Soil Tillage in Organic Farming Systems
Conservation Tillage Planters
With the absence of tillage, seed placement, compaction prevention, and weed control become more critical. To accomplish successful planting, conservation tillage planters likely will be equipped with similar but more options than conventional tillage planters (See Figure 6.17). The list may include some or all of the following: 1) residue removers to move residue out of the row area; 2) coulters to cut through crop residue and loosen a small volume of soil around the seeds; 3) metering unit to obtain accurate spacing between individual seeds; 4) seed tube to drop the seeds into the seed furrow; 5) double-disk openers to open a slot to the appropriate depth; 6) seed firmer to press the seeds to the bottom of the seed furrow; and 8) firming and closing wheels to firm soil above the seeds and cover the seeds.
All row cleaners are designed to sweep residue away from the opening disks of the planter units (See Figure 6.18). Moving the residue means that the seed furrow opener no longer needs to cut through it. This should increase the life of the opener disks by reducing wear. Removing residue helps to avoid hair-pinning (bending and pushing straw stalks into soil by double disk openers), which can wick moisture away from the seed in the furrow and prevent good seed to soil contact. By moving residue and exposing bare soil, row cleaners can help increase soil temperatures in the seed zone. This in turn can lead to accelerated germination time. The row cleaners are meant to move residue, not soil.
Most no-till fields have a certain amount of residue that normally must be cut or moved slightly to allow the seed furrow opener and press wheel to function properly. Some coulters (See Figure 6.19) have depth wheels and some are spring-loaded. The coulter should be operated at slightly less than the seed placement depth. This prevents loosening soil beneath where the seed will be placed, and avoids forming air pockets which may dry out the soil. Coulter operating depth in relation to seeding depth is more consistent when the coulter is mounted to the planting unit. Coulters should be mounted close to the seed furrow openers to avoid tracking errors on slopes and curves. The amount, condition, and distribution of previous crop residue as well as soil conditions affect proper operation of the coulter. Fresh, damp, wheat straw is tough and difficult to cut.
The purpose of depth-gauge wheels is to control the operating depth of the seed furrow openers and ultimately the planting depth (See Figure 6.20). In conservation tillage systems, this adjustment is critical and must be evaluated when planting in different types and amounts of crop residues.
On planters, press wheels are meant to close the V-shaped seed slot but not compact the soil on top (See Figure 6.20). Press wheels help provide good seed-soil contact by pushing seed into the furrow, closing the furrow and firming soil over the seed.
Chains trailing behind the press wheels are designed to provide a final closing operation, lightly firming the seed furrow and leveling the planting strip. If crusting tends to be an issue, these might be an attractive option.
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