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Five yrs of research on reduced tillage and earthworm populations – what did we learn? Mirjam Pulleman, Stephen Crittenden, Walter Andriuzzi, Tamila Eswaramurthy, Ron de Goede, Rosanne Michielsen, Bas Oudshoorn, Guenola Pérès, Tamas Salanki Content Effect of soil disturbance on the soil community Why earthworms? Reduced tillage; the Dutch context Objectives and hypotheses 3 Related projects o Hoeksche Waard – arable fields & field margins strips o Flevopolder experimental fields - organic & conventional farming o SUSTAIN project – Brittany vs. NL Results and discussion + future work Effects of disturbance on soil community Direct mechanical damage to body structures Disruption of existing physical structure Redistribution of litter / crop residues Exposure to predation Larger sized organisms affected most More fungal dominated Hendrix et al 1986 Wardle 1995 Effects of disturbance on soil community Bouché 1977 Wardle 1995: Responses to perturbation are best studied at a finer taxonomic resolution than normally used for investigating soil food webs; by emphasizing functional groups based on ecological relationships (e.g. fungi) or trophic interactions (e.g. nematodes). Why focus on earthworms? Large organisms, key stone species Soil ecosystem engineers – affect habitat for other organisms Soil functioning (depending on functional group) Emblematic species.... Keith & Robinson, 2012 Why focus on earthworms? Reduced soil tillage; the Dutch context 99% of arable land in NL is regularly mouldboard ploughed Farmers express a growing interest in reduced tillage No-till is not practiced non-inversion tillage Reduced soil tillage; the Dutch context 99% of arable land in NL is regularly moldboard ploughed Farmers in NL have a growing interest in reduced tillage No-till is not practiced non-inversion tillage All with controlled traffic lanes Objectives and hypotheses To determine the effects of Ploughed (P) vs. Non-Inversion Tillage (NIT) systems on the density and diversity of earthworms (species and functional groups) H1: Total earthworm densities will increase in NIT H2: The contribution of epigeic and anecic species will be higher under NIT than P The projects (2009-2014) 1. Farmers fields Hoeksche Waard 2. Flevopolder, PPO experimental fields 3. Brittany vs. NL (SUSTAIN project) 3 2 1 Farmers fields - Hoeksche Waard Farmers fields - Hoeksche Waard Crittenden et al 2015 Soil: Calcareous marine clay loam Conventional farms, each with tillage pairs (1-4 yrs) and field margin strips as a non-disturbed reference (5 – 9 yrs) Farmers fields - Hoeksche Waard Crittenden et al 2015 Sampling method: o Four 20x20x20 monoliths per sampling location o Formaldehyde extraction o Spring and fall samplings (t=4) Farmers fields - Hoeksche Waard Crittenden et al 2015 Results tillage pairs o Farmers fields - Hoeksche Waard Crittenden et al 2015 Results field margins: o Flevopolder experimental fields Flevopolder experimental fields Marine loam soils NIT vs. P, since 2008 Sampling in 2009, 2010, 2011, 2012, 2014 3 monoliths per plot (n=4) I III II IV Situation 2011 CONVENTIONAL ORGANIC Onion Wheat/Faba bean intercrop + CC Potato Potato Sugar beet Grass-clover Wheat or Barley + CC Cabbage Spring wheat + CC Crittenden et al 2014 Carrot + CC Flevopolder experimental fields Crittenden et al 2014; Oudshoorn 2013 Results Conventional farming o ns Crittenden et al 2014 ns ns MT=NIT>P Flevopolder experimental fields Crittenden et al 2014; Oudshoorn 2013 Results organic farming o ns P>NIT=MT P>NIT=MT ns BRITTANY VS. NL Brittany vs. NL Results SUSTAIN - Organic o Results and discussion H1: Total earthworm densities will increase in NIT Data on total earthworm densities were highly variable, but when a sign difference of tillage is found: ORG: NIT/MT < P CONV: NIT/MT > P Endogeic species are very dominant (>80%) Results and discussion H2: The contribution of epigeic and anecic species will be higher under NIT than P The relative importance of epigeic species is increased under reduced tillage Anecics are extremely rare in arable fields (but not in France!) Anecics are present in grassy field margins Future work Reduced soil disturbance: Earthworm diversity Increased OM inputs: Earthworm densities / biomass Dispersal and survival and dispersal of anecics in(to) NIT fields? Generalizations across sites with different species (classifications)