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By: Jeanne Falk Jones, K-State Multi-County Agronomist
Wheat is considered a highly responsive crop to starter fertilizers, particularly phosphorus (P) and nitrogen (N). Application of P as starter fertilizer can be an effective method for part or all the P needs. Wheat plants typically show a significant increase in fall tillers and better root development with the use of starter fertilizer (phosphorus and nitrogen). Winterkill can also be reduced with the use of starter fertilizers, particularly in low P testing soils.
Phosphorus fertilizer application can be done through the drill with the seed. This would either be in addition to, or instead of, any preplant P applications depending on soil test and recommended application rate. The use of dry fertilizer sources with air seeders can be a very popular and practical option, however, other P sources (including liquid) are agronomically equivalent and decisions should be based on cost and adaptability for each operation.
When applying fertilizer with the seed, rates should be limited to avoid potential toxicity to the seedling. When placing starter fertilizer in direct contact with wheat seed, producers should use the following guidelines (No urea, UAN or KTS): for 15 inch rows – 16 pounds of N+K20 on medium to fine textured soils and 11 pounds on sandy or dry soils. For 10 inches – 24 pounds for medium to fine textured soils and 17 pounds for sandy or dry soils. For 6 to 8 inch – 30 pounds for medium to fine textured soils and 21 pounds for sandy or dry soil.
Air seeders that place the starter fertilizer and seed in a band an inch or two wide, rather than a narrow seed slot, provide some margin of safety because the concentration of the fertilizer and seed is lower in these diffuse bands. In this scenario, adding a little extra N fertilizer to the starter is less likely to injure the seed - but it is still a risk.
What about blending dry 18-46-0 (DAP) or 11-52-0 (MAP) directly with the seed in the hopper? Will the N in these products hurt the seed? The N in these fertilizer products is in the ammonium-N form, not the urea-N form, and is much less likely to injure the wheat seed, even though it is in direct seed contact. As for rates, guidelines provided in the table above should be used. If DAP or MAP is mixed with the seed, the mixture can safely be left in the seed hopper overnight without injuring the seed or gumming up the works.
Although the response of wheat to these starter fertilizer products is primarily from the P, the small amount of N that is present in DAP, MAP, or 10-34-0 may also be important in some cases. If no preplant N was applied, and the soil has little or no carryover N from the previous crop, then the N from these fertilizer products could benefit the wheat, in addition to the P.
Dual-placement of N and P (anhydrous ammonia or UAN plus 10-34-0 applied in the same band below the soil surface) is a fertilizer application method usually used in preplant applications. Ammonium-N has long been known to increase P uptake by crops, and dual-placement can be very effective. Sometimes, producers will use this method at planting time, trying to position the band to the side of each row of wheat seed. Use caution, however.
If adequate separation of fertilizer and seed is accomplished, this is a good method of application that fits into many farmers' overall no-till system. If adequate separation of the ammonia/UAN and seed is not accomplished, wheat germination/stand establishment can be severely affected.
Should your wheat seed BE wheat seed? The importance of checking germination
Did you save some wheat for seed? Have you checked the germination on it to make sure it will be quality seed wheat for this fall? With the delays at harvest because of the rain and black point showing up on some wheat samples, it is even more important this year. There are two main options for germination testing - an at-home test or testing by a laboratory.
If you do a home germination test too soon after harvest, you will be shocked at the low germination. That's because wheat has a post-harvest dormancy requirement (some varieties more so than others). Even high quality seed will not germinate right after harvest in most cases.
It's important to make sure the wheat is pre-chilled before taking a germination test. The pre-chilling helps break the dormancy in the seed. Any reputable seed lab will do that on a routine basis. Producers testing their seed at home should also pre-chill the wheat by putting it in the refrigerator at about 40 degrees for 5 days and then move to room temperature for an additional 5-7 days. If the seed is not pre-chilled, producers should wait a month and a half after harvest before testing for germination.
There is some difference among varieties regarding how long their summer dormancy requirement is and even that can vary from year to year. We believe the challenges at harvest have likely lengthened the dormancy in the wheat seed this year. Hard white wheats with poor sprouting tolerance, for example, have almost no summer dormancy requirement. They will germinate almost as soon as the seed is harvested. Other varieties have a relatively long summer dormancy requirement, and may not germinate well for five or six weeks after harvest unless the seed is pre-chilled. Unfortunately, there is no routine testing of varieties for their summer dormancy requirement, so we have no way of knowing which varieties will germinate shortly after harvest and which will take a longer period of rest.
By Labor Day, all varieties will have lost their summer dormancy and should germinate unless the seed is defective in some way. In addition, if seed is tested soon after harvest, it would still be a good idea to test again prior to harvest to be sure the germination has not been compromised due to heating or insect damage.
