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Refuge Requirements for Field Corn

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With the corn growing season rapidly approaching, many producers are faced with the task of deciphering what refuge their chosen variety or varieties require.  First, many of the varieties available have Bt genes solely for control of western corn rootworm. Western corn rootworm is rarely a problem in Louisiana and varieties containing this gene will not control the predominate species of Southern corn rootworm our producers face every year.  However, varieties containing the corn rootworm trait require a specific in-field or adjacent refuge instead of the ½ mile refuge Louisiana producers are familiar with.

Below is a link to a list of corn varieties, their refuge requirements, and target pests from Mississippi State. Mississippi is considered a cotton growing area and the refuge requirements, including the corn rootworm trait, are the same for Louisiana.

http://www.mississippi-crops.com/wp-content/uploads/2012/03/P2471_p471.pdf

*Beware that any variety that specifies corn rootworm control must have a refuge in the same field or adjacent to the Bt corn. If the variety does not specify corn rootworm, as a target pest, then the refuge can be a ½ mile distance from the Bt corn.

For more information or if you have any questions or concerns please contact Sebe Brown, or Drs. David Kerns or Julien Beuzelin.

Sebe Brown   Cell: 318-498-1283   Office: 318-435-2903

Dr. David Kerns  Cell: 318-439-4844    Office: 318-435-2157

Dr. Julien Beuzelin Cell: 337-501-7087  Office: 318-473-6523

Richland Parish Soybean and Corn Update

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Corn yields in Richland Parish continue to be good.  With 40-50% of the corn harvested, we are averaging 10-15 bushels per acred higher than last year. We had corn planted into late April so some producers have not started harvesting yet while others have completed harvest or will be in a day or so.

Soybeans planted in late March and early April are being harvested. A couple of dryland yields were 40 bu/a or better which is excellent and irrgated beans much better.  Soybean dessication will continue on a weekly basis from this point forward.  Stink bugs have been very light this year but we had to treat some beans for stink bugs in some fields I have been scouting. Some of these had to be treated for loopers as well. These were soybeans planted the last week of April.

Early Corn Yields in Richland Parish

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Corn harvest began in mid-July in Richland Parish and early yields are good. With approximately 5-10% of the acreage harvested, yields reports are  ranging from 180-220 dry bushels per acre.  Grain moisture is 19-22% which are getting dried and going to bins.  Planting dates on harvested corn started with mid-February to first week of March plantings on corn currently being harvested.  One farm has harvested about 600 acres with center pivot yields at 200 bu/a and furrow irrigated around 225 bu/a.  Corn yields normally get better as harvest progresses but time will tell.

The dangers of irrigating with low quality water

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Figure 1. Typical visual symptoms of salt injury in soybeans
Figure 2. Canopy view of early salt injury with no evident signs of damage
Figure 3. Early visual symptoms beginning at 2nd node

By Dr. Josh Lofton, Agronomist – Macon Ridge Research Station

Throughout the month of May and the first week of June the majority of the state experienced hot and dry conditions. Coupled with the rapid growth rates experienced by corn, soybeans and cotton, this situation has required some producers to irrigate for almost two months. While this is a mild concern for some, this intensive irrigation season is a major concern for producers with irrigation water containing elevated levels of salt. Many may not be aware of their potentially low quality irrigation water or may be experiencing this threat for the first time this year, and if current trends continue, irrigation water with high salt concentrations will become an increasing threat to crop production in coming years.

What is the best way to identify crops suffering from salt injury? Plants will usually resemble drought injury, such as wilting and a reduction in leaf area, even though adequate moisture is present within the soil system. Other visual symptoms include pale green and yellow leaves followed by necrosis. These symptoms usually begin exhibiting themselves around the leaf margins (Figure 1). Continuous salinity problems will cause these symptoms to spread throughout the plant and if severe issues are present the plants will eventually die. Because these symptoms first appear in the lower leaves, early identification may be difficult to spot until serious conditions exist. An example of this occurred in soybean trials at the Macon Ridge Station, where there appeared to be no signs of damage across the canopy (Figure 2); however, there was clear evidence of salt injury in the under-canopy (Figure 3). Therefore, in-field scouting may be needed to help identify this problem.

