ISSUE 4 May 27, 2004
WINTER SURVIVAL OF WINTER WHEAT IN 2003/2004
Based on the reports that I have received this spring, most winter wheat survived the winter quite well, even though conditions for winter wheat establishment were less than ideal last fall and temperatures quite severe during the winter. In most regions of the state good snow cover protected the crop during the coldest months of the winter. Nevertheless, this spring I have passed a number of fields where the winter wheat crop looked ragged. In all cases, these fields had little or no previous crop residue to aid in holding snow. Photo 1 is an example of poor winter survival of a winter wheat crop grown where there was limited previous crop residue.
Photo 1. Poor winter survival
in parts of a field associated with
little previous crop residue
There are a number of factors that affect winter wheat survival, including planting date, temperatures during the winter and early spring, variety, snow cover, fall growth, soil phosphorus levels, etc. In most years, the two most important and easily managed factors are variety and crop residue. I recently evaluated the winter survival of winter wheat varieties that I planted last fall in two location, one in 8 inch tall wheat stubble the other in soybean stubble. Table 1 summarizes the winter survival of selected varieties in these two locations.
|Table 1. Percent winter wheat survival of selected varieties grown near Casselton (soybean residue) and Lisbon (wheat residue) 2003/04 (ranked by highest average survival to lowest average survival).|
These data clearly demonstrate the importance of both variety and crop residue on winter survival. The varieties released by either North Dakota State University (Elkhorn, Jerry, Ransom and Roughrider) or Canadian institutions (CDC Raptor, CDC Falcon, McClintock, and Norstar) tended to be the most winter hardy. Varieties developed for Nebraska (Arapahoe, Goodstreak, Harry, Jagalene, Millennium, Nekota, Nuplains, Wesley, and Wahoo), tended to be the least hardy and those developed in Montana and South Dakota, were somewhat intermediate. Winter survival, moreover, averaged 14% greater in Lisbon where the plots were planted in wheat stubble than in Casselton, where soybean was the previous crop. Photo 2 illustrates the difference in winter survival of two varieties in Casselton in 2004.
Photo 2. Winter survival of a non-winter
hardy (left) and winter hardy (right)
varieties in 2004.
Winter wheat has the capacity to tiller heavily and fill in if stands are sub-optimal. Currently, we recommend that you consider planting a spring crop if your winter wheat stands fall below 5-11plants/ft2 . (That compares to 8-14 plants/ft2 for spring wheat).
If you are planning on planting winter wheat this fall, make sure you select a winter hardy variety and if possible, plant your winter wheat following a crop with sufficient residue to catch and hold at least 2 inches of snow.
ENVIRONMENTAL EFFECTS ON EARLY DEVELOPMENT OF SMALL GRAINS IN ND 2004
There has truly been a "mixed bag" of weather in North Dakota this spring. In the southwest there are concerns about drought while in the northeast plantings have been delayed because of too much rain. Freezing and below average temperatures during the last two weeks have rounded out the weather for the start of the 2004 growing season. How has this weather impacted small grain development?
Temperature effects on early plant development
Small grains are cool season grasses and develop their highest yield potential when temperatures are cool during their early developmental stages. Wheat planted in April (and I advocate early planting of small grains), is currently in the two to three leaf stage. From emergence until shortly after the three leaf stage, the plant is in the vegetative stage and all new growth is directed towards new leaves. At the three leaf stage tiller production begins in earnest and shortly thereafter the main stem will switch from vegetative development to reproductive development. During the early reproductive stage, the spike develops and the number of spikelets per spike are fixed. Though there is a great deal of compensation between the various yield components from the beginning of spike development until anthesis, plant physiologist have found that the short period of active spike development ( three leaf stage until jointing) is probably the single most critical phase in determining grain yield potential. The good news is that cool temperatures slow plant development and slow development during the formation of the spike favors larger spikes. So the unusually cool weather we are having and that is forecast for the next few days will be beneficial for the development of higher yield potential in small grains. For the parts of the state that have been receiving regular rainfall, and in fields that were planted early and that had good emergence, the prognosis for above average yields is very good (provided that future events do not constrain the realization of the potential for yield that is currently being established). If you fertilized at planting for a modest yield goal, you might consider adding some extra nitrogen now (see Dr. Franzenís article elsewhere in this issue). Furthermore, carefully protect the "potential" you now have developing through timely control of weeds, insects, and diseases.
Early Season Drought Effects
In the southwestern region of the state where there has been very little if any rainfall this season, the question is how has this drought impacted small grain crops to date? There are many factors that affect how drought impacts young seedlings, so the answer to that question has to be, "it depends".
