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.
Thursday, March 12, 2009
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.
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.
Monday, February 23, 2009
Benefits of Indoor Plants
The benefits of gardening are not limited to the beauty and productivity of an outdoor garden. Indoor garden plants have long been known to have positive effects on the mental and physical health of office workers. Specifically, a 1998 study by researchers in Norway revealed that workers in offices complained less about fatigue (reduced by 30%) and cough (reduced by 37%), and reported lower levels of throat and skin discomfort (reduced by 23%) relative to workers in offices without plants.
Now, a group of Korean researchers may have identified a mechanism for these positive benefits of indoor plants. (Kwang et al. 2008. Efficiency of Volatile Formaldehyde Removal by Indoor Plants: Contribution of Aerial Plant Parts versus the Root Zone. Horticultural Science 133: 479-627.)
Researchers from Korea's National Horticultural Research Institute examined the ability of Ficus benjamina and Fatsia japonica to absorb formaldehyde from the air. To study this, the researchers pumped formaldehyde into a container that held one of the two plants, or into a container that was empty. On average, containers with plants removed 80% of the formaldehyde from the air in only 4 hours. Containers without plants lost only 7% of the formaldehyde in 5 hours. Plant leaves reduced more formaldehyde during the day, while roots of reduced more formaldehyde at night. This suggests that formaldehyde is taken in through plant stomates during the day, when rates of photosynthesis are highest. The night removal of formaldehyde by the root zone suggests that soil microbes play an important role in formaldehyde removal.
Formaldehyde is a common household VOC (volatile organic compound) that is known to have negative effects on human health. In fact, VOC's, including formaldehyde, have been linked to 'sick building syndrome'.
What is the bottom line for the home gardener, or the party guest who is looking for a suitable hostess gift? Indoor plants will reap multiple benefits, not the least of which is better air quality, for the gardener or the gift recipient.
Now, a group of Korean researchers may have identified a mechanism for these positive benefits of indoor plants. (Kwang et al. 2008. Efficiency of Volatile Formaldehyde Removal by Indoor Plants: Contribution of Aerial Plant Parts versus the Root Zone. Horticultural Science 133: 479-627.)
Researchers from Korea's National Horticultural Research Institute examined the ability of Ficus benjamina and Fatsia japonica to absorb formaldehyde from the air. To study this, the researchers pumped formaldehyde into a container that held one of the two plants, or into a container that was empty. On average, containers with plants removed 80% of the formaldehyde from the air in only 4 hours. Containers without plants lost only 7% of the formaldehyde in 5 hours. Plant leaves reduced more formaldehyde during the day, while roots of reduced more formaldehyde at night. This suggests that formaldehyde is taken in through plant stomates during the day, when rates of photosynthesis are highest. The night removal of formaldehyde by the root zone suggests that soil microbes play an important role in formaldehyde removal.
Formaldehyde is a common household VOC (volatile organic compound) that is known to have negative effects on human health. In fact, VOC's, including formaldehyde, have been linked to 'sick building syndrome'.
What is the bottom line for the home gardener, or the party guest who is looking for a suitable hostess gift? Indoor plants will reap multiple benefits, not the least of which is better air quality, for the gardener or the gift recipient.
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