Plant-soil interaction discussion, Wageningen, 20 April 2016 Soil quality indicators & plant growth Oene Oenema Wageningen University
"What chemical and physical soil properties should every plant ecologist measure as background information for its eperiment, looking at plant growth? Before and after the eperiment? Other properties that are basically always important? What about soil heterogeneity and sample size? And do we always need to include soil properties in the papers with pot/field eperiments?
Defining the quality of soil, water, air HUMANS AIR BIOSPHERE SOIL WATER
Air and Water Quality Water Quality mainly refers to pollutant concentration; Air Quality mainly refers to pollutant concentration in air Transboundary effects; hence need for Harmonization of standards and critical values Harmonization of methods
Soil Quality Very little harmonization of concepts, methods and standards Soil is static, and spatial variability Horizontally (pedo-climatic zones & small-scale variability), Vertically (horizons, influence of bioturbation) Soil Quality is defined in terms of Degree of functioning (over time), qualitatively/quantitatively Characteristics (attributes), quantitatively Pollutant concentrations, quantitatively
Ideal indicators Easy measurable, reliable & cheap Interpretable correlate well with Ecosystem processes and functions Soil threats Sensitive to management accessible to many users components of eisting databases
Which indictors? Depends on the purpose of your project Research / policy / commercial Soil functioning Soil threats
Assessing Soil functions Sustaining plant and animal life (crop productivity) Regulating / buffering water Cycling / buffering nutrients Filtering and buffering potential pollutants Physical stability and support http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/
Assessing Soil threats Soil erosion (water, wind) Soil compaction (topsoil, subsoil) Soil organic matter decline Soil nutrient depletion Soil salinization Soil pollution Landslides Sealing Depend on soil type, geography, climate and management
Soil plant interactions Plant responses (Y) are a function of species composition (G), environment (E, a combination of Climate and Soil), and Management (M). Hence, Y = f(g, E, M), and Y = f(g, C, S, M). Your interest is mainly in Y = f (S) or Y = f(s, M) (note, there may be interactions)
Crop production ecological principles: Y=GEM Production situation Potential Defining factors Crop features Radiation Temperature CO 2 Water & nutrient limited Limiting factors Water Nutrients Actual Reducing factors Weeds Pest Diseases Pollutants Yield, kg/ha After Van Ittersum and Rabbinge (1997).
Soil factors affecting plant responses 1. Water delivering capacity; limiting yield 2. Nutrient delivering capacity; limiting yield 3. Soil-born pest and diseases; reducing yield 4. Soil-born weeds; reducing yield 5. Seed bed / Workability; reducing (harvestable) yield 6. Pollutants; reducing yield Salt-affected soils, aluminium toicity, nutrient imbalances Metals, organic pollutants & pathogens affect food safety
Plant growht controlling soil factors (i) + Significance - -Water -Nutrients -Workability -Nematodes -Weed seeds -Pollutants Management Soil properties Weather conditions Direct control Indirect control
Simple set of indicators for plant growth limiting factors Water holding/supplying capacity Soil depth/ rooting depth Water retention curve Nutrient delivery capacity Soil depth Nutrient delivery: Intensity measure Nutrient delivery: capacity measure
Simple set of indicators for plant growth reducing factors Soil born diseases Number and species of nematodes, fungi Soil born weeds Number and species of seeds of weeds Soil born pollutants Etractable salts, metals, ph Workability Slope, Drainage Teture / Structure / drainage
Commercial labs offer many tests / indicators
