Number 1
September 29, 2005
1. Planting wheat into dry topsoil
2. Causes of poor or dying wheat stands
3. Nitrogen application methods for wheat
4. Considerations for wheat planted into row crop stubble
5. When to make the last cutting of alfalfa
6. Seeding rates for Overley
1. Planting Wheat Into Dry Topsoil
In some areas of the state, the topsoil is very dry. This can create two basic questions from producers.
a. I have not yet planted. What should I do?
Producers can dust the wheat in, but they should keep in mind that the wheat may not get enough moisture to germinate for quite a while – possibly even 3 or 4 weeks. In other words, there’s a possibility the wheat will come up later than the optimal range of planting dates. Wheat that is planted late, or emerged late, usually does not tiller as much as wheat that emerges during the optimal planting dates. In northwest Kansas, for example, wheat planted now into dry soils may not emerge until mid- to late-October. For that reason, and because of the possibility that later rains could cause crusting problems, producers in northwest or west central Kansas who are planting now into dry topsoils should start increasing their seeding rates. If the seeding rate is normally 60 lbs per acre, start increasing now in those areas of Kansas to 75-80 lbs per acre. Even if producers in northwest and west central Kansas decide to wait for a rain to plant, they’ll have to wait for the soil to dry out again after the rain comes, so it’s likely to be on the late side again. So they should increase seeding rates in either case. These producers should also be advised to plant only 1-2 inches deep. The later it gets, the shallower the seed should be planted. Newer varieties do not have long coleoptiles, and they’ll need to be able to emerge as quickly as possible late in the season so that they’ll have enough time to establish a secondary root system before winter.
In other areas of Kansas, there is still time for wheat planted into dry soils to emerge on time, so there’s no need yet to start increasing seeding rates beyond the normal.
b. I planted a week (or more) ago and my wheat hasn’t come up yet. What are the chances that the seed will never germinate and emerge, and I’ll have to replant?
If the wheat hasn’t yet emerged, the seed either has: (1) not yet germinated, or (2) germinated but the coleoptile hasn’t yet come through the soil surface, and may have stopped elongating if the soil is very dry. If the seed has not yet germinated and the topsoil is dry, then everything is fine. This seed will eventually germinate, even if it’s not until winter or next spring (worst case scenario). If the seed has germinated in dry soils but the coleoptile stopped growing before it emerged through the soil surface, this may or may not be a problem. Some research done here several years ago showed that if the coleoptile shoot has just barely emerged and is less than a half-inch long or so, the fact that the soil is dry and the coleoptile shoot has stopped growing is not a big concern. The seed should still have enough carbohydrate reserves to stay alive and resume elongation when moisture conditions improve. But it the coleoptile shoot grew longer than a half-inch or so but did not make it through the soil surface, then the seedling may have exhausted its food reserves and die before moisture conditions improve. Re-seeding may be necessary under those conditions, but it’s a tough call to make unless it’s obvious that the seed and coleoptile have gone soft and squishy – in which case you’ll know they’re gone. If you’re not sure, the best thing you could do would be to scoop up several samples from the field, put some water on the soil, and see if the wheat seedlings resume growth. If the field is re-seeded, increase seeding rates by 15-20 lbs per acre, and plant no deeper than 1.5 inches, if possible.
-- Jim Shroyer, Crop Production Specialist and State Extension Agronomy Leader
785-532-0397
2. Causes of Poor or Dying Wheat Stands
If wheat stands are poor or dying, there are several possible causes:
a. Soil crusting. This is easily detectable. Crusting is more common on fields that have been tilled. If the seed germinates but is unable to break through the soil surface because of crusting, the field will probably have to be replanted. If you dig around and find that the shoot has leafed out underground and the soil is crusted, those plants will probably never emerge. A crust on a tilled field can be broken up with an implement such as a rotary hoe. This is not an option on no-till fields, although fields that have been in no-till for a few years do not crust as easily as other fields.
b. Poor seed-soil contact. If the drill was run too fast, more than 6 mph, or if the ground was too cloddy or had a lot of unevenly distributed crop residue, then it’s very possible that poor stand establishment is due to poor seed-soil contact. Producers who are just planting wheat no-till for the first time may find that their soils are very hard during the first year or two. This is especially a problem where soils have been dry and very little residue has been produced the prior two years. Under these conditions, even no-till drills can have problems establishing good seed-soil contact. Producers may have to till the field before planting wheat, and wait for a year with better soil conditions to start no-tilling wheat. The longer a field has been in no-till, the easier it is (in most cases) to get good seed-soil contact with no-till wheat.
c. Planting depth. Most varieties do not have a long coleoptile and should be planted about 1 to 2 inches deep. Seed that is planted 3 inches deep or more may simply not have a coleoptile long enough to emerge through the soil surface. This problem is most common when planting short coleoptile varieties with a hoe drill. When using a hoe drill, the seed furrows can be several inches deep, and soil can fall back into the furrow and bury the seed deeper than the producer intended to plant it.
d. Herbicide carryover. If atrazine was applied within a year of planting the wheat, it’s possible that atrazine carryover could have damaged the newly seeded wheat. The atrazine label states: “Do not rotate to any crop except corn or sorghum until the following year, or injury may occur.”
e. Hot soils. When soils are hot, coleoptile lengths are shortened. If wheat was planted early, when surface soil temperatures were 90 degrees or more, then a poor stand could occur if wheat was planted a little deeper than optimal and the coleoptiles did not grow long enough to reach the soil surface. Also, Oklahoma State University has found that the first-year seed of some varieties, such as Overley, 2174, Cutter, and Ok102, do not germinate well under hot soil conditions. The seed of these varieties have a longer summer dormancy requirement than other varieties.
f. Insect damage. Wireworms or false wireworms are soil insects that can cause stand establishment problems, although this is not a common problem in Kansas. After the wheat has emerged, stands can quickly deteriorate from army cutworm or flea beetle damage. Both of these insects will cause “windowpaning” of the leaves. Fall armyworms can also damage a young stand before it gets established. Fall armyworms tend to eat the leaves directly rather than cause windowpaning. There have already been reports in Kansas this fall of each of these insect problems damaging young stands before they get established.
