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

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

 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 N fertilizer 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 clay soil.

 Procedures

            A field experiment was conducted in 2011 on Sharkey clay 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 four-leaf growth stage (April 15) as 30-0-0-2 solution (UAN) at N rates of 0, 150, 210, and 240 lb/acre. Urea,with and without Agrotain (3 qts/ton urea), was also hand-broadcast at the rate of 150 lb N/acre at the four-leaf growth stage. For the early-season N rate of 150 lb/acre using 30-0-0-2, a supplemental N rate of 60 lb/acre was applied at about the 12-leaf (May 22) and early-silk growth stages (June 2). Urea was hand-broadcast and UAN was hand-dribbled (to simulate a dribble application) at the 12-leaf and early-silk applications. There were a total of 10 treatments (see Table 2). Pioneer 31P42 was planted on March 23 at 32,000 seed/acre. The trial was furrow irrigated. Cotton was the previous crop and all LSU AgCenter recommended cultural practices were followed.

             The experimental design was a randomized complete block with five 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, ears/acre, kernel weight (g/100 seed), and ear size (kernels/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 4- 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 only totaled 4.9 inches in May and June (Table 1). Furrow irrigations were applied on May 22 and June 2. Across treatments, yields ranged from 15.9 (control) to 197.5 bu/acre (Table 2).

             At early season, urea, urea + Agrotain, and UAN were compared at the 150 lb N/ace rate. Yield responses to treatments had the following rank: UAN > urea + Agrotain > urea (Table 2). There was a 11 day interval between application and rainfall. The late application of 60 lb N/acre increased yields similarly for both the 12-leaf and early-silk applications. There was little difference in yield between sources. Kernel weight was slightly higher for the late compared to early-season applications. 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.

 

Leaf and seed N data are presented in Table 3. Leaf N, seed N, seed N uptake, and NFUE responses to early-season N treatments were highest for UAN compared to urea + Agrotain and urea. There were small differences between the 12-leaf and early-silk N applications for each N trait evaluated. When comparing equivalent N rates, there were small differences between single and split applications for any N trait. Nitrogen fertilizer use efficiency (NFUE) was extremely high, ranging from 0.46 to 0.68. The highest NFUE value occurred for the 150 lb N/a UAN treatment applied early season. SPAD readings reflected trends similar to the yield response (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 Sharkey clay, 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

15.9

33,350

30.4

42

150

Urea

150

114.3

32,700

33.9

270

150

Urea + Ag

150

124.8

32,050

33.4

295

150

UAN

150

164.8

28,780

36.6

414

 

 

 

 

 

 

 

 

 

 

150

UAN

60

Urea

210

187.8

28,780

37.2

441

150

UAN

60

UAN

210

184.4

30,080

38.2

416

Average

 

 

 

 

 

186.1

29,430

37.7

429

 

 

 

 

 

 

 

 

 

 

150

UAN

60

Urea

210

191.1

28,780

37.2

446

150

UAN

60

UAN

210

186.1

34,010

37.6

402

Average

 

 

 

 

 

188.6

31,400

37.4

424

 

 

 

 

 

 

 

 

 

 

210

UAN

210

183.9

32,050

37.6

400

240

UAN

240

197.5

33,350

34.8

471

 

 

 

 

 

 

 

 

 

 

LSD (0.10):

 

 

 

 

 

10.9

NS3

NS

80

                                         

1ESN, early-season N injected at about 4-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 on Sharkey clay, 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

0.98

1.29

11.5

150

Urea

150

1.47

1.24

79.8

0.46

150

Urea + Ag

150

1.60

1.20

84.1

0.48

150

UAN

150

2.50

1.23

114.1

0.68

 

 

 

 

 

 

 

 

 

 

150

UAN

60

Urea

210

2.60

1.27

133.7

0.58

150

UAN

60

UAN

210

2.60

1.32

136.0

0.59

Average

 

