Agronomic Information - Seeding Equipment
Direct Seeding is a system where no tillage occurs prior to seeding. Often, there is a single pass across the field when the seed is placed in a narrow soil opening and the crop nutrients are placed nearby. There is very little disturbance of the previous crop's standing stubble and surface residue.
Direct seeding is a combination of factors included in a Systems Approach to the operation of arable cropping land. The same basic crop growth factors are present in all seeding regimes. They are:
- access to nutrients
- competition with weeds
- access to available moisture
- use of sunlight
Direct seeding involves all of these because they affect decisions on row spacing, seeding rates, fertilizer application rates, rotations, weed control, and most of all, residue management. Good quality seed is a must, and a certified quality is desired to try and assure success at harvest.
Seed placement becomes a direct function of the ability of the opener to manage residue, place the seed and applied nutrients in an accessible and crop-safe manner, apply packing to the soil, and ensure proper depth. The depth becomes critical because of soil temperatures and moisture management. A shallow seeded crop emerges more quickly than one seeded deeper. Moisture must be maintained near the surface for the shallow placed seed in order for the seed to germinate and emerge. The topic of openers and opener selection will appear in more detail later at this site.
Residue management comes into play many times in the seeding operation and is generally one of the two major influences in the transition from conventional high disturbance seeding systems to the low disturbance methods employed in direct seeding. The second factor is weed control. In a direct seeding system, there is no dependence on any type of cultivation to remove early weed growth so a non-selective herbicide must be used to do the job. A pre-seeding burn-off with the herbicide is very fast and effective.(Please refer to the sections on weed control for more details on a workable weed control system in direct seeding).
Residue management should be the first consideration for low disturbance direct seeding as it can mean the difference between good crop establishment and poor. When excess residue prevents good seed-to-soil contact, the seed cannot become established as it has no access to moisture or nutrients, and it will not be compete with weeds. If a weed starts before the seed, the rule of "Mother Nature" says "The weed wins". (See the section on Residue Management for practical solutions for handling crop residue).
Anchored stubble and well-spread crop residue enable a direct seeding system to manage available moisture more efficiently. Direct seeding ensures that the seed has enough moisture to germinate and begin its growth, and that alone, is critical to crop establishment. Standing stubble traps moisture in both winter and summer months and the properly managed residue keeps moisture close to the soil surface.
Row spacing affects the outcome of a crop, and is dependent on the soil type and environmental area. Row spacing also affects nutrient placement, weed control and sunlight utilization. Optimum Row Spacing will depend on the following:
- soil disturbance
- nitrogen placement
- seed bed utilization
- seeding rate
(A further discussion on Row Spacing will be featured in another part of this site).
Seedbed quality is critical in any cropping system. Compromising that quality for any reason is asking for problems to occur. Most seeds prefer to be in contact with firm soil to begin to develop root systems as early as possible after germination. Seedling emergence success is, therefore, dependent on adequate nutrient and moisture and sunlight availability, with suitable weed control to ensure vigorous healthy plants through to maturity. Seeds placed improperly through the use of inadequate openers, or placed at excessive speeds will not perform to their optimum potential, resulting in underachieved yield results.
See also segments on row spacing, rotations, opener selection, fertility, packing effects and seed size. Machinery design and configuration topics also appear in this section.
Low disturbance direct seeding has provided to the producer a number of distinct economic advantages including:
- Lower fuel use to produce a crop
- Less time and labor to seed the crop
- Machinery and power sources last longer due to one-pass seeding system
- Soil quality is enhanced and soil is protected from erosion
- Wildlife habitat benefit
- Increased yield from crops
These advantages are a great help in the quest for more efficient production of food.
The secret to successful direct seeding is a combination of critical factors in a systems approach to the process. There must be the mandatory ingredients for any plant material to grow, including nutrient access, proper temperature, adequate moisture and sunlight availability.
All of these factors can be optimized with some degree of success under a direct seeding system.
Nutrients can be placed in an efficient manner in an air delivery setup, or under a conventional hoe-press seeding tool. Temperature for proper crop growth can also be influenced to some degree in a direct seeding plan, as can moisture content of the soil. Sufficient light to grow the crop is usually a function of the geographic area and number of frost-free growing days.
The effect of rotations, residue management and packing, however, are influenced by management. More discussion of residue management and rotations can be obtained in other areas at this site.
