The primary benefit of catch crops, as most know by now, is their ability to absorb nutrients (hence the name), holding valuable nutrients as well as providing soil cover from rain over the winter. Catch crops are also a good source of feed, especially in years where there is a scarcity of fodder
Once fully grown and not used for fodder, catch crops tend to be incorporated back into the soil, through cultivation, to help build up organic matter levels and release more nutrients over time.
Earthworm activity is also increased as result. Another benefit is reduced compaction and erosion from harsh winter weather.
The earlier the better
There are two major benefits for sowing catch crops early. Firstly, early sown crops are more likely to grow better and, secondly, as result they are able to catch more nutrients.
While early sowing can be seen visually in terms of foliar growth, we must also remember that the growth of foliage is more than mirrored underneath the surface in terms of root growth.
The foliage provides an obvious capture of carbon through photosynthesis but the roots below ground also provide carbon storage alongside many other advantages.
The roots also keep the soil open and alive, making subsequent cultivation easier.
The presence of roots enables the soil to break apart easier and the remnants of those root channels provide a roadmap for the roots of the next crop to follow.
In time, this helps to generate higher yield potential.
Benefits of a mixed species
Part of the science of catch crops is the choice of species and what the different plant roots can do for the soil.
The simplest example of this is the basic structure of the root system. Cereals and grasses tend to have a relatively shallow and fibrous root system, while crops with tap roots such as beet, carrots, oilseed rape and beans produce bigger roots, both vertical and horizontal.
Crops that have physically bigger roots tend to break the soil apart even more to leave the soil more friable, which is also the purpose of cultivation.
Farmers are already conscious of the good structure of the soil after crops such as oilseed rape and beans. The true root crops can do the same, but this does not always happen if one has to harvest in damp conditions. Plants that are deep-rooting, such as tillage radish, help to condition soil, while other species, such as legumes, help to fix nitrogen from the atmosphere.
It makes logical sense to sow a catch crop mix with a variety of plants with fibrous and tap root systems for these reasons. Keeping these plants alive for as long as possible maximises this potential benefit and after a few years of use, catch crops should really provide the opportunity to try some non-inversion tillage, as the soil should be much kinder and easier to manage.
Having more than one family of plant in a crop mix brings many advantages. Broadleaved plants such as brassicas tend to cover the ground more quickly than crops such as cereals. This means a faster soil coverage, which helps to suppress other weeds and these leaves also protect the soil from the damaging impact of rain.
Plant species also have different root systems, which can possess different characteristics. Some of these were mentioned previously, but there are many more.
Many plant roots extrude acids and other substances. Acids can help to strip somewhat unavailable nutrients from the soil, take them up and make them available to following crops.
Plants also extrude other substances which can help promote specific bacteria and perhaps deter others. In this way, they can influence the biological activity of soils.
In doing this, they may help prevent the occurrence of disease in some of the partner plants. It is also likely that the presence of multiple species can remove some or all of the risk associated with the monoculture production of cash crops.
Methods for catch crop establishment
There is no right or wrong method of establishment – it comes down to the type of soil on the farm, how it has been treated in the past, what options are on hand and how much time is available.
Bear in mind, some seeders are designed to either handle small seeds or large seeds, but they may not be capable of handling both.
Usually, the seeding rates will be much lower with catch crops, so ensure the drill or seeder can accommodate the target application rate. This is one reason why air seeders prove popular, as they are well suited to small seed sizes and low seed rates.
Remember, at the end of the day, establishment costs should be kept to a minimum.
Pricing for each of the methods outlined are in accordance with the FCI Contracting Charges Guide 2022.
Most methods advise rolling afterwards (€16/ac or €65/hr) for soil seed contact and to retain moisture, which is especially important this season to date.
This method is probably the most popular on Irish farms. The majority of Irish contractors and tillage farmers have a set of discs of some sort in the yard. Machines such as Pöttinger’s Terradisc and Tegosem, Amazone’s Catros, Lemken’s Rubin or Kverneland’s Qualidisc are all popular examples.
If not already mounted on the disc harrow or present on the farm, then an air seeder, such as an APV or an Einböck unit or similar, would prove suitable. These units can be retrofitted to any disc harrow.
A good-quality retrofit seeder kit, including ground drive wheel, distribution hoses, etc, will set you back from €4,000 plus VAT and upwards. It is advised to roll the seedbed after this method for consolidation purposes, increasing soil seed contact.
This method costs in the region of €40/ac or €135/hr per run, relatively cheaper than some of the other methods. In some cases, a second run of the disc harrow may be required.
The use of a tine cultivator or grubber with either a mounted air seeder or spinner broadcaster is also suitable. Optionally, the seed can also be broadcast via a fertiliser spreader after one pass of the above machines.
These cultivators typically consist of rows of sprung tines or legs which can be operated at both shallow and deep working depths.
The rear-mounted seeder then places the seed behind the tine rows.
Again, rolling is recommended although machines fitted with rear packer rollers often will suffice.
The Väderstad Cultus, Pöttinger Synkro, Amazone Cenio and the Horsch Terrano are all suitable machines. Pricing per run is in the region of €40 to €42/ac (per pass).
Initial cultivation can be done with any form of min-till or stubble cultivator. This is followed by a standard seed drill. Some may opt to use the combination of cultivation and drilling in a single pass using a cultivator drill.
Many farmers and contractors use a disc drill or a cultivator drill on cultivated soil to establish commercial crops.
These drills often consist of a disc arrangement up front to help bury trash and leave a finer seedbed.
The disc coulter arrangement then follows to place the seed in the ground.
All the major brands such offer a number of models and configurations to suit each customer.
Rolling is advised afterwards.
Some drills are fitted with rear packing rollers for consolidation purposes and this may remove the need to roll afterwards with a ring roller.
One run of a disc harrow will cost in the region of €40/ac. Seeding using a conventional-type seed drill will set you back a further €45 to €50/ac. The use of a one-pass system will cost in the region of €55 to €60/ac. For the complete job, this is one of the more expensive options.
A tine harrow and air seeder (like one used for pasture rejuvenation) is another low-cost option. Typically, tine harrows comprise up to six rows of spring tines, in addition to optional spring-mounted levelling boards.
These can tear the stubble, helping to produce a seedbed before seed is broadcast or sown via an air seeder in between the rows of tines.
The row of tines behind where the seed is dropped helps to cover the seeds with a layer of tilth. Brands include Einböck, Güttler and APV, etc. This particular method will cost in the region of €22 to €24/ac (per pass).
Direct drilling is a very suitable method of establishing catch crops in a low soil disturbance fashion. It can also be fast, as there is no cultivation required.
These drills simply cut into the stubble ground and place the seed below the surface and retaining moisture.
There are a number of no-till farmers throughout the country whose main planting drills include the John Deere 750A or the Weaving GD drill which they use to plant commercial crops. These machines prove very suitable for planting catch crops too. There are also many contractors using machines such as the Erth Agriseeder or the Moore Unidrill that can do this same job.
This method may be among the most expensive options, typically costing in the region of €60 to €65/ac.
There are a number of different methods which can fall under this heading. Seed can be broadcast on to disced ground and rolled afterwards.
Seed can also be broadcast directly on to stubble ground with a spinner mounted on a tractor’s front linkage, followed by a light cultivator or a ring roller.
Alternatively, seed can be spread with a fertiliser spreader and then followed by a roller or light cultivator. Simple broadcast seeding will cost around €105/hr. This is the cheapest method available but generally offers the lowest level of establishment.