Monday, March 30, 2009

Edible Portland Magazine

I will return to blogging on the science underlying gardening and issues related to gardening soon. Currently, I am writing a short piece on compost teas.

In the meantime, I wanted to draw attention to Organic Gardening Certificate Program, which is currently taught in the Portland Metro area. This 57-hour training was created by OSU Extension, Oregon Tilth, and other program partners to support the groundswell of interest in organic gardening, ecological landscaping, and food security in the Portland metro area.

The 2008 Organic Gardening Certificate Program (OGCP) is the focus of the cover story for the spring Edible Portland magazine in both the print and online versions.

Check it out at and click on the “Dig in” link and look for the article entitled “First Class.”

Saturday, March 28, 2009

It's Like NPR for Insect Geeks

I don't consider the word 'geek' to be a pejorative. In fact, I consider it a compliment when someone calls me a 'geek'. Even better is to be called a 'bug geek'. Thus, you can imagine my delight when I found out that Anna Fiedler (a Ph.D. candidate in Entomology at Michigan State University) partnered with Jake McCarthy (an editor in the Department of Animal Science at MSU) to write and produce InsectaPodCast.

In a recent American Entomologist article, Anna wrote that the target audience for the podcast is primarily kids and young adults. One of the goals of InsectaPodCast is to get kids excited about the field of entomology. I'm MUCH older than the target audience (by about 30 years), yet I found myself LOVING the segments. The episode about insect collections is thus far my favorite, perhaps because of my own mixed feelings about collecting insects that I love (i.e. killing insects that I love), for scientific study.

Check it out, and perhaps subscribe to the RSS feed, if you like what you hear.

Thursday, March 12, 2009

A Request! Do sonic deer deterrents work to prevent deer damage in yards?

A Master Gardener in Clackamas County, OR requested that I blog on sonic deer deterrents as a potential means to keep the often ubiquitous and unwanted garden visitor away.

A 1995 study found the Yard Gard (sic) Ultrasonic Yard Protector to be ineffective at deterring deer from feeding on apples in two yards with a history of deer damage. Control (no Yard Gard device) and treatment (Yard Gard device present and turned on) feeding stations were established at each yard. Twenty apples were placed at each feeding station. Feeding stations were restocked for the duration of the study.

Deer consumed 96% of the 380 total apples at the control stations (no Yard Gard) and 98.9% of the 380 total apples at the experimental stations (Yard Gard device present and turned on). Behavioral observations suggest that the deer were alert or nervous when the Yard Gard device was 'on', but this behavior did not translate into reduced deer damage.

The scat (poop) and tracks of several other vertebrates were found near the feeding stations. These include squirrels, crows and turkeys.

The bottom line for the home gardener: the ultrasonic deer deterrents are not likely to reduce deer damage to your garden.

Tuesday, March 10, 2009

Organic Produce – More Nutritious than Conventionally Grown Produce?

At last year’s Mini-College, a presentation on organic food production caused a minor amount of controversy when the speaker mentioned that organically produced foods are healthier than conventionally produced foods. Since the OSU Master Gardener Program strives to rely upon and present unbiased, research-based information, some Master Gardeners questioned the research underlying this statement. Thus, I thought I would blog on what is known (from peer-reviewed scientific studies) about the nutritional content of organic versus conventional produce.

First, let me define organic versus conventional farming methods. Although the USDA lists a lengthy definition and regulatory text for organic production systems, I think that it will be more useful to distill down the definition for this blog. Organic farmers work to build and maintain the organic matter in their soils and the natural pest control agents in and near their fields (i.e. predators and parasitoids). Organic farming systems tend to be more diverse (in both their crops and associated organisms) than do conventional systems. Cultural, physical and biological controls of pests are emphasized over chemical controls. External inputs of pesticides and fertilizers are reduced. When pesticides and fertilizers are used, organic forms of these products are used. Synthetic forms of these products are not allowed in organic production systems.

Conventional farming systems, by comparison, do not focus on soil management, biodiversity within their fields and cultural or physical controls of pests. Biological control of pests is often disrupted or difficult due to the use of pesticides (which may be organically derived or synthetically manufactured).

Organic farm production often occurs at a smaller scale, and requires more labor, than does a conventional farm. This is why organic produce can be more expensive than conventional produce.

In fact, a 1998 study of the cost difference between organic and conventional produce in Tucson, AZ found that red delicious apples were 44% more expensive than conventionally grown applies. Similar results were found for broccoli (+76%), carrots (+78%), leaf lettuce (+92%), and tomatoes (+62%). [Gary D. Thompson and Julia Kidwell. 1998. Explaining the Choice of Organic Produce: Cosmetic Defects, Prices, and Consumer Preferences American Journal of Agricultural Economics, Vol. 80: 277-287.]

Unfortunately, I could not find more recent numbers in the peer-reviewed literature. OSU Master Gardeners – would you care to help me out with a quick and easy research project? If so, contact me via this blog.

What about the nutritional content of organic versus conventionally-produced foods? A 2003 study by Asami and colleagues looked at the total phenolic content of marionberries, strawberries and corn that were produced by organic, ‘sustainable’ and conventional methods. In this study, organic fields were managed to adhere to USDA organic production standards. Sustainable fields were managed to ‘meet the needs of consumers without compromising the ability of future generations to meet their own needs’. Information is presented on the fertilization regime of the sustainable fields (synthetic fertilizers were used), and on the pesticides used (none in one field and herbicides in a second field) but additional information on sustainable management practices were not presented in this paper.

The authors looked at total phenolic content of these plants, because polyphenols, in particular, are known to have anti-oxidant properties. For marionberries and corn, higher levels of total phenolics were found in organically and sustainably produced, relative to marionberries and corn from conventionally managed fields. Sustainably produced strawberries had higher total phenolics, relative to conventionally produced strawberries (the authors did not include organically grown strawberries in their study) – but only when strawberries were frozen, and not when they were freeze-dried or air-dried. [Asami, D. K., Hong, Y-J., Barrett, D. M. & Mitchell, A. E. (2003). Comparison of the total phenolic and ascorbic acid content of freeze-dried and air-dried marionberry, strawberry and corn grown using conventional, organic and sustainable agricultural practices. J. Agric. Food Chem. 51(5):1237-1241.]

Two recent review papers found similar results (Zhao et al. 2006, Benbrook 2009). Nutrient density and secondary plant metabolites (many of which are known to have anti-oxidant properties) tended to be higher in organically-produced foods than in conventionally grown foods.

Why might organically grown foods have more nutrients and anti-oxidants that conventionally grown foods?

First, organically-grown foods are often grown in soils with abundant and balanced micro- and macro-nutrients. This is because organic food production emphasises the accumulation and retention of organic material in the soil. This may translate into produce that contains a more balanced array of vitamins and minerals.

Second, insects may feed upon organically-grown crops more often than they damage conventionally grown crops. This may be due to differences in pesticide use in organically versus conventionally-managed fields. When insects feed upon a plant, they can induce or trigger the plant’s chemical defenses against herbivory. These chemical defenses can include polyphenols – which are known to have antioxidant properties.

What does this mean for the home gardener?

Managing your soil to encourage and maintain a high level of organic matter, and minimizing or removing pesticid use in your vegetable garden can yield multiple benefits. First, these management practices are generally more environmentally friendly than are the repeated and unncessary use of synthetic fertilizers and pesticides in the home garden. Second, these management practices may result in you and your family enjoying fruits and vegetables that contain more vitamins, minerals and antioxidents than those that come from vegetable gardens that are managed without regard to soil health or the non-target effects of pesticides.