New Animal-Drawn Machine Concepts for Future-Oriented Agriculture – part 2
Multi-Purpose Spreader SmP Kombi-Stree 1.0
by Paul Schmit of Luxembourg
Schaff mat Päerd
Embarking on New Paths
Hardly any other activity is as dependent on the weather as agriculture. The current climate change is often reduced to the keyword of “anthropogenic global warming”, but it is much more. Climate change not only increases the average temperature, but there is also a shift in phenological phases, a change in the spectrum of pathogens and more intense and frequent extreme weather events such as heat waves, late frosts, long-lasting droughts, heavy rains, and severe storms.
Extreme weather events have existed since time immemorial. Nevertheless, the weather conditions of the last few years are more than just outliers. These increased seasonal fluctuations disrupt agricultural operations and if occurring in a plant’s sensitive development phase, reduced yields or even total failure are unavoidable. Every plant has its physical limits when it comes to drought, waterlogging or frost. Unfortunately, the all-rounder doesn’t exist.
One way to deal with these different weather extremes is to spread the risk through diversification. When arable farmers expand their crop rotations, they will always have crops that are better adapted to the extreme situation that arises than others. However, in vegetable growing this is much more difficult to implement.
Future food security can only be created through an improved climate resilience of our social-ecological system. This requires developing or rediscovering more stable and resilient systems that do not rely on optimizing a single factor. In recent decades, yields and earnings have counted too much.
This long-term transformation includes learning processes and particularly the exchange of information and experiences. This essay is another attempt to share thoughts about climate-adapted vegetable cultivation practices and newly developed animal-drawn equipment, after the first part has been published already in Small Farmer’s Journal 47-3. However, this part does not include a report on the first field operations of an implement but is limited to its design study.
Dealing with Freak Weather
Some regions of Europe have been hit by pronounced dry weather conditions since 2018, others by excessive rain. During drought periods irrigation can be an option, especially in light soils used for vegetable growing, with little water storage capacity. However, wells for tapping into groundwater or taking of water from rivers are rarely approved these days and collecting rainwater in sufficient quantities during winter all too often requires significant investments.
Furthermore, in summer the sun’s rays are at their highest. This energy should not hit the bare ground and cause the soil life to boil. Besides suppressing weeds, a dense stand of crops shades the ground and protects it against this abiotic stress. But not every vegetable plant can fulfill this function. Here, mulch can help.
As a recent three-year study by the University of Kassel and the Saxon State Office for the Environment, Agriculture and Geology in Germany showed, mulch can reduce the temperature in a potato ridge by up to 3°C.
Furthermore, mulching improves the water availability for the plants. Water savings occur through slowing down the drying of the soil surface, which leads to a reduced rising water movement and evaporation from deeper soil layers.
Hoeing, as common practice in vegetable growing for weed control, reduces water loss through evaporation as well, by breaking the capillaries. However, every mechanical agitation of the soil, be it for weeding of tilling, is a kind of disruption for the soil with far-reaching consequences. Besides initiating soil degradation, also referred to as tillage erosion, nitrogen is mobilized as well in the soil. This constantly results in N surpluses, which not only provoke losses and water pollution, but massively promote root weeds, such as thistles, as well. Here it is important to fix the system error first rather than trying to get the problem under control by hoeing even more.
While suppressing weeds, reducing soil temperatures and retaining water in the soil are one of the most important reasons for mulching in dry periods, it has some other advantages regarding heavy rainfalls. Proper mulching not only helps keeping the vegetables cleaner as there is no contact with wet and sticky soil, but it protects the ground as well. Because the kinetic energy of the raindrops is reduced when hitting the mulching material, compared to the bare ground, it prevents an erosive effect. Gradual soil erosion is viewed as one of the most serious problems affecting worldwide food security, biodiversity, water quality and resilience to climate change, as fertile soil is transported every year irretrievable into the oceans by running waters.
Following the 2024 State of Soils in Europe Report, launched at the end of October 2024 at the 4th EU Soil Observatory Stakeholder Forum, overall soil erosion is estimated to 1 billion tons per year across the EU. Approximately a quarter (24 %) of EU soil is affected by water erosion, mainly in cropland. This report brought together research results from the 32 member states of the European Environment Agency (EEA), along with six cooperating countries from the Western Balkans, Ukraine and United Kingdom. Furthermore, nutrient imbalances, mainly nitrogen and phosphorus excesses, are also on the rise, estimated to affect 74% of agricultural land. In addition, many soils are losing stored carbon, endangering the EU’s climate protection efforts. An estimated 70 million tonnes of organic carbon were lost from the mineral soils of croplands across the EU and UK between 2009 and 2018.