Rotations generally are dictated by whatever the producer can grow in the geographic area and what the market will purchase. A generally accepted rotation that contains alternate crops of broadleaf (oilseeds and edible legumes) and annual grasses (cereals) over a four year period includes many of the necessary elements to help manage and prevent problems of disease, crop residue control, and the mechanics of seeding.
Rotations are more than just a market-driven cycle; they allow for the application of different herbicides, which prevents the development of resistant populations. The rotation also allows for control measures to vary, such as those employed in winter cereal production. Winter cereals are a great way to confuse weeds, since they are often treated with crop protection products and receive fertilizer applications at times in the production year different from spring seeded crops. A good adage here is the rule that "any time you get to fool a weed - take it".
Residue tends not to be a significant problem when a high residue producing crop, such as a cereal, is followed by a low residue producing crop such as peas, or canola, or lentils. The standing stubble into which a broadleaf crop is seeded benefits the seedlings greatly by protecting them from the wind. As well, the increased moisture from the snow trapped in the stubble usually results in a significant gain in yield.
The cereal crop planted into a low residue crop stubble tends to have less disease but quicker emergence due to the warmer temperature on the more open ground. Rotations must allow sufficient time between pulse crops and same species oilseed crops. While alternating cereals between broadleaf crops is a good practice, the cereal species should be altered from year-to-year. More about Rotations can be found elsewhere at this site.
Residue management can be one of the key factors in whether a seeding tool is able to perform properly. Some types of residue are more difficult to clear than others, and require some prior planning before moving the seeding equipment on to the field. Farmers in some areas of the world use straw spreading machines like heavy harrows to deal with high straw residues. Fine textured residue such as the chaff of wheat must be spread by the combine, because it can't be moved after it hits the ground. The objective is to spread the entire residue over as much of the width of cut as possible. More about Residue Management can be found elsewhere at this site.
Few seeding tools will produce good seed-to-soil placement in situations of heavy trash, with the result usually showing up as poor establishment and the affiliated problems of weed infiltrations and lower yield potential. High amounts of trash also make it nearly impossible to adequately pack the soil at seeding time, further compounding the establishment problem for seeds.
Seedling establishment is still the key factor in producing a high quality, good yielding crop; if it isn't in the ground properly, there is less chance of success from the start.
Speed of operation has a great influence on the seed bed quality, since excessive speed will result in far greater spread of the seed and fertilizer outside of the respective rows. Mixing of the two ingredients can result in seedling death if high concentrations of fertilizer are used. Separation of seed and fertilizer rows is one of the very important factors for success in the direct seeding operation. High operating speed has been noted to increase soil pulverization in systems that employ separate packing passes over the field.
Packing is the much-misunderstood factor in crop establishment under a low disturbance direct seeding system. How much is enough, or too much, or just right? Good questions are often brought out at table discussions about just what is the right amount of packing pressure.
Packing improves the germination of a crop by increasing the contact between the seed and moist soil, and thus on-row packers tend to produce more consistent results than random packing. On-row packing provides no advantage to the weeds present between the seeded rows, but gives full benefit to the seed. Seed drills with on-row packing usually have more consistent depth control, and with even seeding at a shallow depth into moisture, produce a desirable field finish, quick emergence, and even maturity in the crop.
Effective packing is reduced where large amounts of inadequately spread residue is present. An increase in packing weight to overcome this is unjustified much above 35-40 pounds per wheel, and often increases draft requirements significantly. Very dry conditions at seeding time will, however, require more packing pressure for good results. Packing of any type does help; the optimum being only enough to benefit the seed without degrading the soil structure. Smaller seeded crops and some edible legumes may be adversely affected by over packing, especially in wet, heavy soils. As the amount of crop residue on the soil surface and the organic matter increase over time, over packing becomes less of a problem.
Packer wheel shape, width and placement are all very important in relation to the shape and placement of the seed opener. An important rule is to remember to pack the seed, not the fertilizer row. Packing recommendations in direct seeding operations favor on-row configurations, since they give advantage to the crop and not the area between the rows where most weed seed accumulations occur. Random packing methods such as harrow-packer bars used separately after the seed placement operation tend to produce uneven results, when compared to the on-row systems.
