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Economic Impact of Excessive Rain to Louisiana Agriculture Exceeds 276 Million Dollars

Economic Impact of Excessive Rain to Louisiana Agriculture Exceeds 276 Million Dollars published on No Comments on Economic Impact of Excessive Rain to Louisiana Agriculture Exceeds 276 Million Dollars

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Louisiana Rice Notes #9 – 2nd Flood Edition

Louisiana Rice Notes #9 – 2nd Flood Edition published on No Comments on Louisiana Rice Notes #9 – 2nd Flood Edition

The 9th installment of Louisiana Rice Field Notes is now available. This is the second flood edition this week.  This edition covers recommendations on how to proceed with harvest with all of the flood damaged rice, a very important proposed changed to the crop insurance “practical to replant” definition and the final planting dates (FPD) for rice, corn, sorghum, cotton and soybeans, and an important flood recovery meeting in Crowley tomorrow.

LA Rice Notes 9T_Page_1
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Reapplying Lost Nitrogen to Corn After the Flood Waters Recede

Reapplying Lost Nitrogen to Corn After the Flood Waters Recede published on 1 Comment on Reapplying Lost Nitrogen to Corn After the Flood Waters Recede

By Dustin Harrell

Since writing the article yesterday that discussed estimating nitrogen (N) losses in corn following flooding events (http://louisianacrops.com/2016/03/18/corn-with-all-the-flooding-how-much-nitrogen-have-you-lost/), many new questions have been raised by producers. They are concerned that young corn will need to have the N replaced quickly after the flooding waters drain off fields in order to replace lost N and maximize the yield potential of the corn. This is a valid concern especially if little N is left in the soil after the floods recede or if N has not been applied at all and the corn is reaching the rapid vegetative growth stages. For example, a 200-bushel-per-acre corn crop will take up approximately 200 pounds of N during the growth and development of the crop. Seedling corn, prior to the V6 stage of development (6th leaf collar) will take up very little N, approximately 5% of its seasonal need. However, from V6 to VT (tasseling) corn will take up approximately 60% of its seasonal needs, or about 120 pounds of N for a 200-bushel corn crop. If that N is not available during that rapid growth period (approximately 30 days), then yield losses are certain to occur.

As the flood waters recede, many producers have questions about the best way to replenish the lost fertilizer N quickly to avoid yield losses. Most soils in north Louisiana are too wet to apply N with ground rigs, so that removes the Volatilization of urea on a dry and moist Crowley silt loam soilpotential to band or knife-in liquid N fertilizers. The only application method currently available to supply a large rate of N is to surface broadcast granular N fertilizer sources such as ammonium sulfate (21-0-0-24) and urea (46-0-0). Urea is less expensive than ammonium sulfate per pound of N; however, it also has the potential to volatilize. The volatility potential of ammonium sulfate is minimal. Volatilization is the conversion of ammonium (a solid) to
ammonia (a gas), which will be lost to the atmosphere. Trials evaluating urea volatility potential of N fertilizers have been conducted at the H. Rouse Caffey Rice Research Station over the past several years. Trials have shown that 30% or more of the N from urea surface broadcast on a dry soil can be lost by ammonia volatilization in a 10-day period of time. Of course, rates of volatilization can vary considerably across soil types. Typically, higher pH soils will have a greater N volatility potential as compared to acidic soil. Treating urea with a urease inhibitor with the active ingredient NBPT or NPPT will protect the urea from volatilization for a given amount of time, depending on soil properties and environmental conditions.  In the same studies mentioned above, urease inhibitors greatly reduced ammonia volatility for a 10-day period when applied onto a dry soil. Incorporation of urea into the soil by irrigation or rainfall will minimize volatilization losses. Therefore, if incorporating N into the soil by irrigation or rainfall soon after application is not a possibility, then a urease inhibitor is recommended.

Surface soil moisture will have a tremendous effect on the volatility potential of urea. Typically, urea applied on a dry soil will begin to slowly volatilize initially, but the rate of volatilization really takes off around three days after application. When urea is applied onto a soil that is saturated (without standing water), the rate of volatilization will begin much quicker, and the potential for volatilization losses over a given period of time will be much higher. Figure 1 above, which came from a volatilization trial conducted at the Rice Research Station in 2014, illustrates this phenomenon.

