Field trials on reduced soil tillage under organic farming conditions across Europe were used to compare the soil quality changes over time. Soil organic carbon fractions, soil carbon stocks and microbial community structure were analysed. Most severe differences between plough and reduced tillage were found in the top ten cm of the soil profile. Differences became less or not significant in deeper layers. Analyses are still ongoing and will only be ready to be presented at the conference

Antichi, Daniele

Barberi, Paolo

Berner, Alfred

Bufe, Cornelia

Delfosse, Philippe

Fliessbach, Andreas

Gattinger, Andreas

Grosse, Meike

Haase, Thorsten

Hammerl, Verena

Heß, Jürgen

Hissler, Christophe

Koal, Phillip

Kranzler, Andreas

Krauss, Maike

Mäder, Paul

Peigné, Joséphine

Pritsch, Karin

Reintam, Endla

Schloter, Michael

Surböck, Andreas

Vian, Jean François

Organic Eprints

RAHMANN G & AKSOY U (Eds.) (2014) Proceedings of the 4th ISOFAR Scientific Conference. ‘Building Organic Bridges’, at the Organic World Congress 2014, 13-15 Oct., Istanbul, Turkey (eprint ID 24293)   1051 Soil Quality Changes in Field Trials Comparing Organic Reduced Tillage  to Plough Systems across Europe ANDREAS FLIEßBACH1*, V. HAMMERL, D. ANTICHI, P. BÀRBERI, A. BERNER, C. BUFE,  P. DELFOSSE, A. GATTINGER, M. GROSSE, T. HAASE, J. HEß, C. HISSLER, P. KOAL,  A. KRANZLER, M. KRAUSS, P. MÄDER, J. PEIGNÉ, K. PRITSCH, E. REINTAM,  A. SURBÖCK, J.-F. VIAN, M. SCHLOTER Key words: reduced tillage, soil quality, plough Introduction Conserving and improving the fertility and quality of the limited soil resource to produce food, feed and fibre has always been the key to organic farmers’ management practices. This issue is also addressed in conservation agriculture systems that give up on soil tillage (no-tillage) or reduce tillage intensity, but often build on the extensive use of herbicides and mineral fertilizers. Both systems show advantages for soil quality (Holland, 2004; Mäder et al., 2002) and therefore their combination is promising and may provide better soil quality. Challenges of introducing no- or reduced tillage systems into organic farming are increased weed pressure, retarded mineralization of nutrients that both may lead to reduced crop yield (Peigné et al., 2007). Pioneer farmers have developed solutions and new machinery to be applicable in organic farming systems. Comparisons of reduced tillage to the traditional plough system have started on farms and systematic research started a decade ago. It was the aim of our research activities, accomplished within the frame of the European network TILMAN-ORG (www.tilman-org.net), to evaluate changes in soil carbon stocks and biological soil fertility parameters in soils from European field trials that compared reduced primary soil tillage options with standard procedures (mainly plough). The selected sites represent a geo-climatic gradient from the North-East to the South-West. The hypothesis was that reduced tillage is enhancing the stratification of soil organic matter, soil microbial biomass and activity, and is changing microbial community structure and microbial functions.  Material and methods  Soil samples for carbon stock changes were taken in spring 2012 from replicated field plots of short- (< 2 yrs.), medium- (2-7 yrs.) and long-term (> 7 yrs.) field trials comparing reduced tillage, minimum, or no tillage and plough in Scheyern and Frankenhausen (DE), Thil (FR), Windpassing (AT), Fischbach (LU), Gallecs (ES), and Frick (CH), as well as the use of green manures in Tartu (EE) and San Piero a Grado (IT). Soil strata were sampled according to tillage depths and from the deepest tillage depth down to 50 cm. Ten to 15 soil cores from each replicate field plot were combined to one bulk sample per plot and soil layer. Bulk density was measured in the middle of each sampled soil layer. Soil organic carbon was measured by wet oxidation (Nelson and Sommers, 1996). Soil samples from Scheyern (Start: 1992; chisel plough 15 cm, cultivator and rotary harrow 5 cm; sandy loam) (Reents et al., 2008; Sprenger, 2004), Thil (start 2004; plough 30 cm, shallow plough 18 cm, chisel 15 cm, superficial (5 cm) or no tillage with crimper roller; sandy loam) (Vian et al., 2009) and Frick (start 2002; plough 15 cm, stubble cleaner 5 cm with occasional loosening at 15 cm; clayey loam) (Gadermaier et al., 2012) were studied in more detail: Dissolved organic carbon was analysed by infrared spectrometry. Soil microbial biomass was analysed by chloroform fumigation extraction according to Vance et al. (1987). The soil bacterial and fungal diversity has been determined by amplicon tagging of 16S and ITS rRNA genes