NDSU Crop and Pest Report

Plant Science


ISSUE 3  May 15, 2003

 

FLAX PLANTING RESPONSES

Seeding Rates: NDSU Ext. Circ. 1038 entitled "Flax Production in North Dakota" suggests flax seeding rates of 20 to 45 lbs. per acre. Lower rates of 20-30 lbs/A in the west and 35-45 lbs/A in the eastern high rainfall areas. Flax seedling stands may sometimes be poor due to dry soils, deep seeding, soil crusting, herbicide injury or other factors. Results below show that higher yields can result from lower seeding rates and also result in less lodging in lodge prone environments.

Seeding
Rate

Environments

Lodging

Non-Lodged

Lodged

lbs/a

------------Yield (bu/a)-----------

0 to 9

20

23.1

27.2

1.6

30

25.1

27.5

1.9

40

25.6

23.6

4.8

50

26.7

25.0

4.4

60

27.1

23.0

4.3

LSD 5%

1.2

NS

2.4

3 yrs., Langdon, Cavalier and Tolna, ND
Lodging Scores: 0=no lodging 9

 

DECISION TO REPLANT CAN BE DIFFICULT

Unexpected stand losses from flooding, late spring frosts, hail, insect or disease damage, herbicide or fertilizer injury or other causes can put corn and soybean producers in the position of evaluating the crop for possible replanting. Growers should assess the need to replant carefully and not make a quick or uninformed decision. Especially with low crop prices making it important to hold production costs down, careful consideration of the replant decision is essential.

Growers faced with reduced stand should first scout the field thoroughly to determine the plant population and compare the actual stand to the desired population. Requirements of a crop insurance plan may be a consideration when considering replanting. Another major point is to compare the original planting date to the likely replanting date.

Besides considering crop losses from a planting made at a later date, add in the cost of the replant seed and other replanting and pest control costs. This information along with yield loss or gain from a later planting can be used to determine if replanting is worth the time, money and effort.

Estimating plant population involves counting the number of viable plants in a length of row that equals 1/1000 of an acre in several spots across the field—six to eight spots across every 80 acres is a good sample. Average these counts and multiply by 1000 to get the plant population.

Length of row needed to equal 1/1000 acre varies with planting row width. In 22-inch rows the length will be 23.8 feet; in 30-inch rows it is 17.4 feet.

Actual stand counts will give a good estimate of plant population. Guessing at the population remaining in the field is more difficult. The National Crop Insurance Service corn loss instruction book shows with corn under 10 leaf stage that a 75 percent stand will result in a 8 percent yield loss, a 50 percent stand in 27 percent loss, and a 25 percent stand in a 43 percent yield loss. Yield losses may increase with uneven distribution or large gaps or skips in the stand.

Actual stand counts are important in soybeans, as guessing at the remaining population is even more difficult. Length of row to equal 1/1000 of an acre goes from 87 feet in 6-inch rows, to 52.3 feet in 10-inch rows, and 17.4 feet in 30-inch rows. Yield loss in soybeans may increase if seedlings are unevenly distributed.

Growers need to consider the yield loss incurred from replanting at a later date. Yield losses from adapted corn hybrids in North Dakota and northwestern Minnesota are negligible until after May 10th, when later planting will result in a shorter than normal growing season. In this northern corn growing area, yield losses increase rapidly, from 10 percent or more through May 15th, 20 percent or more to May 25, and 33 percent or more after June 1.

With soybean, yield losses of adapted varieties in the Red River Valley are usually negligible until May 20. Depending on weather, possible yield loss can be around 15 percent from May 20 to May 31., and up to June 10, losses can be around 25 percent. Soybeans planted as late as mid to late June can have a 50 percent or more yield loss compared to more timely planting.

 

WET CONDITIONS REQUIRE PATIENCE

With the rain in recent days, demonstrating some patience now will be a key if producers want to avoid potential problems later in the growing season. Waiting until the soil has dried sufficiently before working will result in more favorable seedbed conditions maximizing plant stands and final yields.

Tillage of wet soils for seedbed preparation can result in excessive clod formation, poor seed soil contact, an uneven and dried-out seedbed, poor mixing and incorporation of chemicals, uneven erratic seedling emergence, and reduced plant stands. Don’t be in a big hurry to work wet fields. Patience is the best recommendation when fields are wet. Waiting 1 to 2 additional days usually will not lengthen the growing season, but will greatly aid in obtaining a good seedbed for planting and to maximize plant stands.

When planting in compacted wet conditions the seed is put in an anaerobic environment. When seed germinates in an anaerobic environment, the lack of oxygen generally results in the death of the germ. Seeds that do survive will be weak and the wet soil conditions may be more favorable for the development of soil borne pathogens that otherwise may not be a problem. The end result is reduced stands and lower yields

Germination of soybeans or sunflower in compacted or crusted conditions will hinder seedling growth, preventing hypocotyl arch emergence and soil penetration of the radicle, retarding root development. In addition, any crusting that occurs will further prevent the hypocotyl and cotyledons from emerging resulting in seedling loss. The end result of both is an erratic and reduced stand. Uneven crop stands typically yield lower than uniform stands due to direct competition of plants at different stages of growth growing next to one another.

