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Direct seeding equipment for tractors (conservation agriculture)
Conservation Agriculture (CA) is an approach to managing agro-ecosystems for improved and sustained productivity, increased profits and food security while preserving and enhancing the resource base and the environment.
The three fundamental principles of CA are: (1) Direct planting of crop seeds, (2) Permanent soil cover, and (3) Crop diversity.
(see: Introduction to conservation agriculture (its principles & benefits) for more details)
Direct seeding involves growing crops without mechanical seedbed preparation and with minimal soil disturbance since the harvest of the previous crop. The term direct seeding is understood in CA systems as synonymous with no-till farming, zero tillage, no-tillage, direct drilling, etc. Picture1 shows the basic design of a direct planter.
No till planters or seeders have either all or some of the following components:
- Hoppers for seed (= a tool to funnel seed into the furrow/soil) and, if applicable, for fertilizer with the respective metering mechanisms and delivery tubes.
- Row cleaner, if necessary, to remove excess mulch from the plant row.
- Cutting disc to cut through residue cover.
- Furrow opener (= a tool that makes a channel or flute in the ground) for fertilizer.
- Furrow opener (= see description above) for seeds.
- Seed press wheel.
- Furrow closing wheel (often in combination with depth control).
- Furrow press wheel.
- Row cleaner
Under some circumstances, direct seeders have a row cleaner just before or combined with the cutting disc. (Picture2). Row cleaners make the seeding more efficient under the following conditions:
- Heavy or difficult mulch.
- Delicate seeds.
- In cold climates to warm up the soil.
- Cutting disc
A cutting disc is usually necessary to make a clean cut through residue cover and avoid residue collection around the planter elements or the pressing of residues into the seed row. They are particularly important with heavy residue covers and with chisel type furrow openers. The efficiency of the disc that cuts the (cover) crop residues depends on various factors:
The efficiency of the disc that cuts the (cover) crop residues depends on various factors:
- Soil conditions: texture, resistance to penetration, humidity and porosity.
- Straw and residue conditions: resistance to cutting, humidity, quantity and management.
- Seeder: weight and dynamics.
- Disc: size, shape and profile.
For good results it is recommended:
- To work during the warmest hours of the day (after 10 in the morning).
- Work when the straw is either green or completely dried, never when it is only wilted.
- Operate when soil moisture is at the point of soils being friable.
- When using animal traction, never try to seed when more than 5 tons of dry matter per hectare is left on the surface.
Inefficient cutting leads to an accumulation of residues between the different parts of the seeder and results in seed and fertilizer placement problems, i.e. irregular spacing or complete absence of seeds (Ribeira et al., 1999).
The soil needs to be firm enough to facilitate cutting through the residues, otherwise these will be pressed into the soil, resulting in hairpinning and bad soil contact for the seed. Blockage of the equipment could also result from incomplete residue cutting on soft soils (Casão and Yamaoka, 1990). The cutting discs have either smooth edges that facilitate penetration into the soil or wavy or fluted edges if more soil movement is desired, for instance when Fusarium (= a large genus of filamentous fungi widely distributed in soil and in association with plants) infestation is expected and a drier soil is needed, or to improve disc rotation and avoid blockage.
- Furrow opener
A furrow can either be opened by a chisel tine (= long, straight piece of metal with a flat end) or hoe, single disc at an angle to the furrow, double discs or by punch type injection. Usually the furrow opener is placed just before or on the tip of the tubes that drop the fertilizer and the seeds.The performance of the furrow opener depends on its geometric characteristics, the speed, the texture and density of the soil, the quantity of residues and the pressure placed on it by the seeder. It can take the form of:
- A chisel tine or hoe: commonly used in soils that have a higher resistance to penetration, but these will result in more problems with clogging the implement with residues, and can not be used in areas with stones, trunks or a lot of roots. Chisel openers, either exclusively or in combination with discs are usually preferred for lightweight no-till planters used with smaller tractors as they require less weight due to their better penetration characteristics.
- Single discs at an angle to the furrow.
- Double discs, either the same diameter or not and placed in an angle forming a "V" to each other. The additional effect is that residues not completely cut by the cutting disc, are cut by these discs resulting in less obstruction of the implement. The implement has less capacity to penetrate the soil, especially in clay soils (Ribeira et al., 1999). Discs of different diameter and offset axles have better self cleaning and penetration characteristics than those of similar diameter.
- Other types of openers, like inverted T and cross slot.
