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COG Organic Field Crop Handbook
Buckwheat is a fast-growing summer annual with broad, triangular, heart-shaped leaves and white flowers. It is used as a green manure crop, as a smother crop to crowd out weeds, to produce seed for human consumption and as a source of buckwheat honey. As buckwheat has an amino acid composition that includes lysine, the grain provides a more complete protein than that obtained from other cereals.
1. Reasons for crop selection
* Erosion control
Buckwheat planted in mid-to late August will be killed by frost, but will still provide enough vegetation to cover and protect the soil over winter.
* Market potential
Organic farmers receive premium prices for certified organic buckwheat.
* Nutrient benefits
Buckwheat improves soil fertility. Farmers have found that it accumulates both phosphorus and potassium, and makes these and other nutrients available to the following crop. It produces acidity around its roots which allows it to make use of relatively insoluble fertilizers, like rock phosphate, better than corn and small grains. Because of this and the fact it is not a heavy nitrogen feeder buckwheat can be grown on poor land and is often used to start the transition process when rejuvenating "farmed out" soils.
* Soil conditioner
Buckwheat tends to have a shallow, fibrous root system, which together with its large leaf surface makes it susceptible to wilting during periods of drought. However, because of its dense root system, buckwheat is an excellent soil conditioner. Its high fibre residue improves aeration of the soil and encourages earthworm activity, making the soil more friable and easier to work. The total amount of organic matter added to the soil is relatively low because of the biomass's high water content.
* Weed control
Buckwheat can be used to clean the land of weeds. During the growing season, the fast-growing buckwheat smothers weeds, and the buckwheat residues (decomposing roots) suppress weed seed germination.
When using buckwheat to control stubborn weeds like quackgrass, farmers cultivate a few times in spring, then prepare a good seedbed to ensure strong germination of the buckwheat. After incorporating or harvesting the buckwheat,the field is cultivated again. This works most effectively when buckwheat is planted as a green manure. If the buckwheat is grown for seed and the stand is less dense, its smothering effect will be less efficient.
Buckwheat grown for seed, unless carefully managed ,may result in a problem with volunteer growth of buckwheat in the following crop.
2. Crop requirements
A buckwheat crop which yields 30 bu/ac removes:
N - 42lbs, P - 20lbs, K - 35lbs
If the soil fertility is low, an application of phosphorus (colloidal or rock phosphate) will produce consistent increases in buckwheat yield. Excessive nitrogen will cause lodging and decrease yields.
Buckwheat is adapted to well-drained sand or silt loam, but grows well under a wide range of conditions and will produce a better crop on poor soil than any other grain. It tends to lodge on very fertile soils. Do not plant buckwheat on poorly-drained saturated soils.
Buckwheat is adapted to a cool, moist climate but will also grow well during warm weather. It is sensitive to high temperatures and hot, dry winds. If these conditions occur during flowering, seed-set and yield will be reduced. It is susceptible to late-spring and early-fall frosts and requires 10-12 weeks to reach maturity. Therefore buckwheat can be used as a "catch crop" if seeded when the planned crop does not get planted on time or does not germinate.
The Japanese, North American and European market are demanding large seeded varieties for milling and dehulling purposes. Mancan is one such variety, with a thick stem and medium height which makes it resistant to lodging.
3. Planting methods
When growing buckwheat for seed, avoid planting it in a field that previously grew wheat, oats, barley or flax, because grain from volunteer plants will make the crop difficult to clean. This problem can be overcome by fall tillage and planting a winter cover crop which is incorporated in the spring before planting the buckwheat.
* Planting date
Buckwheat will germinate at temperatures anywhere between 7 and 40.5 ˇC (45 and 105ˇF,). Therefore there is considerable flexibility in planting dates.
Yields are highest if buckwheat is planted immediately after risk of frost, aiming to avoid flowering in the very hot weather of mid-summer. Early plantings help to minimize volunteer problems the next year. However some farmers have experienced more weed problems with early plantings in a cold spring. In this case planting should be delayed. Traditionally buckwheat was planted in mid summer and often combined after frost. Although this method avoids hot weather at flowering time, dropped seed reduces yield and poses a severe volunteer problem for the following crops.
* Seedbed preparation
When preparing the seedbed one should aim for effective weed control, conservation of moisture, and a firm seedbed.
Tillage practices that will help control weeds include shallow tillage in the early spring which stimulates weed germination and helps maintain a firm seed bed. It is followed by a second tillage operation just before seeding, which kills the newly-emerged weeds. Tillage is shallow to avoid bringing new weeds to the surface and to conserve moisture. Harrowing should leave the field ready for seeding.
Frequently, buckwheat is planted in abandoned fields, old pastures or other land that has been neglected for years. Rock phosphate can be spread if required, and then the sod is incorporated. If it was ploughed in the fall, the soil would be disked in early spring, then disked or cultivated about two weeks after that to kill weeds. This sequence can be repeated until seeding time.
