The Potential Use and Benefits of Reduced till in Organic Agriculture Systems.

No Till and Reduced Till are conservation tillage practices with a high potential to restore or improve essential soil functions and mitigate climate change through carbon sequestration and reduced fuel use. While No Till systems are widely used in conventional farming, these techniques are challenging to adapt to organic farming due to weed pressure and frequent nitrogen deficiency in early spring. A potential answer may be Reduced Till, such as shallow inversion ploughing, or non-inversion tillage. The implementation of these practices in European organic farming systems was addressed by an interdisciplinary team of researchers from 11 European countries in a network CORE Organic II project (TILMAN-ORG).

Farmer interviews revealed that No Till and Reduced Till were used more in Mediterranean climates, while green manures were more often used in temperate zones. Yields tended to be lower in Reduced and No Till systems (-7%), while shallow inversion ploughing resulted in yields similar to deep inversion ploughing. Soil mineral nitrogen in the spring was lower under Reduced Till concomitant with lower yields, whereas green manures compensated this reduction. Under drought conditions yields were even higher under Reduced Till possibly due to improved water relations. Although weed infestation was higher in Reduced Till systems, weeds were not always identified as the major cause of lower yields. The reduction in intensity of the soil tillage did not promote higher weed diversity, but it had a strong effect on the weed community composition. Reduced Till positively affected indicators of soil quality such as soil organic carbon, soil microbial biomass and enzyme activities in upper soil layers. Pre-crop (rotational) effects on microbial communities measured using nucleic acid techniques were stronger than tillage effects. Fungal to bacterial ratios were higher under Reduced Till and mycorrhizal fungi and earthworms were positively influenced. Life cycle assessment revealed lower carbon footprints and savings in labor under Reduced Till. Data obtained in TILMAN-ORG were used to prototype optimal cropping systems for various European climatic zones. It is suggested that Reduced Till in organic farming can further contribute to more resilient crop production systems in the future.