Catch and Cover Crops

Development of mixtures and plants suitable for crop rotation to enhance land use and improve soil fertility and main crop yield.

The soil is left without surface cover after the early arable crops. This is accompanied by the leaching of nutrients into surface water and ground water. One possibility to reduce the leaching losses is to cultivate the cover crops, which would fix the ions and water in the soil and, conclusively, would reduce the leaching. To increase the winter surface coverage, it is important to cultivate wintering cover crops, however the suitability of the species is limited in our climate. Therefore, we study the winter cover and catch crops commonly grown in Europe, to test their potential to thrive in local climate and soil conditions.

The following catch and cover crops and their mixtures will be tested:

  • Hairy vetch (Vicia villosa Roth)
  • Winter barley (Hordeum vulgare)
  • Winter rye (Secale cereale L.)
  • Oat (Avena sativa)
  • Buckwheat​ (Fagopyrum esculentum)
  • Forage (tillage) radish
    (Raphanus sativus L. var. longipinnatus)
  • White mustard (Sinapis alba L.)
  • Phacelia (Phacelia tanacetifolia)
  • Crimson (Italian) clover (Trifolium incarnatum L.)​
  • Berseem clover (Trifolium alexandrinum L.)

Mixtures of different plant species offer more possibilities, the advantages of which are the following:

  • Reduction of cultivation risks
  • Decrease in essential nutrient leaching
  • Increase of soil coverage (lowering risk of soil erosion)
  • Enhancement of soil biodiversity

As the dynamics of growth rate depends on plant species, it is assumed that a bigger amount of  biomass will be produced by growing mixtures of different plant species. Additionally, the effects of different inputs on the rate of biomass formation and nutrient uptake are investigated via using mineral fertilisers, biostimulants and liquid manure.


In 2017, 2018 and 2019, experiments were established on the test-plots of the Estonian University of Life Sciences and on cluster members’ production fields. Experimental data was obtained also from similar experiments carried out by Estonian Plant Research Institute. Both overwintering and non-wintering species from different plant families (legumes, cruciferous crops, grasses) were studied. The mixtures were formulated for different crop rotations and cultivation techniques like  plowing, minimal tillage  and direct sowing were studied.

Durign 3 years, biomass formation and nutrient content of 9 different crop mixtures were studied. Each mixture consisted of 3-4 species. The mixtures were prepared on the principle that each mixture contained a legume culture, as it binds nitrogen from the air. In 2017, the mixtures were sown on August 8th and the previous crop grown was winter wheat. In 2018 the mixtures were sown on August 1th, the prevoius crop being winter barley. In 2019 the catch crops were sown on August 6th and the pre-culture being early maturing barley. In all experiments, the grain straw was crushed and left in the field. Biomass size and nutrient content of catch crops were determined in October, at the end of the growing season, and in overwintering crops in spring, just before plowing. In 2017 – 2019, different cultivation methods were tested.

In 2017, experiments were carried out on the fields of Rannu Seeme OÜ (show on photo), where two mixtures of catch crops were used.  30 kg/ha of mineral nitrogen was applied to both mixtures.

In 2018 and 2019, tests were performed at four locations: two in Tartu County (Rannu Seeme OÜ and OÜ Erumäe Kari) and two in Lääne-Virumaa (Avanduse Agro OÜ and OÜ Uuetoa farm). The experiments were set up with both direct sowing and plowing. The pre-cultures grown were early maturing cereals, winter colza or fallow. 

In order to understand whether the rate of biomass formation can be increased with different inputs (biostimulators, liquid manure), studies were conducted in 2018 and 2019 on the field of OÜ Erumäe Kari OÜ. In 2017 and 2018, experiments were set up at test plot areas to assess the effect of biostimulators on the biomass formation of catch crops. In addition, a laboratory experiment was conducted in 2018 using a  biological formula enriched with bacteria (Bioorg) and water-soluble mycorrhiza, which was used to treat the seed of catch crops just before sowing. In order to figure out the optimal sowing time in Estonia’s climate conditions, tests were carried out during 2017-2019. In 2017, three sowing times were determined, in 2018 five, and in 2019 four. The experiments were performed with five different plant species.

Field experiment: direct sowing, cultivation of catch crops, without slurry (Erumäe Kari OÜ, 2018). 

Fertilisation experiment: application of slurry prior to sowing of catch crops (Erumäe Kari OÜ, 2018).

  1. The biomass yield of catch crops can vary considerably from year to year, depending on the sowing time and climate conditions. The size of the biomass depends on the species selected for the mixture.
  2. Based on the results of experiments so far (3 very different years in terms of weather), the  most stable  and  high biomassforming mixture was hairy vetch (10 kg/ha) + forage radish (2 kg/ha) + phacelia (3 kg/ha) + Berseem clover (2 kg/ha).
  3. The optimal time for cultivation of catch crops in Estonia  is the first 15 days of August.
    After that, the biomass decreases. The highest biomass production was fixed in sowing experiments with hairy vetch and forage radish. Of the studied species, the berseem clover was most affected by sowing time. Compared to the first sowing test, the biomass of which was decreased by 47% and 90% in the second and third sowing round, respectively.
  4. Fertilisation of catch crops using mineral (N) fertilisers did not have a one-way effect on the biomass yield indicating further studies are needed. Fertilization tests with liquid manure credibly increased the biomass of catch crops compared to the control area.
  5. Seed treatment with  biostimulants did not yield greater biomass in catch crops tested, although plants showed even sprouting compared to the untreated control.
  6. Nitrogen uptake depends on plant species, the size of the biomass and the overall nutrient content in the plant tissue. In 2017, hairy vetch showed best results in nitrogen binding. 
  7. The biomass yield of  clovers is affected by the weather. For example, dry and hot growing season of  2018 was not suitable for berseem clover to obtain moisture from dry soil because its roots do not reach deep enough. 
  8. Experiments with forage radish indicate that this species is fit to be used in mixtures with other catch crops.

Hairy vetch (Vicia villosa, photo below) is a new catch crop species in Estonia. According to our tests, it is winter-stable in Estonian conditions and starts to grow very early in the spring.  Vicia villosa yields a lot of biomass and has great nutrient binding capacity. Of the new non-wintering species, forage radish (also in direct sowing) proved suitable for growing in local climate conditions. 

Leguminous (Papilionaceae) clovers needs further investigation. Berseem clover tolerates a little cold, but is not winter-resistant. Crimson clover seems to be more resistant to winter hardy, but needs further testing: how sowing time affects its winter hardiness, which temperatures it can withstand, as well as how snow coverage affects its growth.

Among cruciferous catch crops, it is innovative to grow forage (tillage) radish. Experiments so far have shown good results. In terms of growth and high biomass formation capacity, Phacelia (Phacelia tanacetifolia) is also a well-recommended plant species to be used in the mixtures.

Estonian University of Life Sciences – Liina Talgre, Enn Lauringson