Feeding Soil Life
In view of climate change, it is not only a layer of mulch on top of the soil, that is important as a protection, but also its benefits by providing the soil life with food. Soil fungi, bacteria and earthworms need compost or mulch on the soil surface as food. The soil organisms prepare this organic food for the cultivated vegetable plants. Depending on the composition and C/N ratio, mulching materials can be highly effective complex fertilizers and in addition to the underground biomass, the organic residues of the mulching material form a nutrient and structure-building pool in the soil, referred to as humus.
The creation and maintenance of humus in the soil is of crucial importance. Humus releases nutrients during plant growth, but also improves the soil structure, offering a unique habitat for a wide variety of macro, mesa and microfauna in the soil. Furthermore, a good soil structure facilitates water infiltration during heavy rains and increases water retention and therefore drought tolerance in dry periods.
However, contrary to previous assumptions that humus is mainly created from root exudates and plant residues, some recent studies of the BOKU, the University of Natural Resources and Life Sciences in Vienna (Austria), have shown that a large proportion of the organic matter in the soil is also of microbial origin.
Indeed, the formation and stabilization of humus is based on a complex interplay of mineral soil properties, plant inputs and microbial activity. Microorganisms react very sensitively to changes in their environment. Therefore, careful soil cultivation has a strong effect on their growth. Mulching in no- or minimum-tillage farming systems can help here.
In this context, however, it should be considered that humus build-up not only depends on the growing practices but is clearly limited by the soil texture. Light and sandy soils, which are more suitable for growing vegetables, are at a disadvantage in terms of carbon content compared to the heavy, clayey soils.
Transfer or In-Situ
Contrary to so-called in-situ mulch, which is grown on the parcel where it is used and rolled down with a crimper roller (see SFJ 47-3), transfer mulch is moved from a donor parcel to the receiving parcel. This method is also known as cut & carry, as transfer mulch is first cut and then be brought and spread on the parcel. Various plant species are suitable for this, as will be shown below.
In vegetable cultivation, it is not always possible to optimally sow an overwintering catch crop to be used as in-situ mulch in the following season. When sown after the last harvests in late autumn, catch crops often do not develop a dense stand with sufficient biomass. By that, it is also not always possible to keep it free of weeds.
Furthermore, some vegetables require earlier planting and cannot wait for the catch crop to bloom. The catch crop is killed most effectively when it is in full bloom. At this stage of development, the plant is in the transition from the generative to the vegetative phase. While flowering, large amounts of plant sap are sent from the roots to the flowers. By rolling and breaking the vascular system, the nutrient transport is interrupted, and the plant dies.
Where the sowing time of a catch crop as in-situ mulch is not suitable, the so-called combination mulching could be helpful by supplementing the missing biomass in the rolled catch crop with transfer mulch.
The transfer mulching process is always the same: carefully clear the ground of weeds, select suitable mulching material, mulch and then regularly check whether the mulch layer still serves its purpose and, if necessary, add or replace the mulch.
Either before or after sowing, weed control can be done by light hoeing or harrowing. So-called blind-harrowing works very well with beans or peas because they are placed a little deeper in the ground than smaller seeds, like carrots for example.
Clover grass is particularly suitable as a source of mulch for transfer mulch, as it is often present in crop rotation on organic farming and usually not used on vegetable growing farms without livestock or just horses. But grassland cuttings and catch crops are also suitable as transfer mulching materials as well. All plants should be cut before flowering to minimize the risk of seed formation. Straw as mulching material should generally be viewed critically as it is often contaminated with weed seeds and volunteer grain. In addition, less or no nutrient release is to be expected from straw due to its wide C/N ratio.
Sufficient donor mulching areas must be available for the transfer mulching process, if a thick layer of mulch is spread and if your farm should be self-sufficient. The ratio of donor and receiver area is about 3:1.
Care must be taken to allow gas exchange between the soil and the atmosphere to occur. A layer of mulch must always be permeable to air. The roots and soil creatures need oxygen to breathe. Therefore, the optimal cutting length is between 3 and 10 cm and should be longer for finer mulch material and shorter for coarse mulch material. If the material is too short, it will be stored too tightly and there is a risk of rot occurring. If the material is too long, there may be difficulties in spreading it. If the mulch is to be spread widely, heavy mulching material, i.e. fresh grass clippings, is more suitable than dried material. If the material is to be spread only across the width of a single bed or row, the material may be dry, such as chopped hay. Then the material is lighter, which also makes sense for overall transport.
Adapting Density and Thickness
In general, for weed suppression, the ground must no longer be visible through the mulching material. But also, the growth capacity of the crops must be taken into consideration. In early season mulching systems, the cultivation of fine seeds such as carrots, parsnips or beetroots is more difficult. Here a first thinly spread layer of transfer mulch with a thickness of 2-3 cm enables temporary weed suppression, erosion protection and later weed control. After the seeds have successfully emerged, the mulch cover can be increased, but this means an additional work step.
