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Home  > Question of the Week

Question of the Week

Permalink How much land should I leave fallow as part of a long-term soil fertility program in an organic production system?

Answer: The fact that you are farming your site in an organic production system means that you will be improving your soils even as you are farming them. So the longer you farm a piece of ground organically, the less necessary it becomes to worry about fallowing land. Of course, cropping with tomatoes or other vegetables will take some of the nutrients out of the soil, but not nearly as much as if you were farming conventionally. You will continually be adding compost, organic fertilizers, minerals, green manures, etc. to your soils so they will be getting replenished after every harvest. In that case, the answer to your question may be more influenced by other factors.

Your location will greatly determine the answer. For example, in South Texas, one farmer is through with harvesting by mid-July at the latest and typically does not plant fall crops until Sept 1. That gives him at least six weeks to rest a piece of land and to condition it for fall planting. He may also farm a piece of land for three harvests and then let it rest for one season while planting a cover crop of rye or clover. That could be considered leaving the ground fallow for a season. This farmer also rotated crops in addition to leaving fallow. For example, he never planted tomatoes on the same ground more than two seasons in a row. He might grow spring tomatoes, then fall tomatoes, then broccoli, and then fallow for a given piece of land. And then he could start over with tomatoes again.

It is always a good idea to do an annual soil test on your crop land, both to understand how to aid the soil and because it is important for your organic certification. It may also be a good idea to pick your best acres for your first plantings, and fallow the rest until you generate enough working capital to plant all of your acreage.

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Permalink I produce vermicompost tea from dairy waste that is first thermophilically composted to kill all pathogens and weed seeds. Under various food-safety protocols, can I apply this on soil and plants?

Answer: Until the Food Safety Modernization Act is implemented (which may be right around the corner), food-safety protocols will continue to vary slightly from one program to another. For this reason, you may need to ask whichever GAPs/food safety auditor you use for guidance on this issue. Chances are, most auditors wouldn't approve of applying compost tea topically to plants and may not even approve soil applications, although the latter would be less risky. You also need to consider your market--if the grocery store you're selling to requires a certain set of procedures, you’ve got to follow them or lose the market.

Either way, it is a good idea to develop your own food-safety plan, which you can do with the assistance of templates and instructions provided by the University of Minnesota, available at In this plan, you should state that you will get your compost tea tested in a laboratory for human pathogens and that you will keep records to document this.

The USDA National Organic Program (NOP) provides guidelines on compost and has also issued a task force report on the use of compost tea. While raw manure must be applied at least 120 days prior to harvest, properly composted manure can be applied directly. See page 20 of ATTRA’s Guide for Organic Crop Producers for the NOP's guidelines on composting procedures, which outline specific requirements for the length of time a certain temperature should be maintained while making compost, as well as proper aeration. This publication also discusses compost tea and vermicompost. It is available

Compost tea made with additives (such as molasses) may increase the prevalence of human pathogens. To learn more, see the Compost Tea Task Force Report, by the National Organic Standards Board,

For further information, see the ATTRA publication Illustrated Guide to Growing Safe Produce on Your Farm, available at

The Maine Organic Farmers and Gardeners Association (MOSES) also has a useful publication titled Update on Compost Tea: Benefits, Risks, Regulation, which is available at

Rodale New Farm Research Report published a study titled Compost tea research enters its second year: study aims to shed light on current debates over the safety and efficacy of compost tea as an organic material, available at

Finally, the U.S. Food and Drug Administration (FDA) published a lengthy document in 1998 titled FDA Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables. The PDF is available at

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Permalink How can I treat irrigation water to meet GAPs standards? Can I use river water?

Answer: The ATTRA publication An Illustrated Guide to Growing Safe Produce on Your Farm: Good Agricultural Practices introduces all the aspects of GAPs and has a great resource list. It's available on our website at More information can be found on the USDA’s website at

For GAPs certification, surface water that is being used for overhead irrigation of crops should be tested to ensure that it meets the EPA's coliform limits for recreational use of water. This standard is no more than 10,000 count per 100 ml in a single sample. Usually, a test is taken early in the season, another in mid-season, and another toward the end of the season. There are no set standards, but you might ask if this is the standard your GAPs auditor is using. If you have already done testing and it doesn’t meet this standard, then treatment might be necessary to meet GAPs standards.

