The Full Cross Slot® Story


Massey University had backed Baker’s approach and created the Agricultural Machinery Research Centre (AMRC) in 1982, which Baker directed for 10 years. The Food and Agriculture Organization of the United Nations (FAO) commissioned Baker and his fellow researchers to write a book on their findings, which was published in 2006 and remains a standard university text in many countries today. He has been the guest speaker at numerous international no-tillage conferences and written over 80 scientific papers prior to leaving the university in 1995 and setting up several companies to commercialise his technologies.
Many aspects of no-tillage openers (the devices that open slots in the soil to implant seeds and fertilizer) had never before been studied in biological terms. But even some 50 years later, many designers of no-tillage machines still appear to believe that no-tillage machines should do no more than copy the functions of seed drills designed for conventionally-tilled seed beds, with adjustments mainly for robustness.

Baker wanted to know that each of the functions of Cross Slot machines would be backed by robust science. He was certainly not prepared to extrapolate design options that worked in conventionally tilled soils, because he had learnt that in many respects untilled soils possess superior properties to tilled soils. Nor was he prepared to guess at any “best options”. This cautious approach delayed the project many years as the team collected the data on which to base new mechanical designs and much of this information had never been researched previously.

In the end, Baker and his seeding team created a technology that was unique because it operated like no other machine and had been designed from the seed’s and soil’s points of view.

There has probably never been another farm machine designed anywhere in the world about which so much was known in scientific terms before mechanical design took place.

The main driving force was that the prediction that no-tillage would improve the sustainability and yield potential of the world’s arable crops, let alone sequester carbon and microbes back into the soils at the same time, was proving to be unfounded. World wheat yields and the soil carbon levels of arable soils, for example,did not improve noticably the introduction and widespread adoption of no-tillage since the 1960s. The technique developed a “hit and miss” reputation. Baker figured that unless no-tillage could be made to be virtually “fail safe”, only the most dedicated of farmers would use it voluntarily. The rest were likely to remain with the status quo that had served their grandfather for centuries.

An important aspect of Baker’s research was that the team became more interested in researching failures than successes. Unless a scientist or farmer knows exactly why the seeds in a particular no-tillage field germinated and grew well, growing an occasional good crop was unlikely to contribute much to mankind’s knowledge on how best to undertake no-tillage. Successes are often the result of favourable soil of weather conditions that have masked an otherwise poor opener or drilling technique. On the other hand, if scientists can identify why a particular no-tillage opener has failed and then successfully re-test improvements to it under the same repeatable controlled conditions, then that scientist is entitled to conclude that he or she understands the reasons why the original failure occurred in the first place.

In the process of comparing common V or U-shaped slots created by almost every known no-tillage opener shape at that time, Baker also tested an experimental opener shape alongside. The experimental opener reversed the cross section of V-shaped soil slots, which are wide at the top and narrow at the bottom. His experimental opener was wide at the bottom and narrow at the top. There was little more rationale for doing this than to create a slot shape that was as radically different from the norm as possible.

But the results were truly spectacular. Where V and U-shaped slots promoted 24% and 27% wheat emergence respectively in the first experiment that Baker conducted sowing wheat into a very dry soil, the experimental design promoted 77% seedling emergence from the same soil.

The experimental slot shape became known as an inverted T- shaped slot. It had been created by returning soil-plus-crop residues over the slot as the seed covering medium. This, in turn, had trapped soil water in the vapour form (soil humidity) within the slot. Open V and U- shaped slots allowed most of the soil humidity to escape and there was very little liquid water available in such a dry soil anyway. Even loose soil did not trap sufficient humidity to germinate seeds in such a dry soil (most seeds can germinate in 90-100% relative humidity in the complete absence of liquid water). V and U-shaped slots were therefore relying on liquid water for seed germination in the same way as fully tilled soils had been doing for centuries. Seed drill designers simply did not know (and many still do not know) that vapour water even exists in untilled soils and is capable of germinating seeds on its own.

When Baker and his team turned their attention to wet soils they found exactly the same order of slot performance but for quite different reasons. In wet soils, aeration around the seeds is the key objective. When residues cover the slots (as in inverted T shaped slots) they attract earthworms, which in turn aerate the slot zone with their burrows. By contrast, most V shaped slots are associated with localized compaction which discourages earthworm activity and the openers that create U shaped slots tend to brush the residues aside, taking with them the main attraction for earthworms since residues are their main food source.

Some openers smear (or even compact) the soil in or around the slots in damp soils. If smears are allowed to dry (because the slots are not adequately covered) they become crusts which physically restrict root growth. But if smears remain moist they have minimal detrimental effect.

Compaction is smearing on a thick scale. Wet or dry, compacted soil around drilled slots has a detrimental effect on germination and early seedling development by limiting oxygen diffusion in the root zone. In severe cases, root growth may be confined to the slot zone alone.

