David Moseley, Stephenson, Daniel O., Hendrix, James, Foster, Matthew, Parvej, Md Rasel, Towles, Tyler, Morlin Carneiro, Franciele, Miller, Donnie K., Dodla, Syam, Wang, Jim Jian, Conger, Stacia, Shiratsuchi, Luciano
In this article:
|Soybean Webinar: Misconceptions Across Soybean Growth Stages|
|How to Correct a Yield Map When Using Multiple Harvest Machines|
|Managing Irrigation Pumps with Automation|
|Should You Use N-stabilizers to Improve Corn Nitrogen Use Efficiency?|
|Importance of Refuge Compliance in Field Corn|
|2022 Cover Crop Termination|
|Corn Planting is Upon Us|
|Weed Science Fundamentals|
David Moseley, LSU AgCenter Soybean Specialist
A free webinar “Misconceptions Across Soybean Growth Stages” will be held on Thursday, February 24, 2022 at 11 am CST/Noon EST. The webinar will be conducted by Soybean Extension Specialist from across the US who are collaborating on a United Soybean Board funded initiative called ‘Science for Success.’ The soybean specialist will present for 3-4 minutes on each growth stage. There will be a question-and-answer session after the presentations.
Soybean producers, consultants, and agronomist can benefit from attending this webinar.
Examples of each growth stage can be found in the Louisiana Crops Newsletter, Volume 11, Issue 2 - March 2021.
Franciele Morlin Carneiro, LSU AgCenter Postdoctoral Researcher, and Luciano Shiratsuchi, LSU AgCenter Scientist
Grain combines, cotton pickers and other harvest machines collect yield data through yield monitors, and the data is sent by telemetry to places such as John Deere operation center or others. The data then can be used to generate yield maps. However, we need to be very careful during data processing to produce correct maps. Furthermore, some errors may occur during the harvesting operation, such as losing the connection of the GPS signal between machine receptor and satellite, field maneuvers on the borders of the farmer field, field format, labor notation, multiple harvest machines, calibration, and others. In this document we focus on generating correct maps using data that comes from multiple harvest machines.
Figure 1 below shows the flowchart of procedures that we need to follow from raw data to generate a corrected yield map.
Figure 1. Flowchart during harvesting processing.
The first essential thing is to identify how many machines are being used during harvest. If you have just one machine, you just need to filter the data using specific software such as Map Filter 2.0, Yield Editor, Excel, Minitab, and others (Figure 1). When there are two or more machines, it is crucial to normalize the data because the calibration often will not match between the machines, even if you try your best in the process (Figure 2).
Figure 2. Two machines were used during the harvest operation.
Figure 2A shows the raw yield data collected by the harvester highlighting big differences between two machines. Figure 2B shows the track of two harvest machines. One machine collected an average yield of 10,390 pounds per acre and another 11,798 pounds per acre, demonstrating an error between these harvest machines of about 12% (Figure 3).
Figure 3. Harvester path of machine 1 (yellow) and 2 (green) on the left and differences in yield on the right.
We need to calculate the average yield of the raw data per machine to normalize within each machinery. After data collection, divide yield point data per average yield within each machine (Equation 1), and then you have normalized data per machine. After normalization within each machine, you must merge all normalized data to filter out the influence of the machine calibration (Figure 4).
yield = x_i/x_m
Equation 1. Equation to normalize data from multiple harvest machines.
x_i = yield point data
x _m = average yield within each machine
Figure 4. Normalized yield data using multiple harvest machines, raw yield data (A) and normalized yield and filtered data (B).
The last step is to convert the normalized data from multiple harvest machines. To do that you have to multiply the normalized map by the average yield sold from the field.
Figure 5. Corrected yield map from data originating from multiple harvest machines.
If you want to know more details about this process please contact our LSU Precision Ag Team on: https://www.lsu.edu/agriculture/spess/index.php
Stacia L. Davis Conger, LSU AgCenter Engineer
Plans for managing irrigation should be well under way as we approach the beginning of the 2022 crop season under drought conditions. Now is the time to flow test each riser or well, determine the correct hole sizes to punch, unclog sprinklers from algae or debris, and test water quality. It’s also a great time to determine how decisions will be made and who will make them.
