Davies, D. Eagle, and B. Farming Press, Tonbridge, UK. This book is a practical guide to the principles and practices of good soil husbandry with several chapters on tillage written by British authors with a wealth of on-farm experience. Some content is specific to England but most is broadly relevant. Rodale Institute, Kutztown, PA.
Soil dynamics in tillage and traction. Gill and G. Agricultural handbook No. Steel in the field: A farmers guide to weed management tools. Sustainable agriculture network handbook series book 2. In practical language, Steel in the Field presents what farmers and researchers have learned in the last 20 years about cutting weed-control costs through improved cultivation tools, cover crops and new cropping rotations. Stubble over the soil: The vital role of plant residue in soil management to improve soil quality.
Fundamentals of machine operation series. Very readable and highly illustrated presentation of practical information about tillage practices used for agronomic crop production. Tillage equipment pocket identification guide. There are a variety of tillage systems available for crop production. While tillage operations are performed for various reasons, producers must evaluate the need for each and every field operation conducted in order to improve profitability.
In addition, the effects of the tillage operations on the soil system and the environment must be considered. More information is available on the following tillage systems:. Tillage of the soil has been used to prepare a seedbed, kill weeds, incorporate nutrients, and manage crop residues. The goal of the tillage system has been to provide a proper environment for seed germination and root growth for crop production. Throughout the years, tillage systems have changed as new technologies have become available and the costs of fuel and labor increased.
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