If salt damage has been identified, how detrimental is this to your current crop? The answer can be difficult to determine for every situation not only because crops are affected by salt levels differently but also soil texture and location within the field can influence salt injury. Areas that receive higher rates of low quality irrigation, such as within the first third of a field under furrow irrigation, usually show higher incidence and intensity of salt injury than areas further through the field. Lower portions of the field, where irrigation water can accumulate, will show worse salinity problems than higher, well drained areas. Further, sandier soils have greater leaching of salts during rainfall events than soils with higher clay content. However, it takes approximately 5 to 6 inches of rainfall to decrease the salt level of the topsoil by 50%. The crop itself can be highly influential on the severity of the salt injury that occurs. Some crops such as rice, soybeans, and corn, can show a rapid decline in yield compared to cotton and to a lesser degree wheat and grain sorghum (Table 1). In addition, soybean varieties can show higher salt tolerance, termed salt excluders, than others, termed includers. Damage ratings are currently available for soybean varieties through the 2011 soybean OVTs at the Macon Ridge location.

If a problem field is identified, what is the next step? Since salt injury can vary in severity and symptoms can be similar to other deficiencies or toxicities, proper samples need to be collected from the soils and irrigation wells. Samples can be sent to the LSU AgCenter Soil Testing and Plant Analysis Laboratory (STPAL) located on the LSU campus in Baton Rouge. A soluble salts test, at $5 per sample, can be used to determine the amount of salts in your soil that could potentially be affecting your crops. Additionally, irrigation samples can be submitted to the STPAL with a “quick water analysis” for $6 per sample, determining not only total salts in the irrigation water but also electrical conductivity (E.C., estimate of soluble salts), sodium, and chloride concentration.

If your soils are found to be at toxic levels for salts/, what steps can be taken within this growing season to minimize the detrimental effects? Unfortunately, based on the current data available unless another fresh source of water can be obtained, little can be done in-season. However, at this point one of the greatest concerns is high salt accumulation in the soil. If this salty irrigation water continues to be applied to the soil, irreparable damage can be done within a very short time and will be detrimental to crops and soils for many years. The best management practice for the long term sustainability of the production system would be to limit irrigation events or even completely stop irrigating if water is found to be severely low quality.

What steps can be taken during future growth seasons to minimize the impact to production and soil systems? As mentioned previously there are varieties within sensitive crops that are more tolerant to salinity than others. However, if salt levels in the irrigation water are high, switching production systems to a crop that has a lowered irrigation demand, such as grain sorghum or cotton, may be the best alternative. In these instances this would change how both producers and landlords determine the crop rotations and land allocations; however, long term productivity of our valuable resources and being a good steward needs to be a consideration in these situations.

As we continue to see this problem become a greater issue across many areas of Louisiana, everyone within the agricultural community must become more knowledgeable about salinity issues and the damage to our production systems that this issue can cause.

 

 

Year of the Pigweed

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By Dr. Daniel Stephenson, LSU AgCenter Weed Scientist

 

We have all seen or heard about the tremendous troubles glyphosate-resistant Palmer amaranth is causing producers in Arkansas, Georgia, Mississippi, Tennessee, and other states as well as the steps they have to take to manage it.  Applications of residual herbicides preplant, preemergence, early-postemergence, postemergence-directed, and post-harvest in addition to hand-hoeing have been become a requirement.  In Louisiana, the LSU AgCenter confirmed the presence of glyphosate-resistant Palmer amaranth in 2010.  Prior to 2012, we knew it was primarily located in Concordia, Madison, and Tensas Parishes.

