Soil & Fertility
Healthy soil is a foundational principle of organic farming, based on the idea that "healthy soils make healthy plants that make for healthy animals and people." Organic matter is central to soil health, and thus to organic farming. It influences the chemical, physical, and biological properties of soil, and increasing organic matter (humus) in most mineral soils leads to a better soil.
Agriculture, including organic farming, is a disturbed ecosystem where normal nutrient cycles are often broken and nutrients may be exported from the land in large quantities in the harvested crops. Organic farms cannot use high analysis synthetic fertilizers as a nutrient source, and thus must rely on internal mechanisms (e.g. legumes for N fixation, cover crops for nutrient recycling) and/or imported organic nutrient sources such as composts, manures, ground rock products, and micronutrient sprays. Nutrient turnover and plant uptake in an organic system can be different than with synthetic fertilizers, and a soil often goes through a biological shift when transitioning to organic management. There are extensive information resources on the composition and management of many organic nutrient materials. It is less clear how well fertility guidelines developed for synthetic-fertilized systems apply to organic systems. Striving for high nutrient use efficiency is important on both systems.
For related links and resources please see our BIOAg Compost tab.
A series of measurements was begun in 2004 to assess selected soil physical and biological properties in a variety of cropping and management systems. Measurements include bulk density, soil compaction, soil organic matter, and aggregate stability. Biological measurements began in 2005.
Soils and Soil Testing
Links for farmers and gardeners to resources on soil sampling, soil testing, and soil test interpretation.
Using Local Sources of Organic Nutrients
Use of organic materials from livestock farms and recycled urban waste streams can help improve soil productivity and reduce nutrient imbalances, and can contribute to the sustainability of local agriculture. Site includes link to an organic fertilizer calculator.
Organic Farming Systems and Nutrient Management
Beginning in 2002, organic amendments, cover crops, and soil quality have been investigated in our farming systems experiment. An interdisciplinary team is studying a range of issues important to smale scale, direct-market, and organic agriculture, including nutrient management, soil quality, weed management, economics, marketing, and on-farm research.
Composts and Nutrient Management
The WSU Puyallup Research Center faculty have conducted extensive work on compost, manure and biosolids. This website provides information on yard waste and food waste composts, clopyralid, calculating bulk density, nutrient management for organic systems and compost facility operator training events. The site has links to the Compost Mix Calculator the Organic Fertilizer Calculator and Center research publications.
Soil Testing: A Guide for Farms with Diverse Vegetable Crops
Collins, D. 2012. Washington State University Extension. EM050E.
Northwest Soil Science: Nitrogen Mineralization
Soil Scientist Doug Collins published an article on Readthedirt.org that explains his research on how and when soil nutrients are available to crops.
Influence of orchard floor management and compost application timing on N partitioning in organically managed apple trees
TerAvest, D., J.L. Smith, L. Carpenter-Boggs, L. Hoagland, D. Granatstein, and J.P. Reganold. 2010. HortScience. 45:637-642.
Sustainability trade-offs in organic orchard floor management
Granatstein, D., Wiman, M., Kirby, E., Mullinix, K. 2010. Acta Hort. 873:115-122.
Research knowledge and needs for orchard floor management in organic tree fruit systems
Granatstein, D. and E. Sanchez. 2009. Intl. J. Fruit Science 9:257-281.
Mulching options for Northwest organic and conventional orchards
Granatstein, D. and K. Mullinix. 2008. HortScience 43(1):45-50.
Orchard floor management effects on nitrogen fertility and soil biological activity in newly established organic apple orchard.
L. Hoagland, L. Carpenter-Boggs, D. Granatstein, M. Mazzola, J. Smith, F. Peryea, and J. Reganold. 2008. Biology and Fertility of Soils online.
Reduced nitrate leaching and enhanced denitrifier activity and efficiency in organically fertilized soils.
S.B. Kramer, J.P. Reganold, J.D. Glover, B.J.M. Bohannan, and H.A. Mooney. 2006. Proc. Natl. Academy Sciences 103:4522-4527.
Soil and winegrape quality in biodynamically and organically managed vineyards.