 

 

 

 

2.60

1.30

134.9

0.59

 

 

 

 

 

 

 

 

 

 

150

UAN

60

Urea

210

1.31

140.3

0.62

150

UAN

60

UAN

210

1.34

139.5

0.61

Average

 

 

 

 

 

1.33

139.9

0.62

 

 

 

 

 

 

 

 

 

 

210

UAN

210

2.57

1.30

134.3

0.59

240

UAN

240

2.65

1.36

149.9

0.58

 

 

 

 

 

 

 

 

 

 

LSD (0.10):

 

 

 

 

 

0.17

0.05

9.1

0.05

                                         

1ESN, early-season N injected at about 4-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 at the early season and

12-leaf growth stages on Sharkey clay, 2011.

 

 

 

N Fertilizer Source

 

N rate1

Total N

Urea

Urea + Agrotain

UAN

lb/a

lb/a

———————–SPAD readings—————————
              

 

 

 

 

 

 

 

Early-Season N Application

 

150

150

39.6

40.3

54.6

210

210

 

 

59.1

240

240

 

 

56.1

 

 

 

 

 

 

 

 

 

 

 

 

 

12-leaf Growth Stage N Application

 

60

210

54.2

 

56.7

 

 

 

 

 

LSD (0.10):

 

 

3.8

 

                     

 

Nematode Ratings of the Highest Yielding Soybean Varieties for 2012

Nematode Ratings of the Highest Yielding Soybean Varieties for 2012 published on No Comments on Nematode Ratings of the Highest Yielding Soybean Varieties for 2012

