IPM

Feed the soil, not the plants

Soil (aka dirt) is made up of sand, silt and clay particles of different sizes and ratios. Spring Ledge sits on top of clay soils, which are wet longer in the spring and much heavier than a river-valley soil or gravel soil.

We take this into account when planting outside by using a bed-maker and by planting cover crops.

A basic tenet of organic and IPM methods is to feed the soil, not the plant. Soil is the most important part of smart farming and gardening. Besides providing nutrients and holding water, healthy soil is home to all sorts of organisms. Good bugs, worms and microscopic fungi found in healthy soil help the plants combat pests. Enriching the soil itself, not just adding fertilizer to the plant, is the basis of sustainable farming and gardening.

Along with the ecology of your soil, several other factors influence plant growth. Chief among these is pH, which is a measure of the soil acidity. Soil pH affects which nutrients are available to the plant. To test your pH, contact the local extension office for a test kit. The pH is easy to change using lime.

Another important soil characteristic we test at the farm is EC (electrical conductivity). EC measures the amount of free anions and cations in soil. This translates into salt levels. We are most concerned with the EC level in our greenhouse crops as they are grown in pots without much buffering capacity. Too many salts can damage plant roots. Too few salts point to a lack of nutrition. EC levels can be adjusted upward by adding more fertilizer and can be lowered by leaching with clear water.

Because our fields at Spring Ledge are a heavy clay soil, they tend to be compacted and wet. Between the clay, sand and silt particles of soil are pores which can contain either air or water. Ideally, the pore space will contain half air (oxygen for the roots of plants) and water.

To improve our clay soils, we add as much organic matter as we can which “lightens” the soil, allowing better aeration. Think of the clay soil as a deck of cards. Once the cards are wet, it is very difficult to separate them from each other. By adding organic matter, we are helping push those cards apart and allowing roots to penetrate. The bulk of our organic matter comes from compost produced at Spring Ledge using leaves, horse manure, and manure from our small collection of cows and sheep. After this mixture has cooked and digested for two years, it is spread on the fields and turned into the soil.

Another source of organic matter is cover cropping. After the vegetable crop is harvested, we plant the field to oats, winter rye and hairy vetch. These cover crops reduce soil erosion during the off-season and provide organic matter and nutrients when tilled back into the soil. In fact, a well grown crop of hairy vetch can add the equivalent of 90lbs of nitrogen per acre for use by the next crop.

Crop rotation is a very important part of IPM. Plants deplete different amounts and ratios of nutrients from the soil. Changing where we plant carrots each year, for example, balances out this depletion. Crop rotation also reduces buildup of diseases and insects. Many pests simply disappear if denied their favored host.

Building and maintaining a healthy soil is hard but essential work as Spring Ledge remains sustainable for the future.

Discussion

Now for some discussion and questions concerning pesticide use. These thoughts are meant to illicit a dialogue. They are not necessarily the opinions of Spring Ledge Farm or any of its employees.

Pesticides and consumers

How do the chemicals, organic and synthetic, that are applied to fruits and vegetables affect the individual.

The following are some things to consider.

Exposure to residues has historically been in direct proportion to our scientific prowess. For example, the Delaney Clause, passed by Congress in 1957, forbids the presence of ANY carcinogen in any processed food(1). The clause was enacted when science could detect molecules in parts per million. Anything not detected was allowed to pass as “safe” produce. Now we can detect molecules in parts per billion, a thousand times more critical than in 1957(the Delaney clause has since been superseded by the FQPA (Food Quality Protection Act), Yet the question remains as to how low a threshold we should establish. Just because we can detect the molecules, does that make it harmful?(1A)

Consider high risk groups, including children, the elderly and pregnant women. Perhaps chemicals applied to produce affect these groups more than other segments of the population.

Which brings us to our next point to consider: do the benefits of a growing child eating “five a day” servings of fruits and vegetables outweigh the effects, if any, of pesticide residues? If a family can afford five servings a day of conventionally grown produce but only two a day of organically grown produce, what should they do?

Something else to consider is the relative risk of pesticide exposure. Relative to what? To the everyday hustle and bustle of modern life. To sunshine, to exhaust fumes, to secondhand smoke, to saturated fat, to cholesterol, to computer monitors, to electrical fields, to radon, to ice storms, to sugar and caffeine. Again we must consider the benefits of eating fruits and vegetables (folic acid(2), limonoid glucosides found in citrus as a cancer fighting agent(3), anti-oxidants in strawberries(4), Calcium & Magnesium in Snap Beans(5)) versus the relative effects of any pesticide exposure when put in context with our way of life.