Addition of a urease inhibitor will help in reducing the amount of volatilization losses when urea is applied on a soil without standing water. However, the protection time is generally cut in half. Therefore, the 10-day protection time may only be five days if applied on a moist soil. If the urease inhibitor treated urea is dropped into standing water, the NBPT will not give you any protection.

With all that said, if the soil is too wet for ground equipment and your corn needs N as soon as possible, then you must choose between applying granular ammonium sulfate and urea by air. If urea is your fertilizer of choice, then it is best to wait to apply the N (from an N-efficiency standpoint) when the surface of the soil becomes dry. Applications of urea treated with a urease inhibitor will enable applications onto a soil with a wet soil surface without significant N losses for a few days. Expect large losses of N from urea if it is not treated with a urease inhibitor and it is applied onto a soil with a moist soil surface. Expect even greater losses of N from urea if it is applied into standing water.

Corn: With all the flooding, how much nitrogen have you lost?

Corn: With all the flooding, how much nitrogen have you lost? published on 1 Comment on Corn: With all the flooding, how much nitrogen have you lost?

The rainfall events that occurred last week have caused tremendous damage to northeast Louisiana farm land due to flooding. In addition to the water received from the rainfall events, some farms were inundated with even more water as nearby bayous and rivers overflowed a few days later. Many of the hardest hit farming operations are still trying to save equipment, livestock, and assets from the rising flood waters. Some farming operations situated on higher ground, such as the Macon Ridge, may have been spared from the flooding but were still affected from the excessive rainfall nonetheless. One of the most commonly asked questions I have been receiving lately is: How much of my nitrogen (N) fertilizer have I lost in my corn crop? Unfortunately, the question is not that straight forward to answer. You really have to consider several factors. What N source did you use? Was it surface broadcast, was it incorporated in after application, was it banded in the soil (knifed-in), or was it dribbled on the soil surface? What was the soil moisture like at the time of application? How long after the fertilizer application did the flooding conditions occur? Was a urease or nitrification inhibitor used? Just to name a few.

Corn seedlings under high moisture conditions
Corn seedlings under high moisture conditions

Let’s begin by considering the N fertilizer source. First, we need to remember that nitrate-N is not stable under flooded, anaerobic (no oxygen) conditions and that it will be converted to a gas and lost very quickly by a process called denitrification. Ammonium-N, on the other hand, is stable under flooded, anaerobic conditions and will not be lost.  Many farmers in northeast Louisiana use granular urea (46-0-0) or liquid UAN (urea ammonium nitrate; 32-0-0) as their N fertilizer source. The granular urea will be converted into the ammonium form after application through a process called hydrolysis. Therefore, if the flooding occurred quickly after urea application, most of the N will not be lost because it will be in the urea or ammonium form and will remain stable under flooded conditions. UAN on the other hand is made up of both urea and ammonium nitrate. The nitrate portion of UAN is approximately 25% while urea and ammonium-N make up the other 75%.  Therefore, we would expect 25% of the N that is in the nitrate form to be lost very quickly after flooding.

Now let’s consider the amount of time that the fertilizer N was applied prior to flooding. Ammonium can be converted to nitrate under aerobic (oxygen present) conditions by a process called nitrification. The longer ammonium fertilizer was applied prior to flooding, the more of the ammonium will be converted to nitrate through a process called nitrification. The rate of nitrification depends on several factors including soil type, presence of nitrifying bacteria, and the temperature of the soil. Research has shown a wide range of nitrification rates based on the aforementioned soil properties, so for our purposes let’s assume that the average nitrification rate under cooler soil temperatures (<65oF) would be about 2.5% per day and under warmer soil temperatures the average rate would be at least 4.5% per day.

