Development of mixtures and plants suitable for crop rotation to enhance land use and improve soil fertility and main crop yield.
After harvesting early crops, the field is left bare. To avoid nutrient leaching after harvesting the main crop, the field should be sown with catch crops. These crops fix nitrogen and other nutrients from the soil, and the biomass of the ploughed-in cover crops improves soil structure and nutrient availability. Catch and cover crops can penetrate the soil with their deep roots, resulting in improved soil hydro-physical properties. Incline in soil organic carbon increases both microbial community, its abundance and diversity. Intercropping increases soil carbon and nitrogen, too.
The aim of this innovation activity is to develop practices that reduce nutrient leaching to surface and groundwater and to prevent erosion of fertile soil by water runoff and wind. In intercropping, purpose of catch and cover crops is to bind water and nutrients to reduce leaching. The project will identify and investigate different crops suitable for intercropping in the Estonian climate conditions.
During our research work, we study the following winter cover and catch crops (commonly grown in Europe), and test their potential to thrive in local climate and soil conditions:
- 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 many advantages:
🌱 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.
We investigated the suitability of new crops for the Estonian climate and the effect of sowing time on the rate of biomass formation. The most promising mixtures of intercrops for cultivation in Estonian conditions that will give the highest biomass yields and thereby maximise soil organic matter were identified. Among these, some species and/or mixtures were able to take up more nutrients from the soil and reduce leaching, thus also positively affecting soil’s physical properties and contributing to the formation of rich soil with enhanced biological activity.
The identification of suitable species and mixtures for different cropping systems and tillage technologies was also under study. We analysed whether influencing the rate of biomass formation with different inputs (biostimulants, slurry) will increase the biomass formation and nutrient uptake (i.e. fixation of N, P, K, Mg, Ca) of selected catch and cover crops.
Mixture of pea, buckwheat and forage radish (credits Liina Talgre).
Throughout 2017-2020, 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.
During 4 years, biomass formation and nutrient composition of 9 different crop mixtures were measured. 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. As mentioned before, different cultivation methods were tested during this project.
Experimental field (OÜ Rannu Seeme).
In 2017, experiments were carried out on the fields of Rannu Seeme OÜ where two mixtures of catch crops were used. 30 kg/ha of mineral nitrogen was applied to both mixtures.
In 2018-2019, 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). Experimental data for 2020 was collected from the fields of FIE Üllar Kaaver. 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 on the fields of OÜ Erumäe Kari OÜ. Experiments were set up at test plot areas to assess the effect of biostimulators on the biomass formation of catch crops.
Additionally, 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.
Further studies were performed with five different plant species: hairy vetch, forage radish, phacelia, Crimson and/or Berseem clover.
The intercrops were sown immediately after the main crop was harvested, the earliest sowing being on 1 August, with sowing at weekly intervals until the end of August (3-5 sowing dates depending on the year). Photographs show the effect of sowing time on the biomass formation of hairy vetch (right) and forage radish (left).
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).
Photos by Liina Talgre.
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. Lower reductions in biomass at late cultivation dates compared to those sown earlier were identified for forage radish, phacelia and hairy vetch.
Mixture of early barley, spring vetch, phacelia, white mustard and forage radish (2018).
Data obtained show most viable and competitive species are phacelia and forage radish. The most stable and high biomass was obtained with the mixture containing the most dominant species plus the sub-mixed species in following quantities: hairy vetch (10 kg/ha) + forage radish (2 kg/ha) + phacelia (3 kg/ha) + Berseem clover (2 kg/ha).
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 was observed 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.
Seed treatment with biostimulants did not yield greater biomass in catch crops tested, although plants showed even sprouting compared to the untreated control. The use of additional biostimulants for seed treatment is particularly necessary in conditions with low humus content and low natural microbial activity.
The effect of intercropping on the yield of the succeeding crop depends on the species and its N-fixing capacity. Positive effects on yields over the years showed both forage radish and hairy vetch.
Why catch and cover crops should be grown as a mixture of several species?
The advantages of mixing are a reduction in cultivation risks, as different crops respond differently to soil and weather conditions, with consequent reductions in nutrient leaching, soil loss (reduced erosion) and increased biodiversity.
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. Experiments with forage radish indicate that this species is fit to be used in mixtures with other crops, such as pea, buckwheat or barley. We observed, the biomass yield of clovers is affected by the weather, too.
Hairy vetch (Vicia villosa)
Growing catch and cover crops long-term significantly increased soil organic carbon compared to no intercropping. By implementing this practice in rotation, it is possible to reduce soil acidity. The effect of intercropping increased microbial activity and biomass, as well as earthworm abundance.
Liquid fertiliser applied in filed the autumn (at the same time as the catch/cover crops) increases the biomass and nutrient uptake of the crops; fertilising the intercrops with mineral fertiliser is not practical.
The innovation activity on the development of suitable species and mixtures for intercropping and development of agro-techniques for their cultivation was carried out within the framework of measure no 16 “Cooperation” of the Estonian Rural Development Programme 2014-2020. The budget for the innovation activity was €130 000 and the (06.03.2017 – 06.01.2022).
Estonian University of Life Sciences – Liina Talgre, Enn Lauringson.
Contributions: Hille Lass, Helena Madsen, Merili Toom.
We thank also students involved: Sven Eerik Pärendson, Kervin Adamson, Karl Egert Sepp.