Data extracted in February 2021
Fiche created in November 2023

Note to the reader: This general fiche summarises all the environmental and climate impacts of FALLOWING found in a review of 4 synthesis papers[1]. These papers were selected from an initial number of 236 obtained through a systematic literature search strategy, according to the inclusion criteria reported in section 4. The impacts reported here are those for which there is scientific evidence available in published synthesis papers, what does not preclude the farming practice to have other impacts on the environment and climate still not covered by primary studies or by synthesis papers.

The synthesis papers review a number of primary studies ranging from 35 to 127. Therefore, the assessment of impacts relies on a large number of results from the primary studies, obtained mainly in field conditions, or sometimes in lab experiments or from model simulations.

1.     DESCRIPTION OF THE FARMING PRACTICE

• Description:
  • Fallowing refers to the farming practice in which arable land included in the crop rotation system is left to recover, at least for the whole of a crop year, whether worked (e.g. ploughed) or not and with no intention to produce a harvest, including set-aside lands[2].
• Key descriptors:
  • This review includes:
    • Natural fallow: 
      • bare land bearing no crops at all; 
      • land with spontaneous natural growth that may be used as feed or ploughed; 
      • recently abandoned and set-aside lands (<5 years). 
    • Green fallow: land sown exclusively for the production of green manure 
  • This review does not include short and seasonal fallowing periods of annual crops; i.e., summer or winter fallows, whether soils are left bare or are shown with cover crops or green manures. These two practices are assessed in separate sets of fiches. 
  • This review includes spatial and temporal comparisons between fallow lands and cultivated arable lands. Spatial comparisons were simultaneously conducted between nearby fallows and cultivated lands. Temporal comparisons were conducted in the same land before and during fallowing.
    

2.    EFFECTS OF THE FARMING PRACTICE ON CLIMATE AND ENVIRONMENTAL IMPACTS

We reviewed the impacts of fallowing (either natural or green fallows) compared to cultivated arable lands.

The table below shows the number of synthesis papers with statistical tests reporting i) a significant difference between the Intervention and the Comparator, that is to say, a significant statistical effect, which can be positive or negative; or ii) a non-statistically significant difference between the Intervention and the Comparator. In addition, we include, if any, the number of synthesis papers reporting relevant results but without statistical test of the effects. Details on the quality assessment of the synthesis papers can be found in the methodology section of this WIKI.

Out of the 4 selected synthesis papers, 2 included studies conducted in Europe, and 4 have a quality score higher than 50%.

Table 1: Summary of effects. Number of synthesis papers reporting positive, negative or non-statistically significant effects on environmental and climate impacts. The number of synthesis papers reporting relevant results but without statistical test of the effects are also provided. When not all the synthesis papers reporting an effect are of high quality, the number of synthesis papers with a quality score of at least 50% is indicated in parentheses. Some synthesis papers may report effects for more than one impact, or more than one effect for the same impact.

3.     FACTORS INFLUENCING THE EFFECTS ON CLIMATE AND ENVIRONMENTAL IMPACTS

The factors significantly influencing the size and/or direction of the effects on the impacts, according to the synthesis papers included in this review, are reported below. Details about the factors can be found in the summaries of the meta-analyses available in this WIKI.

Table 2: List of factors reported to significantly affect the size and/or direction of the effects on environmental and climate impacts, according to the synthesis papers reviewed. The reference number of the synthesis papers where those factors are explored is given in parentheses.

4.    SYSTEMATIC REVIEW SEARCH STRATEGY

Table 3: Systematic review search strategy - methodology and search parameters.

5.     SYNTHESIS PAPERS INCLUDED IN THE REVIEW

Table 4: List of synthesis papers included in this review. More details can be found in the summaries of the meta-analyses.

Disclaimer: These fiches present a large amount of scientific knowledge synthesised to assess farming practices impacts on the environment, climate and productivity. The European Commission maintains this WIKI to enhance public access to information about its initiatives. Our goal is to keep this information timely and accurate. If errors are brought to our attention, we will try to correct them. However, the Commission accepts no responsibility or liability whatsoever with regard to the information on these

[1] Synthesis research papers include either meta-analysis or systematic reviews with quantitative results. Details can be found in the methodology section of the WIKI.

[2] Statistics explained (https://ec.europa.eu/eurostat/statistics-explained/index.php/Glossary:Fallow_land)