If there is any question about the viability of the seed, it is well worth the $17 it costs to have the seed tested for germination by a professional seed laboratory. This is especially true in areas where there was a rain delay at harvest or herbicide applications to control weeds for harvest. To the untrained eye, seeing some amount of shoot and root development would seem to be sufficient proof that the seed is in good condition. But that alone does not always mean you have a seedling that will develop into a healthy plant. A trained laboratory analyst evaluates each seedling to be sure that all essential parts exist and have sufficient development at the end of the test to, in fact, establish a normal, healthy, plant.
The lab at K-State sends tests to Kansas Crop Improvement Association in Manhattan. Samples can be dropped off at the Extension Office or at the K-State Experiment Station in Colby for shipping. The Extension Office will have the form to fill out to send it in or it is available on the K-State Sunflower District Agronomy webpage at www.sunflower.ksu.edu and click on the Agronomy tab.
|Short (less than 2.5")||Medium (2.5 to 3.25")||Medium Long (~3.25")|
|Medium Short (~2.5")||Everest||Oakley CL|
|SY Grit||Long (more than 3.25")|
|SY Monument||Brawl CL+|
|SY Sunrise||TAM 111|
*These are approximate coleoptile lengths. Growing conditions can change these lengths. Warm soil conditions can shorten the coleoptile.
*Adapted from Wheat Varieties for Kansas and the Great Plains 2016.
Importance of available soil water and in-season precipitation
A full soil profile at planting time is not required for a decent wheat crop. However, increased available soil water at planting does improve greatly the odds of getting a good wheat crop. In-season precipitation and available soil water at planting are both important in determining the ultimate yield of a wheat crop.
The following table is based on results from 30 years of research data collected at the K-State Southwest Research-Extension Center at Tribune. The wheat yields listed were calculated from equation 3.5, table 3, page 1361 of "Yield—Water Supply Relationships of Grain Sorghum and Winter Wheat", L.R. Stone and A.J. Schlegel, 2006, Agron. J. 98:1359-1366. Wheat yields were calculated in response to both available soil water at emergence and total in-season precipitation.
Effect of Available Soil Water at Emergence and In-season Precipitation on Dryland
|Available soil water at emergence (inches)|
|Average wheat grain yield (bushels/acre)|
In the above table, keep in mind that 2 inches of available soil water is equivalent to having moisture to a depth of one foot in a silt loam soil, since a silt loam soil holds about 2 inches of available soil water per foot. Likewise, 4 inches of available soil water means a silt loam soil is moist to a depth of 2 feet. In a sandy loam soil, 2 inches of available soil water would be moisture to a depth of roughly 1.33 feet.
The chart shows the influence of available soil water and in-season precipitation at producing long-term yield results. Having water in the fall is critical for germination, emergence, stand establishment, and vigor. Precipitation during winter is closely related with yield potential, providing for winter survival and increased soil water at the beginning of spring regrowth. Water in spring is normally most effective at increasing wheat yields if received at about boot through head extension, providing for decreased water stress at flowering and grain development.
Preparing for Planting Wheat: Are you a good neighbor?
Controlling your volunteer wheat can put you in the "good neighbor" category! Wheat streak mosaic was quite a challenge last year and had significant impacts on the yield of some fields.
The wheat mosaic virus is moved by the wheat curl mite. This mite is too tiny to see with the naked eye, but can sometimes be seen with a hand lens. It is tiny and cigar-shaped. The mite lives in volunteer wheat during the summer and is happy to move to newly emerged tender wheat. It can move up to a half mile on the wind.
In addition to carrying the wheat streak mosaic virus, it can also move High Plains Mosaic virus and Triticum Mosaic Virus. These viruses are nearly always found in conjunction with wheat streak mosaic and produce more severe symptoms than wheat streak mosaic alone.
To prevent the movement of the mites and viruses, it is critical that all volunteer within a half mile be completely dead at least two weeks prior to planting. Destroying volunteer wheat after the new wheat emerges is too late. The worse scenario is to have volunteer wheat dying as the newly planted wheat is emerging. The mites will move from their dying food source to the new, tender wheat to begin feeding again. The two weeks is critical because that gives the mites time to die due to lack of food.
Herbicide control and tillage are two options for controlling volunteer wheat. Tillage and herbicides are also often combined for an effective control program that leaves much of the stubble in place. Many burndown herbicides, such as glyphosate (Roundup, Durango, Glystar, Makaze, Touchdown, etc) or paraquat (Gramoxone), will provide control. Grazing volunteer is not an effective option because it does not provide complete control. Even intensive and close grazing still has green tissue that the mites can live on.
Neighbors also need to cooperate in finding "hidden" volunteer wheat. the "hidden" places might include field edges, ditches, and in double-cropped ground. Be especially sure to look in the direction of the prevailing wind!
