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Wheat cultural management in Louisiana

Wheat cultural management in Louisiana published on 1 Comment on Wheat cultural management in Louisiana

by:

Josh Lofton and Steve Harrison, LSU AgCenter


 

As much of the state is just gearing up for harvest of corn, soybeans and grain sorghum, it is time to start preparing for the state’s wheat crop. While wheat planting is still months away, it is this early season management that begins to determine the yield potential for the upcoming season.

Variety selection:

Choosing varieties for the upcoming season is potentially your most important decision prior to planting. Most producers agree that grain yield is the most important criterion for variety selection. However, there are many aspects of grain yield that need to be evaluated when selecting varieties. Two-year average yields give some indication of stability. This not only demonstrates the performance of varieties across various growing environments but also attempts to minimize environmental influence on variety performance (i.e. current year was better for early- or late-maturing varieties). Additionally, test weight is important because varieties with low test weight may result in the producer being docked at the mill.  Therefore, when evaluating variety yield performance, it is essential to use as many parameters as possible.

Heading day, plant height, lodging and disease susceptibility are also important selection criteria. Heading day allows producers to gauge relative maturity of the individual variety. Early-heading and maturing varieties permit earlier harvest and timelier planting in a double-cropping system, while later-heading varieties guard against damage from a late spring freeze and can be planted a little earlier. Early-heading varieties should be planted in the second half of the recommended planting window to avoid the likelihood of spring freeze damage. Lodging resistance helps in some years. Intense storms can occur during late grain fill and cause severe lodging, which results in lower test weight, decreased yields and lower harvest efficiency. Disease susceptibility is very important in terms of yield and profitability. It should be noted that varieties less susceptible to disease may not always produce the highest yields, especially if disease pressure is not present. However, in high disease pressure situations, the resistance may result in higher yields as well as enhanced profitability by saving the costs of fungicide applications. Therefore, managers and producers must weigh the benefits of disease susceptibility with potential yields.

Crop management:

Planting dates for Louisiana wheat depend on location and variety. For southern and central Louisiana optimum planting dates range from November 1 through November 30. The optimum planting for northern Louisiana is slightly earlier, ranging from October 15 through November 15. Early-heading varieties should generally be planted after the mid-date, while late-heading varieties can be pushed a little on the early side of the planting window. The weather in north Louisiana is cooler in the fall and early winter, which slows growth and prevents excess winter growth. It is important that the wheat crop be well-established and fully tillered before going dormant in the coldest part of the winter. Additionally, because of the cooler conditions, the threat for fall pests (Hessian fly, army worms and rust) are decreased earlier in the fall compared to south and central Louisiana. While these dates are the optimum planting window averaged over years, the timing will vary in some years depending on weather patterns. Additionally, if wheat cannot be planted within these optimum windows, planting later than the optimum window would be preferred. Early planting can result in greater insect and fall rust establishment and also makes plants more prone to spring freeze injury due to excessive fall growth and development. Planting too late (more than 14 days after the optimum window) can result in significant stand loss due to slow emergence and seed rotting and can decrease yield potential due to poor tillering and decreased canopy density.

Wheat can be planted by broadcasting seed and incorporating; however, it is preferred that the seed be drilled. Drilling the seed increases the uniformity of depth and stand. If drill seeding, wheat should be planted at a rate of 60 to 90 pounds per acre of high quality seed into a good seedbed with adequate moisture. If the seed is broadcast, seeding rates should be increased to 90 to 120 pounds of high quality seed to account for decreased germination and emergence. This higher seeding rate should be adapted for conditions in which high germination or emergence is not expected, as with late-planted wheat or heavy, wet soils. Late-planted seed should be planted at a higher seeding rate using a drill to ensure rapid, adequate and uniform emergence.

