Problem

Insect pollinators continue to decline despite the CAP’s increased focus on environmental outcomes.

Solution

Targeted legume mixtures provide profitable forage for a diversity of pollinators and can complement habitats that offer early season forage, bee nesting sites and resources for hoverfly larvae.

Outcome

Legume intercrops will increase in-field floral diversity resulting in more abundant and stable floral resources, benefitting insect pollinators and helping to sustain pollination services.

Practical recommendations

-Legume intercrops can provide a rich source of forage for pollinators. To benefit a diversity of pollinators, intercrops should focus on legume mixtures that target species with different flowering periods and flower structures.

-As competitive species (i.e., both crop and legume intercrop) can restrict flowering in less competitive species, care should be taken when selecting intercrop species, and consideration given to sowing density. For less competitive legumes, wider but less frequent intercropped strips will help ensure flowering and prevent shading by the crop, which can discourage foraging pollinators.

-Plant protection products can be directly toxic to pollinators. Application should therefore consider pollinators and, where viable, a buffer zone should be around the legume intercrop.

Practical testing/ Farmers’ experiences

Field trials explored a variety of legumes grown as monocultures and mixtures. Targeted mixtures flowered more consistently throughout the summer. While competitive legumes provided good ground cover and reduced the prevalence of weeds, they prevented less competitive species from flowering.

Problem

Organic agriculture prohibits the use of synthetic chemicals and limits the use of inputs, exposing it to limiting factors such as weeds and nitrogen availability.

Solution

Legumes living mulches, if well regulated, are useful in organic farming. They increase nitrogen supplies to crops, improve weed control and enable environmental benefits.

Outcome

A living mulch of lucerne increases the protein content and the yield of organic wheat, provided that biomass regulation of the living mulch can be effectively achieved mechanically.

Practical recommendations

The first step is to sow the cover crop in a host crop at appropriate spacing. This is 30 cm for Arvalis trials with the available equipment. Wheat will then be sown either direct seeded or after a light tillage in the lucerne inter-row. The wheat rows will also be spaced 30 cm apart and located halfway between the lucerne rows. Real Time Kinematic (RTK) guidance is required to achieve this precision. ​

Lucerne goes into dormancy in November, and it is not very competitive with wheat until March. In spring, it is important to regulate the living mulch. In organic farming, this is achieved by mechanical crushing, located on the lucerne row and leaving intact the wheat. Two to three passes throughout the field seem necessary. ​

Practical testing/Farmers’ experiences

This method should be part of a crop rotation. At some point in time, the lucerne will release less nitrogen or be subjected to pest.

Problem

It is not always possible to successfully grow cover crops in a rotation (efficiently sowing and managing them with the crops in the rotation).

Solution

Living mulch is an innovative cover crops. Yet, it is important to identify the benefits and constraints of incorporating them into a rotation.

Outcome

A technical-economic evaluation carried out on several trials in France to assess the impacts of living mulches.

Practical recommendations

-Living mulches can lead to a slight increase in working time: crushing (avoiding weed graining), or even hoeing before sowing. According to the crop nitrogen response curves, it is not always justified to adapt the fertilisation strategy.

-A living mulch does not necessarily lead to an increase in TFI*, especially since weed control programmes are designed accordingly and selective weed control solutions for the cover crop are less expensive.

-Expenses: cost of seeds must be included. The other costs are generally not affected.

-Margin: can be positive or negative

-Cover crops destroyed in the crop generated net margin gains when sown with rapeseed.

Despite the trefoil in Dosnon the net margin was negative. This was due to the cost of the seeds and being insufficiently regulated.

At La Jaillière, the establishment of the clover mixture in the maize crop before sowing wheat was poor. It also generated higher costs (seeds, hoeing).

-Cover crops kept alive generate variable margins depending on their impact on yields.

Practical testing/Farmers’ experiences

Many French farmers establish perennial cover crops in arable crops. They are often sown in a rapeseed as a companion crop. White clover & lucerne are the most common species.

Problem

Cover crops (CC) provide benefits for the next cash crop such as nitrogen supply but maintaining it permanent in a crop can induce a risk of competition.

Solution

Regulating or destroying the CC during appropriate periods to limit the competition between a CC and wheat.

Outcome

The more developed is the perennial CC before wheat sowing, the better it is for the crop but competition risks must be managed, especially in spring.

Practical recommendations

Living mulches establish themselves slowly, sow them in fall in the previous crop.

-Rapeseed, sunflower and peas are adapted crops.

-Cereals are also an option if they allow light to go through the canopy. The CC biomass must reach at least 2tDM/ha before wheat sowing.

Direct sowing of wheat in a CC can reduce wheat emergence but it is compensated by the number of ears per plant, their fertility and a better protein rate.

Kill the CC from fall to the end of winter to avoid competition on the crop in spring.

Soil tillage and herbicides are two means to destroy the CC.

If the CC is kept alive, it is important to regulate the CC in wheat, especially in spring.

-The CC biomass must be kept low from the beginning of stem elongation of wheat to its harvest (< 1 tDM/ha).