There are several management options available that vary widely based on management preferences and comfort with technology. One such option consists of transitioning pump operations, water sensors, pivots, and fuel management from in-person only to web-based monitoring through a website or phone app. Remote access is an additional tool that should be used in conjunction with other efficient irrigation practices such as soil moisture sensors and computerized hole selection. Though it won’t help with valve adjustments for changing fields on the same well, it can save pumping hours when you have watered out but need more time on a pressing matter elsewhere. Also, fuel levels in storage tanks can be monitored proactively and any maintenance concerns logged for attention.
At the Red River Research Station, where we are demonstrating an automated pump control product currently, well activation is not our primary goal for safety reasons. Instead, the product has been most advantageous for increasing communication between irrigators and detailed record keeping. Irrigators can set notifications for when a pump turns on or shuts off, which can be critical during dry periods and operating outside of normal business hours. We can also review or download our irrigation records at the end of the year for each field. Each irrigator has their own account, so accountability is never an issue.
If you have an interest in learning more about these types of products, please reach out to me at email@example.com or (318) 408-0973. Or, all are welcome to drop by the Red River Research Station to see it in action in the coming months.
Fig. 1. Screenshot of the map view from the app with grey circles showing that four wells and the linear move are not activated at the time.
Syam Dodla, Jim Wang, Rasel Parvej, and Matt Foster, LSU AgCenter Scientist
Nitrogen fertilizers contribute to the major share of fertilizer costs, especially in corn production. At present, nitrogen use efficiency (NUE) of the applied N-fertilizers is often below 40% and has great scope to improve it. The NUE tends to be even lower in the hot and humid climates such as Louisiana where the conditions are congenial for nitrogen losses. Soil nitrogen can be lost through volatilization, gas emissions (denitrification process), leaching and runoff. Astronomical increase in the N-fertilizer prices in the last year makes it more critical to improve NUE of high nitrogen using crops such as corn.
Use of N-stabilizer compounds is one of the best management strategies to improve NUE and potentially minimize fertilizer costs. N-stabilizer compounds are generally grouped into urease inhibitors and nitrification inhibitors. Urease inhibitors delay the urea hydrolysis that releases ammonium ions into the soil. Even though soils with a high cation exchange capacity can absorb ammonium ions, they can be lost to the atmosphere through volatilization, especially in alkaline soils. Nitrification inhibitors prevent the oxidation of ammonium ions to nitrite and nitrate that are relatively more prone to losses. Slowing down the urea hydrolysis and oxidation of ammonium ions can minimize nitrogen losses, increase the duration of nitrogen availability, and could provide agronomic and environmental benefits. However, the benefits of N-stabilizers vary appreciably depending on N-stabilizer type, whether nitrogen fertilizer is surface-applied or soil-injected, soil pH, time of application, climate, and interval between nitrogen fertilization and rainfall or irrigation. Many studies were conducted by various scientists throughout the US to evaluate the benefit of N-stabilizer compounds in improving corn NUE and ultimately improving grain yields. However, the findings were not consistent with some studies finding improved grain yields and others finding no yield improvement.
