ISSUE 1   May 5, 2005

PLANTING CORN IN COLD SOILS

The recommended planting date for corn in North Dakota is May 1st. However, with the unusually cold weather of the past two weeks, a common question is, should I wait until soil warm-up before planting corn? Corn begins germination when soil temperatures approach 50 degrees and requires between 120-125 corn growing degree days (GGDs) to emerge. It is not uncommon for corn to take between two and three weeks to emerge in North Dakota if planted in early May. Therefore, there is some risk when planting into cold soils that stand establishment will be reduced because of a prolonged germination process. By planting early, however, the crop will be available during the growing season. This could mean higher yields and lower moisture at harvest for the crop.

In an experiment in Devils Lake conducted last year the yield advantage when planting on May 4th compared to May 26th was between 25% and 50% depending on the hybrid. Furthermore, the early planted corn had 10% less moisture a harvest. Although the differences associated with planting date in this experiment were magnified in 2004 because of the exceptionally cold summer, these data illustrate the potential benefits of planting early. It is my assessment that the advantage of having an early emerging crop in most seasons will out weigh the risk of losing stand due to a prolonged germination process when soils are sub-optimal for germination when planting occurs. I therefore, recommend that corn planting not be delayed this spring because of colder than normal soils.

Establishing a uniform emerging stand is key to high corn yields. To improve stand establishment, make sure that seeds are placed at a uniform depth. A 2 inch seeding depth is recommended in most situations for uniform emergence and better root development later in the season. Also consider using a starter fertilizer so that the establishing plant will have ready access to nutrients. Roots develop slowly in cold soils and phosphorous update is dependant on the roots being clost to it. In no-till fields with medium to heavy residue, residue managers may hasten emergence as dark exposed soil will warm up faster than soil covered by residue.

Joel Ransom
Extension Agronomist
joel.ransom@ndsu.nodak.edu

 

FROST SYMPTOMS, TOLERANCE VARIES BY CROP AND CONDITIONS

Canola, Flax, Mustard: These crops can handle a frost of 24EF for a short time with canola the most tolerant to cold temperatures. Frosted leaves/plants will be dark green or black in color. If discolored or injured, wait at least 2-3 days before any decisions are made to see if the growing point is alive. Within 3 days, there should be a new leaf emerging from the growing point located in the center of the plant. The best indication that the plant has been killed by a frost is the stem. If the stem below the cotyledons is wilted and doesnít straighten out within 48 hours of the frost, the plant is more likely dead.

Pulse crops (field peas, lentils and chickpeas): Similar to small grains, the growing point is below the soil surface to the fifth node stage or about the 4" height stage. If the stem is collapsed, wilted on the soil surface for 48 hours and regrowth has not occurred, that plant has most likely been killed. Recovery is usually quick with the newest leaf emerging from the stem within 3 days.

Sunflower: When in the cotyledon stages, can withstand temperatures in the 25-26EF range for short periods of time if they are just emerging from the soil. Sunflower true leaves in the 2, 4 or 6 leaf stages become more sensitive with each development stage and the terminal bud can be permanently damaged. Itís believed that when sunflower are in the V2 stage, then the lower limit would be 26-27EF, whereas if sunflower are in the V4 or V6 stages then the lower limit would be 28-29E. If sunflowers become brown or blackened and the terminal bud is damaged then the plants will not recover.

Corn: Historically very few northern corn fields have been destroyed by spring freezes, although research is limited on this subject. Plants less than six inches tall (V-5) will usually recover from frost, because the growing point is still below the soil surface and usually not damaged. Lethal cold temperatures (28EF or less) can penetrate the upper inch or two of soil, especially if the soil is dry, and kill plant tissue including coleoptiles and growing points.

Non-lethal injury by cold temperatures may cause deformed elongation of the mesocotyl or physical damage to the coleoptile in non-emerged seedlings, resulting in the "cork-screw" symptom and subsequent leafing out underground.

Soybeans: Broad leaf crops that have the growing point at the top of the plant are more susceptible to frost damage than grass species. Thus, soybeans are quite sensitive to frost, and are easily damaged by frost in the 28-32EF range. Temperatures of 28EF for any extended period of time can completely kill soybean plants (buds, stems and leaves).