-In conventional agriculture, herbicide applications at the 1cm ear stage can help while making it possible to control some dicotyledon weeds still present.

-Well developed in autumn and well-regulated in spring improves the available nitrogen levels.

Practical testing/Farmers’ experiences

In Provence (South France), these results have been confirmed on several farms. It is not the competition for water that impacts wheat yield but the competition for N, especially at the beginning of the wheat stem elongation stage.

Problem

Although the benefits of permanent cover crops (living mulch) have been shown, it is not easy to choose the most suitable species for cropping systems.

Solution

Adaptation to the type of soil, lifetime, growth dynamics, tolerance to herbicides are some of the main criteria used to choose among the species of living mulches

Outcome

Choosing adapted living mulch species can bring several agronomic and ecosystem benefits: carbon storage, erosion limitation, nitrate sequestration, weed management…

Practical recommendation

Before implementing a species for living mulch purposes, consider the following aspects:

-Adaptation to the soil type: It determines the ability of species to survive, wet and dry periods exerting strong constraints on the growth of the cover crop. Be careful that lucerne and sainfoin are poorly adapted to hydromorphic soils.

-Lifespan: Lucerne can grow several campaigns in a row, thanks to its intrinsic perennial characteristics, its tolerance to many herbicides and its ability to grow high up in crops to capture light. White clover is less perennial, partly because of its sensitivity to certain herbicides and its short size limiting access to light under some crops.

-Growth dynamics: They depend on the times of the year. This impacts their interaction with crops, in terms of risks of competition or harvest troubles.

-Aphanomyces: Sainfoin and bird’s-foot trefoil do not multiply the strains. Lucerne and certain varieties of white or red clover do.

Practical testing/Farmers’ experiences

According to a French survey, lucerne is the most common species of living mulch (47% of the plots), followed by white clover (24%). This is followed by red clover (14%) and combinations of several species (15%).

Problem

Growing a cover crop together with a main is complex to. Competition for light and other resources can prevent the main crop from growing properly.

Solution

Different crops are suitable for the establishment of living mulches. The solution is to identify those that could play this role in your crop rotation. The weeding of the crop must also be adapted accordingly.

Outcome

Despite the limitations and constraints of this technique, there are different possibilities to establish cover crops.

Practical recommendations

The requirements for the choice of the main crops are: Moderately covering, leaving enough light to allow the survival and growth of the cover crop. Clean enough to lighten the weed control program as not all programs are selective for young legumes.

-The most used crops are straw cereals, in organic or conventional agriculture. They allow the installation of cover crops, lucerne fields, meadows, seed crops…

-In conventional farming, it is necessary to adjust the cereal growth to make it less smothering.

-Rapeseed is also often used to install living mulches, often in addition to annual companion plants. The crop is sown at the same time as the other species. Weeding of rapeseed must be light and it will not be suitable for unclean plots. In some rotations, sunflower or fodder maize replaces rapeseed to install the cover crop.

-For some farmers, the perennial cover is originally a fodder or seed crop. It is usually lucerne, that is not destroyed before the following crops are planted.

Farmers’ experiences

We recommend that you test it under your own conditions. Start a small-scale trial (one field). Replicate more than one year and contact other farmers, advisors or local seed companies for feedback and knowledge sharing.

Problem

Cover crops (CC) can be difficult to establish in summer due to dry soils or short intercrop.

Solution

Establishing CC in a crop enables to anticipate its emergence before summer. Perennial species can grow for several years under crops or between them (living mulches).

Outcome

CC can be destroyed or kept alive in autumn crops. Some crops such as rapeseed allow to keep CC alive when sown together and well regulated.

Practical recommendations

- Legumes species as living mulches as often complementary to the crops in the rotation (wheat, maize, etc.).

-To overcome long setting up phase, establish them in a crop, so that they can develop in the intercropping period.

-In organic farming: straw cereals are well adapted hosts.

-Conventional: rapeseed or sunflower as cereals are often overcovering.

Implementation of a living mulch in a cash crop

-Host crops should not be too smothering.

-In organic farming: CC can be established after a mechanical weeding.

-Weeding with selective herbicides, to not destroy the young CC.

Living mulch during the intercropping period and in a crop

-After the harvest of the cash crop, CC benefit from light and can develop during the intercropping period.

-The following year, CC can be kept alive or killed in autumn crops, depending on the risk strategy taken.

-CC biomass must be low in spring: control it with herbicides or mechanical regulation.

-Perennial CC kept alive are too competitive of spring crops: destroy them before their establishment.

Practical testing/ Farmers’ experiences

A survey of 57 French farmers shows that mineral input (especially N), soil structure, life health and weed management are the 3 main reasons for installing living mulch. 1/3 of famers had CC harvested or grazed.

Problem

Uncontrolled living mulch growth in an intercropping with wheat poses risks to wheat productivity.

Solution

To regulate the growth of the living mulch: nitrogen inputs favouring cereal over legumes, choice of species and varieties, or herbicides at reduced doses.

Outcome

Important to be aware of the growth dynamics of the living mulch. Depending on the species, it can be highly variable from fall to spring. This makes it possible to identify critical periods.

