9/11/96 BOZEMAN -- A lack of soil moisture in most of Montana has put many winter wheat producers in a dilemma about if and when to plant.
In Montana, winter wheat usually is planted Sept. 10-25 if fall moisture is near normal. However, moisture is not normal in most of the state this year due to exceptionally hot dry weather since the last week of May.
Some people have no moisture in the top six to eight inches of soil, while others report no moisture in the top three feet, says Howard Bowman, Montana State University Extension agronomist.
Under those conditions, producers have a choice of delaying winter wheat planting until it rains or planting into dry soil and hoping it rains. There are potential problems associated with either choice.
"In normal years, the Montana Agricultural Experiment Station recommends planting winter wheat in the north-central areas of the state before Oct. 5 so the plants get enough growth to develop the variety's winter hardiness," says Agronomist Gregg Carlson, at the Northern Agricultural Research Center near Havre and Greg Kushnak, superintendent at the Western Triangle Research Center at Conrad.
Planting later than that can result in substantial winter injury, because not enough time is provided to achieve a three-leaf stage of fall growth.
Since seeding late usually reduces yields, Bowman recommends that the seeding rate be increased from the conventional 60 pounds of seed per acre to 70 pounds per acre to compensate for the late planting.
Where seeding for fall germination cannot be done by Oct. 5, further delaying seeding until November or even later can sometimes prevent winter injury simply by preventing the seed from germinating in the fall. The seed then should germinate early in the spring but still have enough cold to trigger the plant to produce seed.
"It's still best to plant between between Sept. 10 and 25," says Carlson.
The temptation is to plant deeper than two inches to be closer to deep moisture. However, that reduces seedling emergence for most varieties, says Dave Wichman, agronomist at the Central Agricultural Research Center near Moccasin.
If surface moisture is adequate or only three to four inches deep, hoe drills with packer wheels help draw subsoil moisture toward the seed, says Wichman. That can provide ideal conditions for germination and plant growth. If soil moisture is down five inches or deeper, planting deep may only provide enough moisture for germination. Without additional moisture, the seedling would rapidly desiccate.
Some varieties with a longer first leaf that pushes through the soil may be planted deeper, as deep as three inches, says Phil Bruckner, MSU winter wheat breeder, but those varieties have not been tested under Montana drought conditions. In greenhouse tests Roughrider, Blizzard, Weston and Winridge have had the longest first leaf and Norwin, Judith and Nuwest the shortest.
Seeding into stubble provides a longer period with suitable conditions for germination and the seedling, because the environment is moderated. Temperature fluctuations are not as extreme and the surface soil does not dry as quickly. Also, in stubble there is less chance of soil erosion burying emerged seedlings.
Seeding into stubble also gives a longer period with suitable germination conditions for weed seeds, so before producers seed into standing stubble, they should control winter annual weeds and volunteer cereals.
Volunteer grain is always a risk in recropping, says Carlson. This makes variety selection and cropping sequence important to minimize the risks.
Recropping is only appropriate if the variety the preceding year does not have high seed dormancy. If the variety had high dormancy, any seed left in the field at harvest might not germinate when it could be controlled by tillage, spraying or freezing if it is spring grain. It might not germinate until the next spring when it could contaminate either a fall- or spring-seeded crop of a different specie or variety.
Harrington, Chinook and Lewis are popular barley varieties with low fall dormancy and quick germination in lab tests. Baronesse and the variety Bowman are intermediate in fall seed dormancy, with increasing dormancy for Gallatin, Hector, Stark and Steptoe.
If winter wheat follows spring wheat, the volunteer spring grain causes little economic damage, because all varieties need moisture and temperatures above freezing to germinate.
Weed problems also can increase when winter wheat growth is limited.
The less growth winter wheat gets, the greater the infestations of wild oats and other weeds tend to be in the spring. Some producers may elect to apply triallate in the fall to control wild oats the following spring. However, if conditions are not suitable for germination and seedling establishment, the non-emerged wheat seedling can absorb too much triallate over the winter. If winter wheat does not survive the winter, use a triallate-tolerant spring wheat variety to re-seed.
To control Cephalosporium stripe disease, producers should avoid planting until the soil temperature four inches deep drops below 55 degrees at noon," says Jack Riesselman, Extension plant pathologist.
Shallower soil temperatures change dramatically from hour to hour. The four-inch temperature indicates that a trend has taken place rather than a spike in the system.
"Seeding into dry soil also dramatically increases the potential for seed decay by soil-borne fungi," says Riesselman. Fungi that reduce gemination thrive on seed lying in dry soil for extended periods. He recommends that producers forced to plant into dry soil treat winter wheat seed with imazilil. Dividend and captan can also be used, but they are slightly less effective.
Producers may want to fertilize differently if they are seeding into dry soil.
"With the dry seed bed, placement of fertilizer too close to the seed can prevent germination or damage young seedlings," says Jeff Jacobsen, Extension soil scientist.
Under normal planting conditions with good seed bed moisture, Jacobsen said he generally recommends no more than 30 pounds per acre of nitrogen plus potassium be placed directly with the seed. If the placement is with an air-seeder or with an implement with spreader plates that mixes the fertilizer with a large volume of soil, the amount can be increased.
Under dry conditions, the amount of fertilizer that can be put with the seed is less and producers may want to wait to fertilize at all.
"There are probably enough residual nutrients for fall growth," says Jacobsen. When precipitation comes, whether this fall, during the winter or early spring, more nitrogen could be top-dressed. The amount added can take additional soil moisture -- or its lack -- into account as well as residual nitrate-nitrogen levels and the yield potential.
Ideally, some phosphorus should be placed near the seed to promote early root growth in the young seedlings when moisture conditions become more favorable.
If the dry fall continues the producer still has the option to plant spring wheat.