The next issue was finding ways of maintaining a constant seeding depth, which is more important in no-tillage than conventional tillage. Because there is no opportunity to smooth a no-tilled soil surface and variations in the natural settlement of untilled soils creates different soil hardness zones across any field, maintaining a consistent seeding depth is one of the most demanding functions of any no-tillage seeding machine. Baker’s team created two separate but inter-connected systems.

The first seeding depth function ensured that individual openers faithfully follow the undulations of the ground surface. They achieved this by using parallelogram articulating drag arms to attach the openers to the drill frame and pushing the openers into the ground with nitrogen-cushioned individual hydraulic cylinders that maintain a constant downforce on the openers regardless of their vertical positions within an extended range 45 cm (20 inches).

The second seeding depth function (that of ensuring that soil hardness did not affect seeding depth) was solved by inventing a unique electro-hydraulic auto-downforce (ADF) system that monitors ground hardness on-the-move 10 times per second and adjusts the oil pressure in the individual hydraulic cylinders 3 times per second.

These two seeding depth systems operate in harmony but independently, ensuring that no-tillage seeding depth is more consistent than even conventional seed drills operating in tilled and pre-smoothed soils.

An important challenge was to ensure that any type or amount of surface residues could not only be handled by Cross Slot openers without blockage, but that the resulting mulch of residues could be manipulated or managed to provide the all-important water vapour-trapping cover over the sown seeds and also be allowed to decompose and feed the earthworms and microbes that colonise the slot zone. Most crop residues contain about 40% carbon and the natural process of decomposition plus residue-transport into the soils by earthworms and other soil fauna creates a level and certainty of carbon sequestration that mankind can never duplicate artificially.

Positioning of the crop residues to take advantage of this natural process is referred to as micro-management of residues. With Cross Slot low-disturbance no-tillage (LDNT), micro management of residues is achieved by positioning two stationary L-shaped side blades so that they rub against the flat faces of a vertical disc that travels straight ahead. This creates two horizontal shelves on either side of the disc. Cross Slot is the only no-tillage opener in the world that (a) uses a flat vertical disc travelling straight ahead and (b) creates horizontal seed and fertilizer shelves that are easy to cover.

All other no-tillage opener designs create vertical or angled slots that are difficult to cover. Those that use one or more discs arrange the discs to have either a vertical or horizontal angle, or both so as to create scuffing or wedging actions by the discs.

The absence of any form of disc angle or bursting action from the stationary tines on Cross Slot openers is the secret to that opener’s minimal soil and residue disturbance. It is a true LDNT opener and unlike most other no-tillage openers, its slot formation and covering actions are not particularly speed sensitive.

Being able to create inverted T shaped slots became a sacrosanct function of Cross Slot openers from an early date because of the overwhelming evidence of the biological superiority of this slot shape over all other slot-shapes for crop establishment and growth. Even today, many designers make the mistake of considering surface residues to be a nuisance and go to some trouble to either remove them altogether or at least push them aside. Baker’s team regard them as the single most important asset of any no-tillage system.

And of course, on a macro-scale they have always been an essential asset of any no-tillage system.

A common problem in residue handling by competing disc opener designs, is “hairpinning” or tucking of uncut residues into the slot (no disc on any opener - including Cross Slot - can remain sharp enough in the soil to cut all of the residues all of the time, resulting in some lengths of straw being folded and pushed doubled-up into the ground rather than cleanly cut). When seeds become embedded in such “hairpins” they risk being killed by contact with acetic acid that is a product of residue fermentation in wet soils. While such fermentation is not common in dry soils “hairpinning” can physically separate a proportion of the seeds from contact with water-bearing soils and if no vapour water has been trapped in the slots, this commonly leads to germination failures.

The central disc of Cross Slot openers is not immune to creating “hairpins” in certain conditions. But with Cross Slot openers, the seeds are deliberately displaced to one side of the disc and any “hairpins” it creates, which avoids any negative effects arising from “hairpins”. Cross Slot openers are safe to use in even the heaviest and most fibrous crop residues in both wet and dry soils, which is key to its ability to facilitate carbon sequestration.

Another biological challenge was to find a way of banding fertilizer at the same time as the seeds without risking contact between the two. With Cross Slot openers, this happens automatically because the right hand (fertilizer) and left hand (seed) blades are located on opposite sides of the flat vertical disc, allowing dry, liquid or gaseous fertilizer to be deposited on one side and the disc at the same time as seeds are deposited on the opposite side without any chance of the two coming into contact with one another.

Cross Slot is the first no-tillage opener and drill system to be based on scientifically-verifiable biological principles that are backed by innovative and robust engineering.

But Cross Slot® LDNT is now used all over the world and to date has been the principle tool behind 20+ separate environmental awards by farmers in four countries as well as winning numerous crop yield competitions and technology innovation prizes. In several instances it has produced probably the highest crop yields ever recorded by some crop species.

What the science said would happen if seeds and fertilizer were sown into untilled soils in a particular way, has proven to be exactly correct in field practice.