Practical recommendations

-Before sowing wheat, destroy weeds while taking care of keeping the cover crop alive.

-Very shallow tillage before sowing can limit the fall growth of the cover crop without destroying it, to avoid glyphosate.

-Fall: selectivity of herbicides can be a problem on a cover crop that grows strongly at this period (e.g., white clover). In this case, supplement the weed control programme with less selective active substances. In some cases, it is not possible to control difficult flora without destroying the living mulch.

-End of winter: crucial to control the cover crop growth when regrowing, to limit competition with wheat, when the latter has great needs. ReMIX trials showed that white clover can be more competitive on wheat than lucerne. Herbicide applications at the 1cm ear stage can help. While making it possible to control some dicotyledon weeds still present.

-According to the crop Nitrogen (N) response curves, it is not justified to modify fertilisation to the optimum. N piloting during the stem elongation stage seems necessary.

Practical testing/ Farmers’ experiences

Farmers and our herbicide screenings show that legumes do not all have the same sensitivity depending on the detox capacity, the weather and the competitiveness of the cereal.

Problem

Knowledge of the several species of living mulch is important to use them wisely.

Solution

Red clover, used as a cover crop, can bring many benefits to one’s cropping system. A good knowledge of the characteristics of red clover is essential to control its management.

Outcome

Applied research led to a better understanding of the interactions of red clover with its environment. It can be an alternative to lucerne as a legume cover crop.

Practical recommendations

Characteristics to be considered before implementing a red clover cover crop:

-This taproot fodder plant is perennial (2-3 years).

-Establishes quicker than other species.

-Vigour can be a disadvantage in the year when the cover crop is established in a crop. Sowing density limited to 5 kg/ha and sometimes with a sowing date shifted from that of the crop.

-Adapted to humid soil, conversely to lucerne.

-It is a species to be managed well in spring under wheat (late start but potentially troublesome at harvest).

-It is rather easy to regulate as sensitive to herbicides.

-The seeds cost is quite low so that the cover can also be destroyed before sowing the next crop.

-Red clover can be integrated in all crop rotations. Consider that peas, lentils and beans which are sensitive to Aphanomyces. In this case it is necessary to choose varieties that are totally or very resistant: Diplo, Formica, Lemmon, Lestris, Merviot.

-Red clover is a false host species of the Branched broomrape which can contribute to reduce the grain stock.

Practical testing/ Farmers’ experiences

The red clover is not the most used among the different species in France.

Problem

Several species of living mulch can be used. It is important to know them well to use them wisely.

Solution

A good knowledge of the characteristics of white clover is essential to control its management and benefit from the cropping system.

Outcome

Applied research has led to better understand the interactions of white clover with its environment.

Practical recommendations

There are a few characteristics to be aware of before implementing a white clover living mulch:

-This fodder plant with a fibrous root system is perennial (4-5 years). ​

-Seed cost is moderate : 3 kg/ha​

-Adapted to humid or acidic soils (Table 1).​

-Low vigour, increasing the risk of getting an unclean cover crop when established alone. ​

-There are several types of white clovers; Dwarves, small leafed and prostrate. ​

-Short and slow implementation, but still competitive with the crop as it forms a very dense network of stolons. ​

-Intermediate or Hollandicum type, with medium sized leaves and petioles. ​

-Giant clovers or Ladino, with large leaves and long petioles with a less dense network of stolons.​

-Its size limits interference with harvesting​

-Often suffers from very dry conditions experienced in summer. During mild falls, it must be regulated in winter cereals (Table 2).​

-It is rather easy to control as sensitive to herbicides, in particular to "sulfo" as well as to the lack of light (Table 3).​

-As a false host species of the Branched broomrape, it contributes to reduce the grain stock.​

​Practical testing/Farmers’ experiences

White clover can be part of any crop rotations but be vigilant with crops sensitive to Aphanomyces and in this case prefer resistant varieties of white clover : Aberdaï, Aberace, Giga, Lune de Mai, Tara.

Problem

Several species of living mulch can be used. It is important to know them well to use them wisely.

Solution

Good knowledge of the sainfoin characteristics is essential for implementation and benefit from the cropping system.

Outcome

Applied research allows a better understanding of the interactions of sainfoin with its environment.

Practical recommendations

This fodder plant with pivoting root system is perennial (2-4 years). Sainfoin is a specie that adapts to all types of soil except hydromorphic undrained soils. It can be used as fodder as it does not enhance bloat.

-The cost of seeds is important with certified seeds at 90 kg/ha in pods. However, farmers often multiply their own seeds.

-Sainfoin can be integrated in all crop rotations. Sainfoin is a non-host species of Aphanomyces, highly or totally resistant.

-Establishment is easier in limestone drying soils (Table 1).

-Optimum seeding depth of 2-4 cm (to be adapted according to soil moisture).

-Does not germinate in hot or very hot temperatures (>32°C).

-High tolerance to water stress.

-Not very sensitive to herbicides and plant growth regulators are to be preferred to control the cover crop biomass.