Nitrogen fertilization of wheat can be a challenging aspect of production. Total N application should normally range from 90 to 120 pounds per acre, but this will vary depending on soil type and rainfall after applications. Timing of N application depends on several factors. The wheat crop needs adequate N in the fall and early winter to establish ground cover and properly tiller; however, excessive levels of fall N can result in rank growth and increased  lodging potential, as well as a higher probability of spring freeze damage from early heading. If the wheat crop is following soybeans, soil residual or mineralizable N should be adequate for fall growth, and no pre-plant N is needed. However, if the wheat crop follows corn, sorghum, rice or cotton, the application of 15 to 20 pounds of N per acre would typically be beneficial. Where the wheat crop is planted later than optimum, additional N may be necessary to ensure adequate fall growth prior to winter conditions. If the wheat crop did not receive a fall application and appears to be suffering from N deficiency in January, the initial topdress N application can be made early to promote additional tillering. Early spring is when the majority of N for the wheat crop should be applied. There is no universal rule on how early spring N should be applied. Each field should be evaluated based on tillering, stage of development, environmental conditions and crop color. A crop that has good growth and good color should not need N fertilization prior to erect leaf sheath (Feekes 5), usually sometime in February. However, first spring fertilizer application should be applied prior to first node (Feekes 6) in order to ensure optimum head development, tiller retention and head size. Crop N stress around jointing (Feekes 6) will result in yield losses. Any additional N applied following flag leaf typically contributes very little to crop yield. Splitting topdress N into two or three applications is common in Louisiana production systems due to the increased risk of N losses often associated with heavy rainfall and our long growing season. Splitting N typically occurs by applying fertilizer N at or just prior to jointing with a second application occurring 14 to 28 days later. About 50 percent of the topdress N is normally applied with the first split, but this may be decreased if the first split is put out early and plants are not well enough developed to take up that much N.

Phosphorus, K, and micronutrients should be applied in the fall based on soil test reports. All fertilizers applied as well as lime should be incorporated into the soil prior to planting. Required lime should be applied as soon as possible because it takes time for the lime to begin to neutralize the acidity of most soils. The application of sulfur is a growing concern in Louisiana production systems, with increasing deficiencies appearing every year. Oftentimes, early spring S deficiencies are mistaken for N deficiencies and additional S is not applied. Because sulfur is mobile, similar to N, the application solely in the fall will not be adequate. Supplemental applications of S with spring N applications are often warranted.

 

For further questions or comments contact:

Josh Lofton, Wheat Extension Specialist, jlofton@agcenter.lsu.edu

Steve Harrison, Small Grain Breeder, sharrison@agcenter.lsu.edu

 

 

Winter wheat update: How recent rains will influence the wheat crop

Winter wheat update: How recent rains will influence the wheat crop published on No Comments on Winter wheat update: How recent rains will influence the wheat crop

by:

Josh Lofton- LSU AgCenter, State Wheat Specialist

Steve Harrison- LSU AgCenter, Small Grain Breeder

A recent article discussed how much potential the current wheat crop had but we may be seeing that yield potential in jeopardy due to heavy rains for the past week. One of the greatest impacts this can have on wheat seed is in the final harvest test weight. Mature wheat kernels are smooth and have the highest test weight as soon as they initially reach harvest moisture (10 – 14%). Every time a heavy rain falls on a mature wheat field the dry kernels re-absorb moisture and swell up. Upon drying again the kernel shape changes slightly and test weight is lost.  Test weight losses can reach several pounds per bushel, resulting in dockage at the elevator and decreased profitability. The article below, published by the Virginia Cooperative Extension Service, summarizes findings from NC State on the impact of delayed harvest of test weight. Hot weather during late grain fill can also negatively impact test weight, particularly for late-heading varieties. This is why some late-maturing varieties are not suitable for Louisiana, even if they do fully head out and have relatively good grain yields.

Sunken embryo.tif

 

http://www.sites.ext.vt.edu/newsletter-archive/cses/2006-06/wheattestweight.html

 

While decreased test weights may be the most common and damaging condition experienced across the state, others certainly exist. Seed diseases can also be a concern. One that has been identified in the southern part of the state by Dr. Steve Harrison is black point (Shown below).