Planning for Planting Wheat: Seed Quality
There are several things that influence harvest...several things that are out of a producer's control. However, there are several things that can be controlled, especially at drilling time. One is seed quality.
Using good quality seed is the foundation of good stand establishment. Large dense kernels are considered to be better quality seed than kernels with low test weight. Large dense seed tends to produce more tillers than smaller seed.
Protein content is another factor related to seed quality. The amount of protein, not protein percentage, in the seed is very important to early seedling vigor. Large seed may have a lower protein percentage than small, shriveled seed, but because it is larger, it will have more total protein per seed.
Test weight of grain is often used as a measure of seed quality, but test weight is actually a bulk density or a weight per volume measurement. In other words, small seed that packs well can have a high test weight. All in all, we are used to test weights playing a role in having high quality seed. Therefore, seed wheat should have a test weight above 57 pounds per bushel. If thinking along he lines of seeds per bushel, an appropriate guideline for the minimum translates to 15,200 seeds per pound. The only exception to this would be the variety, Overley. This is a variety that has normally large seeds, at around 12,000 seeds per pound. In addition, cleaning seed can add 1 to 2 pounds to the seedlot's test weight by removing the small kernels.
It is also important to know the germination of your seed to determine seeding rate. Seed to be used for planting should be above 85% germination.
If you saved seed and are wondering about your seed's specs, it can be sent to Kansas Crop Improvement. They can help answer several questions associated with saved seed. These are some of the services that they provide as a germination test for $15.00 and a seed count (#/lb) for $4.00. If you are not a member of Kansas Crop Improvement, there is a $2.00 additional fee for the sample. To send a sample in, collect a 2 lb bag of seed wheat for the test. The turn around time for these tests is between 10 and 14 days.
Planning for Planting Wheat: Seeding Rates and Depths
In the scheme of planting wheat, many factors have been determined when the tractor pulls into the field. However, seeding rate and depth can still be decided, within reason.
Seeding rates in western Kansas range from 600,000 to 900,000 seeds per acres planted (40 to 60 lbs at a rate of 15,000 seeds per pound). Considering 80% germination and emergence, the plant population may vary from 450,000 to 750,000 plants per acre. Seeding rates for irrigated wheat are 900,000 to 1,350,000 seeds per acre (60 to 90 lbs/ac of 15,000 seeds per pound). This would result in a final stand of 720,000 to 1,080,000 plants per acre.
Traditionally, seeding rate is viewed as pounds of seed per acre. However, seeding rates of wheat are increasingly viewed similar to corn seeding rates, as seeds per acre. This is due to the variability of seed size in seed wheat. For example, Overley is a variety that normally has large seeds when compared to other varieties. This would result in fewer seeds per pound and if planting in pounds per acre, fewer seeds planted per acre.
Lower seeding rates will tiller more than higher seeding rates. This can allow the wheat plant to make adjustments based on the available soil water. During tillering in the fall (mid October), wheat can use over 0.6 in/wk.
Seeding rates can be adjusted upwards by 10 to 20%, if planting conditions are good or if quicker cover is desired. Seeding rates should also be increased 50 to 100% when double-cropping behind row crops. This is due to the later planting date and compensating with challenges associated with seed-to-soil contact and residue. In addition, this also potentially compensates for the decreased time for tillering by adding more plants per acre.
Wheat can emerge from various depths, but a planting depth of 1 1/2 inches is optimal. The important part of planting depth is the length of the coleoptile. Coleoptile length is related to the height of the wheat. Many times a taller variety will have a longer coleoptile, although there are always exceptions. In addition, wheat emerging in hot soils can experience problems with the coleoptile. Extremely warm soil can cause the coleoptile to shorten and prevent it from emerging from the soil surface.
In dry soil, a hoe drill can help place seed deeper into soil moisture. However, when creating deep furrows, be aware that a heavy rain can further bury the seed. This can cause a deeper "planting depth" than intended and decreased seedling emergence.
Planning for Planting Wheat: Seeding Rates for Later Planting
When planting later in the season, increasing the seeding rate could 'potentially' compensate for the reduced number of tillers from an individual wheat plant. A study was conducted at the Northwest Research-Extension Center in Colby to determine if is possible to receive all or most of the highest potential yields on late-planted wheat by altering seeding rates.
Beginning in 2008, TAM 111 was planted Sept. 26, Oct. 10, Oct. 24 and Nov. 7. On each planting date each year, plots were planted at 60, 90, 120, and 150 lbs/ac. Eighty pounds of nitrogen and 30 pounds of phosphorus per acre were applied to the study area prior to planting.