Coarser seeds such as bush beans or peas are more likely to succeed in thicker mulch because they have a stronger growing force. The easiest way to use transfer mulch is on crops that sprout from a storage organ, i.e. a rootstock, a tuber or an onion, and therefore have a lot of growing power. These include, for example, potatoes, onions or rhubarb.
For vegetables with a short cultivation period, such as radishes, mulching material should be used that decomposes quickly. For vegetables with a medium cultivation period, such as salads, peas, beans or potatoes, the same type of mulch can be chosen, just applied thicker. For vegetables with a long cultivation period, such as carrots, pumpkins or tomatoes, and semi-permanent crops such as strawberries, mulch can be used, which decomposes more slowly.
On the author’s farm, the best results on most of the crops were achieved with transfer mulch layers of 8 cm long chopped hay. The aim here is that the mulch layer covers the soil throughout the entire growing season and weed control is no longer necessary. For semi-permanent crops such as strawberries or rhubarb, 3 cm long wood chips are used. Wood chips decompose more slowly than hay because of their higher lignin content. After the season, the hay is incorporated nearly completely into the ground by earthworms. Compared to fresh grass clippings, dry hay can easily be spread up to 10 cm thick without any risk of rotting.
Hay and wood chips are on-farm products in sufficient quantities. The wood chips are produced yearly during wintertime when maintaining the approximately 2 km of hedges that surround the fields and meadows or when maintaining a pond biotope with pollarded willows, just behind the farm buildings. The hay is sorted out already during the season before. These are round bales that have not reached the required level of dryness, generally the stripes along the shadows cast by forests, or bales that are impured by soil from molehills or wild boar damage.
The wood chips are produced by a tractor-powered woodchipper. The shredding of the hay is done with an electric straw mill, which is normally used to cut the bedding for the stable weekly. This has been done now for over 20 years and results in a soft and very absorbent bedding for the horses, which almost halves the consumption of straw and makes mucking out by hand much easier. By using different sieves, the cutting length for the mulch can be maintained precisely. This is another advantage, in addition to the light weight, of chopped hay compared to other fresh green cuttings.
However, the hay should not contain grass seeds, which would easily germinate under the mulch. Because of the late cutting of horse hay, usually in the 2nd half of June or the beginning of July, this is not the case. However, blowing the chopped hay by the straw mill from the hayloft into the stable below results in good separation. After loading the mulching material by hand, the grass seeds are simply swept up from the concrete stable floor.
Ending the Season
The mulch can remain on the area over the winter. As explained above, this protects the ground and provides food for the beneficial organisms in the soil. In general, not much of the hay mulch material can be seen the following spring, even after crops that have been harvested relatively late, such as pumpkins. Working in the remaining mulch is only necessary if a very fine and clean seedbed is required, e.g. for carrots, which only tolerate a small sowing depth.
If the remaining mulch layer is too thick, the material should not be buried after winter but should be removed and composted as organic fertilizer for the coming season. To decompose large amounts of buried organic matter, the microorganisms need a lot of nitrogen, which is then no longer available to the vegetable plants.
Here, composting excess mulch is more beneficial as it kills disease-causing fungal spores as well. Besides that, the phosphorus content in the soil all too quickly exceeds the permissible limits when too much organic matter is worked in.
Shifting Work Peaks
Using potatoes as an example, the method, the benefits, but also the problems and limits of mulching will be briefly summarized here.
Usually, the mulching material is spread after the first hilling, but before the potatoes close the row to ensure that the ground cover lasts as the growing season. It could also be done before or shortly after planting, but the work peaks in early spring are the limiting factor here.
If there’s only one mechanical hilling of the potatoes with a conventional hilling plow, the hay mulch is piled up by hand to prevent the potatoes from turning green when exposed to light. This additional work is compensated for by the elimination of the second or third mechanical hilling. Furthermore, this grants the soil life more peace and quiet.
Since the potatoes are buried less deeply in the ground, harvesting is easier and less strenuous for humans and work horses. Furthermore, mulching significantly reduces infestation with Colorado potato beetles and late blight.
However, as is often the case, the exception proves the rule. In 2024, potato blight was a huge problem almost across Europe due to the constant waterlogging of potato fields, regardless of whether they were mulched or not. Another problem, as in many other vegetable crops, was the invasion of snails. The only successful method so far was to spread wood ash from our own home heating, which is collected in sufficient quantities over the winter. Nettle manure will also be used on a trial basis for this purpose next year. Another problem that has not yet become too obvious compared to non-mulched areas, can be the increase in mice.
Making Spreading Easy
To simplify mulch spreading in terms of time and effort, a multi-purpose spreader, called SmP Kombi-Stree 1.0, was developed in 2024. In addition to spreading various transfer mulch types, this implement should also enable compost to be spread in and next to the vegetable rows.