J. R. Reeve, L. Carpenter-Boggs, J. P. Reganold, A. L. York, G. McGourty, and L. P. McCloskey. 2005. Amer. J. Enol. Vitic. 56: 367-376.
Measuring Soil Quality - Initial Considerations - September 2003
Article in Sustaining the Pacific Northwest Newsletter
Soil and plant mineral nutrition and fruit quality under organic, conventional, and integrated apple production systems in Washington State, USA.
P.K. Andrews, J.K. Fellman, J.D. Glover, J.P. Reganold. 2001. Acta Hort. 564:291-298.
Organic and Biodynamic Management: Effects on Soil Biology
Carpenter-Boggs, L., A.C. Kennedy, J.P. Reganold. 2000. Soil Sci. Soc. Am. J. 64:1651-1659.
Effects of Biodynamic Preparations on Compost Development.
Carpenter-Boggs, L., J. Reganold, A. Kennedy. 2000. Biol. Agric. Hortic. 17:313-328. The study showed that additions of herbal biodynamic preparations to compost piles resulted in consistently higher pile temperature during active composting, and higher nitrate levels and lower dehydrogenase:carbon dioxide release in mature compost samples, compared to the control.
Organic and biodynamic management: effects on soil biology
L. Carpenter-Boggs, A.C. Kennedy, J.P. Reganold. 2000. Soil Sci. Soc. Amer. J. 64:1651-1659.
Systematic method for rating soil quality of conventional, organic, and integrated apple orchards in Washington State
J.D. Glover, J.P. Reganold, P.K. Andrews. 2000. Agriculture, Ecosystems, and Environment 80:29-45.
Significance of gravimetric versus volumetric measurements of soil quality under biodynamic, conventional, and continuous grass management.
J.P. Reganold, A.S. Palmer. 1995. J. Soil Water Conservation 50:298-305.
Soil quality and financial performance of biodynamic and conventional farms in New Zealand.
J.P. Reganold, A.S. Palmer, J.C. Lockhart, and A.N. Macgregor. 1993. Science 260(5106):344-349.
Comparison of soil properties as influenced by organic and conventional farming systems.
J.P. Reganold. 1988. Amer. J. Alternative Agr. 3:144-155.
Long-term effects of organic and conventional farming on soil erosion.
J.P. Reganold, L.F. Elliott, and Y. Unger. 1987. Nature 330:370-372.
Can we grow more nutritious fruits and vegetables using organic farming methods?
Organic farmers have claimed for years that better quality soils produce more nutritious foods, but until recently scientific evidence for such claims has been wanting. Recent research of organic farming systems provides some evidence that this claim may be true under certain circumstances. Detractors of organic farming claim that the only reason why organic crops may at times have more phytonutrients than conventional crops is that organic crops are exposed to more stresses. This may be because of the lower nutrient availability of organically approved fertilizers or injury caused by pests and pathogens because of limitations on the pesticides that can be used. To evaluate the claims both for and against, research comparing organic and conventional farming systems are presented, along with a discussion of ways in which more nutritious fruits and vegetables can be grown.
Comparing tillage and mulching for organic orchard performance
Wiman, M., Kirby, E., Granatstein, D., Mullinix, K. 2008. Poster presented at 2008 BIOAg Research Symposium.
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Building Soils for Better Crops
Building Soils for Better Crops is a one-of-a-kind, practical guide to ecological soil management, now expanded and in full color. It provides step-by-step information on soil-improving practices as well as in-depth background—from what soil is to the importance of organic matter. Case studies of farmers from across the country provide inspiring examples of how soil—and whole farms—have been renewed through these techniques. A must-read for farmers, educators and students alike.
Managing Cover Crops Profitably
This publication explores how and why cover crops work and provides all the information needed to build cover crops into any farming operation. Revised and updated in 2007, the 3rd edition includes new chapters on brassicas and mustards, six new farm profiles, as well as a comprehensive chapter on the use of cover crops in conservation tillage systems. Updates throughout are based on more than 100 new literature citations and consultations with cover crop researchers and practitioners around the country. Appendices include seed sources and a listing of cover crop experts.
Organic Fertilizer Calculator
An Excel-based tool to help you determine how much nutrient value various organic amendments have, how quickly they release N, and how much they cost. Check the online guide for details.