Question: Has the dry conditions hurt wheat yields?
Situation: The western third of the state has been very dry since last August and central Kansas has had a dry spring.
Answer: We have received about 50% of normal seasonal rainfall in western Kansas, especially west central and southwest, while central Kansas had well below normal rainfall for April. This hurt stand establishment in western Kansas and tiller formation in central Kansas. So, the answer is yes, our yields have been hurt. But, yields could improve if we receive moisture from this point on.
Question: Did stripe rust cause any yield losses this year?
Situation: There were numerous early-season reports to the south about stripe rust coming this way.
Answer: The simple answer is "yes". It appears there wasn't as much stripe rust in South Central as we thought there would be. But it was present. You could see differences in resistant and susceptible varieties across the state. As you move north and northwest, the stripe rust pressure was more severe. However, it was not bad in all areas nor all fields. Generally, yields followed the stripe rust resistance level of the varieties. There were significant responses to fungicide applications this year.
Question: Will wheat rusts be a problem this year?
Situation: With leaf rust and stripe rust present in Texas and Oklahoma there is concern for our wheat crop. Stripe rust has been observed in Kansas and we've experienced strong southerly winds for the past few weeks so we can expect rust spores to arrive daily.
Answer: This is a tough one to answer. We almost always have leaf rust come in sometime from heading to the late dough stages with varying levels of damage. Obviously, the later it arrives the less damage it will do to wheat yields. This year our wheat is earlier because of the warm weather we had in March and April. If the wheat continues to be early, the wheat may be more mature when the rusts, either leaf rust and/or stripe rust, arrive in full force. Also, if weather conditions favor the diseases, we will likely see rust problems.
The main thing producers can do is to scout their crop to watch for rust pustules and then make a decision to use a fungicide.
Question: Is it too late to topdress nitrogen now?
Situation: With the wet and frozen conditions producers have been reluctant to apply nitrogen through the winter until now.
Answer: No, it is not too late to topdress nitrogen at this point (late-Feb--early March). However, it should be applied as soon as possible to obtain the maximum benefit. It is important the nitrogen moves into the root zone so that it can be utilized. If nitrogen is applied after the head size is determined, then it won't have the biggest impact on grain yield. So, it is important that nitrogen is applied before this developmental stage. Head size determination occurs when the wheat begins its upright growth. This occurs first in the southern areas of the state and progresses northward later.
Question: Will there be any winter damage to the Kansas wheat crop this year?
Situation: Some of the Kansas wheat crop was planted later than normal and October was cool. This did not allow the wheat to develop normally. Also, we experienced bitterly cold temperatures in early January, 2010 and there is some concern about winter damage.
Answer: Generally, across the state soil temperatures were in the 20s F. which will not cause winter damage. The snow cover insulated the soil from rapid temperature fluctuations, however in northwestern Kansas the snow had been blown from the fields exposing the soil. In fact, at Colby the soil temperature at the 2-inch depth on Jan 8 was 7 F. We often see winter damage when soil temperatures reach single digits. Thus, I would not be surprised to see some winter damage, especially on terrace tops and north facing slopes.
Question: How long can wheat stand in saturated soils and survive?
Situation: With extensive rains in Southern Kansas and continued rain and cloudy conditions, wheat in the area has experienced saturated soils.
Answer: Well, there is not a real good answer to that question other than the fact wheat does not do well under anaerobic conditions which occurs when soils are saturated. During winter dormancy periods when the wheat is not actively growing, wheat can tolerate longer periods of saturated conditions compared to when it is actively growing. Now, when the wheat has headed, flowered and started to fill grain it can tolerate only a few days in saturated soils before it starts to turn yellow. Basically, the wheat will stop grain-filling and start to senesce. This can result in drastic yield and test weight losses if it occurs early in the grain-filling period. Interestingly, there is research being conducted regarding wheat varieties that can tolerate short-term waterlogged conditions. Obviously, this would be a good trait for varieties to have in these wet years.