There are different opinions about the function of furrow openers in direct planters and seeders. Some believe that the furrow opener should, while placing the seed into the soil, at the same time provide some seedbed preparation in the furrow. The planters for this purpose often use hoe-type furrow openers and create considerable soil movement. This leads to higher draught power requirements, soil moisture losses and the germination of weed seeds might be stimulated. Under CA it is therefore preferred to use furrow openers which are designed to create a minimum of soil movement, regardless whether they are chisel or disc type. (Picture3)
Generally, there are four basic slot shapes (Baker et al., 1996):
- V-shaped slots;
- U-shaped slots;
- Inverted T-shaped slots;
- Cross slot.
- V-shaped slots;
V-shaped slots are almost always created by two discs which touch in the front and open at an angle at the back. The angle of the V is usually about 10 degrees. Each of the angled discs pushes roughly an equal amount of soil sideways when both discs are at the same angle to the vertical. The biggest advantage of double discs (Picture4&5) is their ability to handle surface residues, stones and minor obstacles without blockage. The construction is relatively simple and maintenance free.
When the front edges of the two discs leave a gap open at ground level, this can cause problems with residues and soil entering. This can be avoided through:
- Placing a third disc ahead of, or in between the two angled discs, which cuts the residues; or
- Positioning one of the two discs forward of the other to present a single cutting edge (offset discs); or
- Replacing one of the two discs by a smaller one; the larger disc becomes the leading edge to cut the residues.
Disadvantages of V-shaped slots:
- Need high penetration forces
- Intolerance to sub-optimal soil conditions
- Tendency to 'tuck' residues into the slot (hairpinning)
- Tend to concentrate seed and fertilizer at the base of the slot if applied in the same furrow
U-shaped slots have a broader base than V-shaped slots. They are created by a variety of opener designs:
- Single angled disc type openers.
- Hoe openers.
- Inverted T-shaped
- The Cross-Slot
- The rolling punch
All of these designs produce some loose soil on the surface near the slot that can be used to cover the slot again. Angled disc type openers scrape soil away from the centre of the slot; hoe and furrow type openers burst the soil upwards; power tiller openers chop the soil with a set of rotating blades; and furrow openers scoop the soil out from the slot zone.
- Single angled disc type opener
Single disc coulters (=A blade or wheel attached to the beam of a plow that makes vertical cuts in the soil in advance of the plowshare)
- Produce U-shaped slot
- Simple and robust
- Compact (often used for small grain seed drills)
- Good residue handling
- High penetration force required
- Considerable soil movement (depending on the angle)
- Hoe openers
Hoe type openers refer to any shaped tine or chisel, which is designed to vertically penetrate the soil. Seed is delivered either down the inside of the hollow tine itself or down a tube attached to it, which is usually open at the back. The biggest disadvantage of hoe openers is the fact that they do not handle even modest levels of residues without blockage, unless a leading disc is placed ahead of the hoe opener to cut the residues.
- Low cost.
- They penetrate the soil better requiring less weight of the implement.
- They do not tuck residues into the slot, but 'brush' them sideways.
- they do not create smear surfaces at the sides of moist planting furrows creating a better seedbed
- Problems with stones and obstacles.
- Require a good cutting disc for long residues.
- Considerable soil movement depending on shape and width.
- Inverted T-shaped
The inverted T-shaped (Picture6) slot was developed as a result of inverting the wide-top, narrow-base of the V-shape. The main objective for the development was the ability of the implement to fold the residue-covered soil back over the slot for moisture conservation. The second objective was to find a design that would be able to handle proper fertilizer placement at the same time as seeding. The implement consists of a vertical shank that curves out at its base to form two wings that are inclined towards their fronts at 5-10°. A disc in front is used to cut the residues.
- No compaction of the soil.
- Self-closure of the slot.
- Maintenance of a constant seeding depth by closely following the soil surface.
- Capable of seeding very superficially through reduced inclination of the wings
- Considerable wear on sandy soils.
- No proper furrow opening on loose soils.
- Difficult residue handling (requires a cutting disc).
- The Cross-Slot
The Cross-Slot (Picture7) furrow opener is a further development resulting from the inverted T-opener. It provides close to ideal germination conditions for the seed. It consists of a vertical cutting disc, with two small wings attached to it on both sides. The wings open a horizontal cut, in which seed is placed on one side and fertilizer on the other, separated by the vertical cut of the cutting disc.
- Ideal germination conditions for seed
- Efficient separation of seed and fertilizer
- Low draught requirement
- Good residue handling; no hairpinning problem
- Considerable wear on sandy soils
- The rolling punch
The rolling punch injection (Picture8&9) is another form of furrow opener. The seed is placed between the fingers of two star-wheels which are at an angle comparable to a double disc, punched into the soil and released. It handles residues quite well, but tends to clog when used in sticky soils.
It is recommended for annual crops that fertilizer should be placed about 5 cm besides and beneath the seeds. In a direct seeder this would mean that the furrow opener for fertilizer is offset to one side of the line of work of the seeder. However, in many planters the fertilizer is placed under the seed, but in the same line.