Charles Overstreet, Extension Nematologist

Highest yielding cultivars in Group III and Early Group IV Soybean Varieties

Soybean Variety

Soybean Cyst Nematode

Reniform Nematode

Root-knot Nematode

Delta Grow 4460RR

R 3

NA

S

Pioneer 93Y92

R 3, MR 14

NA

NA

Progeny 3911RY

S

S

S

Progeny 4211

R 3, MR 5, 14

S

S

Rev 44R22Tm

S

NA

S

S42-T4 Brand

R 3

S

S

S44-D5 Brand

R 3,  MR 14

NA

NA

 Highest Yielding Group IV Late Soybean Varieties

Soybean Variety

Soybean Cyst Nematode

Reniform Nematode

Root-knot Nematode

Armor 55 R 22

R 3, MR 14

NA

NA

Armor X1210

S

S

S

Armor X1211

S

S

S

Asgrow 4832

R 3

S

S

Asgrow 4932

R 3

S

S

Delta Grow 4670 R2Y

S

S

S

Delta Grow 4875 R2Y

R 3, MR 14

S

S

Delta Grow 4975 RR

MR 5

NA

S

Dyna-Gro 31RY45

R 3, MR 14

S

S

GoSoy 4810 LL

R 3

NA

NA

HBK R4829

MR 3

NA

S

HBK R4924

R 3, MR 14

S

S

HBK RY4721

R 3, MR 14

S

S

Miami 949LL

R 3

NA

NA

Morsoy 4707

R 3

S

S

Morsoy Xtra 46X29

NA

S

S

Morsoy Xtra 46X71

R 3

S

S

Pioneer 94Y70

R 3, MS 14

NA

S

Pioneer 94Y80

R 3, MS 14

NA

S

Pioneer 94Y82

R 3, MR 14

NA

S

Progeny 4510RY

S

NA

S

Progeny 4611RY

R 3, MR 14

S

S

Progeny 4710RY

S

NA

S

Progeny 4750RR

MR 3

NA

S

Progeny 4807RR

R 3

NA

S

Progeny 4811RY

R 3, MR 14

S

S

Progeny 4906RR

S

NA

S

Progeny 4911RY

S

S

MR

Soybean Variety

Soybean Cyst Nematode

Reniform Nematode

Root-knot Nematode

Progeny 4928LL

MR 3

NA

NA

REV @46R73TM

NA

S

S

REV @47R53TM

NA

S

S

REV @48R10TM

R 3

NA

S

REV @48R21TM

NA

S

S

REV @48R22

NA

NA

S

REV @48R33TM

NA

S

S

REV @49R10TM

NA

NA

S

REV @49R11TM

R 3

NA

S

REV @49R22TM

NA

NA

S

REV @49R43TM

NA

S

S

S08-14087 RR

R 3, MS 14

S

S

S08-17361

R 3, MS 14

NA

NA

Schillinger 457.RCP

R 3, MS 14

NA

S

Schillinger 458.RCS

MR 3

NA

S

Schillinger 478.RCS

MR 3, MS 14

NA

S

Schillinger 495.RC

MR 3, MS 14

NA

S

Highest Yielding Group V Soybean Varieties

Soybean Variety

Soybean Cyst Nematode

Reniform Nematode

Root-knot Nematode

AGS 568 RR

S

NA

MR

AGS 5911 LL

NA

NA

NA

AGS 597 RR

S

NA

S

Armor DK5363

MR 3

NA

S

Armor X1213

S

S

S

Armor X1215

S

S

S

Asgrow 5232

R 3

S

S

Asgrow 5332

R 3

S

S

Asgrow 5632

R 3

S

S

Delta Grow 5110R2Y EX

MR 5

S

MR

Delta Grow 5545RR

S

S

MS

Delta Grow 5555RR

R 1, 3, 5, 9

NA

S

Delta Grow 5625R2Y

S

S

S

Dyna-Gro 32RY55

R 3, MR 14

S

R

Dyna-Gro 35F55

R 1, 3

NA

S

Dyna-Gro 35P53

MR 2

NA

S

Dyna-Gro 37RY52

R 3, MR 14

NA

S

Dyna-Gro 39RY57

R 3

NA

R

GoSoy 5111 LL

R 3

NA

NA

HBK R5529

MR 1, R 2

NA

S

HBK RY5121

R 3

S

S

Soybean Variety

Soybean Cyst Nematode

Reniform Nematode

Root-knot Nematode

HBK RY5421

NA

S

S

HBK RY5521

NA

NA

S

Morsoy 5168

NA

S

S

Osage

S

NA

MS

Pioneer 95Y01

R 3, MR 14

NA

S

Pioneer 95Y10

R 3, MR 14

NA

NA

Pioneer 95Y20

NA

NA

NA

Pioneer 95Y31

R 3, MR 14

NA

S

Pioneer 95Y50

NA

NA

S

Pioneer 95Y70

NA

NA

S

Progeny 5111RY

R 3

S

MR

Progeny 5330RR

R 1, MR 2

NA

MR

Progeny 5610RY

R 3, MR 14

NA

R

Progeny 5655RY

S

S

S

Progeny 5711RY

R 3

S

S

Progeny 5811RY

S

S

S

Progeny 5960LL

NA

NA

MR

REV @51R53TM

S

S

S

REV @56R63TM

MS 3

S

MS

S54-V4 Brand

R 3

NA

S

USG 75Z98

S

NA

NA

 Letter designations for nematode reaction are: S = susceptible, MS= moderately susceptible, MR= moderately resistant, R= Resistant, and NA= no information available. All information in this table was provided by the seed companies or the University of Arkansas variety testing program at http://www.arkansasvarietytesting.com/crop/data/5.

 Soybean cyst nematode (SCN) continues to be a very minor nematode pest in our state. Currently, selection of a variety based on this nematode is not very important. None of the varieties on our list have any resistance against the reniform nematode which is found in 60% or more of our soybean fields. A few varieties have some level of resistance against the root-knot nematode.