One last thing one our list to consider is that most plants have some sort of toxin already present in their systems. More than 2,000 species of plants are said to have some value as insect killers.(6) The tomato plant is a perfect example. In the nightshade family, the tomato was rarely eaten by Europeans who considered it poisonous. In fact, the leaves and stems do contain a toxin, known as tomatin. The potato plant, eggplant, and even peppers contain toxins. Do these “natural” toxins affect us the same way as synthetic pesticide residues?

(1) Ward, J.C. “A Dynamic Statute of Pesticides” in USDA 1966 Yearbook of Agriculture, 1966. Govt. Printing Office, Washington, D.C. pp.275-278. (1A) Ames, B. “Cancer Scares Over Trivia” Los Angeles Times, 5/15/86. (2)Tucker, K.L., “More Fruits, Veggies, Cereal Reduce Risk” Agriculture Research Service Bulletin. Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA. 1997. (3) Hasegawa, S. “Citrus Squeezed for Cancer Fighters” Agriculture Research Service Bulletin. USDA-ARS Process Chemistry and Engineering Unit, Albany, CA. 1997 (4) Joseph, J. “Berry Good Food for the Brain” Agriculture Research Service Bulletin. Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, MA. 1997. (5) Abrams, S. “Snap Beans Fingered as Mineral Source” Agriculture Research Service Bulletin. Children’s Nutrition Research Center, Houston, TX. 1997. (6) Feinstein, L. “Insecticides from Plants” in USDA 1952 Yearbook of Agriculture. 1952. Govt. Printing Office, Washington, D.C. pp. 222-228.

Environmental Effects of pesticide use.

How do the chemicals, organic and synthetic, that are applied to fruits and vegetables affect the environment?

The following are some things to consider.

Soil health, under a strictly conventional system of agriculture, tends to be poor. As long as there are chemicals and fertilizers that will feed the plant and kill the bugs, then soil health is rarely considered. (soil tilth, however, is usually of concern).(1) If synthetic pesticides and synthetic fertilizers are reduced, farmers utilize other methods for pest control and fertility. Cover crops, compost, crop rotation, windrows, and other management practices create a living soil ecology. Something to consider when discussing pesticide use is how the farmer treats the soil. Is the soil health being considered as a way to combat disease and pestilence? Or are chemicals the only source of control?

Spray drift is another consideration. Drift refers to the amount of pesticide, synthetic or organic, that does not reach the target crop. Air currents might move the pesticide past the intended crop, into another crop, into the woods or into the atmosphere. This is usually a bigger issue where pesticides are applied by airplane. But even here in New Hampshire, drift can occur if the wind is blowing too much, or even if the wind is not blowing enough. Of course the type of pesticide used has an enormous effect. Should the consumer be concerned about the effect to the surrounding environment because of possible spray drift? Does the farmer do anything to minimize the possibility of drift?

Resistance by organisms because of years of continued use of the same pesticide, organic or synthetic, or even the same class or family of chemicals, brings up some interesting points to consider.(2) Just as the repeated use of antibiotics in human health care has created some resistant strains of bacteria and viruses, insects, diseases and weeds all have the potential to evolve immunity to pesticides. Should we use a new class of chemicals, organic or synthetic, to treat infested crops if it means retaining the lowest cost for food in the world? Are there ways to reduce the selective pressures on the pests so that they do not evolve so quickly? Does the farmer practice these integrated pest management strategies?

Fossil fuels are readily available and inexpensive. We use enormous amounts of fossil fuels to make the fertilizers that feed the plants that feed our families. Does that cheap food justify the use of all those fossil fuels? If we use cow manure instead, will that help?

If we do not use chemical fertilizers or synthetic pest controls, that means we must substitute some resource for those items in order to produce a crop. That resource is usually a tractor for cultivating and spreading manure. There is an enormous amount of bulk in natural fertilizers (manure, compost, seaweed), and it takes fossil fuels to run the trucks and tractors that haul and spread those materials.(3) Are we using the same amount of fuel either way? What about proximity to the farm. If you buy a head of lettuce from California, it takes three times as much energy to produce and ship it to NH than a head of lettuce grown in NH. What exactly are the external costs of our foods?(4)

(1) National Research Council, Alternative Agriculture. 1989. National Academy Press, Washington, D.C. pp.119. (2) Ibid pp. 121 (3) Pimentel, D. “Energy Flow in Agroecosystems” in Agricultural Ecosystems: Unifying Concepts, 1984 John Wiley & Sons, New York. pp.121-132. (4)Steinhart, J.S., Steinhart, C.E. “Energy Use in the U.S. Food System” Science. 1974 Vol. 184.

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