The bottom line on packing is that it should be adequate to produce good seed-to-soil contact. Management of rotations, residue and soil quality will help to ensure that goal is achieved.
Seed Row Spacing and Fertility
Depending on soil type and local environment, a farmer becomes an instant crop manager for his/her seeded acres, with widely varying results over the years. Well planned Rotations and the correct decisions on Row Spacing and Fertility can produce anything from a bountiful crop to a wreck. Too much nitrogen in close proximity to the seed will surely produce some measure of seedling damage, or crop maturity delay at harvest time. (See elsewhere at this site for more information on Fertility).
The type and form of the fertilizer in combination with the crop selected often dictates what result to expect, and, at what time in the crop production year. Seed-fertilizer separation is the key area to watch, and is influenced by a number of things such as soil type, moisture availability, seeding implement, and operational speed in the field. Soil conditions and seeding depth are other factors to consider.
Fertilizer can be placed in a separate banding operation, broadcast over the surface, side or mid row banded, placed with the seed, or by a combination of these methods. Forms of nitrogen containing fertilizer vary from liquid, granular, to anhydrous, with adjunct factors to control release, if desired.
Soil type will often dictate what seeding tool is selected for the farming operation. Light sandy soils will require specific attributes of the implement such as the ability to separate the seed from the fertilizer, and still seed to moisture, in order for the crop to establish. Heavy clay type soils, on the other hand, require good penetrability along with a light packing, often difficult when these soils become sticky due to the better moisture holding capacity.
Moisture availability is more prevalent in low disturbance seeding regimes after about 3 or 4 years, because of the return of all residue to the soil surface from previous crops. This allows for shallow seeding of the crop, resulting in quick emergence, usually translating into higher yields in areas of moisture deficits.
The choice of seeding implement is influenced by soil type, horsepower availability, size of farm and form of fertilizer selected. A disc type seeding tool will travel through more residue provided the standing residue is anchored, and the chaff is adequately spread. Disc machines, while they are easier to pull and require less horsepower per foot than hoe type machines, do not function as well as hoe type machines in areas of stony land. A mid row fertilizer band (MRB) is usually necessary to place adequate amounts of fertilizer in the ground with sufficient separation from the seed. Producers using disc machines without MRB, often use a separate operation to place fertilizer in the soil at a different time from seeding, to avoid problems.
Hoe type openers with sufficient spread boots can place fertilizer in the ground at seeding time, without damage to seedlings. Hoe openers will produce a somewhat more uneven surface in the seeded field, and can result in difficulties for machines such as sprayers. Most hoe type openers are selected as a single side band fertilizer applicator with the seed or a double side band, often referred to as a paired row boot. Producers who feel they are unable to justify a new seeding machine will often retro-fit an older machine to enable them to direct seed on a modified basis. More information on Retrofits is available elsewhere at this site.
Newer hoe openers can be equipped with a carbide leading edge to resist wear deterioration on the opener.
Operational speed is a critical factor in the success of direct seeding technology. A poor quality seed bed results when a field has been seeded at a high speed. Seed and fertilizer are more likely to be partially mixed where a high speed has been maintained. Furrows, which do not adequately close, are also a cause for establishment concern. Seed will lie in the bottom of the furrow and will not likely germinate unless rainfall is immediate and sustained for a day or two. Open furrows are normally accompanied by furrows with a very deep covering over them, caused by excessive dirt thrown from the back rank over the front ranks by the speed and soil disturbance.
Potential problems for wide row spacings include less support for swaths and possible high concentrations of fertilizer in the seed row. These are offset by lower machinery costs because of fewer openers, better drill clearance in heavy residue and lower power requirements. Less soil disturbance from the wider spaced openers always means less moisture loss in the field and less weed pressure due to fewer weeds germinating between the rows.
Consistent seed placement with a minimum amount of soil disturbance is a primary goal in direct seeding. The opener is an important factor in determining seed and fertilizer placement and the amount of soil disturbance. A properly selected opener will create an acceptable amount of disturbance while providing accurate seed and fertilizer placement for optimal germination and plant development. Major factors to consider when selecting an opener include: seedbed quality, seed and fertilizer separation, draft and wear.
Single Shoot Openers
The simplest openers are single shoot openers. Single shoot openers place all the product (seed and fertilizer) down a single band. A variety of designs are available on the market. They are either a narrow sweep, spreader tips, knife or disc. Large sweeps disturb a lot of soil and, therefore, are not classified as a low disturbance opener.
