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Late-season weather affecting corn crop

Late-season weather affecting corn crop published on No Comments on Late-season weather affecting corn crop

by:

Josh Lofton and Dan Fromme, LSU AgCenter

 


 

Over the past several days Louisiana has experienced some severe weather across the state. Most notable was the severe weather of August 11. Damage from this storm has been felt from northern Louisiana through the rice-growing areas of southern Louisiana. While reports of hail have been sporadic, damage from wind and heavy rains have been the primary concern. Unfortunately, with the rains that have been experienced across the region in the past several weeks, little of the corn crop has been harvested. This means that a large portion of the state’s crop was at risk for this damage. Driving across the state, many fields have been spared damage; however, others have not. Damage includes lodging of the tops of the plants to complete stalk lodging. At this stage in the corn growth cycle, anything short of complete stalk lodging should be of minimal concern, and there should be little effect on final yields. However, greater concern may be warranted for those with more intense lodging.

The next couple of days will determine how damaging complete stalk lodging will be. At this stage, corn lodging will not correct itself as it will at earlier vegetative stages. However, with most modern day harvesting equipment, producers will be able to capture most of what is currently on the ground.  Where the problem arises is with the rain associated with the windy conditions. Lodged corn lying in standing water will begin to be an issue as time progresses. Not only will this corn not dry like the rest of the crop, seed sprout will start to develop. This sprouted seed will maintain relatively high moisture, and dockage will be incurred if high rates of sprouted seed develop. Therefore, it will begin to be essential that these spots dry in the coming days.

While it seems the extent of this damage will be minimal across the state, yield losses on affected fields will be more substantial. Conditions will not be fully known for the next several days.

 

For further questions or comments, contact:

Dan Fromme, Corn and Cotton Extension Specialist, dfromme@agcenter.lsu.edu

Josh Lofton, Research Agronomist, jlofton@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

Damage to corn with severe weather

Damage to corn with severe weather published on 1 Comment on Damage to corn with severe weather

Josh Lofton, Field Crop Agronomist, Macon Ridge Research Station

Beatrix Haggard, Soil Specialist, Northeast Region

Dan Fromme, Corn and Cotton Specialist, Dean Lee Research Station

 

As the weather around the state is finally transitioning from spring to summer conditions, the corn crop has seen abundant growth in the past several weeks. With these increasing temperatures, it can also be expected that the number and severity of thunderstorms will continue to increase. Two major concerns with these increased thunderstorms for the corn crop are wind and hail damage. With the current corn crop beginning to reach critical growth and developmental stages, it is often wondered how much yield loss can be associated with these potential injuries. While the answer to this question seems somewhat straightforward, there are many factors that determine how detrimental the injury will be and how much yield loss can be expected.

Wind damage

When looking from a turn-row at a field that has been dam
aged by wind itmay appear that all wind damage is similar; however, this is far from the truth. Root lodging appears as the entire stalk has been blown over at the ground level with the roots appearing to be dislodged from the soil surface.  This occurs when soil from heavy rainfall events becomes saturated and the roots can no longer support the corn stalk. While this may appear to be very detrimental to the corn crop, oftentimes, given good growing conditions following the event, the crop will reroot and the crop will continue to grow upward. In later growth stages, these stalks can be identified with having a more “goose necked” appearance. While the damage this lodging will have on yields will not be understood until harvest, root-lodged corn often looks worse immediately following the lodging event than the related yield damage; this is especially true prior to reproductive growth.

lodge1

Snapped corn is a more severe effect of wind damage (often referredto a “green snap”). This effect can be seen after the emergence of the growth point from the soil surface. However, it is more common during late-vegetative or early-reproductive growth when high biomass is paired with high winds. Unlike root lodging, it is unlikely a plant that has experienced green snap will recover from the injury. However, the overall effect on field scale yield will vary based on how widespread the damage is and what stage the crop was when damage occurred. Studies from Iowa State University indicated that when green snap occurs early in the season, prior to V8, yield losses expected should be less than 15 percent. This is due to the ability of many of our modern corn hybrids with flex to adjust seed set. Prior to V8 stage, both ear size and kernel set, which occur from V8 through V14, have often not been fully determined. Therefore, with decreased surrounding competition, these plants have the potential to produce larger ears to compensate for the losses. However, when snapped corn occurs during late-vegetative or early-reproductive stages, both the severity and the yield impact are often higher with as much as 50 percent yield loss expected in severely damaged corn.lodge3

Hail damage

Hail, in addition to tremendous rain potential and damaging winds, can also be a damaging aspect. Hail damage can be very disheartening since the visual damage is often worse than it really is. With this being said, it is best to not attempt to evaluate a hail-damaged field the day of or the day following the event. Corn has an amazing ability to recover from damage, especially during early-season growth. Evaluation of these fields should be delayed until favorable growing conditions with adequate moisture have returned. This will allow the manager to determine which plants have recommenced growth and which have not. After these conditions have returned, managers can cut down the center of the stalk and look at the growing point. When determining the yield reduction of hail damage, two aspects should be considered: 1) stand loss and 2) reduction in photosynthetic leaf area. During early-season growth, if the growing point is firm and white, these plants are likely to survive; however, if the growing point has lost firmness or has turned brown or light grey, severe damage has occurred and the plant is not likely to survive.

 

The primary loss of yield due to hail damage comes from loss of leaf area. However, determining leaf area damage can often be challenging. Two critical aspects in determining how this reduction in leaf area can influence yield are: 1) percent defoliation and 2) growth stage in which the damage occurred.  Determining the percent defoliation is probably the most challenging aspect. Often, even minimal to slight defoliation can appear to be severe defoliation. Evaluate damaged leaves compared to undamaged leaves to try to minimize the bias nature of this estimate. Once percent defoliation is determined, growth stage at which the event occurred will be needed. Often, following a hail event, growers and managers will scout the field the day of the event or the day following and growth stage should be evident. However, if time occurs between the hail event and scouting, in general, corn leaf emergence occurs at 1 leaf per 80 GDD prior to V10 and one leaf per 50 GDD after. Once these two aspects are determined, Table 1 can be used to assess potential yield reductions due to loss of photosynthetic tissue.

 

Table 1. Estimation of percent grain yield loss associated with leaf area defoliation. (Adapted from National Corn Handbook, Climate and Weather, Vorst 1993).defoliation1

Damage from severe storms can be a very disheartening time. Luckily, the damage is rarely widespread, and therefore field- and farm-scale yield losses will be minimal. Currently, there have only been scattered reports of either hail or wind damage during the 2014 season, but we can expect storms to continue throughout the year.

 

 

For further questions regarding damage throughout the season, feel free to contact:

Dan Fromme, Corn and Cotton Specialist, 318-427-4424

Josh Lofton, Field Crop Agronomist, 318-498-1934

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