to determine microbial genotypes as well as phospholipid fatty acid (PLFA) fingerprints to analyse the microbial phenotype (analyses on-going). Dried samples were used for soil chemical analyses, field moist samples were stored at 4°C for soil microbial biomass and samples for DNA and PLFA analyses were kept frozen at -80°C.                                                       1Research Institute of Organic Agriculture (FiBL), Switzerland, andreas.fliessbach@fibl.org, www.fibl.org This research was carried out within the frame of TILMAN-ORG a project funded by CORE Organic II Funding Bodies, being partners of the FP7 ERA Net www.coreorganic2.org. FLIEßBACH A, et al. Soil Quality Changes in Field Trials Comparing Organic Reduced Tillage to Plough Systems across Europe   1052    Figure 1. Field trials and farm surveys under investigation in the European network TILMAN-ORG. Preliminary results from 9 field trials across Europe as shown here will be presented in more detail including hitherto not accomplished soil biological assessments. Results Soil organic carbon (SOC) content decreased significantly with soil depth in all soils. Ploughed soils showed a relatively homogenous distribution of SOC within the plough layer but decreased sharply thereunder. The reduction in primary soil tillage intensity and depth caused a relative accumulation in the uppermost soil layer being most important in no tillage soils. In Windpassing (AU) SOC in the uppermost layer was higher in reduced (stubble cleaner) as compared to plough (p=0.05), whereas below this horizon the ploughed soil showed higher SOC values than the reduced tilled one (p=0.05). In the soil beneath the plough layer that has not been tilled at all, SOC ranged between 0.7 and 1.4% across all sites. Compared to this soil layer, where differences between ploughed and unploughed soils at each site were small, SOC in the plough layer was higher by the factor 1.5 to 1.9. In reduced tillage soils this factor ranged between 1.7 and 3.2 for the uppermost layer (0-10 cm) and 1.3 to 2.1 for the layer beneath (10-20 cm). In minimal tillage soils in Scheyern this factor was 2.5 as compared to 1.9 in reduced tillage. Reduced tillage soils over all study sites showed a topsoil (0-10 cm) accumulation of SOC by 15 to 35% as compared to the plough system.  SOC stocks that consider bulk densities in each soil layer showed a decrease with soil depth. Over the 50 cm sampling depth, SOC stocks in reduced tillage soils were not significantly different from those under plough use. In the top ten cm SOC stocks were higher for reduced tillage in Frick and Windpassing and for no tillage in Thil as compared to plough (p=0.05).  Dissolved organic carbon (DOC) decreased with soil depth, except for the site Windpassing, where DOC increased strongly by the factor 5 in the ploughed soil and by the factor 8 in reduced tillage soils. The decrease in DOC was generally stronger in reduced tillage soils than in ploughed soils. In the uppermost soil layer of reduced tillage soils DOC was between 28 and 70% higher than in ploughed soils.  Soil microbial biomass carbon (Cmic), as an active soil organic matter pool, also showed a stronger stratification in reduced tillage soils as compared to ploughed soils. Compared to the untilled soil layer below the deepest tillage depth Cmic in the topsoil layer of ploughed soils was higher by the factor 2 to 2.9. This factor in reduced tillage soils was 3.4 in Frick and 4.2 to 5.5 (no tillage) in Thil. A repeated analysis with Thil soils in 2013 confirmed these results also for microbial biomass nitrogen. In Scheyern this comparison showed a factor of 2.3 in reduced tillage soils and 3.1 with minimum tillage.  RAHMANN G & AKSOY U (Eds.) (2014) Proceedings of the 4th ISOFAR Scientific Conference. ‘Building Organic Bridges’, at the Organic World Congress 2014, 13-15 Oct., Istanbul, Turkey (eprint ID 24293)   1053  Table 1: Significant soil tillage effects in field trial soils on SOC content (Corg) and stocks, dissolved organic carbon (DOC) and microbial biomass carbon (Cmic)  Site Tillage Depth [cm] Corg  [%] C-stock  [g m-2] DOC  [µg g-1] Cmic  [µg g-1] Scheyern DE Chisel 18cm (C) vs. Rotary harrow + Cultivator 8cm (R) 0-10 R > C n.s. n.s. n.s. 10-25 n.s. n.s. n.s. n.s. 25-50 n.s. n.s. n.s. n.s. Frick CH Stubble cleaner 5-7 cm (R) vs. plough 15cm (P) 0-10 R > P R > P R > P R > P 10-20 n.s. n.s. n.s. R > P 20-50 n.s. n.s. n.s. n.s. Thil FR Plough 30cm (P) Plough 18cm (sP) Chisel 15cm (C) No till 5cm (N) 0-10 N > all N > P N > P N > P 10-20 n.s. N > P n.s. n.s. 20-30 n.s. n.s. n.s. n.s. 30-50 n.s. n.s. n.s. n.s.  