Soil health and how to measure it Lori Hoagland Assistant Professor Department of Horticulture & Landscape Architecture Purdue University
Outline What is soil health and why should we care about it? What constitutes healthy soil? How can you build soil health? How can you measure soil health?
Why should you care about soil health?
Analogy You re going on a trip which tires do you want? Leaky tires OR Fully inflated tires Eric Brennan USDA ARS
Analogy = Poor soil quality Leaky tires
What is soil health? Definition: The capacity of a living soil to: function within natural or managed ecosystem boundaries sustain plant and animal productivity maintain or enhance water and air quality promote plant and animal health (Doran et al.,1996, 1998)
Why care about soil health? Alleviate soil compaction Increase water infiltration and waterholding capacity Rd Reduce irrigation i i costs and improve the potential for your soil to withstand drought Rd Reduce erosion and keep your soil in place
Consequences of poor soil health A single inch of topsoil can take 500 years to form naturally Erosion in the Palouse Surface runoff from a farm field in Iowa during a rainstorm Columbia River Basin from space Fall 2009
Why care about soil health? Reduce incidence of pest outbreaks and lower pesticide costs Increase nutrient holding capacity of the soil, reduce nutrient loss and lower fertilizer costs Improve crop productivity and quality of your produce
What constitutes healthy soil?
Components of soil health Chemical well understood and applied Physical fairly well understood, but not often applied Biological the least understood and applied Moebius, 2004
Relevance of chemical soil health ph measure of acidity or alkalinity of the soil impacts: nutrient availability availability of toxic metals activities of microorganisms that facilitate nutrient cycling and reduce disease risk
Relevance of chemical soil health Salinity salt content of the soil in irrigation i i water, fertilizers, composts and manure accumulation can degrade soil structure and restrict vegetable growth Cation exchange capacity quantity of cations in the soil cation is a positivly charged ion (ie. Ca 2+,Mg 2+,NH 4+, Zn 2+, Cu 2+, Mn 2+ ) depends on amount of clay and organic matter in the soil impacts the soil s nutrient holding capacity
Relevance of physical soil health Soil texture proportion of sand, silt and clay particles in thesoil function of soils parent material virtually unchangeable except through erosion important for soil test interpretation
Relevance of physical soil health Soil structure (or tilth) arrangement of soil particles into aggregates can change rapidly in response to management Together texture t and structure t impact: Wt Water and nutrient ti tholding capacity Water infiltration Aeration Seed germination and root proliferation Biological activity Erosion potential Moebius, 2004
Relevance of biological soil health Megafauna mice, ants, earthworms, spiders, etc. It s Alive! initiate organic matter decomposition aerate the soil Mesafauna nematodes, mites, springtails regulate microbial populations Microfauna bacteria & fungi
Regulate nutrient cycling
Improve plant health Rhizobia Rhizosphere zone of greatest microbial activity Microbes aid plants Roots support microbes Fix nitrogen Solubilize phosphorous Enhance root growth Suppress plant pathogens Release signals & nutrients Provide protection
More benefits of soil biological health Build soil aggregates secrete biological glue Filter and detoxify chemicals Make that sweet smell Streptomyces & geosmin Guides camels Glomalin production by mycorrhiza
How can you build healthy soil?