Lack of moisture at planting can delay germination or cause variable emergence. My sense is that for the early planted fields in the southwestern region of the state, there was sufficient moisture to enable good germination and emergence. For well established seedlings the effect of drought on their development is determined by factors such as timing and duration of the drought, its severity, and the crop and variety grown. Drought first begins to impact the plant when its demands for water exceeds that which is accessible by it. The first manifestation of drought stress is wilting or curling of leaves during the warmest part of the day.
On the positive side, temperatures have been very low and for spring planted small grains the leaf area is minimal, so the demands for water have been very low. Furthermore, most small grain crops are still in their vegetative stage of development. During this stage, plants are not particularly sensitive to drought; plants are producing new leaves and leaf number is rarely limited by drought (though leaf size can be impacted). So for spring planted cereals, if rainfall returns to normal, the drought effects to date should not seriously impact yield.
The potential for a negative impact of early season drought on winter wheat is much greater than that for spring wheat. Winter wheat in many regions of the state is now starting to joint. This means that tillering is almost complete and that the spike size on the main stem is already set. Drought stress during tillering and spike development can reduce both the potential number of spikes per unit area as well as their size. The amount of damage to the plant will depend on the severity of the drought stress (which may have been limited somewhat by the cool weather we have been experiencing). Spike size may have been limited by the dry conditions this spring. If rains return to normal, however, I would not be overly concerned as cool temperatures have helped reduce the level of stress that most crops may have experienced, and the wheat plant has the ability to compensate (to some extent) for loss in spike size with increases in floret numbers and grain size.
NDSU Extension Agronomist - Cereal Crops
ANNUAL FORAGES FOR CONSIDERATION
The threat of a short hay crop in the SW and SC part of the state means that seeding annual forages could be important, especially if June stays dry. Even if CRP is released, good quality hay could become short and raising a high quality annual forage could bring top dollar this winter. The continued drought in Montana and South Dakota could result in a higher demand for all hay this coming fall.
When planting annual forages in June, the warm season forages will have a higher yield potential than the cool season forages such as oats, barley, or Triticale.
Warm Season Forage Selection:
Hay millet will produce a hay crop in 50 to 60 days from planting and can be planted as late as mid-July. The optimum stage of cut is a week to ten leaves and has a finer stem than German millet. German days after heading.
Siberian millet will produce a hay crop in 50 to 55 days from seeding. Siberian millet has narrow millet will produce a hay crop in 60 days and usually produces higher tonnage than Siberian millet. Annual forage trials from the past ten years at Dickinson, Carrington, and Minot indicate that German millet is the most consistent yielding annual forage that produces a good quality hay as well. If summer conditions are hot and dry or cool and wet, German millet tends to produce a consistent yield; while other annual forages vary depending on the weather conditions.
Hybrid sudan-sorghum and sudangrass will produce a hay crop in 60 to 75 days. They have excellent regrowth potential and are more drought tolerant than pearl millet. These forages have higher tonnage potential than hay millets and have a proven "track record" in western North Dakota. Hybrid sudan-sorghum and sudangrass should be seeded by mid-June.
Cool Season Annual Forage Selection:
If seeding a cool season annual forage in June, research results from late planting date forage studies at Minot indicate that triticale or barley are better adapted planted in June compared to oats. Oat yield (tons/acre) was drastically reduced when planted in June compared to planting in mid-May. Triticale or barley yields were reduced with the June planting date as well; however, not as significantly as oats.
SUNFLOWER PLANT SPACINGS: INTRA-ROW
Poor seedbed conditions and cool soils may have result in uneven stands of sunflower. Last years sunflower survey pointed out that stand establishment was a major problem in sunflower production. Plants too far apart, too close together and different sizes were common in fields and can result in reduced overall yield potential. Unevenness is assumed to be undesirable, but the lack of response to increased uniformity from narrow row spacing suggests that moderately uneven stands of sunflower may not affect yield. The effects of uniform and nonuniform plant spacings within an overall population of 20,000 plants per acres in rows 30 inches apart were studied at five locations over two years in Minnesota.
The distributions tested included uniformly spaced, clumped, and widely spaced plants: a) uniform single - plants 10.5 inches apart, b) uniform double - two plant groups 21 inches apart, c) 5-5-5 - five plants 5.25 inches apart, 31.5 - inch space, etc., d) 7-1-7 - seven plants 3.5 inches apart, 31.5 - inch space, one plant, 31.5 - inch space, seven plants 3.5 inches apart, 31.5-inch space, one plant, etc.