Question: What are the chances we will see winterkill damage this year?
Situation: We've seen some very cold temperatures across the state this winter and in some areas the wheat plants are not very big.
Answer: Well, of course we don't want any winter damage, but there are some situations where winter damage is possible. Generally, we observe winter damage first on terrace tops and north-facing slopes. Also, we can observe winter damage in dry, loose soil. In this situation the cold air is able to penetrate better than in wet soils and the cold temperatures damage the crown area of plants. Often, plants will green-up when temperatures warm, but then plants slowly die. In severe cases plants will not survive the winter and will not green-up as temperatures warm.
This year we have better stands in western Kansas than we did last year, but we also could use some moisture. Without surface moisture, soils will continue to dry-out due to the continual freeze drying of the soil surface. If we are going to observe winter damage this year, I would expect to see it in western Kansas. And we often see winter damage in central Kansas in heavier soils where the soils cracks over the seed row and cold air is able to penetrate into the crown area. I start to become very concerned about winter damage when soil temperatures fall below 10-12 F degrees in the crown area.
Question: What were the white heads I saw in the wheat this year?
Situation: Across the state one could see white heads in many fields.
Answer: Generally speaking there are only a few things, five to be more specific, that cause wheat heads to turn white before it is mature.
1. Low areas where water stands can cause plants to die prematurely resulting in white heads.
2. Wheat stem maggot enters the stem just below the head near the uppermost node. If you gently tug on the head, it will pull up easily and if you look at the stem you can see where it has been chewed.
3. Dryland root rot causes heads to turn white, but if you tug on these heads they won't pull out. You have to pull the plant out the ground and you'll probably notice it won't have an extensive root system, but if you cut the stem lengthwise, you'll see the inside of the stem will be pink. That's the root rot fungus.
4. Head scab also causes all or part of the head to turn white. If you pull the glumes back and expose the floret, you might see the floral parts have died or the developing kernel has a chalky-white appearance. Also, you might see a pinkish-salmon color somewhere in the head, usually where the spikelet is attached to the head or inside the floret.
5. The fungal disease, Take-all causes heads to turn white. You won't be able to tug on the heads like with the stem maggot, but you will be able to pull the whole plant out of the ground easily. Also, if you remove the leaf sheath at the base of the plant, the lower part of the stem will be shiny black or very dark brown. That is take-all.
Question: Will wheat seed that hasn't emerged yet be vernalized?
Situation: Some wheat in south central Kansas and northern Oklahoma was planted late into dry soils and hasn't emerged yet.
Answer: Vernalization occurs when the seed has started the germination process and soil temperatures are below 48F for 4 to 6 weeks. When the seed imbibes water the germination process has started. So, the wheat seedlings do not have to be emerged when vernalization occurs.
Question: Will low-test-weight wheat be suitable to use for seed this fall?
Situation: Due to the Easter freeze, leaf diseases, and heavy rains wheat yields and test weights in central and eastern Kansas are below normal.
Answer: Thereís no simple answer to this question. Producers who want to plant back some of the wheat they harvested from this yearís crop should have it cleaned out to a test weight of at least 56 pounds per bushel if possible. Wheat with a lower test weight may have a good germination test, and may even emerge just fine (just look at all the volunteer wheat that emerges from small or shriveled seed that is blown out the back of the combine!), but will often have lower vigor and yield potential than wheat with a higher test weight.
The effect of test weight on emergence, vigor, and yield potential will vary from year to year. When there is stress on the seedlings or young plants in the fall from freeze or drought or some other factor, the effect of higher test weight seed is often greatest.
There have been a few studies many years ago in Kansas on the effect of seed test weight on germination, field emergence, and the ultimate yield and test weight of the subsequent grain crop.
The charts below show the results of two tests done at K-Stateís Agronomy North Farm in 1950 by H.H. Laude, professor of agronomy, with seed provided by Frank Bieberly, Extension agronomist.