-Potential beneficial effect on the nitrogen fertilisation of the following crop, after the cover is destroyed or regulated at the right time in the rotation.

-Regulation at the end of winter and spring is important not to become a constraint to the harvest of the main crop (Table 2).

-Its chemical regulation is quite difficult in rapeseed and difficult in wheat and maize.

Practical testing/Farmers’ experiences

In a healthy and dry environment (summer), sainfoin is very well adapted. In French Provence region is an alternative to lucerne.

Problem

Several species of living mulch can be used. It is important to be familiar with them to use them wisely.

Solution

Knowing the characteristics of lucerne is essential to master its implementation and maximise the benefits for the cropping system.

Outcome

Applied research has led to a better understanding of the interactions of lucerne with its environment.

Practical recommendations

-This fodder plant with a taproot is perennial (3 to 5 years or more). ​

-Lucerne is a deep-rooted plant, well adapted to healthy, non-acidic soils (Table 1). It should be avoided in healthy but drained soil (risk of clogged drains). ​

-As a cover crop, sowing density must be much lower (6-8 kg/ha) than as a fodder crop (20-25 kg/ha).​

-For the perenniality of lucerne (root reserves), let it flower at least once during the season (10% of flowering plants are sufficient). ​

-On the variety side, choose winter-dormant varieties and if possible, late in spring.​

-Winter-dormant varieties show very low growth/competition in winter and medium growth/competition in fall (Table 2).​

-Lucerne can be integrated in all crop rotations, except those incorporating peas, beans or lentils because it potentially multiplies Aphanomyces. ​

-In the presence of Branched broomrape, lucerne is also not recommended because of the risk of multiplication of this parasitic plant.​

-Regarding ease of chemical control, while its regulation is easy in rapeseed, it is quite difficult in wheat and maize (Table 3). ​

Practical testing/Farmers’ experiences

Varieties: consider Flemish varieties (dormant in winter) and if possible, late in spring. You can find out more about varieties on the Herbe-book website.

Problem

Broccoli is affected by a wide variety of pests. There is a decrease in the number of insecticides that can be used, and customers are increasingly demanding to farmers zero residue crops.

Solution

Habitat diversification can be an effective measure to reduce the level of pests in crops. The inclusion of vetch (Vicia sativa) as a companion plant between broccoli may help reduce the level of pests.

Outcome

Broccoli-vetch intercropping entails the reduction of the level of some pests compared to broccoli monocrop, in particular the level of Plutella xylostella, Aleyrodes proletella, and Brevicoryne brassicae

Practical recommendation

-It is recommended to sow vetch (Vicia sativa) between broccoli rows. ​

-Vetch needs more time than broccoli to complete its life cycle, and broccoli is harvested before vetch seed production, avoiding vetch development as weed in the following crops.​

-The pest reduction observed in intercropping might be related to the physicochemical characteristics of the mixture, which make it less attractive to pests than broccoli monoculture or could interfere with pest plant location behavior.​​

Practical testing/Farmers’ experiences

The effect of broccoli-vetch and broccoli-floral strip intercropping on the level of pests and auxiliary fauna was evaluated using three replicates. No effect of the floral strip was observed, however vetch showed positive effect reducing the level of Plutella xylostella and Brevicoryne brassicae by almost 50% compared to monocrop. No differences were found in the level of auxiliary fauna.

Problem

Find an alternative to neonicotinoids to avoid wireworm damage on maize.

Solution

Sowing barley with maize to concentrate wireworm attacks on barley (lure effect) instead of maize.

Outcome

When wireworm attacks are significant, the barley reduce the damage on maize plants from 12 to 82 % compared to the maize alone.

Practical recommendations

-Farmers can use barley seeds from their previous harvest;​

-Barley can be replaced by others cereals (wheat, oat, …) but with higher risk of competition on maize;​

-For better protection, lure crop must be sown the same day or a few days before maize;​

-At least 100 kg.ha-1 of lure seeds must be sown;​

-Lure seeds must be sown deeper than the maize (at least 5cm with an optimum of 10-15 cm);​

-Lure seeds must be sown neither too close nor too far from the maize rows (optimum of 20 cm) to avoid competition with maize and to facilitate the mechanical destruction of lure crop;​

-Lure crop must absolutely be destroyed at the 3-leaf stage of the maize preferably mechanically (e.g.: hoeing).

Practical testing/Farmers’ experiences​

Intercropping barley with maize has been tested for 2 years by 21 “forward-looking” French farmers (conventional or organic), with the help of Terrena and Arvalis (ReMIX partners). Each of these farmers tested the crop mixture on one part of a field while the other part consisted of maize alone.

Problem

Soil legume fatigue causes severe root diseases and crop failure. Heavy conjoint infestation (e.g., Didymella, Fusarium, Aphanomyces) may accumulate in the soil in crop rotations with pea, faba bean, vetch, red clover or lucerne and lead to total legume loss.

Solution

With a simple legume fatigue test, soil can be examined for the fatigue syndrome prior to cultivation.

Outcome

The test reveals soil contaminated with the pathogens mentioned above and can point to the need for a legume break.

