NDSU Crop and Pest Report

Plant Science

ISSUE 12  July 17, 2003


Recent wet conditions in soybean fields have, in some cases, resulted in very yellow soybeans. Many different causes or a single stress may be contributing to the change of color. Start by checking the variety planted and the soil pH. Iron chlorosis is showing up in many of the fields, especially those planted to varieties with poor iron chlorosis tolerance and on soils having a pH of 7.8 or higher. Iron chlorosis can be accentuated with soil wetness that increases bicarbonate solubility in soils and may elevate soluble salt levels, further stressing the soybeans.

Any herbicide applications that were made right around the first trifoliate leaf stage on soybeans may also contribute to the stress on the soybeans if the plants were already stressed with iron chlorosis, varying temperatures, wet feet, insects, weed competition, disease, soil compaction or other previous damage such as hail. Generally, yellowing quickly disappears from soybeans once drying occurs and warmer sunny weather. However, this year the problem seems to have come early and is still lingering. Top growth on the soybean plants should now begin to green and continue if the plants are to have good recovery. Hopefully green color should return within two to three weeks unless continued stresses further slow plant development.



Pea growers need to carefully monitor the crop as it nears maturity in order to harvest on a timely basis. Harvest timing is especially important if the crop is to be marketed as seed, or to meet contract specifications for human food or specialty feed markets.

Field pea generally reaches physiological maturity in 85 to 105 days depending on the variety. Field pea may be swathed before combining or straight (direct) combined. Peas are normally swathed if a variety with prostrate type of growth is grown, there is uneven crop maturity, or heavy weed pressure is present. When swathing peas, vines and pods should be a yellow to tan color. The crop matures from the bottom pods upward. Yellow-cotyledon peas should have seed that has turned yellow in color.

Field peas should be combined when the seed contains 14 to 20% moisture, to reduce splitting and cracking of the seed coat. At this moisture level, the seeds are firm and no longer penetrable with a thumbnail. Also, pea vines must have turned yellow (no green color present) otherwise harvest will be extremely difficult.

Straight combining is possible depending on variety grown and harvest equipment available. Short-vine and semi-leafless pea grain varieties have characteristics that are adaptable to straight harvesting compared to varieties with indeterminate and prostrate-vine growth. For example, semi-leafless peas have a more open canopy, remain erect longer, and dry down more rapidly after a rain or heavy dew compared to conventional vining varieties.

Direct harvesting can be accomplished using a combine header with a floating cutter bar or a flex header. Also, attachments such as lifter guards and pickup reels reduce losses and improve harvest efficiency. Direct harvesting of weak and prostrate vine cultivars is most efficient with a an aggressive pickup attachment and a lead coulter on a standard combine.

Correct combine settings and operation are important to maintain seed quality. Low cylinder speeds of 350 to 600 rpm, should be used to minimize seed cracking or splitting. Initial concave settings of 0.6 inch front clearance and 0.2 inches at the rear are suggested. Also, adjust combine settings as weather and harvest conditions change. Combine and all portable augers should be operated at full capacity and at low speeds to minimize seed coat damage and reduce splits.



An open invitation is extended to soybean producers, their families and friends to the annual Soybean Plot Tours and Suppers during the first week in September. The events are free of charge and sponsored by the North Dakota Soybean Council, the North Dakota Soybean Grower’s Association and Agri Business leaders in the area.

The evenings will begin with field tours followed by research updates on the latest developments for the future of the soybean industry. The Council has invested checkoff dollars in a series of promising research endeavors from production issues to industrial uses. All researcher conducting projects funded by checkoff dollars will be providing producers with insight into their objectives and potential impact on the industry.

The plot tours are scheduled at the following locations:

Tuesday, September 2, 2003 at 5:00 PM
Jeff and Maxine Leinen’s Farm, Great Bend, ND

Wednesday, September 3, 2003 at 5:00 PM
Jon McSparron’s Farm, Grandin, ND

Thursday, September 4, 2003 at 5:00 PM
Dennis Feiken’s Farm, LaMoure, ND

Following the research portion of the program, all participants are invited to enjoy cold beverages and an evening meal. Door prizes will be awarded throughout the evening.



Yield loss in soybeans is determined by the stage of growth of the soybeans at the time of damage and the degree of plant damage. Damage can be due to leaf defoliation, stand reduction, stem damage and pod damage. The calendar date and pest control later also affect ultimate yield.

Check stands 7-10 days after a storm to determine the stand reduction. Determine the current stand versus the original stand. Count these losses as total losses if the plants are totally damaged below the cotyledons. Shredded or cut stems may lead to bruised plant stems. Mild bruising may only break in the outer stem tissue but severe bruising may expose the cental stem tissue and lead to more losses. Unfortunately, bruised stems that recover may break any time before harvest as they are weakened. They may lodge and make harvest very difficult. It is very difficult to determine yield loss from bruised plants until harvest.

Defoliation is a measure of the leaf area destroyed by the storm. Leaf loss on soybeans during vegetative stages has little effect on yield (if only the leaves are shredded); however, defoliation during reproductive stages does affect yield. Added damage to stems and branches may also decrease yields more, depending on the weather events the remainder of the season and if additional disease or insect damage results on damaged soybeans. The further along in maturity a soybean is, the more detrimental effect on yield.

Growth Stage

% Defoliation







% Yield Loss (estimated- with no flower/pod loss)

R1 - R2












Loss of excess flowers beyond the normal losses on soybeans or losses of pods will increase yield losses.

Duane R. Berglund
Extension Agronomist



There has been a great deal of lodging of small grains in North Dakota in the last week to 10 days. Some of these fields had the makings of exceptional crops. Depending on when it occurs, lodging can significantly impact yield and even if yield is only slightly reduced, lodging almost always negatively impacts grain quality. It can also make harvesting a nightmare. Unfortunately, there is really nothing that can be done at this point to reduce the impact of lodging as "lodging management" begins early in the season.

What is lodging?

Lodging is the term used to describe a crop when its stems have partially or completely fallen over from their normal near vertical orientation. There are two types of lodging. Root lodging is lodging that occurs at the base of the plant as a result of roots failing to anchor the plant. Root lodging is the most common of the two types and is the type that occurs earlier in the season. Stem lodging occurs when the stem breaks. Stem lodging can occur at any point in the stem, but most commonly occurs at the lower portion of the plant and usually later in the season as the plant begins to mature and stems become brittle. When root lodging occurs early (before grain filling), it is possible for some stems to partially erect themselves. This is accomplished by the plant bending at one of its nodes. These nodes tend to enlarge and have the appearance of "elbows".

What are the cause of lodging?

Lodging results from the combination of a number of factors, and is usually induced by strong winds. Lodging is most common in the later part of the crop’s growth, particularly during grain filling as more of the plant’s weight is shifted to the upper portion of the plant. The main factors that predispose a crop to lodging are:

What kind of losses are associated with lodging?

Yield losses resulting from lodging vary considerably. Some data suggests that losses up to 40% can occur if lodging occurs during the 10 days following heading. Grain yield losses will be much less if the grains are nearly filled. However, kernel damage and sprouting can occur in lodged fields that become wet. There may also be losses in labor as combining takes longer.

What can you do to prevent lodging in the future?:

A number of farmers have expressed interest in knowing how they might manage their fields in the future so that they do not have the problems of lodging that they are experiencing this year. Some suggestions are:

Joel Ransom
NDSU Extension Agronomist - Cereal Crops


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