Corn Insecticide Seed Treatment Options

Corn Insecticide Seed Treatment Options published on No Comments on Corn Insecticide Seed Treatment Options

Sebe Brown, Extension Entomologist

 Selecting corn seed treatments can be a challenging and expensive undertaking faced by many producers across Louisiana.  Corn seed treatments target three spectrums of pests: nematodes, fungal seedling diseases and insects.  This article will address insecticide seed treatment options available for corn.

Insecticide seed treatments are usually the main component of a seed treatment package.  Most corn seed available today comes with a base package that includes a fungicide and insecticide.  The insecticide options for seed treatments include Poncho (clothianidin), Cruiser/Cruiser Extreme (thiamethoxam) and Gaucho (Imidacloprid).  All three of these products are neonicotinoid chemistries.  Cruiser and Poncho at the 250 (.25 mg AI/seed) rate are the most common base options available for corn.  These insecticides are a good foundation; however, do not expect these treatments to give you extended protection from all below ground pests. If sugarcane beetles have been a problem in the past, Cruiser at the 250 or 500 rate will not provide adequate control; consider using Poncho at the 500 rate with 1250 providing better protection.  None of these products provide adequate control of cutworms.  Each company offers treatments that provide differing levels of early season insect protection, outlined below are some options available to producers with regards to insecticide seed treatments.

Pioneer’s base insecticide seed treatment package consists of Cruiser 250 with Poncho/Votivo 1250 available upon request.  Votivo is a biological agent that protects against nematodes.

Monsanto’s products including corn, soybeans and cotton fall under the Acceleron treatment umbrella.  Dekalb corn seed comes standard with Poncho 250.  Producers also have the option to upgrade to Poncho/Votivo, with Poncho applied at the 500 rate.

Agrisure, Golden Harvest and Garst have a base package with a fungicide and Cruiser 250.  Avicta complete corn is also available; this includes Cruiser 500, fungicide, and nematode protection.

Another option is to buy the minimum insecticide treatment available, and have a dealer treat the seed downstream.

Avipel was re-issued a section 18 for field and sweet corn seed in Louisiana.  The exemption is effective from February 24, 2012 through February 24, 2013.  Avipel can only be applied at the dealer and is used as a humane bird repellent.

It is important to note that below ground Bt traits available for western corn rootworm will not work on our strain of root worm in Louisiana.  Look at using in-furrow applications of Counter (organophosphate) or Force (pyrethroid) to help keep rootworms under control.  If an ALS herbicide was used in burndown applications or is anticipated, organophosphate insecticides should not be used.

Insecticide seed treatments are a valuable tool that allows producers a head start on early season protection from a variety of pests.  Minimizing damage below ground will help get this year’s corn crop off to a promising start.

The LSU AgCenter Explores Biofuels as an Alternative Crop for Growers

The LSU AgCenter Explores Biofuels as an Alternative Crop for Growers published on No Comments on The LSU AgCenter Explores Biofuels as an Alternative Crop for Growers

Authors:  John Kruse, Michael Blazier, Richard Vlosky, Vadim Kochergin, Glenn Hughes, Dek Terrell, Paul Darby, Roger Smithhart

Research scientists and extension specialists from the LSU AgCenter are participating in federally-funded research and extension efforts to explore the potential that biofuel crops may hold for Louisiana producers.   These efforts have great potential to expand the energy production portfolio of Louisiana.  An ambitious five-year study will involve growing and selecting cultivars of energy cane (sugarcane varieties with characteristics better suited for biofuel production than conventional sugar production) and sweet sorghum well-adapted to Louisiana.  Agronomic practices such as planting rates and dates as well as fertility will be developed for these crops.  Processes for converting these crops into an array of biofuels and biochemicals are being developed in partnership with collaborators in the biofuels industry. Louisiana is particularly well-suited to develop biomass crops due to its climate, well-developed agricultural and energy infrastructure, and central location within the U.S.