Unfortunately, Louisiana is experiencing an explosion of instances where glyphosate is not controlling Palmer amaranth in 2012.  Whether I have personally seen locations or had numerous calls from producers, consultants, or industry representatives telling me about the failures, the problem is ballooning.  Locations where I have received calls in 2012 include Northeast, Northwest, Central, and South-central Louisiana, so it isn’t just a problem for a few Mississippi River parishes anymore.

Although corn weed control in-crop is over, producers need to utilize post-harvest weed management techniques.  Considering the early corn crop Louisiana will have this year, we will be left with many months of excellent growing conditions for Palmer amaranth and all other weedy species.  Post-harvest weed management techniques include multiple tillage operations, applications of a non-selective herbicide plus a residual herbicide, or a combination of both tillage and herbicides.  The goal is to prevent weeds from producing seed.  Another consideration is sanitation during and after crop harvest.  Harvesting and tillage equipment are excellent tools for spreading weed seed.  All equipment should be thoroughly cleaned to remove weed seed before moving to the next field.

Hand removal of weeds that escaped herbicide applications is very important also.  For example, a soybean field has lapped and you spot a couple of pigweeds still growing out in the field.  It is not that difficult to walk out in the field, pull them up, take them out of the field, and burn them.  The old saying is “an ounce of prevention is worth a pound of cure”.  With potentially glyphosate-resistant weeds, prevention is worth much more than a pound.

LSU AgCenter weed scientists feared that we’d have a year were pigweed populations exploded.  Well, 2012 is that year!  If you suspect a problem, call your local county agent for help and remove the weeds from your field.  Don’t just ignore this issue.  It must be taken seriously.

Adult and Immature Chinch Bugs

Chinch Bugs in Late Corn and Grain Sorghum

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With the lack of rainfall in much of Louisiana, Dr. David Kerns and I have been receiving more calls regarding chinch bugs in late corn and grain sorghum. Chinch bugs are small insects 1/5 to 1/6 inch in length, with a black body and white front wings creating a white X when viewed from above. Immature chinch bugs resemble the adults only smaller and lacking wings.  Nymphs range in color from reddish brown to black in later instars.

Chinch bugs are typically active on grasses in and around fields and movement to seedling corn and grain sorghum is common. Damage by both adults and nymphs causes corn to have a reddish appearance on the stem and leaves.

Chinch Bug Damage in Grain Sorghum
Chinch Bug Damage in Grain Sorghum : Photo Courtesy of LSU AgCenter

Continued feeding can cause plants to wilt and eventually die.  Corn is most susceptible in the seedling stage when plant growth is slow and conditions are dry.  Seed treatments and soil insecticides will typically give an 18 day window of protection after emergence. However, during dry conditions water stressed plants are more susceptible to injury and seed treatments may not provide as long of protection as under adequate moisture conditions. Once plants have surpassed the most susceptible stage, chinch bug damage becomes less of an issue.

Adult and Immature Chinch Bugs
Adult and Immature Chinch Bugs: Photo Courtesy of Bart Drees TAMU Agrilife

If plant growth is slow and chinch bug numbers have reached 5 or more on 20% of plants 6 inches tall or less, a foliar rescue treatment should be applied to stop injury.

When using ground equipment, a high volume, high pressure sprayer delivering a minimum of 20 gpa should be used.  Aerial applications should only be used if ground equipment cannot make it across a field.

If you have any questions or concerns feel free to contact Dr. David Kerns or Sebe Brown for more information.

Dr. David Kerns                Cell: 318-439-4844                          Office: 318-435-2157

Sebe Brown                       Cell: 318-498-1283                          Office: 318-435-2903

Cutworm damage in corn

Cutworms in Corn

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 Sebe Brown, Dr. David Kerns, LSU AgCenter Entomologists, Dr. John S. Kruse, Cotton and Feed Grain Specialist

 This week, Dr. David Kerns and I scouted corn fields at V1 in Evangeline Parish for cutworm damage.  Cutworms are usually problems in reduced tillage or no till fields that received a late burndown application leaving weed hosts. However, the fields we scouted were very clean and above ground damage was evident with clipped leaves and larvae being easily found on the tops of rows. Starting clean can help alleviate many problems from early season insect pests; however, clean fields should be routinely scouted for cutworms.

