Other Crops: Buckwheat

Excerpt from Agronomy Guide for Field Crops (Chapter 9)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
2. Tillage Options and Seedbed Preparation
• Field Selection
3. Variety Selection
4. Planting
   • As a Green Manure
5. Fertility
• Phosphate and Potash Recommendations for Buckwheat and Flax Based on OMAFRA-Accredited Soil Tests - Table 9-1
• Nitrogen Requirements for Buckwheat Based on OMAFRA-Accredited Soil Tests - Table 9-2
6. Harvest and Storage
   • Harvest
   • Storage
   • Livestock Feed
7. Weed Control
8. Insects and Diseases
9. Updates on Other Crops: Buckwheat

Introduction

Buckwheat is a fast-growing summer annual with broad, heart-shaped leaves and white flowers. It takes approximately 10-12 weeks from planting to harvest. It is frost sensitive and is usually planted later than other field crops.

Buckwheat is used for human consumption, as an ingredient in livestock feeds and as a source for buckwheat honey. It is also commonly used as a cover crop for weed suppression and green manure. The grain of buckwheat has an amino acid composition that includes lysine and thus provides a more complete protein compared to other cereals.

The most lucrative market is for the export of quality, large-seeded buckwheat to the Pacific-rim countries, particularly Japan.

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Tillage Options and Seedbed Preparation

Frequently buckwheat is planted in abandoned fields, old pastures or other land that has been neglected for years. When preparing the seedbed, one should aim for effective weed control, conservation of moisture and a firm seedbed.

If the field was plowed in the fall, the soil should be disked in early spring, then disked or cultivated approximately 2 weeks later to kill weeds. This sequence can be repeated until seeding time.

Spring plowing is an option, however, be sure to plow as shallow as possible. To improve the soil condition and destroy weeds, work the soil every 7-10 days until seeding time. Shallow tillage minimizes new weeds coming to the surface and conserves moisture. Harrowing should leave the field ready for seeding.

If a hay or pasture is plowed in late-June or early-July, buckwheat can follow and be used as a cover crop to control weeds or to act as a green manure.

Field Selection

Buckwheat grows best on light-to-medium-textured soils but will grow on a wide range of soil types, producing a better crop on poor soil than any other grain. Buckwheat prefers well-drained soils with a pH of 5.0 to 7.0. It is intolerant of severely dry, saturated or compacted 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. Buckwheat is susceptible to late-spring and early-fall frosts and requires 10-12 weeks to reach maturity.

When growing buckwheat for seed, avoid planting in fields where other grains were previously grown, in order to reduce volunteer grain. This problem can be overcome by tilling in the fall and planting a winter cover crop that is incorporated in the spring before planting the buckwheat.

Weed control options in buckwheat are limited, so best yields will be obtained from clean, weed-free fields.

Also avoid fields that contain very high levels of nitrogen, since this can cause crop lodging. Often the lush growth associated with fields high in nitrogen has led to a higher incidence of white mould. White mould is a problem in soybeans, canola, sunflowers and buckwheat. If possible, avoid fields where white mould has been a problem.

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Variety Selection

If the crop is being grown for export markets, variety selection becomes important. The Japanese, North American and European markets demand large-seeded varieties for milling and de-hulling purposes. Mancan is one popular variety that has a thick stem and medium height characteristics, which makes it more resistant to lodging.

New varieties tend to have larger seed size along with increased bushel weight. These large-seeded varieties have larger leaves, and as a result do not require higher seeding rates than the smaller-seeded types.

For cover crop seed sources, refer to Cover Crop Seed Suppliers at www.omafra.gov.on.ca/english/crops/resource/covercrp.htm.

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Planting

Buckwheat will germinate at temperatures anywhere between 7°C and 40.5°C (44°F and 105°F), so the planting date can be any time after the risk of frost has passed.

Yields are highest if buckwheat is planted immediately after the risk of frost has passed. Where possible, try to avoid flowering in the very hot weather of mid-summer. Early plantings help minimize volunteer problems the following year, however, in cold springs, some have experienced more weed problems with early plantings. In a cold spring, planting should be delayed until conditions are more favourable for crop emergence.

Traditionally, buckwheat was planted in mid-summer and often combined after frost. Although this method avoids flowering during hot weather, dropped seed reduces yield and poses a severe volunteer problem for the following crops.

Planting seeds with a grain drill will produce a more even stand, but satisfactory results can also be obtained with broadcast seeding. Plant seeds at a depth of 4-6 cm (1^1/2-2^1/2 in), in moist soils. Place seed only deep enough to reach consistently moist soil, to obtain rapid and uniform emergence. Seedlings should emerge in 2-5 days.

Recommended seeding rates for seed production are 50-65 kg/ha (45-60 lb/ac), which is equivalent to
1-1.25 bu/ac. This will achieve the ideal plant stand of 140-183 plants/m² (13-17 plants/ft²).

When planting buckwheat for a green manure crop, the optimum seeding rate ranges from
0.054-0.108 t/ha (1-2 bu/ac). Higher seeding rates result in higher plant populations, producing a smothering effect for weed control. However, even if the stand is thin, the plant's ability to branch out will often compensate for the thinner stand and will still result in good weed control. When using the higher seeding rate, divide the seed in half and cross-plant the field with the grain drill. This appears to give better spacing of plants with fewer tall, thin stems and subsequent lodging problems.

