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Home  > Question of the Week

Question of the Week

Permalink What information can you give me on the effects tillage has on soil tilth?

Rhode Island

Answer: I am pleased to provide you with information regarding the effects tillage has on soil tilth. Below is some information taken from the ATTRA publication Sustainable Soil Management.

Tillage can be beneficial or harmful to a biologically active soil, depending on what type of tillage is used and when it is done. Tillage affects both erosion rates and soil organic matter decomposition rates. Tillage can reduce the organic matter level in croplands below 1%, rendering them biologically dead. Clean tillage involving moldboard plowing and disking breaks down soil aggregates and leaves the soil prone to erosion from wind and water. The moldboard plow can bury crop residue and topsoil to a depth of 14 inches. At this depth, the oxygen level in the soil is so low that decomposition cannot proceed adequately. Surface-dwelling decomposer organisms suddenly find themselves suffocated and soon die. Crop residues that were originally on the surface but now have been turned under will putrefy in the oxygen-deprived zone. This rotting activity may give a putrid smell to the soil. Furthermore, the top few inches of the field are now often covered with subsoil having very little organic matter content and, therefore, limited ability to support productive crop growth.

The topsoil is where the biological activity happens—it's where the oxygen is. That's why a fence post rots off at the surface. In terms of organic matter, tillage is similar to opening the air vents on a wood-burning stove; adding organic matter is like adding wood to the stove. Ideally, organic matter decomposition should proceed as an efficient burn of the "wood" to release nutrients and carbohydrates to the soil organisms and create stable humus. Shallow tillage incorporates residue and speeds the decomposition of organic matter by adding oxygen that microbes need to become more active.

In cold climates with a long dormant season, light tillage of a heavy residue may be beneficial; in warmer climates it is hard enough to maintain organic matter levels without any tillage. The passage of heavy equipment increases compaction in the wheel tracks, and some tillage implements themselves compact the soil further, removing oxygen and increasing the chance that deeply buried residues will putrefy. Tillage also reduces the rate of water entry into the soil by removal of ground cover and destruction of aggregates, resulting in compaction and crusting.
Both no-till and reduced-tillage systems provide benefits to the soil. The advantages of a no-till system include superior soil conservation, moisture conservation, reduced water runoff, long-term buildup of organic matter, and increased water infiltration. A soil managed without tillage relies on soil organisms to take over the job of plant residue incorporation formerly done by tillage. On the down side, no-till can foster a reliance on herbicides to control weeds and can lead to soil compaction from the traffic of heavy equipment.

Other conservation tillage systems include ridge tillage, minimum tillage, zone tillage, and reduced tillage, each possessing some of the advantages of both conventional till and no-till. These systems represent intermediate tillage systems, allowing more flexibility than either a no-till or conventional till system might. They are more beneficial to soil organisms than a conventional clean-tillage system of moldboard plowing and disking. The principal benefits of conservation tillage are improved water conservation and the reduction of soil erosion. Additional benefits include reduced fuel consumption, reduced compaction, planting and harvesting flexibility, reduced labor requirements, and improved soil tilth (Sullivan, 2003).

There is quite a bit of research looking at the different types of tillage systems and their associated benefits and disturbances. The Rodale Institute, in Kutztown, PA, has the longest running research project on tillage. Much of their current research focuses on no-till and rolling cover crops. Please visit their website for more information at In addition, their New Farm website provides information and resources on the different types of tillage.

The University of California, Davis, is another resource that is involved in studying the effects of tilling the soil. In fact, they have worked with the Beltsville Agricultural Research Center, Beltsville, MD, to conduct a long term no-till sustainable research experiment. UC Davis has published information relating tillage and carbon cycling. The following publication and contact may be of use:

(PDF/191 KB)
Soil Scientist, USDA-Agricultural Research Service, North Central Soil Conservation Research
Laboratory, 803 Iowa Avenue, Morris, MN 56267 USA.
(320) 589-3411 ext. 144; FAX: (320) 589-3787, E-mail:

There are a few ATTRA publications that provide additional information and resources on tillage:

Conservation Tillage by Preston Sullivan (2003).

Pursuing Conservation Tillage Systems for Organic Crop Production by George Kuepper (2001).