Cutworm damage in corn
Cutworm damage in corn

The largest amount of the damage was found in non-Bt refuge corn. Fortunately, the larvae were feeding above the soil surface clipping early leaves and not burrowing down to the root zone damaging the growing point. Seedling corn (up to V4) can withstand injury from cutworms as long as the growing point has not been damaged.

Thresholds for cutworms in Louisiana corn are 6 to 8% damage from above ground cutting or 2 to 4% from below ground boring. With cooler weather moving into Louisiana, cutworms may be located closer to the soil surface in seedling corn. Warmer weather drives the cutworms to burrow down deeper into the soil increasing the risks of having corn injured at the growing point.

Cutworm next to damaged corn
Cutworm next to damaged corn

 

Insecticide seed treatments should not be expected to give adequate control of cutworms and Bt technology can provide some protection. VT3 Pro, VT2 Pro, Herculex and SmartStax technologies should help reduce cutworm injury: however, large larvae may overcome these traits. Large larvae are less susceptible to Bt toxins than small larvae.

 

If an insecticide application is deemed necessary, a relatively low label rate of a pyrethroid will reduce cutworm injury. Bifenthrin would be a good choice due to its soil activity.

 

True Armyworms Damage to Corn

True Armyworms and Chinch Bugs in Corn

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I have been receiving reports of true armyworms and chinch bugs in corn. True armyworms will usually move into corn once grass hosts have been exhausted or a recent burndown application has been made removing their primary host source.

Corn planted in close proximity to wheat is also susceptible to damage by migrating armyworms. Infestations are typically found around field margins where armyworms have migrated from a wheat field or grassy area. True armyworm damage gives corn plants a tattered appearance with frass (insect feces) present on the leafs or in the whorl of the plant during active infestations.

True Armyworms Damage to Corn
Photo Courtesy of Ron Hammond OSU extension

Most transgenic corn varieties offer protection against armyworm damage. However, single gene varieties such as Yield    Guard and Herculex 1 may be overwhelmed when large populations of armyworms are present. Adverse environmental conditions can influence the expression of Bt genes in corn, and larval size is also a contributing factor for control. Normally large larvae are more difficult to control than small larvae.

As long as the growing point has not been injured, young corn (up to V4) can withstand substantial amounts of defoliation and not see a significant drop in yield. Grass control around fields can help prevent outbreaks of armyworms.

Chinch bugs are small insects 1/5 to 1/6  inch in length, with a black body and white front wings creating a white X when viewed from above. Immature chinch bugs resemble the adults only smaller and lacking wings.  Nymphs range in color from reddish brown to black in later instars.

Chinch bugs are typically active on grasses in and around fields and movement to seedling corn is common. Damage by both adults and nymphs causes corn to have a reddish appearance on the stem and leaves.

Chinch Bug Damage in Grain Sorghum
Chinch Bug Damage in Grain So

 

Continued feeding can cause plants to wilt and eventually die.  Corn is most susceptible in the seedling stage when plant growth is slow and conditions are dry.  Seed treatments and soil insecticides will typically give an 18 day window of protection after emergence.  Once plants have surpassed the most susceptible stage, chinch bug damage becomes less of an issue.

Adult and Immature Chinch Bugs
Photo Courtesy of Bart Drees TAMU Agrilife

If plant growth is slow and chinch bug numbers have reached 5 or more on 20% of plants 6 inches tall or less, a foliar rescue treatment should be applied to stop injury.

When using ground equipment, a high volume, high pressure sprayer delivering a minimum of 20 gpa should be used.  Aerial applications should only be used if ground equipment cannot make it across a  field.

If an application is deemed necessary, bifenthrin would be the product of choice for ground and air.