Spring ploughing is possible, but keep the ploughing as shallow as possible. The soil is then worked every 7 to ten days until seeding time, to improve the soil condition and destroy weeds.
If a hay field or pasture is plowed up in late June or early July, buckwheat can follow and be used as a cover crop to control weeds or as a green manure.
Planting the seeds with a grain drill will produce a more even stand, but you can also get satisfactory results with broadcasting. Plant seeds at a depth of four to six centimetres, in moist soil, and seedlings will emerge in two to five days.
The bushel weight for buckwheat is 48lbs/bu., (60kg/hl).
Recommended seeding rates:
For seed - Ontario 45-60 lb/ac 50-65 kg/ha 1-1.25 bu/ac.
- Prairies 35-50 lb/ac 40-55 kg/ha .75-1 bu/ac.
For green manure - 2bu/acre.
As the higher population of plants gives a better smothering effect, the higher seeding rate is used when weeds may be a problem. But even if the stand is thin, the plantŐs branching will often compensate for the thinner stand and will still result in good weed control. When using the higher rate, it is recommended that the seed be divided in half and the field be cross-planted with the grain drill. This appears to give better spacing of plants with less legginess and subsequent lodging problems.
4. Crop management
After the seedbed preparation, no further weed control will be needed.
Buckwheat seldom has problems with insects and diseases.
Flowering begins five to six weeks after sowing and continues for at least a month. Insects, honey bees and leafcutter bees, are the main pollinating agents. Having an arrangement with an apiarist would be of mutual benefit.
5. Buckwheat as a green manure
BuckwheatŐs ability to use phosphate which is unavailable to other crops, and its ability to make the phosphorus available to following crops, is one of the reasons it is useful as a green manure.
Buckwheat is also an excellent soil conditioner. To take advantage of its large biomass, buckwheat is incorporated between four and seven weeks after planting, before the first seeds have set. It is disked down at 10% bloom and left on the surface for a few days to dry. When it starts to crinkle when trod on, it is disked into the soil. If the field is left until full bloom there is more liklihood of volunteer problems. If you have a long growing season, a second or even a third planting maybe possible.
Buckwheat is an indeterminate plant, so flowers, green seed, and mature seed are present on the plant at the same time. Harvest must occur prior to development of over-ripe seed. This will be about 10 weeks after planting. The crop is still growing and flowering at this time, but 70 to 75 percent of the seeds should be brown and mature and not yet dropping from the bottom of the bloom spike.
If harvest is delayed until the seeds nearest the ground begin to fall, you will have decreased yields, and the volunteer population will cause problems for the next crop. Yields of 40bu/ac are possible but 20-30 bu are more commonly reported.
Swathing is necessary if the crop has not been killed by frost. Cut the buckwheat, and place it in windrows on a high stubble to facilitate drying. Leave it to dry until moisture in the seedhead reaches 16 percent. Then combine.
Swathing should be done in the early morning when the dew is present, or in damp weather to help keep losses due to shattered seed down to a minimum. When combining, the pick-up speed is reduced to match the ground speed so as to reduce shattering. The draper type of pick-up causes less shattering than the drum type. To minimize breakage, the cylinder speed should be reduced to one third that used for cereal grains, and the concaves set to approximately 13 to 16 mm in the front, and 9 mm in the rear. The upper sieve is set at 16 mm and the lower sieve is set at 8 mm. The lower sieve can then be opened gradually to the setting that does not allow excess foreign material to pass through. Check that the wind blast is strong enough to remove the maximum amount of trash without blowing out clean grain.
When using a summer planting system, growers can wait until 7 to 10 days after a light fall frost before direct combining. Keep your cut as high as possible and ground speed low to prevent overloading the combine. Give attention to the amount of coarse material that is allowed to pass through so that only a minimum of seed enters the return, and in this way, breakage will be reduced.
A moisture content of less than 16 percent is needed for safe storage. The Japanese buy only freshly harvested buckwheat, so do not store seed to sell the following year. It is easy to detect the difference between previously stored and newly harvested buckwheat by the colour of the grain just under the hull. It goes from light green to reddish brown when aged.
8. Suitable following crops
When selecting crops to follow buckwheat, the main consideration is the problem of buckwheat volunteers the following year and this is especially problematic if the buckwheat is grown for seed. This problem can be greatly reduced with a spring planting system which allows for more time for tillage in late summer and early fall to stimulate germination of any fallen seed. After harvesting the buckwheat, disc to incorporate the residue and disc again 7 days later. Wait another 7- 10 days, disc again if necessary and plant a winter rye cover crop. Any buckwheat that germinates after this will be winterkilled. Some growers use forage harvesters to chop the buckwheat straw after combining to make the residue easier to incorporate. If you follow the winter cover crop with a row crop such as soybeans rather than with a small grain, you will be able to control any volunteer buckwheat with cultivation.
When buckwheat is grown as a green manure crop, it can be left to winter kill and then the field can be planted with a spring grain.
Copyright © 1992 Canadian Organic Growers. Inc
Reprinted with permission. All rights reserved.
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