Multiple studies conducted by LSU AgCenter scientists at the Red River, Northeast and Central Research stations showed benefits of N-stabilizers are significant when used for surface applied of N-fertilizers compared to the soil injected nitrogen fertilizers. Nitrogen fertilizers could be surface-applied because of granular fertilizer use after the germination of crop or UAN applied using Y-drops or applied at pre-tassel. When the nitrogen fertilizers are surface applied, they lose appreciable amount of nitrogen through NH3 volatilization and nitrogen gas emissions. A two-year study conducted at St. Joseph and Bossier City in 2019 to 2020 showed that application of N-stabilizer (NBPT, a urease inhibitor) coated urea compared to uncoated urea improved corn grain yield up to 23% under a single surface band application at 4-5 leaf stage (Fig.1). The longer the gap between the surface application of N-fertilization and a rain or irrigation event, the higher the benefit of N-stabilizer use. The same study showed that urea coated with N-stabilizer (urease inhibitor) had 86% lower nitrogen loss through volatilization than uncoated urea in the initial 5-days before a rain event as well as improved leaf nitrogen content by 15%. In another study conducted in Red River (Latanier clay with pH 7.4) and Mississippi alluvial soils (Sharky clay with pH 6.01) from 2018 to 2019, we evaluated the benefit of different N-stabilizers with soil injected UAN (knifed in) applied at 120 or 240 lbs N/ac rate. In the Red River alluvial soil, UAN plus N-stabilizer increased grain yields in both years by up to 14% (Fig. 2). However, in 2018, yield improvement was observed only at 120 lb N/ac rate while in 2019, a yield improvement was observed for both rates. This could be due to poor crop growth during drier conditions in 2018, thus eliminating any benefit of minimized N-losses. On the other hand, in the Mississippi alluvial soil, grain yield was increased only in 2018 at the lower N-rate. In the Red River alluvial soils, alkaline soil pH (above 7) is more congenial for nitrogen loss through volatilization; hence, these soils could benefit from the use of N-stabilizer with urease inhibitor that slows down the release of ammonium ion from urea. Generally, there is a potential benefit from the use of N-stabilizers in Louisiana even with the soil injected UAN application, however the benefits could vary depending on the given year’s weather conditions. These findings are different from many studies conducted in northern parts of the U.S., where they did not see any yield benefit from the use of N-stabilizers with soil injected UAN. Potential yield gain observed in our studies is attributable to Louisiana’s hot and humid climate that is more congenial for N-losses. Further, application of high rates of nitrogen than the crop can use takes away the benefits of N-stabilizers. So, if N-stabilizers are used, decreasing the planned fertilizer application rate by 5 to 10% is desirable.
Overall, use of N-stabilizer benefits the most under the following conditions:
1. Nitrogen fertilizers are surface applied.
2. Nitrogen fertilizers are applied late in the season, such as pre-tassel application, when the temperatures are high.
3. The soil is light textured such as very fine sandy loams. Use of N-stabilizers containing both urease and nitrification inhibitors may provide the most benefit.
Figure.1: Effect of surface band application of urea and urea plus N-stabilizer on corn grain yields during 2019 and 2020 at St. Joseph and Bossier City. Control plots received no nitrogen application.
Figure 2: Two-year (2018 and 2019) average corn grain yields at two nitrogen rates treated with different N-stabilizers. Control plots received no nitrogen application. DCD: Nitrification inhibitor; NBPT: urease inhibitor. Nitrogen was applied as UAN-32. Experiment was conducted under rainfed conditions.
Tyler Towles, LSU AgCenter Entomologist
With field corn planting rapidly approaching in Louisiana, it is important to keep in mind the value of planting refuge. The vast majority of the field corn acreage planted in Louisiana express Bt proteins for protection against lepidopteran larval such as corn borers and corn earworms. A refuge serves as a method of insecticidal resistance management or IRM. A refuge can be deployed in several ways but should be within ½ mile of the Bt expressing field corn and should mature concurrently. The EPA mandates that for every 80 acres of Bt field corn, there should be 20 complimentary acres of non-Bt field corn. Refuge deployment strategies can be seen below.
To better understand the theory behind utilizing a refuge in field corn, I will use corn borers for an example. Since insecticide resistance is a naturally occurring phenomenon, there is a low possibility that some corn borers may survive after feeding in Bt field corn. Simply put, if two Bt resistant corn borer moths were to mate, the subsequent offspring would be more likely to survive Bt in the future. A refuge is an area of non-Bt field corn planted alongside Bt expressing field corn and it acts as a source of Bt-susceptible insects. In the rare instance that a corn borer larvae were to survive to adulthood in Bt field corn, it would likely mate with one or several of the many Bt-susceptible moths produced by the refuge, ultimately passing on Bt-susceptible offspring. However, in an instance where field corn refuge isn’t utilized, there would be fewer Bt-susceptible insects in the landscape, increasing the likelihood of two resistant insects mating.