Several conclusions can be made from this study:
* Test weight had no effect on germination
* Higher test weight seed had 20-40% improved field emergence
* Higher test weight seed emerged 4-6 days sooner
* Higher test weight seed resulted in about a 5-bushel yield increase
* Test weight of the seed had no effect on the final test
weight of the subsequent crop
In addition, in 1990 a study was conducted on seed of Arkan wheat from 25 demonstration plots around the state. Yields averaged 2.4 bushels per acre higher with the high-test-weight seed.
Field observations have shown that higher-test-weight seed results in improved vigor and fall tiller development. A note from K-Stateís Department of Agronomy in 1935 substantiates this, and summarizes the situation regarding low-test-weight seed. These comments still apply to todayís varieties:
ďShriveled seed, even when it has a fairly high germination percentage, is likely to produce weak sprouts and plants that do not have enough vigor to survive unfavorable conditions. Professor J.W. Zahnley, Director of the State Seed Laboratory, states that the germinated seed of several samples of shriveled wheat with test weights ranging from 46 to 55 pounds, was characterized by weakness of the first or temporary roots. Normal wheat seedlings should have three strong roots at the end of the germination period of seven days. Many of the badly shriveled seeds produced only a single, weak primary root, or one fairly strong root and one or two very weak ones. Such seed will not produce a normal plant under average field condition. And in case of adverse circumstances, these weak plants will perish more quickly than normal seedlings.
ďIn cases where it seems necessary to plant wheat having test weight less than 55 pounds, it should be cleaned and graded to remove the light-weight, shriveled seed. When wheat of light test weight is used for sowing, the drill should be adjusted to avoid planting at too heavy a rate and to avoid obtaining a thicker stand than is desirable.Ē
If producers are planning to save their grain as seed and have it cleaned to raise the test weight, what should the minimum test weight be? How low is too low? In truth, there is no absolute minimum for farmer-saved seed, but yields and vigor are more likely to be affected at test weights below 54-56 lbs/bushel. Below 54-56 lbs/bushel, the plants are likely to have more problems in the fall and in surviving the winter. Producers planting low-test-weight seed will also have to be extra cautious not to plant the seed too deeply, since seedling vigor will be below average.
The effect of seed test weight on emergence, vigor, and yield potential will vary from year to year. When there is stress on the seedlings or young plants in the fall from freeze or drought or some other factor, the effect of higher test weight seed is often greatest.
Question: What are the symptoms of freeze damage that we should be looking for?
Situation: Over Easter weekend we experienced bitterly cold temperatures across Kansas.
Answer: Because much of the wheat was in the early stages of jointing in the northern areas of the state to near boot stage in the southern areas you'll need to look at different parts of the plant.
If wheat was jointing, then you need to look at the stem below the node or joint. If damage has occurred, the stem will be kinked or collapsed. It will start to discolor and begin to have a dry appearance. There may be some darkening at the node. If you cut the stem open to look at the growing point, it may appear to be okay but with time it will begin to dry up and have an off-white, feathery appearance.
Sometimes there will be no apparent stem damage, but to be certain that particular tiller is okay you'll need to cut open the stem to look at the growing point or small head. If it is damaged directly by the freeze, it will be off-white to yellowish and appear limp or flaccid. A healthy head at the jointing stage should have a crisp, clear to whitish appearance. Also, if the growing point has been damaged, it will be difficult to separate the growing point from the tissue around it. That's to say, the tissue is beginning to become mushy.
If the growing point or the stem has been damaged, the wheat will not continue to grow. The leaf coming out of the whorl will be yellow and the other leaves will turn yellow. Also, undamaged tillers will grow up past the damaged stems and cover them. So, if you see areas of the field that have continued to grow while other parts are turning yellow, then you know there is damage.
To determine if wheat in the boot stage has been damaged, you will need to either wait until the head emerges from the boot or open the stem and look directly at the head. Damaged head will have a water-soaked appearance and can be either yellowish to white. A healthy head will be lime-green until it emerges and then it will turn darker green.