Another thing we have to consider is whether or not a urease inhibitor or a nitrification inhibitor was applied on the granular fertilizer or mixed in with the liquid N fertilizer. A urease inhibitor (active ingredient NBPT or NPPT) will temporarily delay the conversion of urea to ammonium form (urea hydrolysis) and will therefore temporarily delay volatilization losses (conversion of ammonium-N to ammonia, a gas) and subsequent nitrification reactions (conversion of ammonium to nitrate).  Nitrification inhibitors (active ingredients nitrapyrin or DCD) will temporarily delay only the nitrification process.  Urease inhibitors and nitrification inhibitors will not last forever. Research at the H. Rouse Caffey Rice Research Station has shown that urease inhibitors will typically give you protection for approximately 10 days when applied on a dry soil, approximately five days when applied on a moist soil, and will provide no protection when applied into standing water. Recent research out of northeast Louisiana indicated that nitrification inhibitors can give you protection 10-30 days, depending on the environmental and soil factors involved.

Using the N source, nitrification rate, and the addition of a urease or nitrification inhibitor, we can begin to estimate how much N will be lost under various scenarios.

Scenario 1. A corn farmer on the Macon Ridge knifed-in UAN at a rate of 200 pounds of N just after planting. The UAN was not treated with a urease or nitrification inhibitor. Saturated soil conditions occurred 12 days after planting and lasted for 2 days. The soil temperature was <65oF.  How much N was lost?

Well, we know right away that 25% of the UAN is in the nitrate form and will be lost under saturated, anaerobic conditions. We also know that we have had 12 days for nitrification (conversion of ammonium to nitrate) to occur in a cool soil and that a nitrification or urease inhibitor was not used, so the nitrification rate will be about 2.5% per day.

Therefore, the N loses from denitrification = (0.25 * 200 lb N/A) + (12 days * 0.025 * 200 lb N/A) = 80 pounds of N per acre lost.

Scenario 2: Granular urea (46-0-0) was treated with a urease inhibitor and was applied on moist ground 3 days after planting at a rate of 50 pounds N per acre. A one-half inch rain occurred 2-days later that incorporated the urea into the soil, minimizing volatilization (ammonia gas) losses from the urea.  Flooding conditions occurred 15 days later and the field stayed under water for four days. The soil temperature was <65oF. How much N was lost?

This time all of the N is in the urea form to begin with and was protected from volatilization losses prior to the small incorporating rain.  However, the urease inhibitor probably only kept the fertilizer in the urea form for approximately 5 days before it was converted into the ammonium form.  Nitrification (conversion of ammonium to nitrate) could then occur for about 10 days.

Therefore, the loss of N from denitrification = 10 days * 0.025 * 50 lb N/A = 12.5 pounds of N per acre lost. In addition, I would expect that the corn would not be able to survive this situation and would have to be replanted.

Remember, these N loss estimates are not perfect. There are a lot of factors involved in estimating N loses that were not covered and it could be argued that the rates of nitrification or the time that a urease or nitrification inhibitor could differ depending on the research you use as your source. However, it is a good starting point and should help growers in northeast Louisiana determine how much N will be available in the soil once saturated soils dry and flood waters recede.

2014 Grain Sorghum Research and Extension Summary

2014 Grain Sorghum Research and Extension Summary published on No Comments on 2014 Grain Sorghum Research and Extension Summary

By: Rick Mascagni and Josh Lofton, LSU AgCenter

Sorghum_research_summary

Extension_Summary

 

For further questions, please contact:

Josh Lofton, Field crop agronomist, LSU AgCenter, jlofton@agcenter.lsu.edu

 

Sorghum Midge and White Sugarcane Aphid Concerns

Sorghum Midge and White Sugarcane Aphid Concerns published on 3 Comments on Sorghum Midge and White Sugarcane Aphid Concerns

David Kerns and I have been receiving numerous phone calls this week about problems with applications of pyrethroids tank mixed with Transform for control of midge and white sugarcane aphid. The use of a pyrethroid for control of sorghum midge is a common practice in Louisiana; however, pyrethroids are very toxic to beneficial insects and are very likely to flare white sugarcane aphids in grain sorghum. Co-appliations of Transform and a pyrethroid have led to white sugarcane aphids recolonizing fields very rapidly and often resulting in poor control of aphids overall.