In another study, a team of researchers led by Dr. Richard Vlosky submitted a survey to producers in Pointe Coupee, Concordia, Catahoula, Tensas, Madison, Richland, West Carroll and East Carroll Parishes, as well as several counties in Mississippi’s Delta region. The purpose of the survey was to gauge initial interest in producing biofuel crops, as well as find out what factors are important to making it a success. Well over 700 surveys were returned, providing a solid sample to study the responses.  Roughly 60% of the respondents farmed less than 250 acres and 40% farmed more than 250 acres. Thirteen percent of the respondents farmed over 1000 acres, providing a good cross-section of producers. When asked their overall opinion of using biomass for bioenergy, two thirds of the respondents were somewhat or extremely positive. Only 17% were pessimistic that a bioenergy market will be competitive relative to conventional energy markets.

When growers were asked about their perceptions of biofuel crops, 56% felt that economically viable technologies already exist for converting biomass to bioenergy and half of all respondents believed that agricultural biomass transportation can be conducted with existing equipment. When it came to on-farm equipment needs, 43% believed that some sort of specialized equipment would be necessary to get the job done.  A plurality (41%) neither agreed nor disagreed with the statement that converting agricultural biomass to bioenergy is a simple process that can be done at most agricultural processing facilities, and almost a third were not sure if agricultural biomass requires utilizing the entire crop as well as residual feedstock. These responses strongly indicate that growing biofuel crops is a new frontier for most producers, so agronomic education will be critical to its successful adoption by growers.

The majority of producers surveyed were clearly willing to give biofuels the benefit of the doubt when it comes to potential impact on the environment, with roughly three-fourths of respondents believing that raising a biofuel crop would not negatively impact wildlife, air and water quality, or soil quality. The majority of growers surveyed felt that government had a clear role to play in the development of this potential market. Two-thirds of respondents felt that tax credits should be given to landowners, harvesters, and companies that produce and utilize biomass for bioenergy. Well over half believed that subsidies should be provided as an incentive to companies for selling biomass residues from agricultural operations. Over 60% agreed that incentive programs should be provided to defray the costs of establishing biomass crop species and that secured loans should be provided to develop and construct commercial-scale bio-refineries. Almost three quarters of responding growers specifically saw a lead role for research institutions such as theLSU AgCenterwhen they agreed that grants should be awarded for research and development capable of advancing biomass production technologies. When it came down to individual participation, the jury is still out: When asked, “Would you be willing to participate in management activities specifically geared toward biomass production from your agricultural land?” the response was virtually evenly split, with 49% saying “No” and 51% saying “Yes.”

The fact that half of responding growers were willing to participate in bioenergy feedstock production and the high percentage of neutral responses to many of the questions indicates that many producers would benefit from additional information. It was also concluded that a gap exists between the desire to utilize agricultural biomass and the current viability of bio-based markets. The survey seems to reveal that a biofuel-based crop production system in Louisiana is still in its infancy, and that many producers are open to the idea of making it part of their production systems. They just need more information before they can make a decision.

 

 

Fall Fertilizer Applications – Are They Worth It?

Fall Fertilizer Applications – Are They Worth It? published on No Comments on Fall Fertilizer Applications – Are They Worth It?

ByDonna S. Morgan, Associate Area Agent, Louisiana Master Farmer Program

Traditional methods of applying fertilizer to cropland primarily include fall applications of Phosphorus (P) and Potassium (K), which are usually broadcast, and then may be incorporated if conditions permit. Nutrients are then left on the soil surface, or slightly beneath, for 6-7 months prior to planting of the crop. Soybeans, for example, are categorized as legumes and therefore fix their own nitrogen, but do require adequate amounts of P and K, if soil tests results recommend it (this is based on soil type and texture, soil pH, previous crops, and other variables). A medium soil type (such as a silt loam or clay loam) would normally require the application of 200#/acre of 0-18-36. If these nutrients are applied this far in advance of planting, is it really beneficial to the crop and to the environment to do so? What happens to the nutrients during typical, heavy winter rainfall events? What if the soil has a high pH (such as those found in the Red River Alluvial soil class) and the Phosphorus becomes bound to the soil particles, thereby becoming unavailable to the plant when it needs it the most? Do you apply the nutrients anyway? Or is a spring application more beneficial? These are some of the questions that prompted a study at the Dean Lee Research Station to determine if fall and spring fertilizer applications, as well as the application methods, had any impact on agronomic traits, yield, and water quality.

