Weed control a key factor in meeting increasing demand for organic grains

The growing demand for organically grown grains for livestock feed is creating a large, niche market for Carolina/Virginia grain farmers.

The limiting factor is weed control, and in many cases putting a few acres into organically grown grains provides an excellent means of overcoming herbicide resistance.

For the past 10 years, the U.S. demand for organic foods has grown an average of 16-18 percent annually. The big push has been for organic meat, which has grown over 75 percent in the past 10 years, according to the Organic Trade Association.

To be certified as organic by the U.S. Department of Agriculture, livestock must be fed organic grains. The demand for organic meat has created a niche market for organic grain that currently comprises nearly three percent of grain sold for livestock consumption in the U.S.

The largest seller of organic milk and beef in the U.S. is Walmart. According to North Carolina State Agronomist Chris Horton, about 75 percent of U.S. grocery stores now stock some organic products.

In North Carolina, Horton says, $8 million to $10 million worth of organic grain was bought in state last year, but over 90 percent of it was grown in other states. In North Carolina, buying points are being established, and one buyer near Rocky Point, N.C., bought over 500,000 bushels of organic corn, 17,000 tons of soybeans and 150,000 bushels of wheat.

Prices have remained good for traditionally grown corn, soybeans and wheat, but cannot compare to prices being offered for the organic version of these commodities. In 2006, organic corn sold for over $7 per bushel, organic wheat for $6.50 and organic soybeans for $15 per bushel.

Since 2002, organic foods have to be grown under Federal guidelines. There is a USDA sticker that goes on all organic food. In North Carolina, the State Crop Improvement Association is the leading operator in the state running organic certification.

For growers, organic certification involves a lot of record keeping. Most growers contend the level of record keeping comparable to keeping NRCS records, according to Horton.

Most organic growers in North Carolina, grow these products on a split operation with conventionally grown grain, according to Horton. Typically, a 2,000-3,000 acre grain farmer will convert 200-300 acres to organic production. Horton says several of the top grain farmers in North Carolina have converted some acres to organics and treat it as a small niche crop in their overall farm enterprise.

The biggest challenge to organic grain production is weed management. “On many of the farms we work with in North Carolina, there has been little cultivation in the past 10-20 years, so there is some degree of re-learning that technology,” Horton says. Cultivation technology and strategies have changed dramatically in the past few years with the onset of precision technology, and to be competitive in the organic grain arena, farmers have to be up to date on what, how and when to use cultivation, he adds.

The first step in weed management in organic grains is to insure high quality seed are planted. Seed that has not been carefully screened (especially farmer-saved seed) is often of lower quality than certified seed and may contain unknown quantities of weed seed or disease.

Planting farmer-stock seed may result in the introduction of pests not previously observed on the farm. Using this seed may also defeat the purpose of ridding an area of weeds that are resistant to glyphosate or other herbicides.

Germination rate and vigor are equally important to weed management, because they collectively affect stand quality and time to canopy closure.

Shading out weeds is the oldest and most consistent means of controlling weed populations, having been displaced in part by cultivation and in the 1960s by chemical herbicides. Both advances in weed control have left a generation of growers who probably pay too little attention to sowing date and seeding rate, except in terms of cost management.

The final crop population, which must be optimum to compete with weeds, also has to be evaluated for its impact on other pest problems and harvestability. Carefully maintained and adjusted planting equipment will ensure the crop seed is uniformly planted at the correct depth for optimum emergence. Narrower rows and a slightly increased plant population (up to 10 percent higher than usual) will also help the crop compete with weeds.

If a goal of planting organic grain is to clean up fields that have been plagued with weeds that are hard to manage, seeding rate and timing of planting must be careful considerations.

“I originally thought narrow-row spacings were not feasible for organic grain production because of the difficulty in getting cultivation equipment between the rows. In the past year, I've been proven wrong on several farms, including one organic grower who has done well with 20-inch row spacings on corn,” Horton notes.

Use of cover crops to build soil quality by reducing soil erosion, increasing soil nitrogen, and weed suppression has been used extensively in no-till and minimum-tillage systems in the past few years.

Cover crops such as rye, triticale, soybeans, cowpeas, or clover can be tilled in as a green manure, allowed to winter kill, or be killed or suppressed by undercutting with cultivator sweeps, mowing, or rolling.