 

Zinc Deficiency in Corn: Post-Planting Analysis

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By Dr. John S. Kruse, Cotton and Feedgrain Specialist

Several producers and consultants have contacted me this spring with photographs and reports of yellow-striped corn in the two to three leaf stage. ]

In many instances, these symptoms appear to be zinc deficiency, and what is so interesting is how widespread it was in the corn planting areas of Louisiana. Zinc is a trace element, meaning the corn plant does not require very much of it (compared to nitrogen or potassium), but it is very much needed in small amounts, and the lack of it can result in measurable yield reductions. Zinc is absorbed by the plant as a positively charged ion (cation: Zn2+), and is important in the synthesis of tryptophan – a building block of certain proteins that are needed for the production of auxins (growth hormones). Zinc is generally more available in acid soils and less available in neutral to alkaline soils.

Zinc can also react with phosphate to the point that it is bound up and less available to the plant. Many soils in the Red River Valley, with high pH and sometimes high phosphorus, often need supplemental applications of zinc to optimize yields.

However, apparent zinc deficiency has been observed on the Macon Ridge (generally acid soils) and in the Delta (generally slightly acidic soils) this year, as well. The causes can be varied, but certainly repeated corn production can result in less than ideal soil levels of zinc. Also, if a producer has historically planted cotton and/or soybeans for a number of years and has not had to pay close attention to zinc levels, a switch to corn may reveal the need for supplemental zinc. If soil test zinc is less than 1 ppm, supplemental zinc should be applied.

If soil test zinc is between 1 and 3 ppm, it may be needed, and if it is above 3 ppm it should not need to be applied under most circumstances. An ideal time to apply zinc is at planting in a band across the surface of the planting zone.

Recent research suggests between 2.5 to 5 pounds of actual zinc per acre is a good rate. If it is too late for a zinc application at planting, a second choice would be to include the zinc in the nitrogen sidedress application at 2.5 lbs per acre actual zinc. If a foliar application is desired, apply 0.1 to 0.25 pounds of actual zinc per acre in 20 gallons of solution.

The high volume of water is needed to prevent foliar burn. Repeat this application 10 to 14 days later, if possible. Mixing zinc with phosphorus fertilizer is not recommended due to the potential for nutrient binding. Chelated zinc, particularly EDTA-chelated zinc is a very good source of zinc. Zinc sulfate granules can also be dissolved in solution and applied as a spray.

Spreading granular zinc is not an ideal method due to the fact that such a small amount is spread over such a large area that many corn plants will not come into contact with it. Zinc oxides are relatively insoluble and slow to break down and become available, and are not recommended sources of zinc.

A consultant recently asked if grain sorghum needs supplemental zinc. It turns out little research has been done in this area, but several University-authored sorghum production manuals did not emphasize sensitivity to zinc as a major issue. Texas producers are cautioned to maintain optimal levels of iron (Fe) in grain sorghum due to the nature of their soils.

Figure 1. Apparent zinc deficiency in young corn. Note interveinal striping. As the condition worsens, striping may appear white and become broader.

Influence of Nitrogen Fertilizer Rate, Source, and Time of Application on Improving N Efficiency: Silt Loam

Influence of Nitrogen Fertilizer Rate, Source, and Time of Application on Improving N Efficiency: Silt Loam published on No Comments on Influence of Nitrogen Fertilizer Rate, Source, and Time of Application on Improving N Efficiency: Silt Loam

