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Home  > Question of the Week

Question of the Week

Permalink What information can you give me on comparing energy requirements for different irrigation systems?


Answer: Thank you for contacting ATTRA, the National Sustainable Agriculture Information Service for comparisons across drip, trickle, flood irrigation systems in terms of energy requirements.

Comparing different systems for energy requirements can be difficult. Below are just a few preliminary observations and things to consider:

1. Generalized comparisons across irrigation systems are tricky and somewhat unreliable. For example, there are some extremely efficient flood, ditch/furrow, and sprinkler systems, and some extremely inefficient drip systems.

2. I would treat published averages and energy savings with caution. Estimating energy-savings in the world of irrigation is a surprisingly difficult thing to do. After making various seemingly arbitrary decisions in how you calculate your baseline, you then need to cope with many inevitable unknowns: possible changes in the crop or variety being grown, acreage, management practices, weather-related impacts, equipment breakdowns, power outages, etc. Utilities, state agencies, and private companies in the energy conservation business often have an incentive to exaggerate energy savings.

3. People who study energy usage in irrigation are mostly engineers and so (not surprisingly) they tend to focus narrowly on engineering calculations: the volume of water you are moving, how far you are vertically lifting the water, how much pressure you are placing it under, and how much energy is "lost" to factors such as pipe wall friction, leaks, and various kinds of inefficiencies in pumps, motors, engines, nozzles, and so on.

These factors are all important, but equally important is how the system is managed. The connection between higher "pumping plant efficiency" and lower energy usage is usually taken for granted but is actually questionable. On this topic, I would recommend Blaine Hanson's article "Improving pumping plant efficiency does not always save energy."

Soil quality is another example of an important factor that is routinely ignored. There's a direct connection between soil quality and water-holding capacity, which reduces energy requirements. For example, one UC Davis study showed 50 percent higher water infiltration in organic plots compared to conventionally managed ones. Here's a link:

4. Each type of system is also prone to environmental tradeoffs that go beyond energy. For example, flood irrigation often uses little or no energy, but can waste a lot of water and cause soil erosion. Drip systems often uses less energy than higher-pressure systems, but require intensive management and often heavy doses of biocides (such as chlorine) and acids to keep the lines from clogging.

For more information on irrigation and energy use see ATTRA's Irrigation Efficiency page.

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Permalink What information can you give me on weed control in newly planted asparagus?


Answer: Thank you for your recent request for information from ATTRA, the National Sustainable Agriculture Information Service regarding weed management in your newly planted asparagus.

As you are finding out weed management is critical to growing asparagus, since it is a perennial crop and tillage options are limited once the asparagus is planted—especially during the spear and fern stages of production. I usually recommend a strict cover-cropping strategy before the asparagus goes in, but since you have existing plants I will recommend a few options.

The weed management strategies are different for annuals than perennials. I will make some recommendations based on each kind of weed.

Annual weeds will be easier to control in your asparagus crop than perennials. At this point, hoeing and hand weeding may be your best option, but shortly after this, you can apply a mulch either living or straw to help keep down the weeds. A living mulch of oats and peas could be seeded in the fall, then allowed to winterkill and provide a cover to keep the weeds at bay. If you choose to use straw, be sure that it is indeed straw and not spent hay, which can make your weed problem worse.

Another option for annual weeds the following spring before the asparagus begins to emerge, is to use a flame weeder. This product can efficiently and effectively help with weed management if done early on. It is important that you flame weed before the tips emerge. As a general rule, flame weeding is most effective against annual broadleaf weeds, moderately effective against annual grasses, and a poor option for perennial weed management. See the ATTRA publication, Flame Weeding for Vegetable Crops.

For perennial and annual weeds during spear and fern production weeder geese are an option. In order to make cost comparisons between geese and other weed control methods, you will need to keep a record of the time spent moving, feeding, and watering the geese. A good book on raising geese and using weeder geese is The Book of Geese available from many sources, including Metzer Farms. This book along with more information on this topic is available by visiting their web site:

Another option for perennial weeds, besides hand-weeding, is to use a burn-down organic herbicide such as acetic acid or clove oil. These products can be most effective when the perennial weeds are just emerging and the key is to use it every time you see them re-emerging to exhaust their root reserves. This may need to be done several times in the season.