Sullivan, Preston. 2003. Conservation Tillage. ATTRA Publication. Butte, MT: National Center for Appropriate Technology.

Sullivan, Preston. 2004. Sustainable Soil Management. ATTRA Publication. Butte, MT: National Center for Appropriate Technology.



Permalink What certifications are available for livestock besides organic?


Answer: One of the first places I would begin to look for information on certifications and marketing strategies is the Agricultural Marketing Resource Center run by Iowa State University. I use this site a lot for information on value-added marketing, including certifications. Also, you might try the USDA Process Verified program. According to their website, the "USDA Process Verified Program uses the International Organization for Standardization's ISO 9000 series standards for documented quality management systems as a format for evaluating program documentation to ensure consistent auditing practices and promote international recognition of audit results." In other words, it is a third-party verifier of a particular production process, which a company would be able to document on a product label. Several beef ranches, coops, and firms are doing this. Information on Process Verified can be found on the Agricultural Marketing Resource Center website under Branded, Certified, Verified Beef, or at the USDA website.

The Food Alliance out of Portland, Oregon, recognizes and rewards farmers who produce food in environmentally friendly and socially responsible ways through their third party certification service. According to their website, they operate "the most comprehensive third-party certification program in North America for sustainably produced food. Food Alliance Certified distinguishes foods produced by farmers, ranchers and food processors who use environmentally and socially responsible practices." The Food Alliance is administering a grass fed certification program on behalf of the American Grassfed Association, and more information can be found at the Food Alliance website or the AGA website.

Another method of "telling the consumer how you farm" that is different from third party inspections and certification is exemplified by the New York chapter of the Northeast Organic Farming Association's Farmers' Pledge. While not a certification, it can be a tool to tell people that you produce food and farm products in a sustainable, ecological way. Please visit the NOFA website to see a copy of the pledge and how farms are registered. This model could be replicated by local groups in your own state.

Grass Fed Label

United States Standards for Livestock and Meat Marketing Claims, Grass (Forage) Fed Claim for Ruminant Livestock and the Meat Products Derived From Such Livestock, USDA Agricultural Marketing Service, Docket No. AMS–LS–07–0113, LS–05–09: This is a voluntary standard being adopted by the USDA with input from business, industry, and consumer groups. The Standards are available from the USDA-AMS website. Query "grass fed claim." The details may not have been worked out yet...but my understanding is that if you want to use a USDA sanctified claim, you will have to use the USDA process verification system. It will require annual verification and the initial cost will be relatively expensive. For more information see the USDA Process Verified website.


Agricultural Marketing Resource Center

The Agricultural Marketing Resource Center is an electronic, national resource for producers interested in value-added agriculture. Browse commodities and products, investigate market and industry trends, study business creation and operation, read research results and locate value-added resources.

AGMRC – Beef Branding and Marketing Resources

Information, links, case studies, and reports on the following topics:

* Commodity Beef
* Branded, Certified, Verified Beef
* Natural Beef
* Organic Beef
* Direct Marketing Beef
* Dried Beef
* Marketing Beef to Latino Consumers

AGMRC – Lamb Branding and Marketing Resources

AGMRC – Pork Branding and Marketing Resources

American Grassfed Association

Animal Welfare Information Center
USDA National Agricultural Library

Audit and Assessment Programs, Certification Programs, Standards and Guidelines, Food Industry Animal Welfare Policies, and International Programs.

Northeast Organic Farming Association of New York, Inc.
PO Box 880
Cobleskill, NY 12043-0880
607-652-NOFA (6632)
The Farmer’s Pledge

The Food Alliance
1829 NE Alberta Street, Ste. 5
Portland, OR 97211



Permalink What information can you give me on crop oilseed yields?


Answer: I am pleased to provide you with information on crop oilseed yields. I have also included some information and resources on using peanut oil for biodiesel production.

Below is a table taken from the ATTRA publication, Biodiesel: The Sustainability Dimensions, that lists various oil producing crops and their relative oil yields in gallons per acre. One gallon of oil = 7.3 pounds (Hill, Kurki, and Morris, 2006). Please keep in mind as you examine this table that the yields will vary in different agroclimatic zones. Plant variety and the type of production system will also affect oil yields.


Adapted from Joshua Tickell, From the Fryer to the Fuel
Tank: The Complete Guide to Using Vegetable Oil as an Alternative
. 3rd Ed. 2000.