The narrow sweep, knife and disc openers differ in design and the way they 'process' the soil. Sweep openers cut and lift the soil out of the way. Knives wedge their way through the soil, pressing the soil into the furrow walls. The difference is less soil disturbance with knife openers, but often higher draft requirements. Disc openers cut a narrow opening in the soil, creating virtually no soil disturbance and some have relatively little draft requirements. They, however, have higher maintenance requirements and if not designed properly can encounter penetration problems with hairpinninng. However, most new disc units are designed for direct seeding conditions. Disc openers have an advantage in tall standing stubble, while hoe openers tend to work comparatively better with higher quantities of chopped straw on the surface. The disc openers will leave the soil relatively undisturbed while the hoe openers will leave small ridges of soil with bare soil where the opener went.
Single shoot openers limit the amount of fertilizer that can be placed with the seed. High concentrations of inorganic fertilizer near the seed can create problems by preventing the seed from germinating or damaging the emerging seedling. The amount of fertilizer that can be safely seed placed is dependent on the seedbed utilization, crop grown soil type and moisture conditions. Saskatchewan Agriculture, Food and Rural Revitalization has published seed-placed fertilizer guidelines at the following link:
http://www.agr.gov.sk.ca/DOCS/crops/integrated_pest_management/ soil_fertility_fertilizers/Revguide01.asp?firstPick= Crops&secondpick=Soil%20Fertility_Fertilizers& thirdpick=Null
Fertilizer over the recommended safe rates in a single shoot system must be applied by a different operation or through a separate delivery mechanism in the same operation. Separate fertilizer openers on the seeding implement will band all of the fertilizer requirements in one operation. Separate fertilizer openers provide the benefit of one pass seeding, complete separation between fertilizer and seed, and desirable fertilizer placement. However, reduced trash clearance, extra pressure on the frame, extra power requirements, extra hydraulic requirements and a separate fertilizer delivery system can limit the ability to have this type of one-pass seeding operation. A two-pass system can still provide low disturbance and good fertilizer placement while minimizing your machinery investment. The drawback is, of course, the extra operation.
Double Shoot Systems
Double shoot systems provide a separate metering and delivery system for the fertilizer and seed. This provides fertilizer and seed separation. In double shoot systems all of the fertilizer requirements are provided in a band separate from the seed. Placement and opener options are numerous and varied. There is not one best system. All are intended to separate the fertilizer from the seed to allow the fertilizer to be placed at the time of seeding. The independent nature of the seed and fertilizer placements allow all types of fertilizer to be applied at seeding. Provided there is sufficient seed and fertilizer separation, the fertilizer used can be granular, liquid or anhydrous ammonia. Double shoot opener systems can be double shoot boots, side banded fertilizer or mid row banded fertilizer.
Double Shoot Boots
Double shoot boots are a single boot that provides the opener band for both the seed and fertilizer. Most are designed to provide separation of the seed and fertilizer. There are many designs of double shoot boots. These openers provide the ease and convenience of purchasing and maintaining a single shank and a single opener for both the fertilizer and seed. Providing the cultivator can handle the extra requirements of the double shoot boots, this provides a simple and often cost effective conversion from single shoot systems.
Since a single opener is required to place all of the seed and fertilizer safely, the boots are usually larger than single shoot boots. The larger size of double shoot boots creates a higher amount of disturbance and a higher draft requirement. Although it varies with boot design, generally draft requirements increase with width and greatly increase with depth. Boots that place the fertilizer lower than the seed will increase the draft requirements dramatically over the boots that place the fertilizer to the side or above the seed.
Optimal fertilizer placement is to the side of or below the seed. However, if fertilizer is placed directly below the seed, the integrity of the soil below the seed must be maintained. Seed placed on fractured soil creates potential for uneven seed placement and mixing with the fertilizer. A poorly designed boot, a worn boot, too much packing or an improperly shaped packing wheel can cause poor seed placement. If the fertilizer is not lower than the seed then integrity of the soil below the seed is not a concern.