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Permalink What information can you give me on small-scale grain production for livestock feed?


Answer: Thank you for your recent request for information from ATTRA, the National Sustainable Agriculture Information Service. I am pleased to provide you with information on grain production for livestock feed.

When transitioning from a fallow field to cultivated system of crops, the pattern may differ slightly from moving from a conventional to organic cropping system. In either case, weeds that were previously suppressed—either by herbicides or by the continuous cover of sod or pasture, and the weeds may become problems again as conditions favor their growth—sometimes emerging with greater vigor in the second year. In either scenario, different weeds will germinate and grow at different times of year. By planting a series of different cover crops with different seasons and growth patterns and working them in sequentially, one can allow different types of weed seeds to germinate and die, eliminating large numbers of different kinds of seeds from the soil seed bank. Crops such as buckwheat, rye and other cereal grains have allelopathic qualities, the best cover crop is often a mixture of different species. Legumes such as vetch or clover not only add organic matter and nitrogen from biological fixation, they also help suppress weeds that germinate in the gaps in plantings between other crops such as buckwheat or rye. Grasses and other vigorous cover crops can effectively suppress weed growth. And, crops that are densely planted, and/or skillfully cultivated can also suppress weeds.

Good implements for effective mechanical cultivation weed control are needed. In order to achieve close cultivation without damaging plants, one also needs good land preparation, including straight rows and accurate seeding or transplant lines in the beds. The resources below review cultivating tools and implements, guidance systems, and flame weeding equipment, and may help you choose appropriate strategies and implements:

Steel in the Field; A Farmer’s Guide to Weed Management Tools
Edited by Greg Bowman. 1997. Sustainable Agriculture Network, National Agricultural Library, Beltsville, MD

The September-October 2006 issue of the ATTRA newsletter was dedicated to weed management. If you do not read that already, the link to it is:

Another useful website is: European Weed Research Society, Physical and Cultural Weed Controls This multi-lingual site has photos as well as a description of the use and application of each tool.

Options: When beginning, I suggest spring plowing or tilling of some sort to control your current weed population. Establish a warm-season cover crop that will give you lots of organic matter and compete with weeds and prepare you for a perennial or annual cover crop that you can incorporate into a no-till system. Legumes such as cowpeas, soybeans, annual sweetclover, sesbania, guar, crotalaria, or velvet beans may be grown as summer green manure crops to add nitrogen along with organic matter. Non-legumes such as sorghum-sudangrass, millet, forage sorghum, or buckwheat are grown to provide biomass, smother weeds, and improve soil tilth. Sorghum-sudan grass is very effective at smothering weeds and producing a lot of organic matter in a short period of time and might be a good selection for your particular situation.

In the fall, this cover crop should be mowed with a rotary mower (or “brush hog”) and incorporated with a tillage implement, or if you have access to some type of reduced tillage implement, you can direct seed into the Sudan grass residue. At this point, it would be possible to plant a perennial cover crop mix. Perennials more regenerative than annuals, given their rooting depth and growth habits. A perennial legume will help provide some nitrogen, such as alfalfa or white clover planted with a grass, such as orchardgrass. Another option would be to plant another cool-season annual that will over-winter such as a rye/vetch combination. This will establish in the fall and go dormant through the winter. In the spring the crops will begin growing again. When they begin to flower, rotary mow or flail chop the cover crop and either plant directly into the dead standing plants or till in and plant your desired cash crop.

For additional information on Reduced/ no-till systems see the ATTRA publication Resources for Reduced Tillage on Your Organic Farm available from or by calling the toll free number referenced at the end of this letter.

The New Farm web site also has a lot of great information on no-till farming. The direct link to this section is

Some other options: Consider utilizing forages as cover crops for two or more years during the transition. Organic alfalfa/grass hay is well sought after in many regions of the Northeast and can be a great boost to farm income. Also, spring oats followed by alfalfa hay might be a great way to reduce weed pressure while building soil fertility during organic transition. Other crops to consider that are generally high value include organic flax or annual rye. Organic oats and peas can make a great hay or silage for cattle while building soils for growing annual cash crops later in the rotation.