Plant Latin Name Gal Oil/ Acre Plant Latin Name Gal Oil/ Acre
Oil Palm Elaeis guineensis 610 Rice Oriza sativa L. 85
Macauba Palm Acrocomia aculeata 461 Buffalo Gourd Cucurbita foetidissima 81
Pequi Caryocar brasiliense 383 Safflower Carthamus tinctorius 80
Buriti Palm Mauritia flexuosa 335 Crambe Crambe abyssinica 72
Oiticia Licania rigida 307 Sesame Sesamum indicum 71
Coconut Cocos nucifera 276 Camelina Camelina sativa 60
Avocado Persea americana 270 Mustard Brassica alba 59
Brazil Nut Bertholletia excelsa 245 Coriander Coriandrum sativum 55
Macadamia Nut Macadamia terniflora 230 Pumpkin Seed Cucurbita pepo 55
Jatropa Jatropha curcas 194 Euphorbia Euphorbia lagascae 54
Babassu Palm Orbignya martiana 188 Hazelnut Corylus avellana 49
Jojoba Simmondsia chinensis 186 Linseed Linum usitatissimum 49
Pecan Carya illinoensis 183 Coffee Coffea arabica 47
Bacuri Platonia insignis 146 Soybean Glycine max 46
Castor Bean Ricinus communis 145 Hemp Cannabis sativa 37
Gopher Plant Euphorbia lathyris 137 Cotton Gossypium hirsutum 33
Piassava Attalea funifera 136 Calendula Calendula officinalis 31
Olive Tree Olea europaea 124 Kenaf Hibiscus cannabinus L. 28
Rapeseed Brassica napus 122 Rubber Seed Hevea brasiliensis 26
Opium Poppy Papaver somniferum 119 Lupine Lupinus albus 24
Peanut Ariachis hypogaea 109 Palm Erythea salvadorensis 23
Cocoa Theobroma cacao 105 Oat Avena sativa 22
Sunflower Helianthus annuus 98 Cashew Nut Anacardium occidentale 18
Tung Oil Tree Aleurites fordii 96 Corn Zea mays 18

According to this chart, peanuts yield about 109 gallons of oil per acre. There are four types of peanuts to consider for production which is limited to the southern regions of the U.S., where nearly 15% of peanuts are crushed for oil in the U.S. (Piedmont Biofuels, 2008). The Virginia peanut has the largest peanut kernels and is the most commonly sold snack peanut (, 2008). This peanut is also sold in the shell for roasting. The Virginia peanut is grown in Virginia (as the name implies) and in North Carolina. The Spanish peanut has a smaller kernel and reddish-brown skin. This variety is used to make peanut butter, snack nuts and peanut candies. These peanuts are grown mostly in Texas and Oklahoma. The Runner variety is the most dominant of all peanut varieties in the United States. Over half of these peanuts are used for peanut butter. Their yields are extremely high and are grown in Oklahoma, Texas, Alabama, Florida and Georgia. The Valencia peanut variety has very bright red skin and small kernels. This variety is very sweet and is sold roasted in the shell. These peanuts make excellent boiled peanuts when cooked fresh. Valencia peanuts are primarily grown in New Mexico. Listed below is an article from the Southeast Farm Press titled, Improved Peanut Varieties in Pipeline. This article offers an extended list of peanut varieties by type.

Many old and new peanut varieties are being tested for field performance, and their oils are being analyzed for diesel performance characteristics (Durham, 2007). It has been found that high-oleic-acid peanuts are desired for extended shelf life of food products and also makes the best biodiesel fuel.

Scientists at the ARS National Peanut Research Laboratory at Dawson, Ga., in collaboration with the University of Georgia, are testing 24 high-oil peanut varieties that have reduced production costs and increased yields (Durham, 2007). This biodiesel screening project is noted for breeding a peanut called Georganic. It's not suited to current commercial edible standards for peanuts, but is high in oil and has low production input costs.