Add organic matter Beneficial impacts on soil properties: Chemical higher CEC, ph buffer, ties up metals, interacts with xenobiotics Physical stabilizes soil structure, improves water holding capacity, reduced compaction, dark color helps warm soil Biological supplies energy and body building constituents for soil organisms, source and sink kfor nutrients ti t (soil fertility bank account), ecosystem resilience
(H. Atthowe)
Apply biological amendments Eric Zakarison demonstrates his solor powered tractor
Plant cover crops
Reduce tillage No till vegetable transplanter http://www.separcd.org/no till_vegetables.htm
Restoring organic matter & soil health (Brady and Weil, 2002)
Restoring organic matter & soil health Impact of tillage on soil physical health Soil health Silt loam Silt Loam Clay Loam Clay Loam indicator Plow till No - till Plow till No till Bulk density Not Not 1.21 1.03 (g/cm 3 ) significant significant Pores > 30 microns (%) 13 17 12 16 Pores < 30 microns (%) Not significant Not significant 29 24 Available water 12 16 Not significant Not significant capacity (%) Water stable aggregates 0.25-0.2 mm (%) 20 41 30 68 (Idowu et al., 2006)
Restoring organic matter and soil health Impact of orchard floor management on soil health compost application coupled with high tillage does not positively impact soil health characteristics cover crops result in dramatic improvement in soil physical, chemical and biological properties
Restoring organic matter and & soil health Managing soil borne pathogens in apple with wheat cultivation Impact of wheat cultivation on Fluorescent Pseudomonans eudomonas g 1 so oil # of Fluorescent ps 100 80 60 40 20 0 a a a ab bc c Control Pasteurized Wheatgrass Modern Organic Perennial Wheat Wheat Wheat Impact of wheat cultivation on soil borne pathogens (Hoagland et al., 2010) borne pathogens g 1 soil # of soil 60 50 40 30 20 10 0 a c Control Pasteurized Wheatgrass Modern Wheat c c b Organic Wheat b Perennial Wheat
Can you add too much organic matter? In some cases yes Nutrient immobilization Watch the salt Careful with newly incorporated fresh residues Requires careful management Material C:N Microbial Tissues 6 12:1 Soil Humus 10 12:1 Animal Manure 13 25:1 Legume Residues/Green Manures 13 25:1 Compost 25 30:1 Cereal Residues/Straw 60 80:1 Forest Refuse 150 500:1 il cfu pyth/ g soi Impact of Brassica seedmeal Tukey incorporation on Pythium 6000 5000 4000 3000 2000 1000 PAR IRR ECH ULT HET ATT 0 Control Cnt Pasteurized Past. Bj Sa Bn Gm (Hoagland et al., 2008)
How can you measure soil health?
Standard fertility test at a commercial lab Recommended every 3 5 years Generally cost $10 20 Typically includes: ph, available phosphorous, nitrogen, potassium, calcium, magnesium and organic matter
Collecting the soil sample Sample at the same time each year to achieve more accurate trends Tools: sampling tube or spade, buckets, plastic bags Collect representative sample Soil type, management practices, crop growth & yield Avoid irregular areas 20 30 cores per 10 20 acre field Collect samples to a depth of approximately 8 Mix and air dry
Cornell Soil Health Lab Basic test ($40) Comprehensive ($65) Standard soil fertility test Basic test (ph, OM, P, K, Ca, Mg, Al, Fe, Zn, Mn) Potentially mineralizable Particle size distribution ib ti nitrogen (PMN) Wet aggregate stability Root health bioassay Available water capacity Surface hardness Active carbon * Samples should be taken in the spring prior to tillage http://soilhealth.cals.cornell.edu/extension/test.htm
Soil Food Web Soil food web http://oregonfoodweb.com/
Measuring soil health on the farm NRCS Soil Quality Test Kit Electrical conductivity & ph Soil nitrate Wt Water infiltration ti & water quality Bulk density Aggregate stability Slake test Soil respiration Earthworms
Measuring soil health on the farm Soil quality score cards subjective tests based on feel, site and smell May include characteristics such as: Earthworms Water holding capacity Organic matter color Drainage/infiltration Organic matter roots/residues Crop condition Subsurface compaction ph Soil tilth/friability/mellowness i / ll Nutrient holding t capacity Erosion Talk to local NRCS office
Interpreting results Depends on: soil type crops grown farm size and management Use to evaluate changes in practices over time Practice on farm experimentation
Resources Building Soils for Better Crops Fred Magdoff and Harold van Es Sustainable Agriculture Network http://www.sare.org/publications/soils.htm Sustainable Soil Management Soil System Guide ATTRA http://attra.ncat.org Natural Resource Conservation Service Purdue Extension Educators Lori Hoagland lhoaglan@purdue.edu