Details on Cover Cropping Prior to Planting Cash Crops: A vigorous summer annual crop followed by a winter perennial cover crop would help combat perennial weed problems and improve soil organic matter at the same time. Buckwheat is an aggressively growing cover crop that has large cotyledons that shade and often out-compete other weeds. It put on a lot of biomass in a very short period of time. Mow the buckwheat shortly after it begins to flower (before it begins to seed) with a rotary mower. After this has sit and broken down for a few weeks to a month, you can plant a fall cover crop of annual (cereal) rye (this cover crop has shown to have allelopathic [suppresses plant growth] properties and could help prevent weed seed germination) and hairy vetch. Rye and vetch begin to grow in the fall (if planted before September 15th) and go dormant through the winter. In spring the rye and vetch will begin to grow again. Rotary mow the rye and vetch once in June after is begins to grow and put on a lot of biomass and then plow or rotovate it into the soil. At this point you should have a better handle on your weeds and may begin cropping whatever it is you decide to plant.


Logsdon, Gene. 1977. Small-Scale Grain Raising. 320 pages. Rodale Books.

Sustainable small-scale grain raising. WSARE Project Report FW01-081.

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Permalink What Information can you give me on how the composting process affects antibiotics in manure and soil amendments?


Answer: Thank you for your recent request for information from ATTRA, the National Sustainable Agriculture Information Service. I am pleased to provide you with information on the resistance of antibiotics and hormones to the composting process and if they are present in animal-based soil amendments.

Many feedstock materials used in the composting process contain chemicals and heavy metals. There are many published studies that have looked into the impacts composting has on heavy metals and chemicals, including pharmaceuticals and pesticides. Research has repeatedly shown that pharmaceuticals break down in compost if the compost is properly managed for moisture, oxygen, temperature, and a good carbon-nitrogen balance. Yet small levels may still exist after composting and may be taken up by plants; eventually posing a treat for food and groundwater supplies. Some antibiotic levels are actually produced by compost microorganisms.

One study that I have read examined the ability of compost to break down ten pharmaceutical and personal-care product residues in biosolids collected from a wastewater treatment plant. The results found that composting for 45 days reduced residues of nine out of ten products by at least 85 percent. Another study performed by the USDA’s Agriculture Research Service, in 2005, found that composting reduced the incidence of estrogen (17B-estradiol) and testosterone in chicken manure by 84 to 90 percent in 139 days. Scientists concluded that the rate of hormone degradation is affected by how well the compost is aerated, and by the moisture level, porosity and particle size of the compost.

Time is another key variable in the reduction of antibiotics and hormones through composting. Most commercial composting facilities compost for at least 60 days and some wait six to eight months. According to many states, you can meet EPA law in five days with in-vessel composting, or 15 days for other systems, but then you need to store it for 30 days as a safeguard.

With the exception of the standards set by the National Organic Program (NOP) for compost used in organic farming systems, national standards, regulated by the EPA, only exist for composts made from biosolids, or solids that have been treated by municipal wastewater treatment facilities. The EPA along with individual state standards for finished compost generally requires regular testing for heavy metals and pathogens. Tests for pharmaceutical compounds and pesticide residues are not required. Biosolids must meet these standards before the compost can be spread on fields or sold to wholesalers and retailers.

It is unclear as to whether or not antibiotics are present in soil amendments derived from animal by-products. I was unable to locate research regarding this topic. However, my thought is that any chemical residues in soil amendments may be targeted by soil microorganisms that activate the nutrients in the soil amendment. In other words, the soil microorganisms will break down residues once the amendments are incorporated into the soil. In addition, the processes of creating bone meal and blood meal may reduce levels of antibiotics and hormones present in the animal source. Bone meal involves steaming the bones to sterilize them, then crushing them into a meal. Whole blood meal is produced by spray drying the fresh whole blood from animal processing plants at low temperatures. The fresh blood is collected in cooling tanks that utilize agitation to prevent coagulation of the fresh blood. The whole blood is then centrifuged to remove foreign material and then circulated through a disintegrator to remove all remaining foreign particles.