Historically, field corn refuge compliance has been relatively low across the midsouth for various reasons. Due to this, we have seen a decrease in Bt protein efficacy primarily in corn earworm populations over the last several years. Field corn producers are less likely to realize this decrease in product efficacy because corn earworm isn’t a yield limiting pest in field corn. However, the corn earworm is a yield limiting pest in cotton on an annual basis. Crop consultants and cotton producers have noticed this decrease in Bt efficacy because additional chemical control measures are being warranted for corn earworm control in Bt expressing cotton.
Going forward, I am recommending that two-gene Bt field corn hybrids be utilized because it still provides excellent control of corn borers, which can be yield limiting pests in field corn. A newer Bt protein, Vip3A, is being marketed in field corn hybrids and cotton varieties. To prevent the selection of Vip3A resistant corn earworm, planting field corn hybrids expressing this protein should be avoided. There is data indicating that field corn hybrids expressing 2nd and 3rd generation Bt trait packages yield similarly signifying that there is little to no economic benefit to planting Vip3A expressing hybrids in the midsouthern US. In Louisiana and across the midsouth, the true value of the Vip3A protein lies in cotton and should be utilized in cotton only.
By James Hendrix, Dr. Donnie Miller, and Dr. Daniel Stephenson, LSU AgCenter Scientists
Termination methods and timing can be some of the most critical and frustrating decisions you can face in cover crop management. Soon, covers will be shifting to spring growth. Management practices, based on the specie(s) you planted, intended purposes and the successive crop, need to be finalized to maximize the benefits from the covers and allow a smooth transition to your following crop.
As we begin the 2022 crop season, it is important that you continually monitor your cover crop growth. We can expect sporadic periods of warm weather and rainfall during January through March, causing some covers to switch from fall/winter to spring growth. During these events, rapid growth can be expected in most covers, especially early spring legumes such as clovers, winter peas and vetches. Until now, most of these probably have provided only minimal ground cover since most of their vegetative growth occurs in the spring. The cereals can produce abundant biomass and groundcover in the fall, due to tillering, but will continue considerable vegetative growth during this time. Once past jointing, moisture intake by cereals can increase rapidly, which is necessary for progressing to the reproductive stage. This rapid uptake before termination can affect the soil moisture availability for the next crop and should be considered in your management plan. The Brassicas, such as tillage radish, should have produced most of their vegetative growth and ground cover in the fall. Once they enter the reproductive stage, chemical termination may not be effective, so termination by chemicals at the onset of this stage is advised. Based on which cover crop or mix you planted, the rapid growth can benefit or cause adverse results to your expected cover crop intentions, as well as your future crop.
If planting corn, covers generally will be terminated in February, allowing four to six weeks before planting for best IPM practices. This period can provide needed time to break the green bridge between crops, reducing insect issues. Also, this allows time for the covers to breakdown, potentially maximizing benefits and minimizing nutrient losses which may be utilized by the corn. Generally, as covers decompose, nutrients are released within four to six weeks post termination.
For crops with later planting dates, such as cotton or soybean, there are several issues to be considered in termination of some covers. Brassicas will soon be transitioning to the reproductive stage as the temperature warms. Both Brassicas and legumes should be terminated early in reproductive stages. If terminated later, chemicals may not be effective. Even after termination, Brassicas can cause possible green bridge issues due to their fleshy roots. Easily terminated cereals and legumes still in the vegetative stage can be terminated similarly but allowing a minimum of two to four weeks of non-actively growing covers crops before planting the successive crop. If Brassicas are planted in a mix with a cereal, termination of the Brassicas early in the year can significantly reduce the biomass produced by the cereal.