Question: Are there any chances of winter injury this year?
Situation: We are seeing some fields slow to green-up.
Answer: Yes, there are chances of observing winter injury in our wheat this year. Wheat that was planted into fluffy soil and planted more shallow than normal appears to be suffering a bit. The fluffy soils allow the cold to penetrate and cause injury. Also, where there was winter grain mite feeding late last fall those fields appear to be a little slow to green-up.
Question: How long can wheat stay under snow and ice and still survive?
Situation: We've had wheat covered with snow and ice for more than a month in northwestern Kansas.
Answer: There's no real good answer to this question. Ice is the potential problem and not the snow at this point. Wheat that is dormant can tolerate ice cover longer than if it wasn't dormant. An ice sheet cuts off the gas exchange and plants eventually die from the byproducts of anaerobic respiration. A Canadian study indicated plant losses after 4 to 6 weeks covered with a sheet of ice.
In our case, time will tell.
Question: What's making the wheat turn yellow?
Situation: There are concerns about the wheat leaves turning yellow in some areas of the state. The wheat doesn't appear to be growing very much and some might say the wheat is going backwards.
Answer: Cold weather will make the leaves turn yellow and sometimes leaves will turn purple when they are under some stress, but I don't think cold weather is the real problem. I think we're seeing some drought-induced nitrogen deficiencies symptoms and just plain drought stress. The lower leaves are turning yellow from the leaf tip and moving back on the leaf blade. The root systems are not extensive and in many cases there are very few roots. The first few inches of the soil are very dry. So, considering these conditions the symptoms point to the effects of dry soil.
Question: What's the germination of this year's wheat seed?
Situation: With the poor growing conditions there are concerns the wheat seed may have lower germination than usual.
Answer: This yearís wheat crop is averaging about 97 percent germination in laboratory tests so far, which is very good. For the first several weeks after harvest, itís important to make sure the wheat is pre-chilled before taking a germination test. The lab will do that on a routine basis. But 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. Wheat has a physiological characteristic called post-harvest dormancy. If you take a germination test immediately after harvest the germination can be quite low. The pre-chilling treatment breaks the post-harvest dormancy and will allow the seed to germinate normally.
There is some difference among varieties regarding how long their post-harvest dormancy period is. Hard white wheats with poor sprouting tolerance, for example, have almost no post-harvest dormancy. They will germinate almost as soon as the seed is harvested. Other varieties, such as Overley, have a relatively long post-harvest dormancy, and may not germinate well for five or six weeks after harvest unless the seed is pre-chilled. By Labor Day, all varieties will have lost their post-harvest dormancy and should germinate unless the seed is defective in some way.
If there is any question about the viability of the seed, it is well worth the $15 it costs to have the seed tested for germination by a certified seed laboratory. This is especially true in areas where there was freeze damage, severe drought, a rain delay at harvest, or scab on the wheat last year.
Question: With the warm weather we had in January, did the wheat vernalize?
Situation: January, 2006 was the warmest January on record in Kansas.
Answer: Vernalization is a cool-period requirement that winter annuals, such as wheat, need to switch from vegetative to reproductive stages. Freezing temperatures are not required, but rather, temperatures at 48F or below will initiate vernalization. Varieties differ on the length of the cool period required, but generally, 3 to 6 weeks will be sufficient for complete vernalization. Also, wheat doesn't have to be emerged to start the process, it only has to have initiated seed germination.
Well, back to the question. The wheat was probably already vernalized by the time January got here because December was fairly cool. Generally, that's the situation with wheat planted at optimal planting times and normal growing conditions . . . wheat will have been vernalized by Christmas because the late fall and early winter are cool enough for the process to have occurred.
Question: What are the disadvantages of planting wheat earlier than the recommended dates for a specific area?
Situation: Some producers, especially in western Kansas, start planting when they receive rain in early September.