 The Louisiana Soybean and Grain Research and Promotion Board funded a project titled “The Effect of Phosphorus and Potassium Application and Timing Methods in Soybeans on Yield and Water Quality”. This project was funded in 2011 and will continue through harvest in 2012.  Dr. Brooks Blanche, (former LSU AgCenter cotton and soybean agronomist), and J Stevens, LSU AgCenter state soil specialist, cooperated with me on this project to ensure accurate agronomic data would be collected and nutrient recommendations would be applicable to this project. This study was implemented in November, 2010 and included a fall broadcast treatment (FBT) of P and K, a spring broadcast treatment (SPT), a spring liquid injected treatment (SLI), as well as an untreated check (UTR). Included in these 12 plots were automatic water sample collectors, also known as ISCO samplers, which were programmed to collect 200 ml of runoff every 5 minutes for four hours. The fall and winter months produced fairly significant rainfall events, where several collections were able to be made. After spring treatments were applied and a Maturity Group V soybean (Pioneer 95Y01) was planted, a lengthy drought ensued, which severely limited the water quality data that was able to be collected and analyzed. Growing conditions were fair to good for most of the growing season, with the exception of the summer months. Stand counts, plant heights, tissue samples, and soil samples were collected throughout the growing season to determine if any differences were seen in high pH conditions with each treatment. The plot was harvested on September 21, 2011 with average grain yields ranging from 32-34 bushels per acre.

 Data collected was analyzed and results showed no statistical differences in yield, plant heights, plant stand populations, and soil and plant tissue P and K levels. Plants heights and stands all fell within acceptable ranges to maximize yields. Soil samples (regardless of timing of sample collection) showed higher levels of Phosphorus across all treatments and adequate levels for Potassium. Phosphorus levels in many of the fields at the Dean Lee Research Station have continued to increase because of the limiting crop removal rate with these nutrients being applied annually. Tissue samples collected at the R3 growth stage showed the plants had sufficient levels of P and K during that growing period. And even though the soybeans visually appeared healthy, yields were compressed across all treatments with the onset of lengthy dry conditions.

 Field variability, equipment failure, and lack of field runoff limited the water sample collections and make comparisons for each treatment difficult, to say the least. Analysis showed no differences in the amount of total Solids, total Phosphorus, and Phosphates that left the field during rainfall events. Even though 31 inches of rain fell from November, 2010 to September, 2011, the majority of events were not sufficient to cause high volumes of runoff from plots. Total Solid levels were high in every treatment, primarily because the field had been sub-soiled after the previous crop harvest, and was bare during the winter months. This was due to lack of residue, cover crop, and even natural vegetation during this time period.

 One statistical difference that was noted was the level of Potassium that left the field in water sample collections. The fall broadcast treatment levels were significantly higher than those of the untreated and spring broadcast. No differences were seen in fall broadcast and spring injected. At this point, conclusions cannot be drawn from one year of data collection, but it is a possibility that Potassium levels were higher in fall treatments due to the high volume of rainfall that occurred during that time period. Potassium is also very water-soluble and this may have affected the levels found in the sample collections. Additional replications of this trial would be needed in order to determine any trends in application timings or methods.