Using ultraviolet (UV) as a water treatment system for irrigation has its share of problems. First, there are large industrial-size systems and small household systems available, but the size you would need for a flow of 40 to 60 gallons per minute is hard to find. In addition to problems of availability, water from a river would need to be pre-filtered in order for UV treatment to be effective. You may also need to treat with chlorine in addition to pre-filtering and UV treatment because UV is not effective protection against viruses. That means three separate systems to do the job. As for coliform bacteria, UV treatment is not recommended for coliform above 1,000 counts/100 ml. For all these reasons, it doesn't seem to be a practical solution for treating irrigation water to meat GAPs standards.

According to Berry Hill Irrigation, there are chlorination treatment units that would handle lower flow rates. One is a Regal chlorinated filter that uses chlorine gas to treat the water. This filter costs about $1,200. However, chlorine gas can be very dangerous and, although plants need a minute amount of chlorine, this above system could possibly introduce levels of chlorine that would damage the plants.

The proposed federal drinking water standard, from the Safe Drinking Water Act, for chlorine levels is 4 ppm. This is the limit for the use of chlorine in organic standards, as well. The effectiveness of the chlorine treatment is determined by the amount of organic matter in the water and the pH of the water. If you did decide to use a chlorine system, you may need to still pre-filter the river water to remove organic matter before the chlorine would be effective.

There is also a hydrogen peroxide treatment system from a company called Flow Tek that requires a water sample to determine the level of hydrogen peroxide that is needed. Because chlorine and hydrogen peroxide are both restricted under organic standards, the use of a treatment system that used these materials would jeopardize organic certification for your farm. If organic certification is one of your goals, be sure to contact you certifying agent and ask if there is a treatment for your irrigation water that would meet his or her standards.

(Note: The mention of specific products or companies does not constitute an endorsement by NCAT, the ATTRA program, or the USDA.)

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Permalink Do larger vegetable seeds result in higher yield or bigger fruit?

Answer: The answer to this question depends on whether you are asking about seeds in general or about different seed varieties of the same fruit.

Regarding seeds in general, there is much literature about the fact that plants with larger seeds emerge faster than plants with smaller seeds and therefore have an evolutionary advantage. Early emergence gives plants speedier access to localized nutrient sources and will give them advantage over plants that germinate later in the same spot.

Regarding different seed varieties of the same fruit, ATTRA is unaware of any research that shows a correlation of bigger seed size to bigger average fruit size. Take tomatoes, for example. There are many varieties—some produce small, cherry-type fruit and some can produce huge, two-pound fruit. But the seed size for each is the same. For any given seed variety, the catalogue or supplier from which it is purchased should state the average fruit size at harvest.

For some vegetable categories, you could make the case that there is a difference in seed size and fruit size in related fruit products, say yellow squash and zucchini squash. The zucchini squash has the bigger seed and one can let an individual zucchini squash get really big, say two feet long and weighing four to five pounds. Yellow squash will not get that big. But one must question the reason to let an individual zucchini fruit get that big. In the commercial trade, the highest monetary returns go to zucchini squash that is six to eight inches long. Fruit that is larger than 18 inches really has no commercial value. The same can be said of yellow squash. There is a size limit to what is called #1 fruit and fruit larger than that limit gets less valuable as it gets bigger.

The only vegetables that are almost always rewarded for ever-increasing size are tomatoes and bell peppers, and even then, there is an upper limit on size. Tomatoes are classified as extra large when they get to a diameter of about three inches. Fruit larger than that is sold, but anything over about four inches starts getting viewed negatively by the trade because really big fruit tends to go bad much quicker than smaller fruit. And besides, what customer wants to pay $5 for one tomato?

Of course, there is one exception where bigger fruit is better: growing the "biggest" something for some kind of contest or county fair prize. There are still some pumpkin-growing contests around in the Northeast and even some "biggest watermelon in the county" contests around in Texas and other southern states. But these outrageously large fruits are the result of production process, not seed size.

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