I have been receiving questions about the impact of early planting on agronomic performance of field peas and chickpeas, especially as it relates to disease management.

FIELD PEAS

From 2017 to 2020, the Carrington and Williston Research Extension Centers conducted field studies evaluating the impact of planting date on field pea agronomic performance, with studies conducted in Carrington, Williston, and on-farm locations in Mountrail, McLean and Williams Counties. These studies were conducted to identify strategies to improve management of root rot in field peas, but the lessons learned from these studies are broadly applicable to all field pea production. Two sets of studies were conducted: studies planted to fields with a history of severe root rot in field peas, and studies planted in fields with no history of root rot but inoculated at seeding with the pathogen causing Fusarium root rot.

In fields with a prior history of root rot problems in peas, early planting was associated with sharp reductions in root rot severity. However, early planting was associated with reduced emergence, especially when soil temperatures averaged less than 45°F (at seeding depth, 2 inches deep) in the 7 days after seeding. Yields were maximized when soil temperatures at seeding depth averaged 45 to 50°F in the 7 days after planting. 

Similar results were observed when peas were grown in fields with no history of root rot in field peas and inoculated with the Fusarium root rot pathogen, except that field pea emergence was higher across all planting dates and no yield penalty was observed in early planting.

The results indicate that early planting carries the risk of reduced emergence in field peas. In most cases, this reduced emergence is due primarily to seed decay and damping-off caused by Pythium or Rhizoctonia, diseases which are most severe in cool, wet soils. When soils are dry, such as is being experienced across much of North Dakota and northeastern Montana this year, the risk of reduced emergence is lower.

When cool, wet soils are anticipated between planting and emergence, the use of a fungicide seed treatment with activity against Pythium and Rhizoctonia improves field pea emergence. In field trials conducted in fields with a history of root rot in field peas, fungicide seed treatments increased field pea yield by an average 3 to 5 bu/ac when soil temperatures were <55°F (at seeding depth, 2 inches deep) in the 7 days after seeding. 

CHICKPEAS

There are strong agronomic advantages to planting chickpeas early - at the same time as planting wheat or very shortly after planting wheat. The Kabuli-type chickpeas with reduced susceptibility to Ascochyta blight that are widely planted in the Northern Plains are late maturing, especially when wet weather occurs in July and August. Early planting facilitates timely crop senescence.  When planted at the same time as wheat, the widely planted Kabuli-type varieties 'CDC Frontier', 'CDC Orion' and 'CDC Leader' generally begin senescing in the second half of August even when wet weather extends into July and August. When chickpeas are planted in the second half of May and wet weather occurs mid-summer, these varieties often remain green until the first killing frost.

Early planting of chickpeas has been limited primarily by concerns about soil-borne and foliar diseases. Chickpeas are very susceptible to seed decay and damping-off caused by Pythium and Rhizoctonia, diseases which are most severe when soils are cold and wet. Chickpeas are also very susceptible to the foliar disease Ascochyta blight, and airborne spores released from diseased, overwintered chickpea residues are one of the most important mechanisms of Ascochyta infection. These spores are carried aloft by air currents, travel hundreds of miles in the upper atmosphere, and are deposited during rainfall events. The release of these spores is highest in early spring, and, in the Pacific Northwest, delayed planting has been used to try to reduce Ascochyta infection.

However, with proper attention to disease management, early planting of chickpeas can be very successful in our geography. Soil-borne diseases can be successfully managed with fungicide treatments, and Ascochyta blight can be successfully managed with timely applications of the most effective fungicides.

Fungicide seed treatments with activity against Pythium and Rhizoctonia facilitate excellent chickpea emergence and vigor when cold, wet weather develops after planting.

The following picture illustrates the effectiveness of fungicide seed treatments very clearly. These chickpeas were planted in Carrington on April 22, 2017. Strips of chickpeas were planted to untreated seed or seed treated with Apron Maxx RTA (5 fl oz/cwt). Soil temperatures at seeding depth were above 50°F at planting, but cold, wet weather set in shortly thereafter. Over the next 4 days, 0.53 inches of precipitation fell as a mixture of rain and snow, daytime highs dropped to 33-35°F, and soil temperatures at seeding depth dropped to 36 to 37°F. The chickpeas planted without a seed treatment had very poor stand establishment and never developed a good canopy. The chickpeas planted with the fungicide seed treatment showed good emergence and strong vigor, developed an excellent canopy, and yielded 2,500 lbs/ac.

In the Pacific Northwest, chickpeas are commonly planted relatively late in order to reduce exposure from air-borne spores of the Ascochyta pathogen that are produced on overwintered chickpea residues, but the effectiveness of this strategy in the Northern Plains is unclear. In the Northern Plains, spring comes later and mid-summer rains are more common, and significant Ascochyta blight pressure is often observed even when chickpeas are planted late.

When the most effective fungicides are applied when Ascochyta is first developing (one to two lesions per plant on up to approximately 5% of the plants) and follow-up applications are made 10-14 days apart as long as wet weather persists, Ascochyta blight can be managed very successfully. When chickpeas are planted early, senescence is generally observed in mid-August even if rainfall continues through July and August. The earlier senescence conferred by early planting facilitates timely harvest and also reduces late-season disease development on chickpea pods after fungicide applications cease.

In Carrington, we have found that we optimize chickpea agronomic performance with early planting even in wet years. The use of fungicide seed treatments is critical in chickpeas when soils are cool and wet after planting, but the fungicide seed treatments are highly effective even when soils remain cool and wet for an extended period after planting. In dry weather and dry soils, such as that observed across much of North Dakota and northeastern Montana this year, the risk of poor emergence in early-planted chickpeas is greatly reduced, and fungicide seed treatments are less likely to be needed.

Michael Wunsch, Ph.D.
Michael.Wunsch@ndsu.edu
Plant Pathologist