 Though this particular study, under these specific field and environmental conditions, proved no differences in most of the parameters, does not mean the information can’t be useful. If multiple years of data are collected, and no statistical differences are determined, wouldn’t that prove useful to a producer in his nutrient management plans? Variables such as post-harvest field conditions, fertilizer prices, cropping systems, and application equipment all affect when and how nutrients are applied. This also has an effect on how many nutrients enter the surrounding water bodies and contribute to water quality issues related to production agriculture. So answering the question, “Are they worth it?” is more complicated than a simple yes or no. Conducting studies such as this will not only help producers answer these questions to maximize their nutrients, but minimizing water quality and environmental impacts as well.

Current Weather Conditions May Affect Burndown Strategies

Current Weather Conditions May Affect Burndown Strategies published on No Comments on Current Weather Conditions May Affect Burndown Strategies

From: Daniel Stephenson, Ph.D (Weed Scientist), Sebe Brown (Extension Entomologist) and John Kruse, Ph.D. (Cotton and Feedgrain Specialist)

Historically, many corn producers in Louisiana desire to plant corn in February. LSU AgCenter weed scientists and entomologists suggest burndown applications occur 4 to 6 weeks prior to planting to prevent competition from weeds and to remove vegetation that may be infested with insect pests – collectively known as “breaking the green bridge”.

Fields intended for corn should have already received a burndown application; however, weather conditions during January and early February may have prevented herbicide applications. As an example, 14.5 inches of rain were recorded at the Dean Lee Research and Extension Center in Alexandria since January 1.

The wet fields prevented ground application of burndown herbicides. Also, there were only a few days since January 1 that an airplane was able to make these applications due to wind conditions. As a consequence, Louisiana producers may be faced with weedy fields that are intended for corn.

A failure to “start clean” can greatly influence corn yields. Data have shown that corn determines its leaf orientation very soon after emergence. Leaf orientation perpendicular to the planted row is desired for maximum light interception, which influences growth and yield potential. If a spiking corn plant perceives any competition from an adjacent winter weed, the leaf orientation will be altered, thus potentially reducing that corn plant’s ability to intercept enough light for maximum yield. Therefore, planting into a weed-free field is very important.

Focus on Weed Control

Traditionally, a burndown application of glyphosate plus 2,4-D has been the standard protocol. This treatment usually provides good to excellent control of many winter/spring annual weeds common in Louisiana fields.

When applied 4 to 6 weeks prior to planting, a producer has time to evaluate the efficacy of glyphosate plus 2,4-D and decide if an additional herbicide treatment is needed prior to planting. If a producer is prevented from applying the burndown application in a timely manner, then weed competition and insect pressure may be an issue for emerging corn. Henbit in particular may be a refuge for cutworms and spider mites.

If a field scheduled for corn has received a burndown application, then these fields need to be evaluated to determine if corn will be planted into a “clean” field.

If the weather has prevented a burndown application and a producer intends to plant corn within the next few weeks, several factors must be considered.

The first issue is the 2,4-D plant-back restriction, which is 7 days for corn. If you are within this window, then you should not apply 2,4-D, to prevent herbicide injury to the corn. Second, maximum efficacy of glyphosate will not be observed until 21 to 28 days after application, so glyphosate applied 7 to 10 days before planting may not provide acceptable weed control and may allow insect populations to survive.

If a producer is within 7 to 14 days of planting corn, he/she should consider the following burndown treatments:

  • Gramoxone SL at 1.5 qt/A plus atrazine at 1 lb ai/A plus 0.25% v/v nonionic surfactant.
  • Gramoxone SL at 1 qt/A plus Leadoff at 1.5 oz/A plus 0.25% v/v nonionic surfactant.

Gramoxone SL will provide control of existing weeds, but coverage is essential. Therefore, a minimum of 12 gallons of water per acre and flat-fan nozzles should be utilized to maximize coverage. Also, Gramoxone SL efficacy can be increased when the air temperature is high and cloud cover is minimal.