When considering double shoot boots, seed and fertilizer separation is critical. The separation should be sufficient to provide all of your fertilizer requirements in your respective soil and moisture conditions. The separation cannot always be determined from the showroom floor. The above ground distance between the seed and fertilizer exit points aren't necessarily the distance of spread between the seed and the fertilizer. Actual separation of the seed and fertilizer can be less than the distance between the seed and fertilizer tubes. Separation can further decrease with worn boots and increased speed.
Placement of seed and fertilizer varies considerably with boot design. The seed and fertilizer can be delivered in a narrow band, spread, split, or a combination of all three options. When the seed is split it is referred to as a paired row opener. The advantages of this system are a lower seed density in each row and greater seedbed utilization. Fertilizer is often banded below and between the paired seed rows.
Side-band and Mid-Row band
Separate fertilizer openers can place the fertilizer either in a side-band or a mid-row band (MRB) arrangement. Both systems have an essentially separate opener that creates a distinct fertilizer band separated from the seed band by varying amounts of undisturbed soil. Seed and fertilizer are both placed with single shoot openers. Any single shoot opener can be used, although side-band openers usually have the seed and fertilizer openers paired as a set.
A MRB is always an independent opener. As the name indicates, the opener is placed to put the band of fertilizer in the middle of two seed rows. Each band provides enough fertilizer for the two adjacent seed rows. Each seed row has access to only one band of fertilizer. This reduces the fertilizer opener requirement to half of the number of seed openers.
The maximum distance between the seed and fertilizer is equal to half of the distance between the seed row. Therefore, with 12 inch row spacings, the distance between the seed row and the fertilizer is 6 inches. The large distance between the seed and fertilizer allows any rate of fertilizer to be applied without creating any risk of seed damage. The large distances between the seed and fertilizer create two potential problems. One is the distance the seedling has to go to access the fertlizer, the second is the potential for increased nutrient losses due to the higher concentration of fertilizer in a band.
The distance required to access the fertilizer facilitates the need to provide the developing seedling with some starter nitrogen and some phosphorus. Nitrogen and sulfur are mobile nutrients that will be transported closer to the developing roots, but the early need for nitrogen will not be met unless some starter fertilizer is placed with the seed. Phosphorus and potassium are immobile, therefore must be intercepted by the roots to be useful. The early need for phosphorus dictates that some of the nutrient must be close to the seedling.
Side-banded fertilizer is placed close to the seed row, usually at least one-inch below and one-inch to the side of the seed row. However, a laterally placed side-band opener can reduce draft requirements. Each fertilizer band is matched with a seed row. All formulations and rates of fertilizer can be safely applied with side band openers under most conditions. The fertilizer is placed close enough to the seed to become available for the developing seedling.
Mid-Row banding (MRB) has been criticized for feeding the weeds between the seed rows and starving the seedlings until the roots can reach the fertilizer band. None of these arguments against mid-row banding have been scientifically proven or disproved. Many producers are successfully using the system by providing the seed row with some starter fertilizer. The weed pressure does not increase as packing does not occur except for on the seed row.
Liquid, dry and anhydrous ammonia fertilizers have all been used with MRB. Higher concentrations of fertilizer in each band may cause increased gaseous losses, however this may be more problematic if the soil does not seal behind the opening. Low organic matter areas and clay soils are particularly susceptible. Losses also vary with soil type, moisture conditions and depth of injection.
Packing is one of those conditions where everyone you talk to believes they have the best solution when it comes to packing of the seed during the seeding operation. This is an indicator that there are huge differences existing in soil types, crop rotations, seed sizes, machinery, seeding speed and management of the various crops. Packing is also very dependent on the weather and environment at, before and following the seeding operation itself.
Effects of Packing
Packing causes changes in the soil density. Compacting the soil around the seed increases the ability of the seed to contact moisture-laden soil, facilitating germination. Optimal packing pressure is not quantifiable given the number of variables. It has been found that the lightest packing force per wheel that effectively packs the soil should be used. This benefits emergence as much as higher packing pressure, while reducing the draft force. Over packing can be a distinct problem, especially when it comes to seed size. The trend is that the smaller the seed size, the shallower it must be planted and the lighter the packing force necessary to ensure seed-to-soil contact and thus adequate germination. Large seeded crops are seeded deeper, therefore require higher packing pressure to change the soil density at the seed. Pulse crops, although large and seeded deep, are susceptible to over packing. Wet, heavy clay soils are particularly susceptible to over packing.
