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2/11/2013 - 2/17/2013

Commercial Pesticide Applicator Test Help Session

By Jim Fawcett, ISU Extension field agronomist

 All commercial pesticide applicators must take exams in order to become initially certified and some choose to become re-certified by exam rather than by attending continuing instructional courses. 

 A training session designed to help prepare individuals for the commercial pesticide applicator examinations will be offered in Washington on Monday, March 11 in the Washington County Extension Office at 2223 250th St. The test help session will run from 8:30 a.m. to 1:00 p.m. The Department of Agriculture and Land Stewardship will be giving tests for both private and commercial pesticide applicators in Marr Park at 2943 Highway 92, Ainsworth, on the same day from 10:00 a.m. to 2:00 p.m.

The training session will cover the Iowa Core Manual and categories 1A (Agricultural Weed Management), 1B (Agricultural Insect Control), 1C (Agricultural Crop Disease Management), 3O,T, and G (Ornamental, Turf, and Greenhouse Pest Management), 4 (Seed Treatment) and 6 (Right-of-Way). Training on the Iowa Core Manual will be given for the first two hours, with the training on the other categories following.

There is a $25 fee per person for the training session. The session does NOT qualify as a continuing instructional course. For more information, please contact Jim Fawcett, fawcett@iastate.edu,  at (319) 337-2145, Patrick O’Malley, omall@iastate.edu, at (319) 337-2145, or Virgil Schmitt,vschmitt@iastate.edu, at (563) 263-5701.

ISU Extension Offers Introductory RUSLE2 and P Index Workshops for Manure and Nutrient Plan Writers

Iowa State University Extension and Outreach, in collaboration with the Iowa USDA-Natural Resources Conservation Service, has scheduled a workshop to train livestock producers, consultants and agency staff how to use the Revised Universal Soil Loss Equation 2 (RUSLE2) and the Iowa Phosphorus Index for use in nutrient management and manure management plans in Iowa.

 

The workshop will be held on March 20, 2013, at the Polk County Extension Office in Altoona.  The workshop starts at 9:00 a.m. and ends at 4:15 p.m.

 

This workshop is an introductory level, hands-on workshop that will provide the participant with software orientation. It will also introduce participants to the operating parameters, selection of input values and developing and saving management operations for RUSLE2. In addition, real field examples will be used in the workshop to determine risk calculations of the Iowa Phosphorus Index and how to incorporate these numbers into manure and nutrient management planning requirements.  Also included will be parameters for RUSLE2 and P Index calculations on snow-covered or frozen ground. Soil sampling requirements, common errors and DNR’s review process will also be discussed.

 

The cost of the workshop is $200 if registered on or prior to March 18; the registration fee is $225 after March 18. The workshop fee includes handout materials, a CD with software, refreshments and lunch. Because software will be provided, participants are required to bring a MS Windows compatible laptop equipped with a CD-ROM drive and Microsoft Excel Software. Participants must have their administrator password to the computer they bring in order to install software. The workshop is limited to 30 participants and walk-in attendees are not allowed.

 

On-line registration, program information and directions to the workshop are available at http://www.ucs.iastate.edu/mnet/introrusle2/about.html.

 

If you have questions please contact Kapil Arora, ISU Extension Field Ag Engineer, (515) 382-6551, or Angela Rieck-Hinz, ISU Extension Program Specialist, (515) 294-9590

 

Corn and Dry Soils at Planting, Looking Ahead to 2013 - Part II

Part II: Hybrid Reltive Maturity Changes

By Roger Elmore, Department of Agronomy

In Part I of this article, I addressed the current situation and Iowa corn performance in 2012. In that article, I discussed modeled results relating to whether or not we should alter seeding rates if soils are dry at planting this spring. Here I intend to discuss how changing hybrid relative maturities affects yield with different starting points for soil moisture.  I addressed both of these issues in January 2012 in a series of three ICM News articles.

Some may know that in more southern parts of the Corn Belt, farmers often plant hybrids that are 5 to 10 or more days earlier than typical adapted hybrids in an effort to avoid late-summer heat and drought.  Will this approach work in Iowa if our soils remain dry at planting?
Should you consider planting earlier-season hybrids if it is dry at planting in 2013?

 

Methods

As in the other article of this pair, I used a corn simulation model (Hybrid-Maize) to answer this question. The model uses historic weather data from automated weather stations. I used data from seven of Iowa State University's Research and Demonstration Farms, one in each of the four corners of Iowa, one in both west central and northern Iowa, and another near Ames in central Iowa.

The model allows users to change soil moisture conditions at planting to simulate different possibilities. With this capability, we can address the question, “What if the soils are only one-quarter field capacity (FC) at planting?”

I compared two moisture levels:

  • A ‘normal:’ 75 percent field capacity (FC) in the topsoil (0-12 inches) and 100 percent FC in the subsoil (12-40 inches), and
  • B, ‘very dry:’ 25 percent FC in both topsoil and subsoil.

I realize that some Iowa soils now are perhaps wetter than 25 percent FC so the second possibility may be pessimistic for those areas. Other common inputs for each site modeled are provided in Table 1 (with the exception of hybrids). Factors that varied across locations such as soil textures are shown in Table 2.

Table 1. Hybrid-Maize model input factors

that were the same across locations and years

Factor

Factor Input Value/ Date

Emergence date

1 May

Plant population

32,000 plants per acre

Soil moisture

 

Situation A (Normal)

 

Top soil

75% Field Capacity

Sub soil

100% Field Capacity

Situation B

(Very Dry)

 

Top soil

25% Field Capacity

Sub soil

25% Field Capacity

Rooting depth

40 inches

 

† Year when automated weather data collection began
‡ Si = Silt, Cl = Clay, Lo = Loam.
§ GDU = Growing Degree Units; 2300 = about 95 RM; 2400 = about 100 RM; 2500 = about 105 RM; 2600 = about 110 RM.