If stands are poor, producers will have to decide when it pays to replant. Recent research here has shown that wheat yields can still be within 75 percent of normal when stands in fall or early spring are only half of normal. It’s a tough call, but in most cases producers should not replant unless their stand is only 30 percent or less of what they intended.
-- Jim Shroyer, Crop Production Specialist and State Extension Agronomy Leader
785-532-0397
3. Nitrogen Application Methods for Wheat
Subsurface banding (knifing) of nitrogen (N) as either anhydrous ammonia, liquid UAN, or dry product provides for the greatest N use efficiency by the wheat crop. This is especially true for no-till wheat production. If knife N applications are not used, the next best application method would be surface banding (dribbling) of UAN solution in streams 15-18 inch on-center. While broadcast urea, ammonium nitrate, or UAN applications are not generally as efficient as subsurface banding, they are often the best choice due to equipment, logistics, or weed management considerations. Broadcast applications of N will have the most consistent performance if followed by light incorporation, precipitation, or irrigation. While a minimum preplant N application of 20-40 lbs N per acre is often desirable, especially in no-till production systems, it is important to avoid placing urea containing fertilizers in direct seed contact. We suggest that NO UAN solution or urea be placed in contact with the seed. If the fertilizer N applied at seeding will be separated from seed by 1 inch or more, urea containing fertilizers can be safely used.
-- Dale Leikam, Nutrient Management Specialist
785-532-6183
4. Considerations for Wheat Planted Into Row Crop Stubble
Where fall moisture is good, producers may want to plant wheat directly into row crop stubble. If the row crop was harvested 2 or 3 weeks earlier than the optimal seeding dates for wheat, producers would have enough time to till the field and apply anhydrous ammonia if they wanted. Tillage may be helpful if the field is compacted or the soil surface is very rough. Otherwise, it’s probably best to no-till the wheat, unless the crop residue levels are high and the producer has an older model conventional drill that cannot easily go through residue. The later the row crop is harvested, the more important it is to get the wheat crop planted quickly, and no-till is the best way to accomplish that.
There are three main questions when planting wheat directly behind row crop stubble.
a. What variety is best for doublecropping? Unfortunately, we have no recent research that directly addresses this issue. From demonstration plot comparisons, performance test data, and field experience, though, it would appear that there are no particular varieties that stand out as especially good for doublecropping.
b. What seeding rate should be used? If planting dates are within the optimal range, use a seeding rate of at least 90 lbs per acre when doublecropping wheat behind a row crop. This applies to planting after either grain sorghum, soybeans, corn, or sunflower. If planting dates are later than the optimal range, seeding rates should be increased to a maximum of 120 lbs per acre when planting directly into the stubble of any of these row crops.
c. How much N should be applied? If the previous crop was soybeans, corn or wheat, your normal N application rate is suggested. If the immediate previous crop was grain sorghum or sunflower, we suggest that producers increase their overall N application rate by 30 lbs N per acre above their normal rate. Additionally, if producers are in a no-till system, we suggest they further increase their overall N application rate by an additional 20 lbs N per acre.
d. How about scab? When wheat is planted directly into corn residue, there is an increased potential for having scab problems in the wheat. Overley and 2137 are unusually susceptible to scab, and probably should not be used when planting directly into corn.
e. Can wheat do well planted into grain sorghum residue? This is probably the toughest situation for doublecropping wheat. Grain sorghum stays alive after harvest until the first hard freeze, so it can compete with newly emerging wheat for water and nutrients. A good crop of grain sorghum also uses a lot of soil nutrients and can dry out the soil, so producers should be sure to apply an extra 30 lbs of N, or more if possible. Grain sorghum can also be allelopathic to wheat, which can be a problem, especially where the wheat is planted no-till. There’s not much that can be done about this except to use a high seeding rate (120 lbs per acre) and high nitrogen rate.
f. What about herbicide carryover? The biggest potential concern in most cases would be where planting wheat into corn or grain sorghum residue where atrazine was applied the same spring. The atrazine label states: “Do not rotate to any crop except corn or sorghum until the following year, or injury may occur.”
-- Jim Shroyer, Crop Production Specialist and State Extension Agronomy Leader
785-532-0397
-- Dale Leikam, Nutrient Management Specialist
785-532-6183
5. When to Make the Last Cutting of Alfalfa
How late can producers make their last cutting of alfalfa? If growing conditions are good this fall, there’s a temptation to get in a fifth cutting, which could yield anywhere from a half to one ton per acre.
Should producers make that fifth cutting or not, and if so, when? This is always a dilemma, assuming the producer wants to keep the stand next season. Alfalfa has to have good root reserves going into winter to minimize winterkill and get off to a good start next spring. The way to ensure this is for the alfalfa to have either: (1) very little regrowth at the time of the first hard freeze, or (2) about 10 inches or more of regrowth at the time of the first killing freeze of 24-26 degrees.
What you don’t want is to have regrowth somewhere in between. If a fifth cutting of alfalfa is made, and there’s just enough good weather that there’s about 4-6 inches of regrowth when the first killing freeze occurs, that’s the worse case scenario. In that situation, the crop will have used up a good portion of its root reserves in producing the new regrowth, and the regrowth will not have had enough time to replenish the root reserves.