The relative merits of different shapes of slots and their effect on seed germination have been discussed in the animal traction section, and should be referred to. The relevant reference is Baker et al., 1996.4. Seeders and planters:
Different crops and seeds require different ways of seeding or planting. The two major types are:
- Seed drill (Picture10): the seed is planted in a continuous band into the crop row. This method is usually used for small grain crops like cereals. The seed is metered with feed rollers of different designs; either positioned one for each seed line and gravity fed or centrally with pneumatic distribution of the seed to the lines. The machines for this type of seeding are usually called seed drill or seeder.
- Precision planting (Picture11): single seeds, or a predetermined number of seeds, are placed at an equal predetermined distance within the row. This method is usually used for row crops like maize, beans, cotton, sunflower etc. The number of seeds per planting hole and the distance between each planting location is determined by seed plates which have cells or chambers to meter the seed. The metering can either be mechanical or pneumatic, where the air is either as vacuum or as pressurized air used to select the number of seeds per position.
There are some modern no-till planters which incorporate both options in one machine, the seed drill and the row-crop precision planter. The farmer only has to equip the seed-drill-cum-planter with the desired number of furrow openers and connects them to the respective metering mechanism.
(Picture12) shows Seed drill-cum-precision planter: on top the feed rollers of the metering system for drill seed, below the boxes for the precision planting seed plates
Upgrading of old seeders/planters into no-till seeders/plantersNo-till seeders and planters often are much more expensive than conventional ones. Therefore the investment in a no-till seeder or planter might create a serious obstacle for the transition process towards CA. In many cases the old conventional seed-drills or planters can be converted at low cost into no-till seeders or planters, either by the farmers themselves or by mechanical workshops. For the conversion the metering systems remains the same, the planter frame might have to be reinforced and the soil engaging parts, namely the furrow openers, are replaced by new no-till units.
(Picture13) shows a modified conventional precision planter for no-till use: adding a cutting disc in front and replacing the furrow openers for fertilizer and seed
(Picture14) shows a modified conventional seed drill for no-till use: adding new cutting discs and furrow openers and modifying the frame
(Picture15) The same seed drill after the finished modification. The upgrading was done by a farmer using modification kits
This technology is part of a series on Conservation Agriculture:
- Introduction to conservation agriculture (its principles & benefits)
- Animal traction and single-axle tractor drawn planters in conservation agriculture
- Direct seeding equipment for tractors
- Crop rotation in conservation agriculture
- Cover crop and residue management
- Weed Management
- Cover crop species, with a special focus on legumes
- Ribeira, M.F.S., A.G. Araújo, R. Casão Jr. and D.A. Benassi.1999. Máquinas para semeadura direta em solos de baixa aptidão agrícola. In: Uso e manejo do solos de baixa aptidão agrícola. Muzilli and Castro Filho (Eds.) IAPAR Circular Técnica 108. p. 139-152
- Casão Jr., R. and R.S.Yamaoka. 1990. Desenvolvimento de semeadora-adubadora direta a tração animal. In: XIX Congresso Brasileiro de Engenharia Agrícola, Piracicaba. Anais. p. 766-777.
- Baker, CJ., K.E. Saxton and W.R. Ritchie.1996.No-tillage seeding. Science and practice. CAB International, University Press Cambridge. 258pp.
More about direct seeding with tractor is available on: http://www.fao.org/ag/ca/3g.html
No-tillage Seeding in Conservation Agriculture – 2nd edition C.J. Baker, K.E. Saxton, W.R. Ritchie, W.C.T. Chamen, D.C. Reicosky, M.F.S. Ribeiro, S.E. Justice, and P.R. Hobbs (C.J. Baker and K.E. Saxton, eds) 2007
Conservation agriculture, what you should know about; tools, equipment and machines for manual use, animal traction and single axle tractors. Hand, tools and equipment manual. (http://www.fao.org/ag/ca/Training_Materials/guide_tools_equipment_animal...)
on-line database on Conservation Agriculture Technology, which is accessible through: http://www.fao.org/ag/catd/index.js
Conservation agriculture (CA) aims to achieve sustainable and profitable agriculture and subsequently aimes at improved livelihoods of farmers through the application of the three CA principles: minimal soil disturbance, permanent soil cover and crop rotations.
The working group of Conservation Agriculture consists of staff from different divisions in FAO, like the Plant Production and Protection Division (AGP), the Land and Water Division (NRL), and Rural Infrastructure and Agro-Industries Division (AGS). This multidisciplinary nature of CA requires a range of expertise available at FAO to promote the CA concept worldwide.