Practical recommendations

1. Extract 10 l soil from the field plot of interest and sieve down to 10 mm

2. Fill 4 aluminium trays with the soil

4. Cover the trays with tinfoil and place in baking oven for 12 h at 70-100°C

5. Let the soil cool down for 12 hours, then fill 4 pots with untreated soil (mark with “U”) and 4 pots with heat-treated soil (mark with “H”)

6. Place 5-10 legume seeds in each pot

7. Place the U and H pots randomly in a tray with some water and keep them in a sheltered place at >18°C and daylight

8. Keep the pots moist by pouring water into the trays (avoid overwatering).

9. After 6 weeks, cut all plant shoots at the stem right above the soil surface, and weigh the shoots of each pot separately

10. Divide the shoot weight of the “U” pots by the shoot weight of “H” pots, e.g., 200 g U plants / 180 g of H plants = a ratio of 0.9

11. This ratio is an indicator for legume fatigue (see below)

Practical testing

A ratio below 0.8 indicates a risk of legume fatigue. Lower the ratio, higher the risk. Decide cautiously whether to cultivate the tested legume. It is also recommended to test any other legume that is planned for the crop rotation. In case of a ratio <0.2, we strongly advice against a cultivation of the tested legume (and possibly any other legume) for 7-8 years.

Problem

Low yields and high sensitivity to weed pressure prevent the spread of blue lupin crop in organic farming despite high protein content and a widespread demand for local protein production.

Solution

Sharing farmer knowledge and experience in associated crops to develop lupin – oat mixture in on-farm experiments.

Outcome

After adaptations of species varieties and seeding densities, blue lupin – oat mixture controls efficiently weeds and presents good yield levels for both species.

Practical recommendations

-Before seeding, check soil lime content: under 5%, blue lupin can be grown without difficulties, above 10%, soil is not adapted as chlorosis can appear limiting lupin growth. Between these two values, test lupin crop in small strips to assess the potential of the field.

-Favour branched lupin cultivars (e.g., Boregine) as they have the highest yield potential. Choose the earliest oat cultivar for synchronous maturity with lupin.

-Seeding densities corresponds to 100% of standard sowing densities for lupin and 10% for oat

-Apply soil tillage to reduce weed pressure.

-Inoculate lupin seeds with rhizobium (e.g., HiStick) and mix them with oat seeds. Sow seeds in early spring with the same row spacing as for cereals at about 3 cm depth.

-If weed control by the mixture is not sufficient, apply mechanical weeding.

-Avoid all compacting operations.

-Harvest when seeds collide in the pods (like bells).

Practical testing/Farmers’ experiences

Also possible to sow lupin and oat in alternate rows in a single pass with a divided hopper seeder or in double pass using a GPS. This design will improve weed control and reduce oat competition over lupin resulting in higher lupin yield. Wheat or triticale can also replace oat.

Problem

Pea is a high-yielding feed and food grain legume, but sowing tends to be out-competed in intercropping with cereals, especially in autumn.

Solution

Genetically: selecting pea varieties with greater competitive ability under severe competition with cereals. Agronomically: reducing nitrogen (N) fertilization and/or increasing pea sowing density.

Outcome

Pea lines evaluated under pure stand (PS) and mixed stand (MS) show wide genetic variation for competitive ability. PS was somewhat reliable to select for MS.

Practical recommendations

-Match carefully the phenology between pea and the cereal. Enable a synchronous maturity for grain harvest. Pea is generally earlier than wheat or triticale, but early variants of these cereals can be found.

-Identify pea lines with greater competitive ability by selecting in MS under conditions that favour severe competitive stress for pea (moderate N; 50:50 pea/cereal sowing densities relative to species densities in PS). Use a mixture of different early maturing cereal testers to breed pea for general compatibility.

-A breeding strategy might be an indirect selection in PS based on a selection index that integrates pea grain yield with improved pea competitive traits such as pea plant height at flowering (for which, genetic variation occurs within semi-dwarf pea germplasm). Pea selection based solely on pea grain yield in PS can be useful only when targeting conditions of modest competitive stress for pea.

Practical testing/Farmers’ experiences

While developing new pea varieties selected for intercropping, the varieties should have similar maturity time (i.e., early heading cereals), preferring tall pea cultivars or taller variants within the semi-dwarf pea plant type.

Problem

Species mixtures in the European farming landscape have almost disappeared despite an increasing number of studies documenting their agroecological benefits.

Solution

Farmers’ collective knowledge is the key in redesigning credible and socially valuable strategies and evaluating how it best fulfils the expectations of involved value-chain actors.

Outcome

11 Multi-actor Platforms (MAPs) were built across Europe to share knowledge on species mixture strategies through a co-design process.

Practical recommendations

-Re-introduction of crop diversity strategies within codes of good agricultural practice is the starting point. To succeed in this, knowledge exchange barriers between research and practice, and along the value chains, need to be broken, increasing awareness and dialogue on valid species mixture use whilst securing implementation of locally relevant, practical and innovative solutions. ​

-Farmers are regarded as the key actors in designing viable and appealing species mixture systems and their input is crucial. The MAP approach creates a positive arena that can empower the farmers to create local solutions, increasing the success of crop mixture use in practice and building up a wider network of agricultural actors in order to develop viable economic/business models.