Black tip

 

This fungus develops when humidity and temperature in the canopy are high during grain fill. While this disease can be damaging, how wide-spread these conditions become are yet to be determined. Additionally, with frequent rainfalls the seed can lose sprouting resistance and germinate in the head prior to harvest (Shown below). This not only influences seed quality but may result in significant dockage at the mill and influence harvest moisture.

sprouting

In addition the effect at the seed head level, these storms can also impact the crop at the field scale level. One common and easily identified impact is lodging in the crop. Lodging can occur when the seed head becomes too heavy and the straw deteriorates and snaps when storms occur. While most producers will be able to harvest, this high rate of lodging can increase seed deterioration and shattering prior to harvest.

Wheat lodging

While these problems may seem like a foreboding effect for the current wheat crop, there is still a large amount of potential for the crop. It will be essential to let the field and crop dry prior to recommencing harvest. However, as soon as these conditions exist, wheat harvest should be the upmost task and mechanical drying may be important. While this will not decrease damage that has already been done, it will decrease the potential of continued damage going forward.

 

For additionally questions or comments, feel free to contact:

Josh Lofton- LSU AgCenter, State Wheat Specialist, jlofton@agcenter.lsu.edu

Steve Harrison- LSU AgCenter, Small Grain Breeder, sharrison@agcenter.lsu.edu

Wheat continuing to grow with colder weather near

Wheat continuing to grow with colder weather near published on No Comments on Wheat continuing to grow with colder weather near

by:

Josh Lofton, LSU AgCenter, Field Crop Agronomist and Wheat Specialist

Steve Harrison, LSU AgCenter, Wheat Breeder

In recent weeks, the wheat crop has experienced near optimum growing conditions across much of the state. This has allowed the wheat crop to develop rapidly, although the crop is still late in heading this spring. The return of cool weather will slow wheat development over the next week, and record-breaking low temperatures are expected for the state, especially in north Louisiana. With the impact of last season’s late freeze still fresh in our minds, it is understandable that many producers and managers are concerned with the colder weather. While the wheat crop has survived one of the coldest winters on record, much of the wheat crop in Louisiana is near the most cold-sensitive growth stage. As with the previous freezes, determining the growth stage of the wheat crop will be critical to determine how much potential damage can be expected should a freeze occur. Wheat still in the tillering to booting growth stages is relatively cold-tolerant and can withstand temperatures around 26 degrees F because the grain head is still relatively protected. Wheat is most sensitive to cold weather in the heading to flowering stages of development. As the crop further progresses to milk, soft dough and hard dough stages, the crop once again gains a degree of colder tolerance. During these cold-tolerant stages, the crop can sustain temperatures as low as 28 degrees F for up to two hours before critical damage can be expected. Wheat in the flowering stage can sustain significant damage with temperatures at or slightly below 30 degrees F for just a few hours, primarily due to sterilization of the pollen and resulting failure to set seed.

weather damage to wheat at different growth states

It is important to understand the damage that can occur with these lower temperatures at these advanced growth stages. Oftentimes, because the reproductive components are exposed, cold damage at these stages can often result in substantial yield reductions. Symptoms experienced at these stages are often associated with aborted kernel production with white, bleached seed heads.

Fortunately, for grower and managers across the state, temperatures are not expected to fall below freezing, and damage should be minimal and limited to cold packets of air. Temperatures are expected to return into the 70s and 80s for the remainder of the week, and the wheat crop should quickly recommence growth and continue to progress.

wheat head damage

 

Wheat that has sustained frost/freeze damage can be noted by bleached or white seed heads.

It can be expected that when this colder weather passes and warmer conditions return, the winter wheat crop will quickly recommence growth. In doing so, most of the wheat across the state will be near or past the flowering growth stage. It is critical to note that fungicides can be applied up to Feekes 10.1 or heading but cannot be applied once the wheat crop reaches Feekes 10.5 or flowering. Any applications at or beyond this stage are considered off-label.

 

For any further questions, concerns or comments, please contact:

Josh Lofton, 318-498-1934, jlofton@agcenter.lsu.edu

Steve Harrison, SHarrison@agcenter.lsu.edu

 

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