These researchers have demonstrated at multiple sites that low input, high yielding peanuts can produce a ton per acre for surprisingly low input costs (Roberson, 2007). Research at the University of Georgia has pegged peanut biodiesel at 123 gallons per acre, based on state average yields, which are 500-600 pounds per acre higher than the low input peanuts in the USDA test. Some researchers contend once better varieties are developed, along with more efficient conversion practices, production may reach 150 gallons per acre. Please be aware that the Peanut Variety Protection Act (PVP) and the awarding of utility patents to the high oleic characteristic may limit the production or sale of seed of certain varieties (Gorbet, Tillman, and Whitty, 2006).

Also listed below is a 2007 report from the University of Georgia on the economics of peanuts for biodiesel production. In addition, ATTRA will be releasing an organic peanut production publication soon. Please continue to check our website or contact us for information on its availability.


Durham, Sharon. 2007. “Peanuts Studied as Source of Biodiesel.” Beltsville, MD.

Gorbet, D.W., B.L. Tillman, and E.B. Whitty. 2006. “Farmer Saved Peanut Seed: Factors to Consider.” Gainsville, FL. Florida Cooperative Extension Service.

Hill, Amanda, Al Kurki, and Mike Morris. 2006. “Biodiesel: The Sustainability Dimensions.” ATTRA Publication. Butte, MT: National Center for Appropriate Technology. Pages 4-5.

Piedmont Biofuels. 2008. “Biodiesel Production for On-Farm Use.” ATTRA. Butte, MT: The National Center for Appropriate Technology. Slide 17.

Roberson, Roy. 2007. “Peanut Biodiesel Could Save Farmers Millions.” Western Farm Press, May 2007. 2008. “Learn Peanut Varieties.” Bellevue, WA: eHow,Inc.

Hollis, Paul. 2008. “Improved Peanut Varieties in Pipeline.” Southeast Farm Press, February 26, 2008.

McKissick, John, George Shumaker, and Nathan Smith. 2007. “Economics of Peanuts for Biodiesel Production.” Athens, Georgia: The University of Georgia.



Permalink What information can you give me on saffron production?


Answer: Thank you for requesting information from ATTRA on planting, growing, and harvesting saffron crocus. You also requested sources of bulbs (corms).

Sources of corms

Listed below are companies that have, in the past, been sources of corms of saffron (Crocus sativus). This is true saffron—not to be confused with “autumn crocus,” or “meadow saffron” (Colchicum spp.) when ordering corms. As the article by Daniel Smoley points out, both are fall-blooming. Colchicum appears on lists of poisonous plants.

Planting, growing, harvesting

The best source of information on growing saffron in the northern U.S. is Daniel Smoley’s reporting on his extensive saffron trials in Paola, Kansas, beginning in 1997. A retired engineer for a major U.S. company, Mr. Smoley invested considerable resources in his experimental plots.

You asked about how many crocus it takes to yield one pound of saffron.

A saffron corm may produce from 3 to 12 flowers. Bulbs for sale in the U.S. typically produce 3 flowers. Commercial saffron producers overseas may well have access to improved planting stock (which they guard jealously).

According to Rodale’s Illustrated Encyclopedia of Herbs, about 35,000 saffron flowers are required to produce one pound of the spice. (However, Smoley says 70,000.)(p. 67)

According to data published by the French Ministry of Agriculture, Spanish commercial producers in 1988 harvested 5 kg. of dried product per hectare (ha) on regular fields and about 12 kg/ha from irrigated fields. This works out to roughly 1/3 lb. per acre and 7/8 lb. per acre, respectively. The international avoirdupois pound equals 0.45359237 kilograms. The hectare is equivalent to 2.471 acres. The French report did not specify how many corms were planted per ha by the Spanish producers, or how many flowers each corm produced.


Follette, Robin. 2006. Saffron crocus. Farm & Garden: Forum.

Hussain, Altaf. 2005. Saffron industry in deep distress. BBC News (International)

Smoley, Daniel J. 2001. Saffron crocus as a crop. Small Farm Today. Part 1, March/April. p. 54–59. Part 2, May/June. p. 66–67.

Suppliers of corms:

Dabney Herbs
P.O. Box 22061
Louisville, KY 40252

Nichols Garden Nursery
1190 No. Pacific Hwy. NE
Albany, OR 97321
800-825-5477 (FAX)

Hirt’s Gardens
(through Amazon Marketplace)

Richter’s ( has bulbs, but cannot ship them outside of Canada.

Several companies no longer sell saffron corms.



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