Practical testing/ Farmers’ experiences

Several events and visits hosted by satellite farms and at the central hub site have been used to stimulate discussion about species mixtures which might work well in a given situation for a particular end purpose (co-design).​

Problem

Pathogens spread easily among genetically uniform plants (Fig. 1 top left). Adaptation leads to resistance breakdown and loss of valuable varieties.

Solution

Grow mixtures of varieties or species that differ in their resistance to air-borne pathogens.

Outcome

Pathogens are slowed down and less likely to adapt to all mixture components. Pesticide use is reduced, and varieties will be useful for a longer time.

Practical recommendations

-Variety mixtures: use varieties that can be harvested and used together but differ in their resistance to the pathogen in focus. Because over time the pathogen may adapt and overcome plant resistance mechanisms (Fig. 1 lower right), change the mixture and resistance composition over time.​

-Species mixtures: use species that are not susceptible to the same pathogen. Choose species that either can be grown and used together (e.g. for feed) or that are easily separated (e.g. with different seed sizes). Alternatively, use a service species (e.g. undersown) in addition to the species to be harvested. In species mixtures, there is less risk for pathogens adapting. If species mixtures are too difficult, strip intercropping of different species is a good option.

Practical testing/ Farmers’ experiences

Variety mixtures of cereals work very well against rusts, mildew and Septoria tritici, or rice blast in rice. Similarly, species mixtures of cereals with beans or peas usually reduce airborne pathogens in both crops. Undersowing clover in cereals can reduce Septoria.​

Problem

EU rural areas suffer from fragmentation. Operators are often small; the communication is difficult, and economies of scale are harder to achieve.

Solution

RDP Measure 16.2 funds pilot projects for the cooperation of farmers, advisors and other actors in order to tackle specific problems.

Outcome

A group of 20+ organic cereal producers jointly purchased portable equipment for grain separation and implemented activities for structuring the regional organic cereal sector.

Practical recommendations

-Pooling different funding streams is a powerful approach to boost interactive innovation in the agricultural sector, especially where there is poor structuration, fragmentation or limited capacity for innovation and diffusion. ​

-Innovation Support Services within the Regional Agricultural Knowledge and Innovation Systems (AKIS), e.g. INTIA in Navarra, are key actors for achieving a strategic combination of EU funding streams in finding innovative solutions for increased sustainability of the agricultural sector. ​

-In the case of the organic cereal growers in Navarra, INTIA has combined European Regional Development Funds, RDP Measure 16.2 and H2020 multi-actor projects for supporting the structuring of the organic value chain based on a demand-driven approach.

Practical testing/ Farmers’ experiences

RDP Measure 16.2 (“pilot projects of OG”) is a popular measure amongst the farming community in Navarra. Farmers can gain access to innovative knowledge and equipment through cooperation with other actors in the AKIS.​

Problem

In intensive farming, monoculture is an efficient procedure but it has adverse effects on biodiversity, soil health and fertility.

Solution

Crop mixtures, like wheat-faba bean, can improve resource efficiency, yields and quality for low-input farming systems.

Outcome

In 11 different pedoclimatic regions, mixed cropping techniques aimed for targets, like improved feed or food quality, weed suppression or yield stability.

Practical recommendations

-The companion crop can be sown in advance or with the main crop. ​

-The seed can be broadcasted or drilled as a mixture, or in alternate rows, with the same or different depth. Consider lowering the drilling rate of the cereal; it’s a strong competitor. ​

-Choose varieties with a synchronous ripeness.​

-Crop rows should match mechanical weed control. Chemical control is a challenge. ​

-The combine harvester must be adjusted to minimize threshing loss and damage to the pulse grains.​

-Faba bean or peas mixed with a cereal, an intercrop example that produces mixed grain feed. It can also be harvested as a protein rich green roughage. ​

-The density of both crops will adapt to the growing conditions. Consider a variable product composition and protein content.​

-Protein rich wheat is interesting for bakers. Also, a composed wheat-faba bean flour is suitable for bread baking!

Practical testing/ Farmers’ experiences

Wheat-faba bean or peas mixture controls weeds well and provides a good nitrogen use. Cereal-lentils mixtures were not always successful regarding harvestability and weed suppression. Sorting costs for mixed grains by a rotary cleaner, vibratory separator, gravity separator and optical sorter are estimated at 11, 11, 45 and 67 € per tonne per pass, respectively.

Problem

Lentil, an important crop known for its nutritional values and taste, is sensitive to lodging, bruchid beetles and weeds. This leads to low and uncertain yields.