Answer: In western Kansas, we're very concerned that earlier than normal planting will cause excessive fall growth, use up available surface moisture and ultimately result in winterkill damage. This is especially concerning when we have a late fall killing-freeze and the wheat continues to grow and use moisture later in the season.
There are other problems associated with early plantings. Wheat streak mosaic is a disease that comes to mind. Some producers wait until the last possible moment to control volunteer wheat and if a field of volunteer wheat is within a half-mile or so of a newly planted wheat field, the likelihood of the newly planted field becoming infected with wheat streak mosaic increases tremendously. (Of course, this could also occur with late-plantings if volunteer wheat is nearby.)
Last year in western Kansas, with the excessive fall growth and good moisture conditions, a considerable amount of leaf rust was observed. Early plantings tend to suffer from Hessian fly infestations because there's a "green" bridge between wheat crops that can harbor Hessian fly. Also, we often see more crown/root rots associated with early plantings into warm soils.
Question: Why did no-till wheat after wheat not fare as well as more conventionally-planted wheat this year?
Situation: Some producers observed that their no-till wheat had thin stands and plants were stunted and yellow.
Answer: There are several issues that arise with no-till wheat. Seeding rate, seeding depth, planting speed, planting date, and nitrogen applications are the first issues that come to mind. The thin stands could be caused by a number of things. The seeding rate might not have been high enough. When planting no-till into crop residues the seeding rates should be increased. It is not unusual to see seeding rates in the 90 to 120 pounds per acre range even with normal planting dates.
This past year we observed that seeding depth and planting speed were related. The faster the planting speed the shallower the seed was placed and with the dry conditions we experienced this past spring, those shallowed-seeded plants did not root very well and showed considerable drought stress. Also, sometimes the soil under no-till situations is harder, itís more difficult to penetrate to the desired seeding depth. We can see more winterkill or winterdamage when wheat is planted too shallow.
This year, late-planted wheat showed more effects of the late April-Early May freezes than wheat planted at a more normal time. Late-planted wheat didnít have a closed canopy and the cold air was able to freeze the lower areas of stems.
However, nitrogen is probably the most important reason no-till wheat didnít look so good. More precisely, how much nitrogen was applied and how was it applied? With heavy crop residues, such as with wheat residue, weíre concerned with immobilization of the broadcast applied nitrogen. Thatís to say, the nitrogen can be tied up on the residue when it is broadcast applied and it wonít be readily available to the growing wheat crop. Thus, there is less total nitrogen available which could result in nitrogen deficiency symptoms, such as yellow plants. For example, if a producer normally applies 60 pounds N per acre and 20 pounds N per acre are immobilized, the crop will not have enough nitrogen to produce a good grain yield.
So, how do we overcome nitrogen immobilization in no-till wheat? If a producer is going to broadcast the nitrogen, then the only solution is to increase nitrogen rates by at least 30-40 pounds per acre. The other solution would be not to make a broadcast application, but rather, inject the nitrogen below the residue into the soil. This would eliminate the immobilization problem caused by the standing residue. The big question is, "how does a producer go about doing that?" Well, nitrogen could be injected before wheat planting or it could be injected at planting, but that would require some modifications of the drill.
There is another aspect of nitrogen that we have to consider and that is the fact that in some fields, producers have removed some tremendous wheat, grain sorghum, and corn crops the past few years. In these cases soil nitrogen levels have been depleted and the normal nitrogen applications have not been sufficient which results in deficiency symptoms.
Question: What symptoms do you look for when assessing freeze damage?
Situation: Over the last two weekends of April and early May temperatures ranged from the low 20's to 32, while wheat was in various developmental stages.
Answer: Initially, the first symptoms were leaf burning where the leaf tips turned brown. Some leaves actually appeared black and water-soaked. My first thought (or hope) was we had only cosmetic damage and no real freeze damage. But now we can see fields, especially low lying areas, that have an odd color to them- sometimes the leaves have purplish color, but mainly leaves are turning yellow to bright yellow, while others have some necrosis. As you know, weíre most concerned when temperatures drop below 32 when the wheat has headed and into the flowering stage.