On-Row versus Coil packing
On-row packing is pretty much mandatory when it comes to direct seeding. You can "get by" the first year or two with coil type packing, but you will soon learn that packing anywhere in between the shank rows will give equal chance to the weed seeds between the rows as to the seed rows themselves. "Mother natures rule" is whomever emerges first-wins, so we will want to discourage the weed seeds between the rows and give favoritism to the seed in the row by on-row pocking. Coil packers are only about 20% efficient when you examine the actual packing of the seed only.
Type of Packers
On row packers are usually pneumatic, rubber, steel, or rubber covered steel wheels. The wheel material only matters for the durability and the ability to stay clean in wet conditions. Smooth pneumatic wheels are the best design for preventing mud buildup under wet conditions. Pneumatic or semi-pneumatic packers are recommended for clay soils. Air filled tires will flex and change shape. This causes the mud to fall off and prevents it from building up on the tire.
The packing wheel should be large enough to cover the width of the seed row. A large spread will require a large packer to cover the seed row. The fertilizer does not need to be packed, however many paired row openers put the seed to the side of the shank, requiring a larger packer or precise alignment to ensure the soil over the seed is being packed. The shape of the packing wheel will influence the direction of packing force. With double shoot boots or side band openers, the seed must be sufficiently packed without affecting the seed placement or causing the fertilizer to mix with the seed. If the wheel shape isn't properly matched with the opener, the packing forces will cause the seed or fertilizer ledges to collapse, potentially affecting germination. Considerably higher packing force is required if the fertilizer is placed lower than the seed. Therefore, paired row openers that place the fertilizer lower than the seed are not recommended for retrofitted air seeders. The air seeders will not have the strength or weight necessary to provide this amount of packing force.
Alternatives to wheel packers
Wheels are not the only type of packers used. Many producers successfully use a small length of chain as a cost-effective retrofit option. Chains attached to the shank will provide some packing pressure that, depending on your situation, may be sufficient. Plates are another type of packer used. One manufacturer has a plate packing system that has been used successfully by many farmers. As with the chains, each producer must individually assess these methods to determine if they are suitable for their situation.
On-row packers can either be mounted on the shank or in a gang at the back of the frame. Equipment manufacturers will mount their packers one way or the other, usually not both. This is a purchasing consideration if you have a preference for one system over the other. Packer configurations added as a retro-fit may be limited to the capabilities of the seeding machines.
Shank mounted packers give the advantage of following close behind the shank to ensure packing is consistently on the seed row. Where there is a long distance between the shank and the packer turning can cause the packers to follow in a line different from the seed rows. Shank mounted packer units often give very good results as a retro-fit arrangement for packing on-row. A shortfall of retrofitted shank mounted packers can be less than desirable trash clearance if tough or damp straw conditions exist in the field.
Mounted packers on the back of the frame will also work, but if a lot of pressure is attempted this can result in the lifting of the back of the machine. This is noticed to a greater extent on fixed compared to floating hitch frames. This condition is readily diagnosed by viewing the emerging seedlings in the sown field. A "lifted" rear rank of shanks will show every third or fourth row as barely covered and poorly established, compared to the rest of the shank rows. Mounted packers have the advantage of allowing a larger sized wheel to be used. Larger wheels create less draft.
While there are many excellent manufacturers of direct seeders, the investment in a new machine is not viable if finances, farm size or direct seeding knowledge aren't adequate. The investment to modify an existing system can be significantly lower than purchasing any new or used direct seeding equipment. It takes a pretty hard swallow to cut a cheque for the amount of a new machine.
Seeding with a modified direct seeding machine requires the same considerations as seeding with a new direct seeding machine. Unfortunately, direct seeding is not as simple as putting on low disturbance openers and eliminating pre-seed cultivations. Prior to any investment, a direct seeding plan has to be made considering crop rotations, residue management, herbicide application, fertility, soil disturbance, row spacing, and power. The ease with which these factors can be satisfactorily managed will help determine if it is feasible to convert an existing machine. There isn't one direct seeding system that will work for all farms. One of the greatest advantages of modifying a seeding machine is the amount invested. The amount invested will not be as much as a new machine. Therefore, if the machine does not match your conditions your cash outlay won't be as great.