Recommended chemicals and rates. Remember to consult the label prior to use.
|Species||Chemical||Rate of Active Ingredient per Acre|
|Wheat||Glyphosate + Clethodim||1 # + .188 -.25 #|
|Legumes (exc. Clovers)||2-4 D||1 #|
|Clovers||Dicamba (approved labels only)||.5 #|
|Tillage Radish||2-4 D or LeadOff||1 # or 1.5 Oz|
|Cereals + Legumes Mixes (exc. Clovers)||Glyphosate + 2-4 D||1 # + 1 #|
|Cereal + Clover Mixes||Glyphosate + Dicamba (approved labels only)||1 # + .5 #|
Example: For rye + hairy vetch + crimson clover use glyphosate + 2-4 D + dicamba (approved labels only) 1 # + 1 # + .5 #
If you have specific issues related to termination: Contact Dr. Daniel Stephenson (Dean Lee RS) or Dr. Donnie Miller (Northeast RS)
By Matt Foster, LSU AgCenter Corn Specialist
With corn planting knocking at our door, now is a great time to review a few key recommendations to ensure the 2022 season gets off to a great start. A rapid and uniform stand is critical in achieving a productive crop. It is very important to plant when conditions are favorable because corn seedlings can be negativity affected by adverse conditions. Soil temperature, soil moisture, and planting depth are three factors that can influence corn establishment.
Soil temperature is the main factor influencing seedling growth rate. Cool soils (below 50 degrees Fahrenheit) can impede germination and seedling growth. Good germination and emergence can be expected once the soil temperature at a 2-inch depth reaches 55 degrees Fahrenheit by 9 a.m. for three consecutive days. This normally occurs in late February and March in Louisiana. In most years, the planting window for south Louisiana is Feb. 25 to March 20. For north Louisiana, it is generally March 10 to April 1. However, planting decisions should be based on soil temperature and not the calendar.
Adequate and uniform soil moisture is needed in the seed zone for proper corn establishment. Adequate moisture is usually defined as soil that is not too dry and not too wet. Excess soil saturation can kill corn seedlings, limit aeration, and hinder root development. Uneven soil moisture in the seed zone can lead to uneven seedling emergence and is generally a result of different soil types, tillage patterns, and inconsistent seeding depth. Closely monitoring soil moisture prior to planting will help ensure your corn gets off to a good start.
Typical planting depth recommendations are 1.5 to 2.5 inches. However, optimal depth can be slightly adjusted based on soil type and moisture conditions. Corn should never be planted less than 1.5 inches deep, as this can lead to root development issues and increased susceptibility to herbicide and insect injury. Deep planting can expose seed to cooler and wetter soils and delay emergence, thus leading to stand issues. Planting corn at a target depth of 2 inches is recommended because this ensures proper seed-to-soil contact and strong nodal root development.
Good seed-to-soil contact promotes uniform and rapid imbibition of water and leads to even emergence. Successful stand establishment is dependent on a good nodal root system. The first set of nodal roots are usually visible by the V2 leaf stage and are dominant by the V6 leaf stage. The nodal roots are a vital structural component of the plant and are responsible for the majority of nutrient and water uptake. A well-developed nodal root system helps reduce early season lodging and rootless corn syndrome. Taking the time to fine tune your planting depth will help optimize your emergence and stand.Best of luck this year!
Daniel Stephenson, LSU AgCenter Weed Scientist
Herbicide prices and shortages have made burndown applications quite complicated so far this year. Glyphosate, clethodim, S-metolachlor, atrazine, glufosinate, and others are either short or rumored to be in short supply. This is causing significant consternation among growers, consultants, retailers, and those of us who are trying to help.
In light of these issues, maximizing the efficacy of herbicides is critical. To do this, fundamentals must be followed. They are:
1. Choose a herbicide(s) that works best for target weed species;
2. Apply the correct herbicide rates for the target weeds species;
3. Utilize correct water volume (GPA);
4. Apply to actively growing weeds 4 inches or less in height/length;
5. Spray nozzles should be no more than 18 inches above target at application;
6. Application when weather is a favorable before, at, and after application.
Louisiana growers usually have 5 to 10 different grassy and broadleaf weed species in their crop each year. For so long, glyphosate has controlled most of them with no problem. Yes, glyphosate-resistant weeds are terrible and we should be utilizing other herbicidal modes of action for their control. However, we rely on glyphosate for so much. Follow the fundamentals of weed science when developing a weed management plan and at application. Make every effort to do it correctly. If you have any questions or concerns, please contact your local parish agent. My contact information is 318-308-7225. We are here to help.