Cornell SHA FAO - VSA SoilQuality.org SoilQuality.org.AU USDA - NRCS Doran & Parkin Karlen et al. 2009/ 2016 2008 2011 2016 undat ed 1996 1997 Comparison of labs: physical properties Physical Bulk density Macro-porosity Meso-porosity Micro-porosity Available water capacity, water holding capacity Residual porosity Penetration resistance at 10 kpa Saturated hydraulic conductivity Dry aggregate size (<0.25 mm) Dry aggregate size (0.25-2 mm) Dry aggregate size (2-8 mm) Wet aggregate stability (0.25-2 mm) Wet aggregate stability (2-8 mm) Surface hardness with penetrometer Subsurface hardness with penetrometer Field infiltrability, infiltration Soil teture Soil structure Soil porosity Surface ponding Surface crusting and surface cover Soil erosion (wind/water) Aggregate stability Slaking Water logging Subsurface compaction Erodability, erosion () Drainage (linked with infiltration) () Soil tilth () Sediment deposition () Aggregation (Top) Soil depth
Cornell SHA FAO - VSA SoilQuality.org SoilQuality.org.AU USDA - NRCS Doran & Parkin Karlen et al. 2009/ 2016 2008 2011 2016 undat ed 1996 1997 Comparison of labs: chemical properties Chemical Phosphorus Nitrate nitrogen Potassium ph Magnesium Calcium Iron Aluminum Manganese Zinc Copper Echangeable acidity Soil colour Number and colour of soil mottles EC Nitrogen CEC Water repellency Boron Nutrient holding capacity () Salinity (linked with EC) () Hydrophobicity ()
Cornell SHA FAO - VSA SoilQuality.org SoilQuality.org.AU USDA - NRCS Doran & Parkin Karlen et al. 2009/ 2016 2008 2011 2016 undat ed 1996 1997 Comparison of labs: biological properties Biological Root health assessment Beneficial nematode population Parasitic nematode population Potential mineralizable nitrogen Decomposition rate Particulate organic matter Active carbon, reactive carbon Weed seed bank Microbial respiration rate Glomalin Organic matter content Earthworms (number, size) Potential rooting depth Particulate organic matter Soil enzymes Total organic carbon Total organic nitrogen Labile carbon Microbial biomass (sometimes including C, N) Root lesion nematode Cereal cyst nematode Rhizoctonia Crop condition () Root mass () Soil smell () Crop residues ()
Minimum set of soil indicators (i)? Site characterization: Climate Land use (previous and current) Morphology & drainage Soil type / soil profile / soil depth
Minimum set of soil indicators (ii)? Soil physical properties (0-25 cm, or 0-10, 10-20, 10-30 Teture (clay, silt, sand, stones) Bulk density Water content / water holding capacity Soil structure Saturated hydraulic conductivity Slaking / aggregate stability
Minimum set of soil indicators (iii)? Soil chemical properties (0-25 cm, or 0-10, 10-20, 10-30 ph / Echangeable acidity SOM Etractable N, P, K Mineralization capacity EC Etractable pollutants Etractable secondary and micro nutrients CEC / Mineralogy
Sampling strategies Stratified at random is prefered method for a field A minimum of 100 samples per field needed for geostatistical analyses Bulked sample from a field A minimum of 40 samples randomly taken (or in W shape Bulked sample from a plot in an eperiment A minimum of 4 samples randomly taken
Which soil depth? Arable land: ploughing depth (0-25 cm) Grassland: 0-10 en 10-25 cm Natural areas: depth stratification depends on soil horizons
Sample size Some physical properties: undisturbed samples (>100 cm 3) For other properties: Core size should be > 2 cm Total sample weight should be > ~100 g (but for chemical analyses you need very little)
What should be measured at the end of an eperiment? Depends on your rearch question. Properties that may have changed during the eperiment: ph Water content Etractable nutrients
Questions? Suggestions?
What is good soil for plant growth? Good soil tilth Sufficient depth Good soil water holding capacity and drainage Sufficient, but not ecessive, nutrient supply Small population of plant pathogens and insect pests Large population of beneficial organisms Low weed pressure No chemicals, salts or toins that may harm the crop Resilience to degradation and unfavorable conditions
Soil quality defined in terms of crop yield & inputs Cassman 1999 PNAS
Muencheberg Soil Quality Rating Mueller et al., 2007, 2010
Eample of soil quality derived from soil characteristics
Conclusions Soil quality is elusive concept, probably best defined in terms of crop productivity Environmental aspects could be captured by crop yield and nutrient use efficiency Soil indicators must define its purpose; Soil quality Soil functions Soil degradation Soil management Soil indicators should be selected with care, using a Tier approach