H.J. “Rick” Mascagni, Jr. and Brenda Tubana

Introduction

            Nitrogen (N) fertilization is a critical cultural practice required for producing maximum corn yield. Many factors, including soil type and crop management systems, determine optimum N rates. Nitrogen is typically knifed-in soon after the crop has emerged and an adequate stand established. Growers often times split N fertilizer applications as part of their management system or, in some cases, due to uncontrollable factors such as excessive or lack of rainfall, may produce soil conditions conducive to N fertilizer loss through denitrification and/or inefficient plant N uptake.  If N is topdressed with a fertilizer containing urea losses may occur due to volatization, which depends to a large extent on climatic and soil factors. If irrigated or rainfall occurs (0.5 inch or greater) within about three days, the fertilize is incorporated and no or minimal volatization losses will occur  Sometimes N applications are delayed or omitted due to inclement weather, while at other times, growers apply the recommended N rate for an expected yield potential. However, as the crop develops yield potential may be higher than expected and additional N may be required. In each of the above situations the question arises, how late can N fertilizer be applied and be effective? The fertilizer N source is also an important component of an effective fertility program. Products are also available such as urease inhibitors (i.e., Agrotain) that minimize urea volatization losses for 7 to 10 days. The objective of this trial was to evaluate N applications, N sources, and an urease inhibitor at different growth stages on a Mississippi River silt loam.

 Procedures

            A field experiment was conducted in 2011 on Commerce silt loam at the Northeast Research Station near St. Joseph to evaluate the influence of N rate, timing, and fertilizer source on corn yield and N fertilizer use efficiency (NFUE). Early-season N rates were injected at about the 3-leaf growth stage (April 16) as 30-0-0-2 solution (UAN) at N rates of 0, 120, 150, 180, and 210 lb N/acre. Urea, with and without Agrotain (3 qts/ton urea), was also hand-broadcast at the rate of 120 lb N/acre at the 3-leaf growth stage. For the early-season N rate of 120 lb/acre using 30-0-0-2, supplemental N rates of 30 and 60 lb/acre were applied at about the 12-leaf (May 23) and early-silk growth stages (June 7). Urea, with and without Agrotain, was hand-broadcast  and 30-0-0-2, with and without Agrotain, was hand-dribbled (to simulate a dribble application) at the 12-leaf and early-silk applications. There were a total of 23 treatments (see Table 2). REV® 28HR20 was planted on March 24 at 32,000 seed/acre. Cotton was the previous crop and all LSU AgCenter recommended cultural practices were followed.

             The experimental design was a randomized complete block with four replications. Grain yield, yield components, plant N, seed N, NFUE, and remote sensing data were determined. Grain yield was determined by machine harvest from the two middle rows of four-row plots and reported at 15.5% moisture. Yield components, seed weight (g/100 seed) and ear size (seed/ear) were also determined from the two middle rows.  Ear-leaf samples were collected at the early- silk growth stage to determine the influence of treatments on the N status of the plant. Seed samples were also collected at harvest. Total N was determined in the plant tissue and harvested seed by the LSU AgCenter’s Soil and Plant Testing Lab. Seed-N uptake (lb N/acre) was calculated by multiplying seed-N concentration by grain yield. NFUE was calculated using the following formula: (seed-N uptake for a given N rate – seed-N uptake for the no-N control) / N rate.   Remote sensing data using a SPAD meter were also determined at the 3- and 12-leaf growth stages. Statistical analyses were performed using the GLM procedure of SAS using a probability level of 0.10.

 Results and Discussion

            Rainfall was extremely low in May with a only a total of 4.9 inches in May and June in this dryland trial (Table 1). However, overall yields were extremely good averaging over 150 bu/acre (Table 2).

             At early-season, urea, urea + Agrotain, and UAN were compared at the 120 lb N/acre rate. Yield response had the following rank: UAN = urea + Agrotain > urea (Table 2). Evidently, there was some N loss due to volatization for the urea fertilizer. There was a 10 day interval between application and the first rainfall event. For the late N applications at the 12-leaf growth stage and early silk, both the 30 and 60 lb N/acre rates increased yields across sources. Yields tended to be a little higher for the early silk compared to 12-leaf applications. There were 11 and 2 day intervals between application and rainfall for the 12-leaf and early-silk applications, respectively. There was a yield response to urea + Agrotain for the 30 lb N/acre late application at the 12-leaf growth stage. When comparing equivalent N rates applied either once early season or split between early season and 12 leaf or early-silk growth stages, yields were similar. The treatment influence on kernel weight and ear size (kernel number) are shown in Table 2.