It takes about 5-7 days for the head to fully extend above the flag leaf and before flowering begins. Flowering will begin in the spikelets (farmers call them rows or meshes) about 2/3 up the head and will progress up and down the head over a 3-5 day period. Within each spikelet there are generally 2-5 florets, but usually only 2-3 florets will produce kernels.
Inside a healthy floret just prior to flowering or pollen-shedding, there are three, lime-green anthers and a stigma that has two, fluffy-white branches. (If you look inside a floret soon after heading, the stigma will not be open yet.) The anthers are pushed upward as the filaments or stems to which the anthers are attached elongate, pollen inside the anthers is released and lands on the stigma. At that time the anthers have started to change from their lime-green color to a yellowish color. The anthers continue to elongate and can be seen outside the florets where they are yellow to white. This is how flowering normally proceeds and within ten days after flowering, kernels should be nearly their full size.
When freezing temperatures occur at this stage there are several things that can occur. With temperatures that are at or below 32 F the anthers, which are more sensitive to cold than the stigma, can be damaged which will lead to floret sterility. The first visible freeze-damage symptom to the anthers is they will become shriveled and twisted while they still have their lime-green color. This can be detected with a hand lens within 24 hours after the freeze. If there is damage, over several days the anthers will not elongate and they will continue to shrivel and turn whitish-yellow. In this situation, pollen wasnít shed, but if the stigma was not damaged it could still be receptive to pollen from anthers in other florets that werenít damaged. However, if the stigma was damaged, it will not open to expose its two, fluffy branches and it will become shriveled and whitish-brown.
Not all wheat was in the heading to flowering stage when the freeze occurred. We generally think wheat is safe if itís not heading when it freezes, but thatís not necessarily the case. Wheat in the boot stage, while it can tolerate colder temperature, can also be damaged. With light damage the head will become trapped in the boot as it emerges and the head will have a gnarly appearance. To determine if thereís more severe damage, you need to look inside the florets to assess the anthers and stigma. If the anthers are white and shriveled then damage has occurred. Sometimes the head (in the boot) will already have a yellowish to whitish color if thereís damage instead of a nice crisp, green appearance. These damaged heads will continue to emerge from the boot as if nothing is wrong, but youíll be able to see the color differences. Sometimes thereís partial damage to the head, thatís to say, some spikelets will be damaged while other spikelets are fine. The glumes will be yellowish to whitish and papery and when you try to open the glumes to check the anthers and stigma the floret or whole spikelet may fall of the head.
Also, weíre seeing damage to wheat in the pre-boot stage, especially in late planted fields that didnít have good canopy coverage or in no-till fields where the residue kept the heat from the soil from rising into the canopy. Itís a little more difficult, but if you slice the stem open just above the uppermost node to look at the developing head you will see a silvery-white cast on a damaged head. The glumes might have a crinkly, papery appearance instead of having a nice lime-green, crisp, turgid appearance of a healthy head.
If you see the leaf coming out of the whorl is yellow or chlorotic, the growing point is probably dead. You will need to cut open the stem above the uppermost node to look at the small head. If thereís damage, you might have difficulty separating the head from the surrounding leaf tissue. If the head is whitish-brown to brown, then you know the head is dead.
In fields that are turning yellow, look at the lower stems. Pull the leaf sheaths back to assess the stem. If the stem between the nodes has collapsed or discolored or if thereís discoloration at the nodes, thatís freeze damage. This damage restricts nutrients from moving upward which causes the leaves to die. Iíve noticed some yellow areas in fields that has been caused by powdery mildew, so youíll need to check for those symptoms. If the wheat hasnít grown or continued development since the freeze, thatís an indication thereís damage.
See the publication, "Spring Freeze Injury to Kansas Wheat," C-646 and "Adopt a Wheat Field" on the K-State Wheatpage (www.ksre.ksu.edu/wheatpage) for more details.
