Part 1, Section 1: Soil Management
In recent years there has been an increasing realization of the negative aspects of soil tillage, which explains the increased adoption of no-tillage:
- Takes time
- Costs money (fuel, equipment, maintenance)
- Increases erosion
- Reduces near-surface organic matter content
- Destroys soil tilth
- Promotes soil crusting
- Increases runoff
- Increases evaporation losses
- Reduces biological activity (e.g., earthworms)
- Brings rocks to surface
A major concern of producers that may have slowed the adoption of no-till is whether they can produce the same yields as with tillage. No-tillage is most challenging on poorly drained soils. In addition, in northern Pennsylvania, a short growing season for corn may sometimes cause lower no-till yields due to the slower warming of no-till soils. On most Pennsylvania soils, however, no-till yields are similar to or better than yields obtained with tillage. A true disadvantage to no-till is that manure cannot be incorporated into the soil. If odor or ammonia losses are of concern, manure can be injected into the soil with special manure injector systems that eliminate most problems with odor and ammonia loss. Another concern with no-till is its reliance on herbicides to control weeds. To guarantee success with no-till in the future, all possible care has to be taken to avoid herbicide resistance or tolerance in weeds. Cultural practices such as crop rotation, mowing, seeding dates and rates, fertilizer placement, and cover crops need to be used in combination with herbicides to increase successful weed control in no-till.
As the adoption of no-till increases, we continue to learn more about it. There is now an increasing realization that:
- No-till without or with little mulch is not a sustainable practice. Almost all environmental benefits of no-tillage are due to the mulch cover at the soil surface. No-till should outyield tilled crops in areas where drought stress is a problem due to the water conserved by the mulch cover.
- Soil improvement with no-till takes years. Continuous no-till is recommended because rotating tillage and no-till destroys the soil-building benefits of no-till.
- No-till affects many other aspects of crop production (e.g., nutrient, weed, and pest dynamics and residue distribution) that need to be integrated into a systems approach to no-till. Crop rotations and cover crops are central to the no-till systems approach.
For farmers who still rely on tillage to do their crop management, a repertoire of primary and secondary tillage tools is available. Among the most important primary tillage tools are the moldboard plow, the chisel plow, and the disk plow.
Moldboard plows are excellent for weed control and to allow preparation of a level seedbed after alfalfa or grass sod or heavy cover crops. The moldboard plow can also be counted on to completely bury surface-applied manure, eliminating ammonia losses and odor problems. Different types of moldboard plows are available, such as wheel-mounted pull hitch and three-point hitch types, one-way and two-way (reversible) plows, and one-bottom and multiple-bottom plows. Some moldboard plows come with trip mechanisms to reduce damage in rocky soil. Moldboard plows can be run at different depths and may be used to completely or incompletely turn the plow furrow. Disadvantages of the moldboard plow include that it leaves no crop residue cover, and therefore it exposes the soil to water erosion. Tillage erosion is also significant with the moldboard plow, which is typically set to deeper depths than the other tillage tools. The moldboard plow can also cause the creation of a tillage pan just below the depth of plowing, especially if one tractor wheel or draw horse runs in the open furrow. The moldboard leaves a “dead furrow,” which sometimes creates an opportunity for gully erosion and inaccurate crop establishment. Moldboard plowing demands a skilled operator and consumes more fuel than the plowing with a chisel or disk.
