1. Valitse pohja temaattisen ohjelman mukaan:
Pohjoinen vihreä biotalous
Innovatiivinen elintarvikeketju
Sininen biotalous
Kestävä luonnonvaratalous yhteiskunnassa
Mikäli kyse on temaattiseen ohjelmaan kuulumattomasta toiminnasta käytetään turkoosia tai oranssia.
Jos asiantuntija- ja viranomaispalveluista käytetään harmaata pohjaa.
Turkoosi ja oranssi ovat Luken päävärejä ja niitä saa käyttää aina ja esimerkiksi temaattisen ohjelman värin ohella.
Catch crops as universal and effective method for reducing nitrogen leaching loss in spring cereal production: A meta-analysis.
Elena Valkama, Riitta Lemola, Hannu Känkänen, Eila Turtola
Natural Resources Institute Finland

2. Background Yield N input reduction affects soil N balance.
Such approach would markedly reduce N leaching loss only in case of abnormally high N balances.
N fertilization
Soil N balance
N leaching loss
Elena Valkama

3. The growing of catch crops - an alternative approach to prevent N leaching
Due to large root systems, catch crops take up N from the soil (30-40 kg/ha).
Thereby catch crops reduce the soil nitrate N content vulnerable to leaching during autumn and winter.
But due to competition, catch crops may also reduce yields of the main crop.
Picture: Jannne Heikkinen. Italian ryegrass

4. The aim of the study was to summarize experiments on catch crops
Soil texture and management (ploughing time, the amount of N applied, fertilizer type).
Climatic (annual precipitation) and experimental conditions (duration of experiments, lysimeter vs. field experiments).
Difference between the countries or over the decades.
Grain yield
and quality
Undersowing
Catch crops, such as ryegrass species, red, white clover, grass-clover mixture, are undersown to the main crop in spring, and after harvesting of the main crops, they continue to grow.
The aim for using catch crops is to take up N from the soil that can reach up to 30 – 40 kg ha-1 for ryegrass species and thereby reduce the soil NO3-N content vulnerable to leaching during autumn and winter.
However, a disadvantage of undersowing catch crops is competition with the main crops for nutrients, soil moisture and light, resulting in some loss of grain yield.
In the Nordic countries, the environmental effects of catch crops in cereal production was studied during the past 40 years, but no meta-analysis has been done.
The aim of this study was to summarize Nordic experiments on the effects of catch crops undersown in spring cereals on N leaching loss or its risk as a measure of soil nitrate in late autumn. The meta-analysis also included the grain yield.
soil nitrate-N
N leaching

5. The database 35 studies (Denmark, Sweden, Finland, Norway)
Over the past four decades
Spring wheat, spring barley, and oats.
Non-legume: Italian ryegrass, perennial ryegrass, Westerwolds ryegrass. Legume: white and red clovers.
Clay and coarse textured mineral soils.
Ploughing time: autumn, spring
N fertilization rates: kg/ha
Fertilizer type: manure, mineral
Duration of experiments: 2-7 yr
Annual precipitation: mm
Kuva: Kari Koppelmäki

6. Meta-analysis
Meta-analysis is statistical analysis of a larger collection of results for integrating the fundings.
Effect size
Log response ratio for each study (ln r)
Weighted mean of log response ratio
Between-group heterogeneity:
Soil texture
Management
Climatic conditions
Elena Valkama

7. N leaching loss Soil nitrate N
- 50%
- 35%
Otherwise, the effect on N leaching and its risk were consistent across the studies.

8. Grain yield
- 3%
+ 6%

9. Conclusions
Ryegrasses are deemed a universal and effective method for reducing N leaching loss across the various soils, management practices and weather conditions in the Nordic countries.
The environmental benefits appear considerable compared to the adverse reduction in grain yields.
Catch crops are advisable for fields at high risk for N leaching (e.g., sandy soils, soils and crops requiring high N fertilization).

11. Future perspective: from the fields to catchment scale
To which extent would catch crops improve water quality on catchment scale?
FRESHABIT LIFE Integrated project aims to improve the ecological status, management and sustainable use of freshwater Natura 2000 sites in Finland. €24.4 million

13. Teppo Tutkija