Solution

The addition of wheat to a lentil crop is a real benefit for farmers as it can increase and stabilize its yield when facing abiotic and biotic stresses.​

Outcome

-Reduced lodging of the lentil crop​

-Improved mechanical harvest efficiency​

-Higher wheat protein content​

-Wheat suppresses weeds for a better control​

Practical recommendations

-Sow lentils at the recommended density (300 gr/m2)​

-Sow wheat at a low density (50 plants/m2)​

-Do not grow this mixture in conditions with high nitrogen availability, and do not fertilise​

-Choose a wheat cultivar with a similar maturity date to lentils​

Practical testing/ Farmers’ experiences

Lentil-wheat is developed in South-Western France but quite new in Western France. Supported by TERRENA, this crop mixture was first tested on three satellite farms. Results were positive, with a significant reduction of weeds and lodging.​

Problem

Studies on crop mixtures are not particularly common, so farmers may lack knowledge about what best suits their objectives and conditions.​

Solution

Principles for crop mixtures design (combinations of species, cultivars, densities, sowing patterns and fertilization) depend upon targeted services.​

Outcome

Tracking farmers’ innovations to: ​

-reveal the diversity of mixtures cultivated​

-show links between objectives and practices​

-develop this practice.​

Practical recommendations

-Intercropping can increase resource use efficiency (light, nitrogen, water, etc.): choose species/cultivars with complementary temporal patterns, morphological and functional traits (height, habit, root system, etc.)​

-Facilitating harvest and reducing losses: choose species/cultivars with robust stems to prevent the lodging of the associated crop (e.g. Barley-pea, camelina-lentil)​

-Ensuring that at least one species is always harvested: choose species/cultivars with complementary growth requirements and sensitivities (diseases, insects, extreme weather, ripening dates, etc.) (e.g. Faba bean-wheat)​

-Harvesting a supplementary crop, achieving two crop cycles in one year: choose species with different life cycles to be sown simultaneously and harvested separately (e.g. Rapeseed-buckwheat)​

Practical testing/ Farmers’ experiences

Tracking farmers’ innovations revealed different practices and sub-objectives with the aim of 1) increasing yield and stability, 2) controlling weeds and 3) increasing nitrogen supply in the cropping systems and then nitrogen self-sufficiency.

Problem

Today lentil production is concentrated in India, Canada and Turkey. Economically competitive, high-quality ecological production in the EU is challenging.

Solution

Intercropping with oat to increase harvest efficiency, suppress weeds, and efficient multi-step technical separation and local marketing.

Outcome

High-quality, ecologically, and efficiently produced lentils are a valuable local product and can be a second crop (cereals, false flax).

Practical recommendations

-Lentil production in Germany requires intercropping to reduce lodging, increase harvest efficiency and suppress weeds. ​

-Possible crop partners are barley, oat and false flax. Short oat varieties avoid competition with the lentil. ​

-A fine-grained seeding bed is required. ​

-Sowing from the beginning to the end of April with 55 kg/ha of lentil and 35 kg/ha of oat at a sowing depth of 4 cm (optimal seeding depends on local conditions). ​

-Five days after sowing, one pass of tine harrow to reduce weeds. Harvest after 120 days. ​

-Technical separation of lentil and oat is critical and requires machinery at multiple steps: a cyclone, a cylinder separator, gravity separator and possibly an optical sorter. Sharing the machinery among farmers or producing the mixtures in large quantities will help reduce separation costs.

Practical testing/ Farmers’ experiences

The company Lauteracher Alb-Feld-Früchte organizes crop production, separation and marketing for 70 farmers. Products are marketed under the brand Alb-Leisa.​

Problem

Weeds compete with the main crop for light, water and nutrients. Chemicals and, to a lesser degree, mechanical treatments are widely used to suppress weeds.

Solution

Mixing species with complementary properties and that benefit from each other. We will focus on living mulch or 'plant teams' (cereal cash crops associated with non-harvested "companion" species).

Outcome

Although the regulation of weed pressure is difficult to quantify for living mulch, ongoing experiments show that living mulch can cover up to 95% of the soil surface during the intercropping period.

Practical recommendations

-Perennial forage legume species can be sown in a first cash crop, for example, red or white clovers established in winter wheat at the end of winter in organic farming or clovers or lucerne sown at the same time as oilseed rape in conventional farming.​

-After harvesting, the living mulch (e.g. clovers) keeps growing during the intercropping period, especially if the summer weather is not too dry.​

-The cover crop can then be destroyed before establishing the following crop or be kept alive during part or the entire cycle of the second crop. In organic farming, the cover crop must be destroyed before sowing the second crop since its development cannot be suppressed with herbicides. In conventional farming, more and more farmers are testing this practice. The biomass of the living mulch shouldn’t exceed 1 ton per hectare, at the wheat flowering stage, for optimal wheat growth. ​

Practical testing/ Farmers’ experiences

We recommend that you test this method under your own farm conditions. Visit the organic farmknowledge platform to share your experiences with other farmers, advisors, and scientists!​

Problem

Optimal sowing density (OSD) depends on factors such as species and pedo-climatic conditions. Problem: difficulties in gaining experience and knowledge on OSD for intercrops.​

Solution

OSD should not be set as a specific recommendation. Sowing densities to use depend on specific situations, factors and different combinations.

Outcome

According to some given abiotic and biotic factors and general rules, farmers can create and evaluate the matching OSD for their fields.