Duane R. Berglund
NDSU Extension Agronomist
dberglun@ndsuext.nodak.edu

 

ERRATIC WEATHER AND EARLY SEASON CEREAL CROP DEVELOPMENT

As a newcomer to North Dakota, I have been surprised by the wild swings in our spring weather this year. After talking with a few "old timers" and reviewing climatic data for the past 30 years, I now appreciate the fact that we are currently enjoying a "typical" (variable and unpredictable) North Dakota spring. The first few weeks of spring represent only a fraction of the total growing season, but the weather during the first few weeks after planting can have a dramatic effect on the overall productivity of a crop. Although there is little one can do to change the weather, there are a few management practices that can be employed to reduce the detrimental effects of adverse weather and exploit the "opportunities" of good weather. During the last month, temperatures have varied from above average in April to below average in May. April was unusually dry, and May has been wet. In the last week there have been reports of water logging, hail damage and freezing temperatures.

The warm and dry weather of April enabled many farmers to plant their small grains early. These early planted crops have now emerged and after the recent moisture and cool days, are beginning to develop nicely. One farmer that called me earlier this month said that his crop of wheat was the best he had had for years. Planting early generally favors the development of high yield potential in small grains as it enables the seedling to be exposed to cooler temperatures, which promotes the development of more uniform and larger spikes and a larger leaf area to support the filling of these larger spikes. Planting early is a management practice that can consistently enhance productivity in small grains.

Many farmers were able to plant some or all of their corn before the heavy and widespread rains that begin on May 3rd put the breaks on planting. May 1st is considered the optimum date for planting corn in all parts of the state. Corn germination, emergence and early growth requires warmer temperatures than small grains, but high yield potential in corn is also favored by moderately cool temperatures during the early growth and development of the corn plant. I have heard reports that corn is starting to emerge, but the corn I planted the last week in April in Fargo has not yet seen the light of day.

Plant growth and development is closely related to the accumulation of growing degree days (also referred to as heat units and growing degree units). Growing degree days (GGD) are calculated by summing for the period of interest the average daily temperature [(max + min)/2] minus a base temperature that is crop dependant (e.g. 32E for wheat and 50E for corn). GDDs can be obtained for a range of locations in ND from the NDAWN website ( http://ndawn.ndsu.nodak.edu ). Table 1 lists the growing degree accumulations for selected sites in ND for both wheat and corn for this year.

Table 1. Growing degree accumulations for selected locations in ND, for the 2003 growing season.

Location

Wheat based GDD 4/15 - 5/11

Wheat Leaf Numbers

Corn based GDD
5/1 - 5/11

Carrington

410

2.1

40

Dickinson

439

2.3

36

Fargo

460

2.5

56

Hettinger

410

2.1

35

Langdon

393

2.0

42

Mandan

444

2.3

44

Minot

454

2.4

41

Wahpeton

426

2.2

53

Small Grain Development and Management

As mentioned previously, the early planted small grain crop has emerged and currently has between 2.0 and 2.5 leaves (see Table 1). Until the four leaf stage, small grain plants are initiating new leaves. The yield component of plants per given area is more or less fixed at this stage (some plants may die but no new plants are likely to emerge). The most important tillers develop during the 2 to 3.5 leaf stage of the main stem. Any stress during this time may hinder the development of these tillers and the adventitious roots associated with them. If they do not form at this time, they cannot develop later.

The reproductive phase begins shortly after the 4 leaf stage. It is during the reproduction phase (4 leaf stage through to flowering) that the vast majority of the yield potential of the crop is established. Tiller numbers, spikelet per spike and grains per spikelet are all fixed during the reproductive phase. Not surprisingly, any stress during this stage can have a dramatic effect on yield. As mentioned previously, controlling the weather is not feasible, but some abiotic and biotic stresses during this period can be managed. Nitrogen stress should be eliminated through top dressing before the 6 leaf stage (more on that elsewhere in this issue). Similarly, weeds should be controlled in a timely manner so that they do no interfere with the growth and development of the crop at this stage.

Corn Emergence

Corn typically requires an accumulation of about 125 GDD from seeding before it emerges. As you can see from Table 1 we have some heat units to go before we reach 125 GDD throughout the state (assuming a 1 May planting date). During cool springs, corn can take between 28-35 days to emerge. Emergence is slowed when seeds are planted deep, in soils that are heavy and/or that have a heavy residue cover, and when soils are drier than optimum. Don’t get too concerned if emergence takes up to 30 days during a cool spring. Most seed treatments provide protection from insects and diseases for more than 45 days.

With the continuing rain, I am now becoming concerned that corn that has not already been planted might be planted too late. Corn yield can decline by 15% if planting is delayed from the 1st to the 20th of May. After the 20th of May it is recommended that you switch from your full season hybrid to an earlier maturing one. In the many states corn borers cause more damage in late planted corn than in early planted corn, making the use of a BT hybrid a more profitable option for later plantings. There is no data, at least that I am aware of, that would indicate that later corn plantings suffer greater losses from stem borers in North Dakota. Nevertheless, it may be something for you to consider if you are faced with switching hybrids and planting late.

Joel K. Ransom
Extension Agronomist - Cereal Crops
joel.ransom@ndsu.nodak.edu


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