 Plant and seed N data are presented in Table 3. Leaf N, seed N, seed N uptake, and NFUE had the following rank for the early-season N treatments: UAN>urea+Agrotain>urea. Similar to yield responses, there were only small differences between the 12-leaf and early-silk late N applications for each N trait. Nitrogen fertilizer use efficiency (NFUE) was extremely high, ranging from 0.36 to 0.78 (Table 3). There were no differences in NFUE between the single and split applications, when comparing equivalent N rates. SPAD readings reflected treatment effects similar to yield responses (Table 4).

 

Table 1. Rainfall in St. Joseph, 2011.

Month

Rainfall

 

inches

 

 

March

8.3

April

3.0

May

0.9

June

4.0

July

4.4

August

1.3

 

Table 2. Influence of N fertility treatments on corn yield and yield components on Commerce silt loam, 2011.

 

 

 

N rate

 

 

 

 

 

 

 

ESN1 rate

ESN

source2

 

12-leaf

Early silk

Late N

source

Total N

applied

 

Yield

 

Ears

Kernel

weight

 

Kernels

lb/a

 

———lb/a——

 

lb/a

bu/a

no/a

g/100

no/ear

 

 

 

 

 

 

 

 

 

 

0

0

39.6

31,390

31.7

124

120

Urea

120

116.7

32,700

32.0

293

120

Urea + Ag

120

141.9

32,700

33.4

329

120

UAN

120

145.8

33,350

34.4

365

 

 

 

 

 

 

 

 

 

 

120

UAN

30

Urea

150

160.7

33,350

34.7

327

120

UAN

30

Urea+Ag

150

169.4

32,700

34.1

386

120

UAN

30

UAN

150

165.8

30,740

34.7

423

120

UAN

30

UAN+Ag

150

165.6

32,700

36.0

385

Average

 

 

 

 

165.4

32,370

34.9

380

 

 

 

 

 

 

 

 

 

 

120

UAN

60

Urea

180

170.0

32,050

35.2

386

120

UAN

60

Urea+Ag

180

176.8

34,010

36.2

397

120

UAN

60

UAN

180

160.3

33,350

35.2

357

120

UAN

60

UAN+Ag

180

166.2

32,700

35.1

378

Average

 

 

 

 

168.3

33,030

35.4

380

 

 

 

 

 

 

 

 

 

 

120

UAN

30

Urea

150

168.5

34,660

35.1

361

120

UAN

30

Urea+Ag

150

151.8

33,350

34.9

368

120

UAN

30

UAN

150

168.7

32,700

35.7

389

120

UAN

30

UAN+Ag

150

168.0

33,350

34.3

386

Average

 

 

 

 

164.3

33,520

35.0

376

 

 

 

 

 

 

 

 

 

 

120

UAN

60

Urea

180

177.0

32,700

35.6

403

120

UAN

60

Urea+Ag

180

172.8

34,010

34.4

383

120

UAN

60

UAN

180

166.5

33,350

34.1

381

120

UAN

60

UAN+Ag

180

170.0

32,700

35.1

393

Average

 

 

 

 

171.6

33,190

34.8

390

 

 

 

 

 

 

 

 

 

 

150

UAN

150

166.2

34,010

34.3

374

180

UAN

180

169.8

30,740

33.9

432

210

UAN

210

178.8

34,010

36.7

380

 

 

 

 

 

 

 

 

 

 

LSD (0.10):

 

 

 

 

14.7

NS3

2.7

53

                                                 

1ESN, early-season N injected at about 3-leaf growth stage.

2Ag = Agrotain; UAN = 30-0-0-2;

3NS = Non-significant at the 0.10 probability level

 

Table 3. Influence of N fertility treatments on N nutrition of corn on Commerce silt loam, 2011.