Practical recommendations

- OSD is influenced by different factors, especially target objectives, soil, vegetation period/climate conditions, choice of species and cultivars, organic vs. conventional system, weeds/pests/diseases control, technical equipment and type of intercropping.

- Proportion in yield can vary largely from sowing proportion. Total yield should be higher than the average of sole crops. In a cereal-legume-intercropping, legumes are responsible for a high protein content and cereals have a high plasticity for tillering/compensation. They suppress weeds but also tend to suppress their mixture partner. For central Europe, 80 % of sole crop sowing rate of legumes and 40 % of cereals can be used as a first start (Dierauer et al., 2017). Matching seed depth and homogeneity of the mixture should be checked.

Farmers’ experiences

Farmers should try out the optimal mixture ratio. Start a small-scale trial (e.g. 10m*100m) with different sowing densities. Replicate more than one year and contact other farmers, advisors or local seed companies for feedback and knowledge sharing.

Problem

The necessity of nitrogen fertilization of cereal legume intercrops

is debatable since this mixture could benefit from complementary N sources (from soil and atmospheric N2). How to determine the

necessity of N fertilizer in intercrop?

Solution

The relevance of N fertilization depends on the farmer’s objectives in terms of grains proportion between the cereal and the legume at

harvest and cereal grain protein concentration.

Outcome

Intercropping cereal legume usually results in a higher cereal grain

protein concentration compared to sole crop cereal, greatest benefit is always obtained without N fertilizer.

Practical recommendations

-The efficiency of synthetic N fertilizer is generally high 75 of N applied) It always increases the proportion

of cereal in an intercrop with legumes, regardless of the sowing density and pedoclimatic conditions

-The efficiency of organic N fertilizer is always low 20 so it is not relevant to apply in organic farming

-For winter intercrops (e g wheat winter pea), the N fertilization must be adapted and based on the i) proportion of species observed in March, ii) grain yield targeted, and iii) proportion of the two species expected at harvest To increase cereal grain yield, N fertilizer could be applied during stem elongation 40 80 kg N/ha), while to increase the cereal grain protein concentration, it should be applied at earing 30 50 kg N/ha)

-For spring intercrops (e g spring barley spring pea), no N fertilization is generally required, except to ensure a high proportion of cereal grains at harvest by applying N fertilizer at the end of tillering 30 60 kg N/ha)

Practical testing/ Farmers’ experiences

Farmers should try different N fertilization rates and/or times, for example, in strips across a field, to visually compare the effect of N fertilization on yield, species proportion and cereal grain protein concentration Start with a small number of rates and/or times (including no fertilizer) and repeat the test for more than a year to improve know how

Problem

Extreme weather, biotic stresses and field-scale variability in soil quality increases the risk of crop yield losses in global sole crop production systems.

Solution

Intercropping is the simultaneous cultivation of more than one species on the same field. One crop in a mixture may compensate for the eventual loss of another crop. ​

Outcome

Pea and oat in sole and intercrop were exposed to severe drought in 2018. Pea did not survive, but the oat harvest in the inter-crop was 86 % of the oat sole crop yield.​

Practical recommendations

-Intercropping is highly relevant for grain legume production in organic farming systems, other low input systems, but also conventional systems. ​

-Over three years of conventional field experiments, sole cropped peas yield variability was more than twice that of barley.​

-N-fertilization reduced the yield variation in barley. ​

-The of the intercrop’s yield was moderate compared to the sole crops. ​-Intercropping can have a major economic impact at the farm scale, especially in drought years, by ensuring a certain amount of production under environmental stresses.​

-Farmers also benefit from additional advantages of inter-cropping.​

Practical testing/ Farmers’ experiences ​

Farmers or advisory organizations interested in determining the stabilizing effect of intercropping in stressful environments can monitor grain yields of sole crops and intercrops over at least three years and determine the variation. ​

Problem:

The increase of the world population requires analogous increases in food production, particularly of wheat with high grain protein content.​ ​

Solution:

Intercropping with legumes, i.e. lentil, pea, etc., improves cereal protein concentration. Selecting wheat cultivars with higher yield and protein content is crucial.

Outcome:

Mixed cropping systems achieve higher protein content of bread wheat, with no need to include nitrogen (N) fertilizers.​

Practical recommendations:

-The seed bed should not be too fine-grained after cultivation.​

-Test soil samples and amend P and K levels, if necessary.​

-Select cultivars (wheat and grain legume) with the same maturity time according to local seed costs and market availability.​

-Mix the seeds 70% grain legume and 30% wheat relative to the standard sowing quantities of the crops in the seed tank. Check that the mixture is homogenous and sow with a conventional seeder

-Use the recommended row spacing of the cereal crop.​

-Apply weed control as needed (organic or conventional).​

-Adjust the height of the harvester to pick up grain legumes close to ground.​

Practical testing/ Farmers’ experiences:

If this crop system seems suitable for you, we recommend that you test this under your conditions. Separate a part of your field before sowing and apply the mixture. Cultivate the rest of the field as usual and compare the intercrop to the pure stand cereals and/or legumes crops.​