Therefore, automatic insecticide applications for midge should be avoided, and applications should only be made if midge are present.  The Louisiana threshold for midge in sorghum is at 25 – 30% bloom, treat for one or more midge per head.  If midge and sugarcane aphids are present, tank mixed applications of chlorpyrifos and Transform will offer good midge control while also reducing the risk of flaring aphids. Chlorpyrifos may not be quite as effective as a pyrethroid for sorghum midge and large populations may require a second application 3 – 4 days later.  Transform tank mixed with Dimethoate is another option for midge and aphid control; however, producers should be prepared to follow up with a dedicated midge application 3 – 4 days later.

Also, pyrethroid applications for the headworm complex in grain sorghum are strongly discouraged. Pyrethroid resistance is very common in sorghum webworm and corn earworm in Louisiana, and insecticides such as Belt or Prevathon should be used for headworms. These chemistries are Lepidopteran specific and will not harm beneficial insects or flare sugarcane aphids.

 

Sugarcane Aphids in Sorghum

Sugarcane Aphid Numbers Increasing in Grain Sorghum

Sugarcane Aphid Numbers Increasing in Grain Sorghum published on 1 Comment on Sugarcane Aphid Numbers Increasing in Grain Sorghum

Infestations of sugarcane aphids in boot to heading grain sorghum are increasing in Louisiana. Many of these populations start off small and exponentially increase in a span of 5 to 7 days. Pyrethroid applications for midge control can reduce natural enemy numbers allowing sugarcane aphids to reach damaging numbers faster.  Honey dew produced by sugarcane aphid feeding will give the crop a glossy appearance and large accumulations will often result in sooty mold growth and harvesting issues later season.

Sugarcane Aphid Damage to Pre-boot Sorghum
Sugarcane Aphid Damage to Pre-boot Sorghum

Sugarcane aphids are difficult to control with currently labelled insecticides; however, Louisiana was granted a section18

Sugarcane Aphids in Sorghum
Sugarcane Aphids in Sorghum

emergency exemption for the use of Transform 50WG for the 2014 production season.  Transform applications should be initiated before grain sorghum becomes heavily infested and producers in Texas are making applications at 30% infested plants with 100 to 250 aphids per leaf present. Use lower aphid numbers with increasing stress due to plant water deficit. This treatment threshold appears to be working for Texas growers; however, these recommendations are not supported by university research due to the recent introduction of this pest to grain sorghum in the United States. Transform applications of 1 oz/acre should be used on medium to high sugarcane aphid populations with the largest gallonage per acre (GPA) feasible for applicators (5 GPA by air or 20 GPA by ground). If 1 ounce applications of Transform are not providing adequate control the rate should be increased to 1.5 oz/acre.

2014 Northeast Research Station Pest Management and Crop Production Field Day

2014 Northeast Research Station Pest Management and Crop Production Field Day published on No Comments on 2014 Northeast Research Station Pest Management and Crop Production Field Day
NERS Field Day Flyer
NERS Field Day Flyer

Transform Granted Section 18 for Control of Sugarcane Aphid in Louisiana Sorghum (Forage, Grain or Stover)

Transform Granted Section 18 for Control of Sugarcane Aphid in Louisiana Sorghum (Forage, Grain or Stover) published on No Comments on Transform Granted Section 18 for Control of Sugarcane Aphid in Louisiana Sorghum (Forage, Grain or Stover)

Transform WG Sec 18 Label for Sorghum                                                     Approval Letter With Effective/Expiration Use Dates

Please follow the link above to access the section 18 label.  The link to the approval letter outlines the effective and expiration dates for the use of Transform in sorghum, as well as specifics regarding number of applications and maximum acreage treated in Louisiana.

If you have any questions or concerns about sugarcane aphids or use of Transform in Sorghum please contact:

Sebe Brown at 318-498-1283 (cell) or 318-435-2903 (office)

Dr. David Kerns at 318-439-4844 (cell) or 318-435-2157 (office)

Dr. Julien Beuzelin at 337-501-7087 (cell) or 318-473-6523 (office)

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