In recent years, catch crops have grown in popularity through promotion from environmental schemes and greening requirements.
Catch crops can also provide a good solution where there may be a scarcity of fodder, which occurred in 2018.
The main reason many tillage farmers sow catch crops is because they work as a nutrient absorber (that is the basis of their name), holding valuable nutrients and providing good soil cover over winter to protect the soil from rain.
Once fully grown, catch crops are often 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.
Catch crops also help reduce compaction and erosion from harsh winter weather. `
Earliest planting for best benefit
Because of what catch crops do, they must be sown early to be given the maximum chance of doing it.
They are sown to grow in the autumn and in doing that, they pick up or catch nutrients from the soil that might otherwise be lost to the environment. The more they grow, the more nutrients they catch for recycling and the earlier they are sown, the more they are likely to grow.
This adage serves as a reminder of the importance of planting time: “A day in July is worth a week in August, which is worth the whole month of September.”
Early sowing is obvious in terms of foliar growth, because we can see and measure it. We must also remember that the growth of foliage is more than mirrored by root growth in the ground.
While the foliage is an obvious capture of carbon through photosynthesis, the roots below ground also provide carbon storage and many other advantages.
As well as holding carbon and other nutrients, the roots act to 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.
Root system functions
Part of the science of catch or cover crops is the choice of species and what the different plant roots can do in and for the soil.
Perhaps 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 very 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 fix nitrogen from the atmosphere.
Having a mix of plants with fibrous and tap root systems can be very advantageous for a catch crop mix 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.
Why opt for mixed species?
Having more than one family of plant in a crop mix brings many advantages, some of which we may not understand fully.
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.
Plants species also have different root systems, which can possess different characteristics. Some of these were mentioned previously, but there are very 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.
There is no right or wrong method – it comes down to the type of soil on the farm, how it has been treated in the past, what establishment options are on hand, and how much time is available.
One thing to bear in mind is that some seeders are designed to either handle small seeds or large seeds, but they may not be capable of handling both.
Usually, the seeding rate per hectare 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 following methods are in accordance with the FCI Contracting Charges Guide 2021.
Machines such as the Amazone Catros, Pöttinger’s Terradisc and Tegosem, Lemken Rubin or Kverneland Qualidisc are all popular examples.
Any disc cultivators married with a spinner or an air seeder, such as an APV or an Einbock unit, would prove suitable.
These units can be retrofitted to most disc harrows. A good-quality retrofit seeder kit, including ground drive wheel, distribution hoses, etc, will set you back from €3,500 plus VAT and upwards.
The seedbed can then be rolled after this method for consolidation purposes, to increase contact between soil and seed.
This method costs in the region of €25 to €30/ac or €100/hr per run, relatively cheaper than some of the other methods, although in some cases a second run of the disc harrow may be required.
Advisory note: This is a versatile establishment option with generally good results. Be careful of very dry conditions. Keep the cultivation as shallow as possible. High weed numbers are likely following the cultivation, so it is worth considering a quick stale seedbed before a second cultivation and planting, if time allows.
Initial cultivation can be done with any form of min-till or stubble cultivator to create a seedbed. 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 both 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 the seedbed with a finer degree of tilth.
The disc coulter arrangement then follows, slitting the loose ground using discs, then placing the seed below the surface using pneumatics to put it there. All the major brands such as Lemken, Horsch, Pöttinger, Kuhn, Amazone and Kverneland, naming just a few, offer a number of models and configurations to suit the customer.
Rolling is advised afterwards for good soil seed contact and to retain seedbed moisture. 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 €25 to €30/ac. Seeding using a conventional-type seed drill will set you back a further €34 to €36/ac. The use of a one-pass system will cost in the region of €44 to €46/ac. For the complete job, this is one of the more expensive options.
Advisory note: This method will produce a better seedbed, which can be more satisfactory where a combination of small and large seeds are to be sown, but planting depth will have to be a compromise.
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 mounted seeder then broadcasts the seed behind the tine rows. It is then recommended that the seedbed is rolled for good soil seed contact.
Some of these machines are fitted with rear packer rollers which often will suffice.
The Amazone Cenius, Vaderstad Cultus, Pöttinger Synkro, and the Horsch Terrano. Pricing per run is in the region of €34 to €35/ac (per pass).
Advisory note: In many ways, this option is quite similar in concept to the disc and broadcaster seeder. Because the soil is loosened, there is the possibility of a significant weed problem in the crop.
The same loosening can also give rise to significant moisture loss in a dry season, so the roller needs to follow immediately after sowing.
In most years, it is advisable to keep the first cultivation and the seeding as close as possible together in order to conserve moisture.
The Irish market is full of tine harrows, many of which are very flexible and can be equipped with multiple add-on features. This can make them suitable for various applications, such as in-pasture rejuvenation or sowing catch crops.
Typically, they comprise of one to three rows of spring tines, in addition to spring-mounted levelling boards or plates.
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 help to cover the seeds with a layer of tilth.
These harrows are typically rear-mounted, but can be configured to fit on to the front of a tractor if required. They can be very simple or very sophisticated.
Some of the brands out there include Palatine, Guttler, APV and Einbock, etc. They are often fitted with spinner broadcasters or an air seeder and combine to be a low-cost establishment method. This particular method will cost in the region of €15 to €18/ac (per pass).
Advisory note: Two runs of a tine harrow followed immediately by rolling may be necessary to establish good soil seed contact and to help lock in moisture in a dry season.
Direct drilling is a very suitable method of establishing catch crops in a low soil disturbance situation. It can also be fast, as there is no cultivation required before planting.
These drills simply cut into the stubble ground and place the seed below the surface. The lack of disturbance is one of the best ways of retaining moisture in years when that matters.
There are a number of no-till farmers scattered throughout the country whose main planting drills are units such as the John Deere 750A or the Weaving GD drill which they use to plant their commercial crops and these drills are also used for, and very suitable for, planting catch crops.
There are also many contractors using machines such as the Erth Agriseeder or the Moore Unidrill that can do this same job.
However, this method may be among the most expensive options, typically costing in the region of €50 to €55/acre.
Advisory note: Performance from this type of drill will be better when the land is level to start with. It is also likely to give best results on land that is in good physical and structural condition. This is important, as it enables the opened slits to crumble and close back in around the sown seeds.
The lack of soil disturbance may help decrease the weed burden in the catch crop, but it may also slow growth post-establishment where there is not natural mineralisation to release nutrients in the soil.
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 €90/hr. This is the cheapest method available but, in most cases, will offer the lowest level of establishment.
Advisory note: Establishment from this method can be quite hit and miss, depending on weather. It has a better chance of being successful where the soil has good structure and is naturally friable. In general, systems that use less cultivation provide less nutrients from the soil and so can produce less crop growth in the absence of fertilisation.