Department of Geography and Environmental Science Organic Matter Soil Health and Crop Yield Dr Tom Sizmur University of Reading 2008 www.reading.ac.uk
Structure of talk How organic matter becomes soil organic matter Organic matter as food for earthworms Earthworms reduce soil strength Lower soil strength accelerates crop establishment Organic matter increases crop yield Can we use organic inputs more smartly?
Organic matter and soil health Organic inputs Soil organic matter Benefits Manure management Compost and AD Crop residues Cover crops Water and nutrient retention Soil structure Aggregate stability Microbial biomass Infiltration Yield Crop quality Soil erosion Reduced inputs Improved water quality
How OM becomes SOM CO 2 Organic Matter (e.g. FYM, crop residues) Soil biology Soil Organic Matter CO 2 Soil biology Modified from RothC: The Rothamsted Carbon Model Kevin Coleman and David Jenkinson 1998 Soil Organic Matter
Historical and emerging views of soil carbon cycling MWI Schmidt et al. Nature 478, 49-56 (2011) doi:10.1038/nature10386
Organic matter feeds soil biology The vast majority of the organic matter added to soils is metabolised relatively quickly by soil organisms Some of these soil organisms improve the structure of the soil.
Minimum tillage experiment Rotation: Spring Barley Winter Oilseed rape Winter Wheat Spring Barley Minimum tillage Farmyard manure and Compost at 0, 2.5 and 3.5 t C ha -1 5 Nitrogen rates (N0 to N4)
Earthworm biomass (g m -2 ) Minimum tillage experiment 250 0 t C/Ha 200 2.5 t C/ha 3.5 t C/Ha 150 100 50 0 N0 Compost N0 FYM N3 Compost N3 FYM Earthworm biomass significantly increased by N rate and OM rate
3 ecological groups of earthworms Surface dwellers Vertical burrowers Horizontal burrowers Aporrectodea caliginosa
You can monitor earthworms http://www3.imperial.ac.uk/opalsoil/earthworms
Earthworms are ecosystem engineers Improve drainage Reduce soil erosion Promote root growth Accelerate nutrient cycling Aporrectodea caliginosa
Earthworms are ecosystem engineers Long before [the plough] existed the land was in fact regularly ploughed and still continues to be thus ploughed by earthworms
Soil strength 0-30cm (Kph) Earthworms reduce soil strength 4000 3500 R² = 0.3496 3000 2500 2000 1500 1000 500 0 No Straw Straw at 5 t ha-1 Straw at 10 t ha-1 Straw at 20 t ha-1 0 20 40 60 80 100 Endogeic earthworm biomass (g m -2 )
Good soil structure: Large pores and small aggregates Plant roots need to push aggregates away from them as they grow. They need somewhere to push the soil that they displace Therefore, aggregates should be smaller than the diameter of the plant roots Lots of small (<1 cm diameter) aggregates are better than a few large aggregates/clods
Impact of OM on crop yield: Manure incorporation experiment Applications (2.5 t C ha -1 ) Farmyard Manure Compost Anaerobic Digestate Straw Five nitrogen rates (N0-N4) Rotations Wheat Barley Oats Wheat Barley OSR Wheat Barley
OSR yield (t/ha) at 90% dry matter Manure incorporation experiment Oilseed rape: Yield 7 6 5 4 3 Unamended 2 1 0 0 50 100 150 200 250 300 Nitrogen (kg/ha)
OSR yield (t/ha) at 90% dry matter Manure incorporation experiment Oilseed rape: Yield 7 6 5 4 3 2 1 Unamended Anaerobic Digestate Compost Farmyard Manure Barley straw 0 0 50 100 150 200 250 300 Nitrogen (kg/ha)
% Oil at 9% Moisture content Manure incorporation experiment Oilseed rape: Oil content 52 51 50 49 48 47 46 Unamended Anaerobic Digestate Compost Farmyard Manure Barley straw 45 0 50 100 150 200 250 300 Nitrogen (kg/ha)
OSR straw yield (t ha -1 ) DM Manure incorporation experiment Oilseed rape: Straw yield 4 3.5 3 2.5 2 1.5 1 0.5 0 Unamended Anaerobic Digestate Compost Farmyard Manure Barley straw 0 50 100 150 200 250 300 Nitrogen (kg ha -1 )
Barley grain yield (t/ha) at 85% DM Manure incorporation experiment Barley: Yield 12 10 8 6 4 2 Unamended Anaerobic digestate Compost Farmyard Manure Straw 0 0 50 100 150 Nitrogen (kg/ha)
Barley straw yield (t ha -1 ) DM Manure incorporation experiment Barley: Straw yield 6 5 4 3 2 1 0 Unamended Anaerobic Digestate Compost Farmyard Manure Barley straw 0 50 100 150 200 250 300 Nitrogen (kg ha -1 )
Grain Yield (t ha -1 ) Grain Yield (t ha -1 ) 6 5 4 3 2 1 0 6 5 4 3 2 1 0 Sandy soils: Woburn organic manuring experiment Data Fitted 0 50 100 150 200 250 Nitrogen (kg ha -1 ) 0 50 100 150 200 250 Nitrogen kg ha -1 0 t C/ha 3 t C/ha 1966 1970 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1995 1999 2003 2007 2011-0.5 0 0.5 1 1.5 2 Potatoes W. Wheat Potatoes Effect size W. Wheat Potatoes Sugar Beet W. Wheat S. Barley Sugar Beet S. Barley W. Wheat Potatoes W. Wheat Sugar Beet S. Barley Sugar beet S. Barley W. Wheat Potatoes W. Wheat W. Wheat S. Barley W. Wheat F. Maize W. Rye S. Barley Potatoes W. Wheat
Effect size Sandy soils: Woburn organic manuring experiment 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 6 6 4 10 Barley Potatoes Sugar Beet Wheat
Grains per plant Yield per ear (g) Yield per plant (g) Ears per plant How does OM improve yield? Pot experiment: Wheat 8 7 6 5 4 3 3.5 3 2.5 2 1.5 2 1 1 0 0 1 2 OM application rate (gc/kg soil) 0.5 0 0 1 2 OM application rate (gc/kg soil) 180 30 160 140 25 120 20 100 80 15 60 10 40 20 5 0 0 0.5 1 1.5 2 0 0 0.5 1 1.5 2 OM application rate (gc/kg soil) OM application rate (gc/kg soil)
How can we use OM to improve soil structure and crop yield? Return crop residues Apply manures Reduce tillage Use cover crops/green manures
Earthworm biomass (g m -2 ) 50:50 Manure/Straw Mixtures 200 180 160 140 120 100 80 60 40 20 0 Unidentified Epigeic Anecic Endogeic All plots received 3 tc ha -1 Straw Compost Comp+Straw FYM FYM+Straw AD AD+Straw
The Future Effect of substrate diversity on biological diversity, ecosystem services and resilience Perturbation Increased resilience Increased resistance
Can we make better use of crop residues? PhD Studentship Starting October 2015
Summary Organic matter feeds soil biology Manures increase earthworm populations Earthworms reduce soil strength Lower soil strength promotes root growth and improves access to nutrients and water Better access to nutrients and water increases crop yield and quality You can monitor earthworm populations using the OPAL Earthworm survey guide
Acknowledgements Andy Whitmore Chris Watts Andy Gregory Elodie Martin Emilie Parmentier Kevin Wagner Karl Ritz Mark Pawlet Jim Harris Agnese Mancini