By Dr. Harold Willis
The tillage methods you use for soybeans should depend on your climate, soil type, slope, crop rotation, machinery and costs.
Traditional Soybean Tillage
Tillage is done for three reasons: to prepare a seedbed or improve-soil structure, to incorporate organic matter and fertilizers, and to control weeds. There are several commonly used tillage methods. The moldboard plow lifts and turns the soil, inverting the plow layer. This causes drastic disturbance in the soil ecosystem, but can be useful in heavy soils if done in the fall. Winter freezing and thawing may improve soil structure.
Chisel plows fracture the soil rather than turning it. Less energy is needed-to pull the plow, and the soil is disturbed less. Some plant residue is left on the surface, which is helpful for reducing erosion.
Discs cut and loosen soil and incorporate much of the plant residue, but they compact the soil beneath the blades.
Field cultivators and springtooth harrows dig and lift the upper layers of soil and do not compact lower soil. Little residue is incorporated.
Rotary hoes break up clods and crusts and leave a fine-particle layer.
Subsoilers and deep chisels are used to fracture subsoil and break up hard-pans, in an attempt to improve drainage and deep soil structure. Generally the effects are temporary, and without increasing soil humus, hard soil conditions will return.
In general, tillage on humus-poor, heavy soils causes deleterious effects, especially if overdone. Soil structure is destroyed, organic matter disappears and erosion increases. Tillage operations should be kept to a minimum if soil is poor.
No-till Soybean Farming
The above disadvantages of tillage in poor soils have led to the development and promotion of various reduced- and no-till systems. By using special planters that can operate in surface crop residue and by using high levels of herbicide for weed control, crops can be grown fairly successfully (except in northern climates on poorly drained clay soils).
While it is true that reduced-tillage systems do reduce erosion and save fuel, the requirements for high amounts of fertilizer and pesticides and the long-term tendency for deep soil to become depleted in oxygen and toxic are disadvantages. Soil-living pests and diseases often increase, and springtime soil temperatures may be cold.
All of these disadvantages of no-till could be eliminated and most of the advantages obtained if an adequate level of humus (up to 10 to 12%) is maintained in the soil and if the use of materials toxic to soil organisms is reduced or eliminated (pesticides, some herbicides, high-salt and chlorine-containing fertilizers, over-use of raw manure). Humus and soil life create loose, non-crusting soil structure and break up hard subsoil and hardpans, improving drainage. Erosion is greatly reduced because humus holds soil particles in small clumps (aggregates).
A fairly new tillage method that works well in some cases for corn and soybeans is called ridge planting or ridge-till. Rows must be at least 30 inches apart to allow ridges and valleys to be built up (branching varieties of soybeans must be used). The crop is planted on top of the ridges, with crop residue left in the valleys. Earlier planting is possible because ridge tops warm up soon, and wind erosion is reduced. Ridges catch more snow in winter. Weeds can be cultivated out in the valleys and if necessary, in-row herbicide can be used. Ridges must be built up each year, and machinery must be compatible with the ridge widths.
Still don’t know? Try these studies to learn more about the practical results from no-till and tillage studies:
Rodale Institute study on No-Till
A Yield Comparison from No-Till & Till (Kansas State University)
Benefits of No-Till (Michigan State University)
Soybean Seeding Rates by Tillage (Ohio State University)
No-Till Versus Conventional Soybeans (University of Kentucky)
Source: How to Grow Super Soybeans