by Keith Brown
Divide County North Dakota Extension Agent
Field Peas: Firm seed to soil contact is critical when seeding peas. Peas take over three times more water for germination than small grains. Peas should be seeded at least an inch into moisture and never seeded at the interface where moist soil meets dry soil. Seeding peas 1 Â½ to 2 inches is preferred, however, if top soil conditions are dry, peas can be seeded up to 3 inches deep.
Pea Plant Population: Most pea varieties will have 1600 to 2400 seeds per pound with 2000 seeds per pound considered average (see the information on determining seed counts and planting rates later in this AgAlert). The optimum plant population for field peas is 300,000 plants per acre or 7 to 8 per square foot. Seeding heavier than the recommended rate can increase the risk of lodging. Reducing the seeding rate will also increase the potential for lodging as plants will be spaced to far apart and have less support structure. In case of stand problems, a minimum stand is considered to be 3 to 4 plants per square foot.
Seed Treatment Considerations: Peas will germinate at 38Â°F soil temperature. If soil temperatures stay cold, low 40's, it will take 14 plus days for peas to emerge. If seeding peas into cold wet soils or onto broadleaf (canola, flax, etc.) ground, seed treatments should be highly considered. Seed treatments such as Apron or Allegiance provide excellent control of soil-borne diseases such as pythium. Pythium has caused poor stands/seed rot recently in peas, especially when emergence is delayed due to cold soils. Maxim can be added to Apron or Allegiance to provide control of rhizoctonia and fusarium. Both seed treatments are safe on inoculants. When using seed treatments the granule inoculant is preferred. If using liquid or peat base inoculants, allow the seed treatment to dry before applying the inoculant to the seed. Do not apply seed treatments and liquid/peat inoculants at the same time with peas or lentils.
Seeding Lentils: Lentils should be seeded 1 Â½ to 2 inches deep. The optimum seeding rate for lentils is 500,000 plants per square foot or 12 plants per square foot. A minimum stand for lentils is 5 to 6 plants per square foot. Lentils require slightly warmer soil temperatures for germination and emergence compared to peas.
Air Seeder Precautions: When seeding pulse crops with an air seeder, caution is advised as seed damage may occur if the seed is too dry (below 14% for lentils and 16% for peas) and/or if the air velocity in the distribution system is too great. Cracking and chipping seed as it goes through the air seeder will reduce the germination percentage of the seed. To minimize damage, the lowest possible air speed that avoids plugging should be used. To obtain low enough airflow rates to reduce seed damage in some machines, it may be necessary to reduce the travel speed. Since a lower speed requires lower seed flow rates, a lower air velocity will carry the lesser quantity of seed without plugging. Refer to your manufacturer's recommendations for optimum fan speeds and air seeder configuration.
Pulse Crops and Ascochyta Seed Tests: Due to regional disease problems in pulse crops last year, many growers have tested their seed for ascochyta. Although all three pulse crops are affected by ascochyta, different fungal pathogens cause the disease on each crop. Thus, ascochyta on lentil will not infect pea or chickpea. Ascochyta is the biggest concern in chickpea. It is recommended that seed lots with no ascochyta detected be used for chickpeas if at all possible. Seed lots with no more than 0.3 percent infection could be used if they are treated with LSP or Mertect.
In lentils, treating seed with LSP or Mertect would be advisable if ascochyta is found in the seed and is highly recommended once seed infection rates exceed 0.4 to 0.5 percent ascochya. A recently obtained section 18 emergency exemption allows for the treatment of lentils with LSP or Mertect. Seed lots with greater than a 2 percent infection rate should not be used for seed, even if treated.
On peas, Ascochyta diseases can be caused by a complex of three different pathogens that are specific to field pea. However, unlike chickpeas and lentils, there doesn't appear to be any disease transmission from pea seed to seedling. As such, seed lots with up to 4 to 5 percent should be ok to plant. No fungicide seed treatments are available for peas that protect from seed-borne ascochyta in North Dakota.
Preplant or Pre-Emergence Weed Control in Pulse Crops: What can we spray as a preplant burndown for the abundant winter annual populations and kochia this spring in pulse crops?
Glyphosate: Glyphosate is labeled as a preplant burndown or a PRE option for control of early emerging broadleaf weeds. Higher rates of glyphosate should be considered for winter annual and kochia control. Do not add 2,4-D, Banvel, or other broadleaf herbicides to the glyphosate as severe seedling injury can occur. The only exception would be Aim, which can be added to glyphosate to improve kochia control as a burndown with pulse crops. Glyphosate is not very effective on kochia that has just emerged or that is in the "fuzzy" stage. Aim should provide excellent control of small kochia; especially under "droughty" or dusty conditions. Do not expect Aim to give satisfactory control of wild mustard or volunteer canola.
Glyphosate can be tank mixed with most preplant herbicides such as Prowl, Sencor, or Spartan. Consult herbicide label for mixing and compatibility restrictions with glyphosate. Avoid early morning applications when temperatures are at or close to freezing. Glyphosate should be applied when air temperatures are above 50Â°F. Keep rates up when going after harder to control winter annuals such as, prickly lettuce, tansy mustard, and field pennycress, or during cool conditions.
Pursuit: Pursuit is labeled as a PRE application in field pea and lentil. Field pea has good tolerance to pursuit; while lentil tolerance is marginal to good. Pursuit at 2 fl oz/acre or Pursuit DG at 0.72 oz WDG can be added to a glyphosate burndown for volunteer canola, improved mustard and winter annual control in field pea. It is recommended that the half rate of Pursuit (1fl oz/A) or Pursuit DG (0.36 oz WDG) be used in lentil. Keep in mind that user assumes all risk of crop injury. Crop injury potential increases when cold or wet soils delay crop emergence. Hill-tops, low organic matter soils, or sandy/light soils also have more potential for increased crop injury with lentil. Refer to label for tank-mix options, application recommendation, rate structure, and crop rotation restrictions.
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