SP FAQ - Residue handling
Without residues the function of retaining soil humidity suffers somewhat because it is the residues covering the soil flap that are responsible for retaining much of the soil humidity. But the sophisticated control of seeding depth, enhanced soil-seed contact, and fertilizer banding functions still give the opener a distinct advantage over other no-tillage openers.
Yes! Their superior seed placement and closing functions together with fertilizer banding ensure they function very well in tilled seedbeds so long as the seedbed is firm. They do not function well in tilled seedbeds that are loose and fluffy. It is not suggested that operators who drill only tilled soils should equip themselves with Cross Slot openers. They are probably an 'over-kill' for tilled soils.
On the other hand they have no disadvantages in firm tilled soils either, so they certainly suit operators who work in both tilled and untilled seedbeds with the same drill.
So long as the openers are functioning correctly it is virtually impossible to block them in heavy residues. They have a unique method of clearing residues while still retaining the ability to micro-manage those residues so they finish up back over the slot zone. They have no problem handling 10-15 tonne/hectare (140 bushel/acre) cereal crops, for example. They have even been known to pass unblocked along the bunched (unspread) windrow left by a combine harvester when harvesting such a crop.
Cross Slot openers regularly cope with this much maize (left), grass (centre) and legume residue (right).
Most people know that residues spread over a field are one of the main attributes of no-tillage in general. This is macro-management of the residues. But most competing openers either push the residue aside at the slot zone or push a portion of it down into the slot where it contacts the seed, simply as a by-product of trying to handle it without blocking.
Cross Slot openers do neither. They raise it up with the soil flap and then replace it back where it came from after the seed is deposited, as a means of trapping soil humidity. Cross Slot openers use residues as an important tool in their superior biological functioning. This is micro-management of the residues. Other openers treat residues as an impediment to their functions. That is a key difference between Cross Slot openers and competing designs.
Operators must choose how much value they place on residues when choosing a no-tillage opener. With Cross Slot, the more residues the better (within reason) as thicker residues trap more moisture for longer than light residues.
There is often a trade-off between the two. Only when there are no residues to speak of (such as after some soybean or canola crops) is there less of a trade off between the two.
Most disc openers handle (i.e. avoid blockages with) residues better than tined openers. But most disc openers are difficult to adjust; hairpin residues in the slot; and cannot band fertilizer without duplicating the number of openers on a drill. So many no-tillers prefer tined openers, which are simpler to adjust; do not hairpin; can band fertilizer and are usually cheaper. In order to handle residues with tined openers, inter-row seeding (using GPS guidance for positioning) has become a common practice. This favours wide rows and also leaving the stubble as tall as possible.
But both tall stubble and wide rows reduce the amount of residues that lie and decompose on the ground, thereby reducing the influence of residues on building soil structure through the carbon they add to the soils during decomposition. Building soil structure is one of the most tangible things you can do towards improving crop yields (in most soils, there is a positive relationship between soil structure and crop yield). Besides, most tined openers disturb too much soil to be considered low disturbance no tillage anyway.
Cross Slot openers allow virtually any amount and type of residues to be handled without blockages, while avoiding the downsides of most other disc openers. Very little (if any) adjustments are necessary when Cross Slot openers pass from one condition to another. Nor are there any hairpinning problems with Cross Slot openers, and they can band fertilizer separately from the seed while drilling through even the heaviest residues. What is more, they can do all of this while maintaining ultra-low disturbance.
In many countries, residue loads greater than 3 tonnes/hectare (approximately 3,000 lbs/acre) are too much for most disc openers, let alone tined openers. Most tined openers will block at much lower levels than 3 tonnes /hectare. As a rule of thumb, 3 tonnes/hectare of grain yield from a wheat crop will result in at least 3 tonnes/hectare of above-ground residues. In some countries that regularly experience favourable spring growing conditions (creating a lot of vegetative growth) followed by hot dry grain-fill conditions, residues yields may far exceed grain yields because of restricted grain-fill during ripening.
Cross Slot openers will handle enormous residue loads (well in excess of 10 tonnes/hectare) with ease, while maintaining all of its desirable functions.
Many farmers are forced to burn their residues, which negates the majority of benefits that no-tillage offers in the first place. Certainly, planting in wide rows and leaving tall stubble, will still get the benefits from decomposing roots, but the biomass of roots only comprises about 40% of the total biomass available from crop residues. Tall stubble too, often stays upright for at least a year and when it does fall over much of it has already oxidized and decomposed, so that its carbon never reaches the soil.
- Farmers do not have to consider residues-handling issues when selecting desirable crop rotations. We know of at least one Cross Slot owner whose main reason for choosing Cross Slot was the drill's ability to handle any type and amount of residues that it encountered, which in turn, allowed that farmer to choose a much wider range of crop rotations than he would otherwise have been able to do.
- There should no longer be any need to inter-row drill, or to use wide rows, or to leave tall standing stubble. If there are other good reasons for doing any of these things, that is also fine, but the negative effects that these may have on improving soil structure can then be given due weight.