During the early seedling stage (VE to VC), soybeans have some tolerance to temperatures of 29-30EF for short periods of time. If the seedlings have been somewhat hardened off by cool temperatures for several days, then temperatures as cool as 28EF can be tolerated. Once true leaves emerge (V1 and V2), soybeans become more susceptible to freezing temperatures below 32EF for any extended period of time. Soybeans in the unifoliolate leaf stage are slightly more frost tolerant than soybeans in the first or second trifoliolate stages.

Average Date of Last Spring Frost

 

28EF

32EF

Fargo

May 4

May 12

Williston

May 4

May 13

Oakes

May 5

May 13

Bowman

May 6

May 14

Mandan

May 7

May 12

Grand Forks

May 6

May 16

Fessenden

May 8

May 17

Dickinson Exp. Station

May 12

May 19

Minot Exp. Station

May 12

May 20

Langdon Exp. Station

May 17

May 28

Source: National Climatic Data Center/ND Ag Statistics Service. Number of years used in average varies by location.

 

DRY SEEDBEDS REQUIRE SPECIAL TACTICS, OR RAIN

This year many North Dakota farmers face dry seedbed conditions as they set about seeding their crops. Both the topsoil and subsoils are very dry in a line from the extreme Northwestern corner of North Dakota to McIntosh county in the south central region of the state. Dealing with such conditions when seeding isnít easy.

Whether fields are dry or not, farmers should stick as closely as possible to the recommended planting schedule for each crop. Late planting can sharply reduce yields of small grains, flax, corn, dry peas, canola and mustard, especially in a year when June and July temperatures are above normal.

Under dry seedbed conditions it is true that planting on schedule may result in uneven stands but this is preferable to planting too late. If rains do come later, most seeds will still germinate if adequately protected with a seed treatment. Some soil crusting could present a problem if seeds are slow to germinate, so farmers should be aware of this possibility.

To minimize dryness problems, till at a shallow depth and cut down on seedbed operations before planting. Direct seeding or no-till may be the best option this year in many extremely dry regions of North Dakota. Itís also suggested that postemergence herbicides be used rather than preplant soil-incorporated herbicides that can cause additional soil drying and may not be as effective in dry soil.

Roots will not grow through dry soil even if seeds germinate. Use deep furrow hoe drills when available to reach soil moisture. Small grains and flax can be drilled directly into standing sunflower or soybean stubble with disc opener drills."

A double disc drill, is not as effective as a notill drill, a hoe drill or a narrow tine equipped airseeder in seeding to moisture in standing stubble. It perhaps would be beneficial in harrowing first and scattering the straw of previous crop residue prior to seeding.

"If newly emerged weeds are present, use a nonselective, burn-down herbicide before seeding." Some residual weed control may be present from dinitroaniline herbicides (Treflan, Prowl or Sonalan) used in 2004 if it was extremely dry in your area but be ready to spray and control volunteer sunflowers or other crop volunteers if they emerge with the crop.

Here are 10 suggestions to minimize effects of planting into dry soils:

1. Avoid excess tillage prior to planting. Each tillage operation causes soil moisture losses (1/3 to Ĺ inch).

2. Use shallow tillage (3 inch depth or less) to destroy weeds and firm the seedbed.

3. Avoid use of premerge soil-incorporated herbicides on crops where post emergence herbicides are available and economical.

4. Plant small grains directly into standing sunflower stalks, soybean, canola and dry edible bean stubble.

5. Crops like corn, sunflower, field peas and dry edible beans can be planted deeper (2 to 3 inches maximum). Flax, mustard, canola, proso millet, or buckwheat which all should be 1 inch or less in planting depth. Intermediate planting depths of 1.25 to 2 inches is best for wheat, durum, barley, oats, lentils and soybeans.

6. In general, large-seed-sized varieties of wheat or durum, oats and barley can be seeded slightly deeper than small-seed-sized varieties.

7. Seed treatments on small grains should be uniformly applied at labeled rates to maximize seedling emergence. Over treatment on some seeds and little to none on others can cause erratic stands.

8. If rains come after planting, watch for soil crusting. Break soil crusts with light harrowing or rotary hoe.

9. Consider post plant applications of nitrogen in the form of urea if good moisture conditions develop later. Rain is usually required in 48 hours after application to reduce N losses due to volatilization.

10. If fairly good stands are established, but dry soil conditions continue, plan a good weed control program to help conserve soil moisture for crop growth and development.

Duane Berglund
Extension Agronomist
duane.berglund@ndsu.nodak.edu


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