The chisel plow is a very popular tillage tool in Pennsylvania. It is easy to operate and helps to loosen the soil to enable operation of conventional planting equipment. The chisel plow is not effective for weed control and is not recommended to terminate or prepare a seedbed after alfalfa, grass sod, or heavy cover crops. Chisel plows mix soil and surface residue or manure, which is sufficient to largely eliminate ammonia losses and odor problems. The chisel plow does not invert the soil much and tillage pans are typically not a problem. Chisel plows can be wheel-mounted pull-hitch types or three-point hitch-mounted types. Chisel plows come with curved shanks. Springs on these shanks determine how well the chisels penetrate soil (especially if soil is compacted). A variety of points can be mounted on the chisel shanks. These points can be wide or narrow, as well as twisted or straight. The wider and more twisted the point, the more soil disturbance will be achieved by the chisel plow and the more residue will be covered. It is important to use points that are sharp and enter the soil under an angle, or the chisel points will merely scratch the surface of the soil. Chisel plowing does not require much skill and it consumes less fuel than moldboard plowing. Dead furrows are not a problem with chisel plows. Although the chisel plow is considered to be a conservation tool, it is not common to achieve 30 percent residue cover after secondary tillage and planting operations are completed, except after high-yielding corn grain harvest. Often, chisel plows are combined with secondary tillage tools on the same frame, enabling farmers to prepare the soil for planting in a one-pass operation.
The disk plow is another conservation tillage tool. It is not as common as the chisel plow in Pennsylvania. It is easy to operate, and helps loosen and break up soil. Disk plows come in many different types, such as wheel mounted pull hitch or three-point hitch types, one-way as well as two-way disk plows. Secondary tillage is mostly required after disk plowing to allow successful seedbed preparation.
Mixing action may be sufficient to largely eliminate ammonia losses and odor after manure application depending on the depth of tillage and coverage of the manure. The disk plow is not recommended to terminate alfalfa or grass sod or to manage heavy cover crops. The disk plow typically does not enter soil as deep as the chisel plow because it does not pull itself in as well. Sufficient weight on the disk plow is needed to guarantee soil penetration. The disk plow can create plow pans, just like the moldboard plow.Its effect on crop residue cover depends on disk type and depth of operation. Disk plowing does take less power and fuel than moldboard plowing.
New tillage tools are continuously being developed. Vertical tillage machines are among them. These tools are a combination of shallow primary tillage and secondary tillage. Narrowly spaced coulters or disks are run up front, followed by secondary tillage tools, such as rolling or tine harrows and rolling baskets. The tools are designed to mix residue with soil to speed up decomposition of high-yielding corn and alleviate surface crusting or compaction and yet leave sufficient residue for erosion control. They do not help control weeds and will have a marginal effect on ammonia volatilization if used to incorporate manure. The tools differ in their aggressiveness and soil inversion. They tend to be very heavy and will cause soil compaction below their depth of operation.
Common secondary tillage tools include the disk harrow, field cultivator, spring-tooth harrow, wire-tooth harrow, and spike-tooth harrows, packer rollers, and rolling baskets. These tools are used to level soil, bust clods, and create a seedbed that is fine and firm enough to guarantee seed-to-soil contact. With improvements in planting equipment, it becomes less necessary to do secondary tillage after primary tillage. However, it is still not common for farmers to plant immediately after, for example, chisel plowing without any secondary tillage. Disk harrows tend to bury more residue than field cultivators, which are preferred for conservation tillage because they bring crop residue to the surface and don’t create tillage pans such as those formed by a disk harrow. Spike-tooth harrows are more rigid and tend to break up clods better than spring-tooth harrows, which are more rigid than wire-tooth harrows. Rolling baskets can also be used to break up clods while smoothing and slightly packing soil. Packer rollers primarily pack soil to eliminate air pockets that could compromise seed-to-soil contact. Crop residue can sometimes create a problem with secondary tillage if there is not good residue flow through the tillage machine.
With the realization that full-width inversion tillage has many disadvantages for soil quality and is expensive, companies are continuously developing new tillage tools for specific purposes. These tools generally do limited soil inversion, but may fracture soil or open it up so that infiltration or aeration is improved. For example, to alleviate soil compaction, straight, narrow-shanked subsoilers have been developed that do very little disturbance above, but fracture soil below the surface. Attachments have been developed to create zones in which a crop such as corn can be planted. The soil temperature warms up faster in the spring in the zones allowing more rapid germination and early growth of corn. These tools are designed to be used in a one-pass operation.