The study indicated that although yield potential is reduced by planting wheat after the optimum window for a given area, some of the potential yield can be recovered by increasing the seeding rate. In the fall of 2008 and 2009 when wheat was planted on Sept. 26 and Oct. 10, wheat yields were similar across the planting rates of 60, 90, 120, and 150 lbs/ac. However, when wheat was planted on Oct. 24 or Nov. 7, the lowest yield for that date was observed with the 60 lbs/ac seeding rate and a stair-step increase was observed with the 90, 120, and 150 lbs/ac seeding rates on these dates.
"But it is important to note, that although the 150 lbs/ac seeding rate on Oct. 24 and Nov. 7 had the highest yield for that date, that yield was not as much as wheat planted during the more optimum planting period for the area of Sept. 26 to Oct. 10," said Northwest Area Agronomist Brian Olson.
In the first two years (2008-09 and 2009-10), moisture was adequate and emergence, development and yields were consistent, Olson said. But just like for producers in western Kansas, dry conditions during fall 2010 impeded the researchers' efforts. After an irrigation event at the end of October 2010, the all of the wheat emerged, regardless of planting date. This illustrates the fact that no matter when the wheat is planted, the potential yield is based on when it comes up!
Planning for Planting Wheat: Influences to Hessian fly fall infestations
Which wheat fields are most likely to be infested with Hessian fly in the fall? Should you wait until the Hessian fly free date to plant your wheat?
In theory, waiting to plant until the best pest management planting date (BPMP) allows time for the main fall brood of adult Hessian flies to emerge and die before wheat is planted. Without live wheat plants, emerging females are deprived of a place to lay eggs, minimizing fall infestation. There is still some risk if a nearby infestation exists and a secondary fall brood develops.
The risk of fall infestation is almost always greater where wheat is planted before the BPMP date, especially during years favorable for fly development. Observance of the BPMP date also reduces the incidence of wheat streak mosaic and barley yellow dwarf viruses. The BPMP date strategy is based on studies conducted from 1918-1935, and BPMP dates are based on data collected more than 70 years ago, but are now being refined. The historical Hessian fly free dates for the following counties are September 15 in Cheyenne and Sherman, September 19 in Rawlins, September 20 in Thomas, and September 21 in Logan. There is not a defined fly-free date in Wallace County. These fly-free dates are still being updated.
The relatively mild fall weather in recent years, along with a slight increase in average fall temperatures over the last 30 years, has reduced the effectiveness of using this date as a planting guide. In studies conducted in Sedgewick County, Kansas, during 2006 -2010 using a Hessian fly pheromone trap, adult flies were active until early December. It seemed that more adult flies were trapped after a rain. The impact of this extended Hessian fly activity on wheat or on fly population density is not known, but it is interesting to note that potential for Hessian fly infestation exists longer into the fall than historical data indicate. In addition, the BPMP date may not always present the best planting date for optimum yield, but on average, it correlates well. The BPMP date can be used on an individual-field basis but will be more effective when it is practiced area wide.
Planting too late is also risky. Growers may be surprised to learn that delaying planting too late in the fall can actually increase the risk of Hessian fly infestation. While late planting dates may protect the field against fall infestation, the result is smaller plants in the spring. And when the spring brood of flies is active in March or April, those females prefer younger plants for egg laying. Thus, if a source of infestation is nearby, very late-planted wheat of a susceptible variety may suffer extensive damage from spring infestations.
With soil conditions getting drier, wheat germination and emerging from the soil is on many producers minds. The wheat seed begins germination by absorbing water and oxygen. Adequate soil moisture is needed for this to occur. As the seed takes in moisture, begins to swell slightly. The embryo, or 'germ', gives rise to the seedling root (radical) and the first leaf. fore the seedlings emerge, the survival often
If the moisture runs out before the seedling emerges, the survival often depends more on the stage of germination than the length of the dry period. Seedlings from seeds that have been germinated for only one or two days can survive dessication (lack of water) and resume growth when moisture occurs. However, seedlings that are 4 to 5 days old probably will not tolerate drying.
How do you know how old your seedlings are? Many start counting the age of the seedling from when the seedling root first emerges. Usually, the shoot (the second item to emerge from the seed) begins to emerge 2-4 days after the root emerges. This timeframe, however, can be altered by growing conditions. For example, the dry conditions can cause the root and shoot growth to occur over a longer period of days.
If some of your seedlings look like they are not going to make it, is your wheat stand still in the range for an optimum plant stand? The recommended seeding rates for western Kansas are 600,000 to 900,000. Considering an 80% germination, the plant population may vary from 450,000 to 750,000 plants per acre. For 7.5 inch rows, there should be between 7 and 10 plants per ft of row. For 10 inch rows, there should be between 9 and 14 plants per ft of row. For 12 inch rows, there should be between 11 and 17 plants.
If you are considering redrilling some wheat, remember the K-State guideline: if there is 50% of your desired stand = leave the stand. If there is 40% or less, redrill to thicken your stand.