Atrazine or Leadoff will assist Gramoxone SL with control by providing residual activity on winter/spring weeds during the first few weeks after corn emergence – if beds are not disturbed at planting. However, if an organophosphate insecticide will be applied in-furrow when planting corn, then Leadoff cannot be applied or injury will occur.

Focus on Insect Control

At-plant bands or post-emergence pyrethroid applications can be used to control cutworms; however, the infestation needs to be detected early to minimize stand loss. Moist soils will help incorporate the application to improve efficacy on any cutworms that may be located below the surface.

Foliar insecticide applications can be applied in bands behind the planter in reduced tillage fields. At planting soil insecticides such as Lorsban 15G can be t-banded with corn to help control cutworms pre-emergence. Lorsban should not be planted in furrow due to possible phytotoxicity. It is important to note that the use of ALS inhibiting herbicides with organophosphates such as Counter and Lorsban have the ability to cause significant crop injury.

If producers used Leadoff in their burn down strategy then Counter should not be used at all, to prevent any negative effects between the two chemicals. Lorsban has greater crop safety than Counter when used in conjunction with ALS inhibiting herbicides.

Force 3G can also be used at plant to help protect against cutworms. Force 3G is a pyrethroid insecticide and the ALS interaction is not a factor. Counter is not effective for control of cutworms but useful for rootworms.

Planting corn into a weed-free field is a must to maximize yield. Regardless of when you apply a burndown treatment, a producer must strive to “start clean”.

Wheat: Cold Weather Means Risk

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We are forecast to finally have some real winter over the next few days. Unfortunately, much of our wheat has already moved on to spring. Temperatures in Baton Rouge are forecast to reach 28–30 ˚F Saturday night. In Monroe (along I-20 in north Louisiana) temperatures are forecast to reach 22-24 ˚F, 18 ˚F at Greenville, MS, and 16 ˚F at El Dorado, AR.

The forecast has been in a state of flux over the past couple of days and it is hard to know what will really happen. I am pretty confident that we will have some freeze damage to wheat this weekend but it is difficult to predict how much. The good news is that it is still very early in the growing season, wheat has lots of time to recover, and wheat is a very resilient crop.

Wheat that is not jointed will not suffer anything more than superficial leaf burn at 20 ˚F. Our wheat has been growing very rapidly and there are lots of tender leaves that will have the tips burned, but this should not impact yield. Prior to jointing wheat is very tolerant of cold weather and damage is infrequent and superficial. Wheat becomes much more vulnerable to freeze damage as it progresses from first node to flowering. Hopefully we will have a cool February and not have to address that issue. There is really not much that can be done at this point. The chart below (borrowed from http://www.ksre.ksu.edu/library/crpsl2/c646.pdf)

shows the relationship between growth stage, temperature, and freeze damage. The months that correspond to the growth stages are appropriate for Kansas, not Louisiana. The growth stages are valid, except that tillering occurs all winter in Louisiana.

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Wheat that has jointed (Feeke’s GS 6) will start to sustain significant damage around 24-26 ˚F. This damage can manifest in several ways. Stems can freeze on one side which weakens stems and can result in lodging at heading and poor grain fill due to inability to supply the developing head with adequate water and nutrients; or stems can completely freeze at the soft growing point resulting in loss of that tiller.

The link below is a good summary of spring freeze damage symptoms in wheat from our friends at Mississippi State. . http://msucares.com/crops/wheat/faq7_damage.html

The amount of damage on tillered wheat will depend on temperature and duration of exposure. I suspect that most of the wheat in Louisiana will only sustain superficial damage. I do know that there are some fields that have one and maybe even two nodes showing and these will be hurt. It normally takes a couple of days after a freeze before symptoms are easily apparent. This comes in the form of dead and dying tissue; lodging and discolored tillers; and a distinct odor of rotting tissue. Again, we won’t know the extent of damage until early next week and there is still a lot of time for the plants to form new tillers and make a near-normal yield. I’m sure the internet will be abuzz with freeze damage discussions next week

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