Soil microbial diversity as assessed by t-RFLP analyses of 16S rRNA genes showed a significant differentiation between soil depths for the field trials in Scheyern, to a lesser extent in Frick and yet not detectable in Thil (analyses are to be confirmed). The different tillage treatments tended to influence microbial diversity patterns in Scheyern, less pronounced in Frick and yet not detectable in Thil. The intensity of change in soil microbial diversity appears to be related to the time of exposure to different tillage systems.  Soil microbial biomass carbon (Cmic), as an active soil organic matter pool, also showed a stronger stratification in reduced tillage soils as compared to ploughed soils. Compared to the untilled soil layer below the deepest tillage depth Cmic in the topsoil layer of ploughed soils was higher by the factor 2 to 2.9. This factor in reduced tillage soils was 3.4 in Frick and 4.2 to 5.5 (no tillage) in Thil. A repeated analysis with Thil soils in 2013 confirmed these results also for microbial biomass nitrogen. In Scheyern this comparison showed a factor of 2.3 in reduced tillage soils and 3.1 with minimum tillage.  Soil microbial diversity as assessed by t-RFLP analyses of 16S rRNA genes showed a significant differentiation between soil depths for the field trials in Scheyern, to a lesser extent in Frick and yet not detectable in Thil (analyses are to be confirmed). The different tillage treatments tended to influence microbial diversity patterns in Scheyern, less pronounced in Frick and yet not detectable in Thil. The intensity of change in soil microbial diversity appears to be related to the time of exposure to different tillage systems. Conclusions Reduced soil tillage often leads to accumulation of soil organic matter at the soil surface resp. in the uppermost soil layers, where crop residues are mixed in. This is one of the common features of all the field trials comparing reduced tillage options with the soil inversion by ploughing. The accumulation, however, was only significant when looking at the topsoil layers. When the whole soil profile down to 50 cm depth was examined no difference between reduced tillage and plough tillage was statistically significant. The stratification of soil organic matter and organic matter fractions was more pronounced in reduced or no-tillage soils, however sometimes at the cost of contents in deeper soil layers. Long-term experiments show stronger effects than young experiments, particularly with respect to the microbial community structure. References  Gadermaier, F., Berner, A., Fließbach, A., Friedel, J.K., Mäder, P. (2012): Impact of reduced tillage on soil organic carbon and nutrient budgets under organic farming. Ren Agric Food Systems 27, 68-80. Holland, J.M. (2004): The environmental consequences of adopting conservation tillage in Europe: reviewing the evidence. Agric Ecosys Environ 103, 1-25. Mäder, P., Fließbach, A., Dubois, D., Gunst, L., Fried, P., Niggli, U. (2002): Soil fertility and biodiversity in organic farming. Science 296, 1694-1697. Nelson, D.W., Sommers, L.E. (1996): Total carbon, organic carbon, and organic matter. In: Methods of soil analysis. Part 3-chemical methods. Sparks, D., Page, A., Helmke, P., Loeppert, R., Soltanpour, P., Tabatabai, M., Johnston, C., Sumner, M. (eds.). pp 961-1010. Soil Science Society of America, Madison, WI 53711 USA. FLIEßBACH A, et al. Soil Quality Changes in Field Trials Comparing Organic Reduced Tillage to Plough Systems across Europe   1054 Peigné, J., Ball, B.C., Roger-Estrade, J., David, C. (2007): Is conservation tillage suitable for organic farming? A review. Soil Use Manage 23, 129-144. Reents, H.J., Küstermann, B., Kainz, M. (2008): Sustainable land use by organic and integrated farming systems. In: Perspectives for Agroecosystem management. Schröder, P., Pfadenhauer, J., Munch, J.C. (eds.). pp 17-39, Amsterdam. Sprenger, B. (2004): Populationsdynamik von Ackerwildpflanzen im integrierten und organischen Anbausystem. In: Lehrstuhl für Vegetationsökologie, Department für Ökologie, pp 151. Technische Universität München, München. Vance, E.D., Brookes, P.C., Jenkinson, D.S. (1987): An extraction method for measuring soil microbial biomass C. Soil Biol Biochem 19, 703-707. Vian, J.F., Peigne, J., Chaussod, R., Roger-Estrade, J. (2009): Effects of four tillage systems on soil structure and soil microbial biomass in organic farming. Soil Use Manage 25, 1-10. 

Soil quality changes in field trials comparing organic reduced tillage to plough systems across Europe (TILMAN-ORG Session)

Soil quality changes in field trials comparing organic reduced tillage to plough systems across Europe (TILMAN-ORG Session)

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