Flowering begins 5-6 weeks after sowing and continues for at least 1 month. There are three flower sets with buckwheat. Insects, honeybees and leafcutter bees are the main pollinating agents and are essential for good seed set. An arrangement with an apiarist will be of mutual benefit.

As a Green Manure

Buckwheat has the reputation of using phosphate unavailable to other crops, thereby increasing the amount of phosphorus available to following crops. To take advantage of its large biomass, buckwheat is incorporated between 4 and 7 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 plants start to crinkle when stepped on, it is time to be disked into the soil. If the field is left until full bloom, there is more likelihood of volunteer problems the following year. A second or even third planting may be possible in long growing seasons.

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Fertility

Fertility requirements for buckwheat are similar to oats. Table 9-1. Phosphate and Potash Recommendations for Buckwheat and Flax Based on OMAFRA-Accredited Soil Tests and Table 9-2. Nitrogen Requirements for Buckwheat Based on OMAFRA-Accredited Soil Tests display the recommended rates of phosphate and potash and nitrogen based on OMAFRA-accredited soil tests.

Caution: Buckwheat is prone to lodging with high soil nitrogen.

100 kg/ha = 90 lb/ac

¹No expected agronomic response from additional application of nutrients. Ratings of "Excessive" may result in reduced yield or affect nutrient balance in crops. For example, additional phosphorus application to a soil>60 ppm phosphorus could induce a zinc deficiency on soils low in zinc and might also increase the risk of nitrate movement into groundwater, while additional potash application to a field already>250 ppm K soil test could induce magnesium deficiency on soils low in magnesium.

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Harvest and Storage

Harvest

Buckwheat is an indeterminate plant. Flowers, green seed and mature seed are present on the plant at the same time. Harvest must occur prior to the development of overripe seed. This will be approximately 10 weeks after planting. At this time, the crop is still growing and flowering, however 70%-75% 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, yields will be decreased due to seed dropping and the volunteer population will cause problems for the next crop. Yields will vary depending on pollination and weather conditions. Yields of 2.2 t/ha (40 bu/ac) are possible but 1.1-1.6 t/ha (20-30 bu/ac) are more commonly reported.

Desiccation weakens the stem and causes lodging. Do not desiccate buckwheat. Swathing should be done before combining if the crop has not been killed by frost. Swathing is best done early in the morning when the dew is present or in damp weather to help minimize losses due to shattered seed. Cut the buckwheat, leaving a high stubble to facilitate drying. Leave it to dry until moisture in the seed head reaches 16%.

When combining, reduce the pick-up speed to match the ground speed so as to minimize shattering. The draper-type of pick-up causes less shattering than the drum-type. To minimize breakage, reduce the cylinder speed to one-third (600-800 rpm) that used for cereal grains and the concaves set to approximately 13-16 cm (5^1/4-6^1/2in.) in the front and 9 mm (^3/8 in.) in the rear. The upper sieve is set at 16 mm (^5/8 in.) and the lower sieve at 8 mm (^5/16 in.). If seed is dehulling, increase concave size or lower cylinder speed. 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, wait until 7-10 days after a light fall frost before direct combining. Keep the cut as high as possible and ground speed low to prevent overloading the combine. Pay attention to the amount of coarse material that is allowed to pass through so that only a minimum of seed enters the return. In this way, breakage will be reduced.

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Storage

A moisture content of less than 16% is needed for safe storage. The Japanese market buys only freshly harvested buckwheat, so do not store seed to sell the following year and do not mix old and new crops. It is easy to detect the difference between previously stored and newly harvested buckwheat by the colour of the grain just under the hull. Old seed oxidizes, and the light green layer just under the hull in new seed gradually changes to reddish-brown during storage.

Livestock Feed

Buckwheat grain can be used for livestock feed on a limited inclusion in the ration. Buckwheat grain can be up to one-third of the grain concentrate portion of the beef or dairy ration. More recent swine feeding research with newer varieties of buckwheat found that the overall performance of growing-finishing pigs was comparable to pigs fed cereal grains. However, the price of buckwheat makes this not as economical as feeding cereals.

Caution: Feeding the fodder, whether fresh or dried, can have toxic effects. The primary toxic effect is a photosensitization in animals with light-coloured skin (this includes cattle, goats, sheep, swine and turkey) exposed to the sun. Jaundice is a secondary toxic effect.

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Weed Control

Weed control in buckwheat can be difficult and requires planning, since there are few herbicides available, particularly for broadleaf weed control. Since buckwheat is sown late, there is ample opportunity to control problem weeds with herbicides or cultivation before seeding. Do not use residual herbicides (i.e., residues from the triazine, sulfonylurea and trifluralin herbicides) before seeding.

For current weed control options, refer to OMAFRA Publication 75, Guide to Weed Control.
(Order OMAFRA Publication 75)

Insects and Diseases

Buckwheat seldom has insects and diseases concerns.

Updates on Other Crops: Buckwheat

No updates available at this time.

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