Chapter 17

Soil Management for Field Crops

Conservation Tillage Implements

This section gives a general introduction into the types of tillage/seeding equipment, farmers have used in their attempts at conservation farming and their relative merits and shortcomings in small grains and oilseed production. Conventional drills or planters are designed to sow into tilled, uniform soil conditions. Conservation tillage drills or planters can operate in tilled fields but are designed for tougher conditions such as sods and firmly compacted, uneven or residue covered soils. The drill or planter has the ability to cut through all types of residues and ground cover and allow the residue to flow by without clogging the machinery. Penetrating the soil and residue requires more down-pressure. This pressure is achieved with more ballast, adding weights on the planters or drills, or by having pneumatic or hydraulic systems that apply downward pressure. Conservation tillage equipment has the added work of making sure the seed can reach the proper depth in the soil. This often involves moving residues to the side or away from the seed trench and adjusting equipment depth settings.

Row Cleaners

Row cleaners move residue (crop or native vegetation) out of the drill area to enable easier in the row area (Figure 17.18). When planting in heavy surface residue in early spring, using row cleaners to move only residue away from the row can aid in soil warm-up. This can be especially helpful on poorly drained soils. Removing residue near the row reduces the chance of hairpinning.

Coulters

Most conservation tillage planters and some drills have coulters in front of the disk openers to ensure residue cutting and to fracture the soil in front of the disk openers—primarily to cut through crop residue and sometimes to help with opening the seed furrow and loosening soil (Figure 17.19). In doing so, coulters protect disk openers from excessive wear. For adequate coulter penetration, weight may have to be added to the carrier. The weight of the planter or drill is transferred to the cutting coulters and the opener assembly through the pressure springs or rubber buffers. The pressure springs or rubber buffers maintain pressure on the coulters for residue cutting and soil penetration yet allow the coulter to trip and reset if it encounters rocks or other obstructions. Some planters or drills use a weight-transfer linkage to transfer some of the tractor weight to the coulters to ensure penetration. Coulters, particularly wider coulters, require more down-pressure to get the unit in the ground.

Types of Coulters

Many types of coulters are available to cut residue and penetrate the soil. Each have advantages and disadvantages, so choosing one can be confusing.

Disk Openers

The major function of disk openers is to create a well-defined groove in the soil where the seed can be placed at the proper depth (Figure 17.20). Disk openers will usually follow a tillage coulter that has cut residue and penetrated firm soil. Single-disk openers, double-disk openers, and offset double-disk openers are available. A single-disk opener forms a slot or groove in the soil for seed placement and one or more press wheels compact soil around the seed. Single-disk openers require less down pressure for soil penetration than double disk openers.

Gauge Wheels

Gauge wheels roll along the soil surface and are responsible for setting the depth of the planting unit and disk openers. Gauge wheels are typically located alongside the disk opener blade(s). Ideally gauge wheels should be as close as possible to where the seed drops to get the most precise depth control.

Seed Metering Devices

Conservation tillage drills are typically used to plant smaller seeded crops such as legumes, oats, wheat, rye, barley, and cover crops. Conservation tillage planters are designed to plant larger seeded crops such as corn, sorghum, sunflowers, soybeans, and cotton. Some crops, such as soybeans, can be planted effectively with either a drill or a planter, given certain modifications. However, other crops can only be successfully planted with one or the other.

Drills

Unlike the planters that are used for row crops, seed drills do not separate and drop seeds. Instead, seed flowing out of the opening at the bottom of a hopper box is metered by the seed metering unit, which is opened a set distance for a given seed size and seeding rate (Figure 17.22). The seed then falls down through the drop tubes and dropped either between or just behind the disk openers. Most drills use air to convey seeds in plastic tubes from the seed hopper to the disk openers. Drills actually meter out a volume of seed rather than a precise weight or number of seeds.

Planters

Precision meters on planters are designed to meter out single seeds at an exact spacing. Precision flow meters are designed to separate out single seeds and deliver them at a preset time interval. This is known as singulation. The metering mechanism should drop the same number of seeds per unit length regardless of variation in seed size and shape, travel speed, and slopes. Planter plates with individual openings for each seed are much more precise in spacing than feed cups used on drills.

Seed Tubes and Guards

Seeds travel down seed tubes before being deposited in the bottom of the seed trench. Seed tube guards are common retrofits that protect seed tubes from wear. After leaving the seed meter, seeds travel down a seed tube, typically located between or beside the opening disks. Seed tubes are engineered to (1) deliver seeds in a uniform spacing and (2) deposit seed at the bottom of the seed trench, typically 1 to 2 inches below the end of the seed tube.

Press Wheels

Press wheels help provide good seed-soil contact by pushing seed into the furrow, closing the furrow, and firming soil over the seed (Figure 17.24). Press wheels improve emergence in all conditions and greatly improve emergence in dry conditions. On planters, closing wheels are meant to seal the V-shaped seed slot but not compact the soil on the surface.

Drag Chains

While drag chains are a simple and economical addition to a drill or planter, they can significantly add to the performance of a drill or planter, especially when the surface finish of the closing system is found to be uneven or not completely closed.

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