Question: Why is there more Hessian fly damage this year compared to other years?
Situation: Last fall, we saw plants with stunted tillers and thick, dark green leaves. Some plants had died or were dying.
Answer: It should be mentioned that for the past several years we've seen stem breaking or lodging caused by Hessian fly, but not so much plant stunting and dying in the fall.
There are three main reasons why we are having more Hessian fly damage this year. First, we are seeing more damage in early planted wheat than later or normal planting dates. That's because more Hessian fly adults are present that time of year and if volunteer wheat is present in late summer and early fall, that allows for another hatch which increases the number of adults to infect the newly planted wheat crop. Second, there is more wheat planted no-till into standing wheat stubble now than in past years. If there was Hessian fly already present in the wheat stubble, the lack of tillage allows more insects to survive to infect the new crop. Third, the prominent wheat varieties planted in Kansas do not have resistance to Hessian fly. Jagger and Jagalene are very susceptible to Hessian fly. Resistance is a very effective method of reducing Hessian fly damage.
When you combine these three reasons, early planting, no-till planting into wheat stubble, and susceptible varieties, it is no small wonder we are seeing an increase in Hessian fly damage.
Question: Will we see much winterkill damage this year?
Situation: Some areas of the state have considerable fall growth, Hessian fly infestations, we had an unusual fall leaf rust infection, and we had some very cold days in late December and January. Producers are concerned this might have set up the wheat for winterkill damage.
Answer: Generally, we don't have too much actual winterkill. Winterkill is when the wheat doesn't survive the winter. We see winterkill on terrace tops or north facing slopes when soils are very dry and soils temperatures at the crown are 10 degrees F or below. The temperature of dry soils fluctuate more rapidly and drops lower when very cold air temperatures arrive. Water in soils acts as a temperature buffer so that soil temperatures don't get too cold when air temperatures are very cold. So, wet or moist soils will protect wheat plants from winterkill damage.
We have "springkill" which is when temperatures warm in late winter and the wheat starts to green-up, then bitterly cold weather quickly moves across the state. As wheat greens-up, it naturally loses its winter hardiness and is subject to rapid drops in temperature. We could see that type of damage later this winter and early spring. Also, adding to the potential problem is the fact we have a variety like Jagger, that greens-up very quickly with warm temperatures and that makes it more vulnerable to cold temperatures.
We worry about winterkill damage after excessive fall growth because that growth removes moisture from the soil. But if the soil remains wet we shouldn't see anymore winterkill damage. Tillers that have Hessian fly "flaxseeds" in them may not survive the winter. The plants that were infected with leaf rust this fall and were very chlorotic (yellow) will probably survive the winter. But plants may be weakened. We haven't seen fall leaf rust infection as severe as it was, so we don't know exactly what will happen to those plants.
Question: How many wheat plants per foot of row are needed to leave a thin stand?
Situation: The recent rains in western Kansas have caused soil crusting which has led to some stand establishment problems for wheat that was planted just prior to the rains. Producers are wondering if the number of plants per foot of row is adequate for excellent yields or should they replant those fields.
Answer: There is no easy answer to this question because of the many variables associated with the problem, such as, is the thin stand uniform across the field? Are there bare areas? Will we have a late fall that allows the surviving plants to tiller? Is the field subject to wind erosion? If we decide to replant ,what seeding rate should be used? If we use a hoe drill, do we disregard the surviving plants? If we use a double-disc opener drill, do we reduce the seeding rate because more of the original plants will survive?
The decision to keep the stand or to replant will be on a field to field basis. The key for making that decision will be how close the average number of plants per foot of row present in the field is to the number of plants per foot of row that should be there.
We have to determine the number of plants per foot of row that is expected in a normal, undisturbed field situation. If a producer uses a drill with 12-inch row spacings, plants at a 60 pound per acre seeding rate with a wheat variety that has 15,000 seeds per pound and expects a germination and emergence rate of 75 to 80 percent, there should be 675,000 to 720,000 plants per acre or about 15.5 to 16.5 plants per foot of row. Next, we need to determine the average number of plants per foot of row that is present by taking numerous plant counts across the field.