 

 

 

N rate

 

 

 

 

 

 

ESN1 rate

ESN

source2

 

12-leaf

Early silk

Late N

source

Total N

applied

 

Leaf N

 

Seed N

Seed N

uptake

 

NFUE3

lb/a

 

———lb/a——

 

lb/a

%

%

lb N/a

 

 

 

 

 

 

 

 

 

 

 

0

0

1.18

1.28

39.7

120

Urea

120

1.57

1.22

82.0

0.36

120

Urea + Ag

120

1.86

1.38

107.9

0.57

120

UAN

120

2.24

1.43

133.0

0.78

 

 

 

 

 

 

 

 

 

 

120

UAN

30

Urea

150

2.30

1.40

116.9

0.52

120

UAN

30

Urea+Ag

150

2.23

1.43

135.0

0.64

120

UAN

30

UAN

150

2.26

1.44

141.7

0.68

120

UAN

30

UAN+Ag

150

2.32

1.45

143.5

0.69

Average

 

 

 

 

2.28

1.43

134.3

0.63

 

 

 

 

 

 

 

 

 

 

120

UAN

60

Urea

180

2.32

1.50

142.4

0.57

120

UAN

60

Urea+Ag

180

2.27

1.55

166.4

0.71

120

UAN

60

UAN

180

2.15

1.50

138.1

0.55

120

UAN

60

UAN+Ag

180

2.36

1.52

145.4

0.59

Average

 

 

 

 

2.28

1.52

148.1

0.61

 
 

 

 

 

 

 

 

 

 

 

 
120

UAN

30

Urea

150

1.40

135.0

0.64

 
120

UAN

30

Urea+Ag

150

1.44

136.1

0.64

 
120

UAN

30

UAN

150

1.48

146.9

0.72

 
120

UAN

30

UAN+Ag

150

1.48

143.7

0.70

 
Average

 

 

 

 

1.45

140.4

0.68

 
 

 

 

 

 

 

 

 

 

 

 
120

UAN

60

Urea

180

1.47

151.7

0.63

 
120

UAN

60

Urea+Ag

180

1.53

149.8

0.61

 
120

UAN

60

UAN

180

1.47

139.1

0.56

 
120

UAN

60

UAN+Ag

180

1.45

142.4

0.58

 
Average

 

 

 

 

1.48

145.8

0.60

 
 

 

 

 

 

 

 

 

 

 

 
150

UAN

150

2.28

1.45

139.3

0.67

 
180

UAN

180

2.50

1.49

146.9

0.60

 
210

UAN

210

2.48

1.48

154.4

0.55

 
 

 

 

 

 

 

 

 

 

 

 
LSD (0.10):

 

 

 

 

 

0.16

0.10

21.7

0.14

 
                                                   

1ESN, early-season N injected at about 3-leaf growth stage.

2Ag = Agrotain; UAN = 30-0-0-2;

3NFUE = N fertilizer use efficiency

Table 4. Influence of N fertility treatments on SPAD readings taken early season and at 12-leaf growth stage on Commerce silt loam, 2011.

 

 

 

N Fertilizer Source

 

 

 N rate1

 

Total N

 

Urea

Urea + Agrotain

 

UAN2

UAN + Agrotain

 

Average

lb/acre   ———————————SPAD Readings ————————————-
 

 

 

 

 

 

 

 

 

 

Early-Season N Application

 

 

 

 

 

 

 

 

120

120

38.5

44.0

46.9

43.1

150

150

48.5

48.5

180

180

51.1

51.1

210

210

52.4

52.4

 

 

 

 

 

 

 

 

 

 

     12-leaf Growth Stage N Application

 

 

 

 

 

 

30

150

49.2

46.4

50.0

50.4

49.0

60

180

50.1

52.2

48.4

51.2

50.5

Average

 

49.7

49.3

49.2

50.8

 

 

 

 

 

 

 

 

LSD (0.10):

 

 

 

3.8

 

 

                   

1N rate applied early-season (3-leaf) and 12-leaf growth stage

2UAN = 30-0-0-2 fertilize solution

 

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