- Because no-tillage generally makes better use of soil water, if anything plant populations should be able to be increased rather than decreased. Eliminating the need for wide rows allows much more flexibility of seeding rates and target plant populations to be introduced.
Cross Slot openers are believed to be the only openers in the world where the central disc remains vertical at all times and also travels straight ahead. With most other disc openers there are sometimes multiple discs involved and most are angled horizontally or vertically, or both. With these other openers, the disc(s) almost always perform dual functions - clearing residues and opening the seed slots. These two functions are often in conflict with one another. Adjusting the opener to optimise one function often compromises the other function and requires considerable skill on the part of the operator to keep them functioning properly.
By contrast, the disc on Cross Slot openers has one function only - handling residues. It is the two side blades that open horizontal seed and fertilizer slots. In order to ensure that the two side blades also clear residues, the front edge of each rubs on the two vertical faces of the disc (left and right hand). Because there are two side blades (one on each side of the disc) this also provides effective horizontal separation (banding) of seed and fertilizer, which is one of the most essential functions that a no-tillage opener can perform and which most other disc openers are simply incapable of achieving at all.
As if that is not enough, Cross Slot openers also micromanage the residues that it passes through.
It is when no disturbed soil at all is visible after passage of a set of openers. The photo below shows a 20 tonne/hectare wheat residue through which 5 Cross Slot openers have passed (indicated by the 5 arrows). This amount of residue was created by the unspread windrow behind a combine harvester that had harvested a normal 6 t/ha wheat crop. The audience at a demonstration in Ukraine wanted to know what the upper limit of residue was that Cross Slot openers could handle. So the operator drilled along the unspread windrow. Such a large amount of residue may be too much for some seedlings to emerge through and we would always recommend spreading the residues as evenly as possible over the field as a sensible management practice, but the demonstration answered the audience's question.
Of course if the operator had just allowed the discs to run along on top of the ground the result may have looked similar. You will just have to take our word for it that in this case the seed and fertilizer was sown perfectly beneath the residue.
Not that we are aware of. It handles them all pretty much the same. For example it does not matter if the residues are long, cut and tangled or alternatively, short root-anchored stubble. Similarly, it deals with wet and stringy residues (including baling twine) about the same as it deals with crisp dry wheat straw. Nor is the height of standing residue an issue. It will handle standing maize (corn) without blocking, for example.
Yes. Cross Slot openers can undertake any of those options equally well. Because Cross Slot openers are strongly directional (due to the disc always pointing straight ahead) operators can seed very close to an existing row if they choose, without the machine wandering away from the chosen path. Nutrients and root residues are concentrated in the old rows and utilizing them to advantage is often a choice that Cross Slot operators make.
It means that the choice of row spacing need not be influenced by residue-clearance issues. There is no longer any need to choose wide rows simply to avoid blockages. Row spacing can then be chosen on the basis of what is agronomically best for the crop. Nor are their limitations about what crops can be grown (including cover crops) that have hitherto been dictated by the machine's ability to sow the next crop.
In short, it re-openers many otherwise-discarded agronomic and crop management options.
That was certainly a fear amongst some operators in cold climates. But in reality it has never happened in arable cropping. Certainly maize stover can take up to two years to fully decompose in cold winter climates but crop rotations take care of that problem by avoiding growing continuous maize. In other situations (with heavy (10-15 t/ha) small grained cereal residues, for example) the soil micro-organisms and fauna increase very rapidly with the change to Cross Slot no-tillage and this accelerates the decomposition process.
Thick residues create their own microclimate as a function of their thickness and continual wetness. This increases the temperature of the mass and further accelerates the decomposition process.
As an example of how the system balances itself, an experiment was carried out in New Zealand where 0, 5 and 11 tonnes per hectare of barley straw were spread on three fields of bare untilled ground in autumn. By the end of the three-month winter (where air temperatures seldom remained below 00C) all of the straw had disappeared, even on the 11 t/ha fields. Most interestingly, the weight of earthworms per hectare in each of the fields almost exactly equalled the weight of residues that had been placed on those fields, indicating that the earthworm numbers and biomass had responded directly to the amount of food available.
We have seen layers of accumulated undecomposed organic matter in non-arable soils in the highlands of Scotland and New Zealand where daytime temperatures had remained low even in summer. Some of these soils still benefitted from no-tillage of improved pasture species. With Cross Slot drills the best method is to spray out the native grass species and no-till in one or more successive forage crops (usually forage brassicas) and feed them in situ to cattle so that hoof action and urine cycling will break up the mat of undecomposed sod before no-tilling a more permanent improved pasture species. Unlike most other no-tillage openers, Cross Slot openers relish these conditions because the side blade wings undercut the dying turf mat and use it as a perfect mulch cover for the sown seeds.
In other cases powered rotary-type openers have been used to chop up the mat at the same time as drilling takes place. But most tined or simple disc openers simply cannot cope with these conditions.