Below is a list of a few studies that investigated antibiotic and hormone levels in compost. I have also included the NOP regulations for compost and manure applications (§ 205.203 Soil fertility and crop nutrient management practice standard). This standard also defines the use of animal by-products in organic production. The use of meat meal should fall under the standard on allowed materials for soil fertility. Relevant sections include 205.203( b), and (c)(i, ii, iii).


Rich, Deborah. 2007. “Questioning the Compost Supply Chain.” San Francisco Chronicle. May 5, F-5.

1). Here is a research project that indicated that antibiotics do degrade in compost. The interesting conclusion is that a pile of antibiotic laced manure, left alone to degrade without any manual management after the pile had been created, was just as effective in eliminating antibiotics as managed compost systems (compost that was turned weekly or compost that was maintained in a vessel).

Dolliver, Holly, Satish Gupta, and Sally Noll. 2008. "Antibiotic Degradation in Manure Composting". Journal of Environmental Quality. 37:3: p. 1245-1253.

2). Here's a study showing that antibiotics in manure can be taken up by plants when they are fertilized with animal manures containing the antibiotics. This is the use of raw manure, not compost:

Kumar, K., S.C. Gupta, S.K. Baidoo, Y. Chander, and C.J. Rosen. "Antibiotic Uptake by Plants from Soil Fertilized with Animal Manure." 2005. Journal of environmental Quality. 34:6 p: 2082-2085.

3). Here's another study using Oxytetracychne (OTC) - a broad-spectrum antibiotic used in livestock production. The OTC did not affect the composting process and within the first six days of composting, showed a 95% reduction.

§ 205.203 Soil fertility and crop nutrient management practice standard

(a) The producer must select and implement tillage and cultivation practices that maintain or improve the physical, chemical and biological condition of soil and minimize soil erosion.
(b) The producer must manage crop nutrients and soil fertility through rotations, cover crops and the application of plant and animal materials.
(c) The producer must manage plant and animal materials to maintain or improve soil organic matter content in a manner that does not contribute to contamination of crops, soil or water by plant nutrients, pathogenic organisms, heavy metals or residues of prohibited substances. Animal and plant materials include:
(1) Raw animal manure, which must be composted unless it is:
(i) Applied to land used for a crop not intended for human consumption;
(ii) Incorporated into the soil not less than 120 days prior to the harvest of a product whose edible portion has direct contact with the soil surface or soil particles; or
(iii) Incorporated into the soil not less than 90 days prior to the harvest of a product whose edible portion does not have direct contact with the soil surface or soil particles.
(2) Composted plant and animal materials produced though a process that:
(i) Established an initial C:N ratio of between 25:1 and 40:1; and
(ii) Maintained a temperature of between 131 and 170 degrees for three days using an in-vessel or static aerated pile system; or
(iii) Maintained a temperature of between 131 and 170 degrees for 15 days using a windrow composting system, during which period, the materials must be turned a minimum of five times.
(3) Uncomposted plant materials.
(d) A producer may manage crop nutrients and soil fertility to maintain or improve soil organic matter content in a manner that does not contribute to contamination of crops, soil or water by plant nutrients, pathogenic organisms, heavy metals or residues of prohibited substances by applying:
(1) A crop nutrient or soil amendment included on the National List of synthetic substances allowed for use in organic crop production;
(2) A mined substance of low solubility;
(3) A mined substance of high solubility, provided that the substance is used in compliance with the conditions established on the National List of non-synthetic materials prohibited for crop production;
(4) Ash obtained from the burning of a plant or animal material, except as prohibited in paragraph (e) of this section, provided that the material burned has not been treated or combined with a prohibited substance or the ash is not included on the National List of non-synthetic substances prohibited for use in organic crop production; and
(5) A plant or animal material that has been chemically altered by a manufacturing process, provided that the material is included on the National List of synthetic substances allowed for use in organic crop production established in §205.601.
(e) The producer must not use:
(1) Any fertilizer or composted plant and animal material that contains a synthetic substance not included on the National List of synthetic substances allowed for use in organic crop production;
(2) Sewage sludge (biosolids) as defined in 40 CFR part 503; and
(3) Burning as a means of disposal for crop residues produced on the operation except that burning may be used to suppress the spread of disease or to stimulate seed germination.

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