Modifying a seeder requires skill and innovation. Direct seeding exerts higher forces on a machine. Unmodified, most machines not specifically designed for direct seeding will not withstand the extra rigors of direct seeding. Reinforcement or replacement of parts at stress points is often necessary. Stress points vary with machines, but common areas requiring reinforcement include the hitch, frame and shanks. Modifying seeding equipment is as individual as the owner and the type of machine. However, innovative farmers have developed, through trial and error, some of the most common considerations for modifying most machines. Producers and manufacturers have developed many off-the-shelf components to simplify machinery modification. These parts will save a lot of time and experimentation.
Seeding under a direct seeding system will alter conditions enough that the performance of the machine will be different from its performance in a conventional system. The ability to improve the machine to accommodate these changed conditions will determine its suitability for direct seeding.
Conventional Double Disc Drills
Double disc press drills are generally inadequate for direct seeding. The drill has insufficient soil penetration for direct seeding. Hairpinning is also quite common. Additional trip pressure and additional weight will help penetration, however it is still often inadequate and causes increased wear on the discs and packer bearings.
Heavy Duty Double Disc Drills
A beefed up version of the double disc drill, heavy duty disc drills are heavier to accommodate ballasting and are equipped with higher spring trip settings. To convert these drills to an effective direct seeding machine, weight must be added and an additional coulter must be placed in front of the discs to prevent hairpinning.
There is a wide variety of hoe drills. Most are rugged, have few moving parts and have on row packing. With the exception of older 2 rank models, most can be used for direct seeding if the residue is well managed. Converting to narrow openers will help reduce soil disturbance and sometimes improve wear characteristics and penetration. Some low draft double shoot openers may be suitable for drills with a high trip pressure. Because of draft pressure requirements and packing requirements, only openers that do not place the fertilizer lower than the seed will be effective. If the drill does not have on-row packing after market gang packers should be added.
Air seeders are the most commonly modified equipment for direct seeding. Heavy and medium duty cultivators are heavy enough to work in unworked ground. Light duty cultivators do not have the penetration ability to work in direct seeding situations. Generally, if the cultivator can penetrate unworked stubble to the depth required for "seeding and fertilizing" it can be used for direct seeding.
Improving ground following capabilities, adding narrow openers and providing on-row packing will make the machine more like a drill. Ground following capabilities can be achieved by adding a floating hitch. Packers can be shank mounted or gang packers. Narrow openers can reduce draft requirements and create less disturbance. Openers must be matched to the cultivator's capabilities. Openers that increase the draft requirements will increase the trip force required and increase the implement draft. This will limit opener selection unless you have a heavy-duty cultivator with heavy-duty trips. Heavy-duty trips may not be suitable in rocky soil. Higher trip forces will increase the wear on the trip mechanism. After tripping on a rock, the shank abruptly slams back into position, creating potential for severe damage to the shank and openers.
Two-pass seeding is rather simple with converted air seeders. The air tank that initially came with the cultivator can supply all of the seed or all of the fertilizer. The seed boot can be a simple single shoot opener and the packers can be mounted whatever way works best. If the cultivator is suited for seeding into stubble, the two-pass operation will be successful.
The difficulty in converting an air seeder comes in the conversion to a one-pass seeding system. Applying all of the fertilizer at seeding requires separating the seed and fertilizer. From distribution to placement, the option to keep the fertilizer separate must be available. At distribution, this requires a separate distribution system for seed and fertilizer. The original air tank can be used for the seed or fertilizer. An extra tank can be added on the frame of the cultivator, as a tow-between or as a tow-behind. These tanks would require a complete and separate distribution system. If the original air tank is a split tank, it can be used if a separate distribution system is present or added. All changes will create changes to the horsepower, hydraulic capacity and frame strength requirements.
Opener selection will also greatly impact performance and conversion adaptability. In addition to the performance of the openers, suitability for use on an air seeder has to be considered. Double shoot boots have a good fit for converted air seeders provided the boots do not exceed the draft limitation or the tripping capacity of the system. The minimal packing potential of air seeders will also restrict double shoot openers to an opener that does not place the fertilizer lower than the seed.
The cultivator may not have the strength or design to handle mid or side row banders. Disc-type mid-row banders require a solid frame and possibly extra weight to the frame. Flexible type frames won't provide enough penetration pressure. Shank type mid row banders do not have the same restrictions.