When designing this single-horse spreader on the computer, attention was paid to light draft and the shortest possible turning radius. The first point mentioned is achieved by 4.00-36 pneumatic tires with ribbed profile on light-weight steel spoked wheels and a direct drive using toothed belts on both sides. The second point is ensured by the three-wheel design as the spreader is coupled to the SmP Mono-Rad 1.0 forecart. This 3.50-21 single front wheel can turn up to 102,5° to either side below the gooseneck tubular frame made of DN32 (42,40 mm) S235JR construction steel tubes with just 2 mm wall thickness. Due to their cranked shape, the work horse does not touch the stainless-steel traction shafts with its hind legs during short turnings at the headlands and the force required to turn is minimal.
The loading capacity is 0.5 l, equivalent to 500 kg for compost, which has the highest specific weight of all spreading materials. With an additional hopper extension this can be expanded by 50%. As a first development step, the required transmission ratio was determined mathematically based on the required spreading density for the various spreading materials. The selected transmission ratio of the belt drive, consisting of two 40 mm wide HTD 14M toothed belts, is 3:1.
For the spreading material transport to the front of the stainless-steel hopper with 2 mm wall thickness, the bottom consists of a 4,6 mm thick and 1100 mm wide conveyor belt, made of double EP135 fabric reinforced styrene-butadiene rubber (SBR). The width corresponds to the maximum spreading width and results in a track width of 1500 mm. Thanks to the three-wheel design, the work horse walks, followed by the single-wheel forecart, in the middle of two rows of vegetables and the two drive wheels run in the middle next to these rows, provided there is a row spacing of 750 mm. Of course, any other row spacing can also be configured.
The rubber-coated top of the conveyor belt is fitted with 48 mm wide and 5 mm high cleats having a pitch of 25 mm, which ensures sufficient adhesion to the spreading material being conveyed. The conveyor belt is not rubber-coated on the underside but consists here of one of the two fabric layers. This prevents slipping on the front drive roller, made of a DN 150 (168,3 mm) steel pipe with 4,0 mm wall thickness.
Although the toothed belt drive is on both sides, to avoid slippage on the pneumatic drive wheels, the spreading mechanism is switched on and off by a stainless-steel bolt coupling only on the left side freewheel. This is achieved by a coupled solid and hollow shaft connection between both finger-type freewheels within the front drive roller of the conveyor belt. This rather complex mechanism required the most consideration and time during the conception phase and several variants were analyzed until the final version was determined. The computer-aided design was extremely helpful here, as it was able to visualize all parts of the transmission in 3D and in sectional views.
This one-sided coupling of the drive mechanism avoids having to move twice to both sides of the spreader on every headland to shut off and on before and after the turning maneuver. The rubber conveyor belt is carried by a total of five steel rollers, all of which rotate in greaseable ball bearings. The rear roller is mounted in two adjustable bearing units enabling the rubber conveyor belt to be re-tightened. The two toothed belts of the transmission system are tensioned via spring-loaded tension rollers.
The spreading density is fine-tuned by pivoting a stainless-steel star roller up or down, which is mounted just above the spreading material outlet at the front end of the conveyor belt. This varies the opening height of the outlet. This star roller itself rotates at the same peripheral speed as the feed speed of the rubber conveyor belt and prevents the spreading material from piling up at the outlet. The one-side drive from the front drive roller of the conveyor belt is realized by two gears made of aliphatic polyketone (PK), a thermoplastic high-performance polymer. A stainless-steel bolt coupling on one of the gears permits the drive to be switched on and off.
Two stainless-steel distribution plates, which are attached by stainless-steel star knob screws to the tubular frame between the spreader and the front wheel, enable three spreading variants. Without installing the distribution plates, the spreading material is spread over the entire width. If the two distribution plates point inwards, the spreading takes place on the vegetable row itself. Swapping the two distribution plates results in a spreading next to the row on both sides.
Innovate on Small Scale
Mulching is not a sure-fire success. As with all new or rediscovered methods, mulching in organic vegetable production can get a challenge, depending on the climatic and soil conditions. But if the available technology and mulching material are used correctly, the amount of work required for weeding during the vegetable growing season is reduced many times over in addition to the discussed benefits in relation to climate change.
Nevertheless, a finding of the past trial-and-error years is that experiments that are too large often lead to frustration if they fail. Therefore, first experiences should always be gained in smaller plots to avoid excessive risk in the learning phase.
One of the next articles will report on the first practical experiences with the new multi-purpose spreader. The follow-up reports will focus on further new developments that mechanize the entire transfer mulching system. These include a newly developed single-horse sickle bar mower, with a modern Italian alternative to the German double-knife cutter bars, as well as a modern version of a single-horse dump rake.
Many thanks go to Cédric Malek and Gary Schoos who contributed to the development of the SmP Kombi-Stree 1.0 multi-purpose spreader.