Warm-season cover crops help to suppress weeds by establishing quickly and out-competing weeds for resources. Horton points out that it is important to manage cover crops carefully so that they do not set seed in the field and become weed problems themselves.

Weeds are often spread from field to field on tillage, cultivation, or mowing equipment. Cleaning equipment before moving from one field to another or even after going through a particularly weedy section can prevent weeds from spreading between fields or within fields. A short investment of time to clean equipment can pay large dividends if it prevents the spread of problem weeds.

When transitioning to organic systems, it is highly advisable to start with fields that are known to have low weed infestations. Fields with problem weeds, such as Italian ryegrass, wild garlic, johnsongrass, or bermudagrass, should be avoided, if possible, as these weed species will be difficult to manage. A healthy, vigorous crop is one of the best means of suppressing weeds.

The goals of mechanical weed control are to eliminate the bulk of the weed population before it competes with the crop and to reduce the weed seed bank in the field. Important factors to consider for mechanical weed control are weed species present and their size, soil condition, available equipment, crop species and size, and weather.

Horton contends most growers know how to use rotary hoes, but not in the production of organic grain production. One implement that fits will is a flex tine harrow. This piece of equipment is used to prepare a seedbed, mix residue, incorporate chemicals/fertilizer, warm the soil, level, break up dirt clods, and more…

“One of our best growers, in terms of weed control, rotary hoes his soybeans about four times. He plants beans and three days later hits the field with a rotary hoe just before soybeans pop out of the ground. When bean plants stand back up, he hits it every five days with the rotary hoe. Any weeds left in-row after the last pass with the rotary hoe will be left until the end of the season,” Horton says.

In some organic fields, it is hard to distinguish any difference between organic weed control and Roundup Ready soybeans planted in the next field. In other fields, with different rainfall patterns and different levels of seed, planting and cultivation timing and quality, the differences can be dramatic, Horton says.

Cost of weed management in organic grains is more expensive than in traditional Roundup Ready systems in a no-till basis, but no more than these systems in traditional-tillage systems.

Blind cultivation is the shallow tillage of the entire field after the crop has been seeded. Generally, it is used without regard for the row positions. It provides the best opportunity to destroy weeds that would otherwise be growing within the rows and that are not likely to be removed by subsequent mechanical tactics.

Blind cultivation stirs soil above the level of seed placement (further emphasizing the need for accurate placement of the crop seed), causing the desiccation and death of tiny germinating weed seedlings. Crop seeds germinating below the level of cultivation should not be injured. The first blind cultivation pass is usually performed immediately before the crop emerges, and a second pass is performed about a week later.

Between-row cultivation should be implemented when weeds are about 1-inch tall and the crop is large enough not to be covered by soil thrown up during the pass. Usually, more than one cultivation pass is needed. It may be useful to reverse the direction of the second (and alternate) cultivation pass in order to increase the possibility of removing weeds that were missed by the first cultivation.

There are many types of cultivator teeth, shanks, and points. Unfortunately, most have not been widely used since the onset of Roundup Ready technology and the subsequent growth in popularity of no-till farming.

Half sweeps (next to the row) and full sweeps (between rows) are probably the most versatile and common, but each type of point works best under certain conditions and on certain weed species

Flame weeding provides fairly effective weed control on many newly emerged broadleaf species and can be used in tilled or no-till fields. Grasses may not be well controlled by flaming because their growing points are often below the soil surface. Flame weeding should only be performed when field moisture levels are high and when the crop is small.

Several herbicides have been approved for certified organic farming. These include acetic acid (distilled vinegar), clove oil, non-detergent soap-based pesticides, some corn gluten meal products, and boiling water. While these products have potential for controlling weeds in organic farming systems, no research has been conducted with them in grain crops in North Carolina, Horton points out.

For many growers keeping a field free of pesticides for the three years required to become organic certified is a challenge. “It really is two years, because of the way the rules are written.

“For example, if I planted soybeans last year. My last application of pesticides was probably in July. If I grow soybeans two years later, these aren't harvested until after July on the third year, so these can be certified organic,” Horton says.

He adds that there is no way around losing money on land for two years to become organic certified. In some cases, he says, there may be some money available from

various sources to help farmers get over that two-year hump with no crops grown in a field.

If land, labor and interest all occur at the right time, organic farming can be a good niche crop and provide some collateral advantages in cleaning up fields plagued with resistance to herbicides.

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