The uniform, single-plant spacing gave the highest average yield. Both oilseed and non-oilseed hybrids responded the same to the plant distributions within the rows.
|Sunflower yields at five locations in MN|
|Distribution of plants||
Average 9 trials (2 years) lbs/A
Plants uniformly spaced in pairs did not support each other; they lodged more and yielded less than uniformly spaced, single plants. Paired plants may provide greater emergence through crusted soil than single plants, but this possibility was not evaluated.
Head moisture differences among plant distributions were highly significant. Plants spaced singly and uniformly had lower head moisture percentages than did the 7-1-7 arrangement in all trials.
The nonuniform plant distributions were uneven in height from preheading to maturity. The center plants of the groups of five and seven plants were 4 to 7 inches taller than the single plants. Average plant heights among the distributions did not differ noticeably.
Plant distribution did not, on the average, significantly affect test weight per bushel of seed.
NDSU Extension Agronomist
FROSTED OR DROUGHT-STRESSED ALFALFA
Drought stress is very common in Southwestern and Northwestern North Dakota and much of the state has experienced hard frost in the last 10 days. How is the mgmt. of alfalfa stands similar or different from these two stresses?
Drought initially causes a reduction in alfalfa growth due to a shortage of soil water and severe drought will cause a cessation in stem growth. When drought-stressed alfalfa receives significant rainfall, growth will re-initiate if the stem is still vegetative. If however the plant has initiated flowering on a couple of nodes, which often occurs with prolong drought, the plant will continue flowering with only limited stem growth. The plant will set seed if wild bees are in the area to pollinate the flowers; otherwise, the flowers will just wither and die. Flowering will occur over a 4 to 6 week period; therefore, the time and soil water spent producing flowers (seed) is the same as that required to produce another cutting under good moisture conditions.
Drought-stressed alfalfa that receives a significant rainfall (1.5 to 2 inches) and has initiated flowering should be clipped or harvested to remove the flowering stems so that the available soil water can be used for forage growth instead of seed production. Since much of the soil water has been tapped during the drought-stress period, the alfalfa will require additional rainfall to produce a good crop since it takes 5 to 6 inches to produce a ton of alfalfa. Normal mechanical harvesting equipment is the best method to clip the alfalfa. We tried to "clip" the alfalfa chemically by using Paraquat, but even the high rate did not totally stop the stem development and was considered unsuccessful.
Frost damage in alfalfa will vary with stage of growth and duration of freezing temperatures. Alfalfa in the fall of the year will put out a winter rhizome that grows outward and upwards, generally just penetrating the soil surface and displaying small leaflets at the soil surface. These new stems will frequently overwinter, so you can dig down through the snow cover and find these stems anytime during the winter or after the snow cover melts off. Normally, these new stems initiate growth in the spring of the year. One form of winter injury is to burn (frost) these new stems off, which forces the plant to initiate new buds elsewhere on the crown.
The new stems that overwinter are very frost tolerant, but once these stems start to elongate, their frost tolerance decreases. Alfalfa stems that are less than two inches in length have a high osmotic potential, are very tolerant to cold temperature, and can survive a short duration of single-digit temperatures. But frost tolerance decreases as the stem elongates because most stem elongation is by uptake of water. Even then, alfalfa is very tolerant of freezing temperatures compared to other crops.
A 16EF temperature on April 11 at Fargo, ND, when the alfalfa was 3 to 4 inches in height did not kill the growing point, but the frost caused some leaflets and leaves to die (brown appearing 10 days later). A 23EF temperature on May 2 when the alfalfa was 8 to 12 inches in height had little effect. Some years ago, a 14EF temperature when alfalfa was about 6 inches in height killed an estimated 30% of the stems, but 70% survived and produced an average yield. An 18EF temperature at Tioga, ND, on May 2 when alfalfa was 10 to 12 inches in height caused some leaf kill and browning of the edge of leaflets, but most stems survived and continued to grow. A 24oF on June 2, 2000 north of Minot caused the alfalfa to turn white looking. Obviously, the alfalfa was more susceptible to cold temperatures as the alfalfa grew taller and approached harvest. Harvest recommendations differ for frost-damaged compared to drought-stressed alfalfa. If the stem has been killed by frost, there is no need to clip the field since the growing point has been killed. The plants will recover from the crown tissue, although slowly. The only decision to be made is whether there is a harvestable crop. If there is about 8 to 10 inches of growth, there should be enough to justify a harvest. You can tell whether the stem has been killed by waiting for 24 to 48 hours after the frost to see if the stems straighten up from the lax position caused by the frost. If they do, the stem will continue to grow and add to yield potential. Drought-stressed alfalfa that has bloomed should be clipped following a significant rainfall, but frost-damaged alfalfa does not have to be clipped.
NDSU Extension Specialist, Forages