Generally, if there is 50 percent of an expected stand or 8 or more plants per foot of row (12-inch row spacings) that is uniform across the field, the recommendation is to keep the stand. With plant stands less than 40 percent of an expected stand or less than 6 plants per foot of row the recommendation would be to replant the field. However, when there are 6 to 8 plants per foot of row the decision is very difficult. Research would indicate that 260,000 to 320,000 plants per acre or about 6 to 7 plants per foot of row can produce respectable yields, especially if the plants are able to tiller well, albeit 5 to10 percent yield reductions can be expected. If there are 6-8 plants per foot of row, a double-disc opener drill and a 30 to 40 pounds per acre seeding rate could be used thicken the stand. However, if there are 6 to 8 plants per foot of row and a hoe drill is used, the seeding rate should be slightly higher than what was originally planted because the hoe drill will destroy much of the original stand. The date for the replanting becomes an issue because later in the planting season the seeding rate needs to be increased to compensate for the lack of tillering. Also, planting at a 45 degree angle across the original stand may reduce the number of plants that are destroyed in the replanting process.
If there are 6 to 8 plants per foot of row and the decision is made to leave the stand, producers should be aware there could be wind erosion problems because there arenít enough plants to provide sufficient soil cover. Also, there could be greater weed pressure next spring because of the lack of plant competition between wheat plants and weeds.
If areas of the field have no plants yet emerged, producers will need to dig through the soil crust to determine if the seeds or seedlings are still viable or if the coleoptiles or sprouts have pushed up to the crust and have been bent or crinkled. Sometimes a light rain on crusted soil will soften the crust so the seedlings can continue to emerge. Otherwise, a rotary hoe will break up the crust allowing the seedlings to emerge. Unfortunately, a rotary hoe cannot be used effectively in fields where the wheat was no-till planted or if there are high levels of crop residues. These bare areas will need to be replanted as soon as possible with slightly higher seeding rates than were used initially to compensate for the lack of tillering and to be competitive with weeds.
Question: What concerns should I be aware of when considering no-till, continuous wheat?
Situation: I know some farmers that have been successful no-till planting wheat into wheat stubble. The conventional wisdom is that it won't work. What are they doing to make it work?
Answer: One major obstacle to overcome in a no-till, continuous wheat situation is the foliar disease, tan spot, because it carries over on the wheat stubble. Tan spot can cause serious yield losses. In the past, plowing took care of the spores on the residue, but with reduced-tillage or no-tillage systems there is potential for high levels of tan spot spores to be present to infect the next crop. We haven't seen very high incidences of the disease recently, which is due to the fact Jagger has been widely planted. Fortunately, Jagger and other varieties such as, 2137, Karl 92, and Overley have good levels of tan spot resistance. When these varieties are planted, especially the first year, the levels of tan spot inoculum are generally lower than if a susceptible variety had been planted. When the second planting occurs into this wheat stubble there is very little inoculum present to cause a problem. Thus, it's important to use a resistant variety. If a susceptible variety has been planted, an option would be to use a fungicide to control tan spot. Most producers that no-till plant into wheat stubble only plant wheat twice in this system before they rotate to another crop.
Other management items to consider are: making sure the drill penetrates the wheat stubble to get good seed-soil contact; delaying planting later in the optimum planting range to reduce the potential of Hessian fly and allowing time to control the volunteer wheat; increasing the seeding rate by 10-15 %; banding a starter fertilizer with the seed; and increasing the nitrogen rate the second year by 15-20 % if it is broadcast applied. This will overcome the immobilization of nitrogen by the wheat stubble. If the nitrogen is knifed into the soil either prior to planting or at planting, use the recommended fertilizer rate.
Question: How does rain during harvest affect test weight?
Back to Top
Send comments, questions, or suggestions to The Wheat Page Committee.