Given the two soil moisture situations at planting discussed above, the model allows us to simulate the effects of changing hybrid maturities. It assumes a generic hybrid and models corn growth based on temperature, solar radiation and precipitation actually recorded in the weather database for each research farm. I compared three hybrids at each location: a full-season and two earlier-season hybrids. The full-season hybrids at the northwest (NW), northern and northeast (NE) locations required 2500 GDD (about 105 days RM) while the early-season hybrids required either 2400 or 2300 GDD (about 100 and 95 days RM, respectively). At the west central, central, southwest (SW), and southeast (SE) locations, the full-season hybrids required 2600 GDD (110 days) and the early-season hybrids required either 2500 or 2400 GDD (about 105 and 100 days RM, respectively).

 

Simulation Results

At all locations, the longest-season hybrids out-yielded shorter-season hybrids in at least three-quarters of the modeled years in each of the respective databases. That was true whether soil profiles were wet at planting or very dry (Table 3).  There were both high-yielding years and low-yielding years in which the short-season hybrids yielded more than the full-season hybrid (data not shown). However, at all locations, there was a tendency at higher yield levels for the differential to widen between the full-season hybrid and the very-early hybrid with the full-season hybrid yielding more.  At low yield levels, as in 2012, there was little yield difference among hybrids.

† The full-season hybrid outperformed both earlier-season hybrids at all locations and with both soil conditions at planting in 2012.

 

The analysis shows that hybrids of both maturities should be grown, similar to last year’s conclusion. This will spread risk and maximize yields over years.  Nevertheless, the data suggest planting most of your acres in what could be considered full-season hybrids for your area.

These simulated data results mirror actual yields obtained from the ISU/Iowa Crop Improvement Association’s Crop Performance Test – Corn. These tests are conducted annually at 20 or more locations with a full-season and an early-season hybrid trial at each site. Means of the two trials in any specific region are usually similar. Again, this suggests planting both early- and full-season hybrids are important to maximize yields while spreading risk.

 

Summary

Many things can happen between now and planting in 2013. If soil moisture conditions do not improve, planting diverse hybrids with a range of maturities is a good approach…as it is every year. Meanwhile, as before, let’s hope for complete recharge of our soil before planting.

 

Endnote

The two articles in this series summarize portions of the 2013 Crop Advantage Series (CAS) talks presented in January 2013.

 

Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. He can be contacted by email at relmore@iastate.edu or (515) 294-6655.

Corn and Dry Soils at Planting, Looking Ahead to 2013 - Part I

Part I - Plant population changes?

By Roger Elmore, Department of Agronomy

Iowa 2012 corn yields ended at 137 bu/acre (see USDA-NASS data), dropping 22 percent below the 30-year trend line yield of 180 bu/acre. For comparison, in 1988 Iowa corn yields were 29 percent below trend line. Based on the U.S. Drought Monitor and modeled soil moisture data from Mesonet (Volumetric Soil Water Map), 2013 conditions so far appear worse than those of 2012. Optimism wanes for normal soil moisture profiles at planting. That concerns most of us connected to agriculture across Iowa, which really should be everyone! Remember, soil moisture conditions were a hot topic for us last winter as well. I addressed that situation beginning with a series of ICM articles in January 2012 (Part 1, Part 2, Part 3).

It doesn’t surprise any of us that in areas of the Corn Belt with poorer soils and/or reduced rainfall, farmers typically reduce plant populations to compensate for conditions. Is that something we should again consider in Iowa if conditions remain dry at planting? In part based on concerns at planting in 2012, Iowa farmers as well as those across most of the Corn Belt reduced plant populations relative to those used in 2011 for the first time since 2000. Iowa corn plant populations in 2012 dropped to 30,100 plants per acre (ppa) from 30,750 in 2011 (see Figure 8 linked in the endnotes). Albeit, that is not a huge decrease; but it does reflect pessimistic sentiments at planting in 2012. This change will slow the consistent trend of increased plants per acre of about 400 plants per acre per year since the turn of the 21st century. With that as history, what should we think about this spring?

Should you consider lower plant populations if it is dry at planting in 2013?

 

Modeling Methods

As in last year’s versions of these articles, I used a corn simulation model (Hybrid-Maize) to answer this question. The model uses historic weather data from automated weather stations. In this case, I used data from seven of Iowa State University's research and demonstration farms, one in each of the four corners of Iowa and the others in northern and west central Iowa and one near Ames in central Iowa.

The model allows users to change soil moisture conditions at planting to simulate different possibilities. This year, I compared two scenarios:

  • ‘Normal:’ 75 percent Field Capacity (FC) in the topsoil (0-12 inches) and 100 percent FC in the subsoil (12-40 inches), and
  • ‘Very Dry:’ 25 percent FC in both topsoil and subsoil.

I realize that some Iowa soils are wetter than 25 percent FC; so the second possibility may be overly pessimistic for those areas. Other common inputs for each site modeled are provided in Table 1. Factors that varied across locations such as soil textures are shown in Table 2.

Table 1. Hybrid-Maize model input factors that were the same across locations and years

Factor

Factor Input Value/ Date

Emergence date

1 May

Plant population Comparisons

27,000, 32,000 and 37,000 plants per acre

Soil moisture

 

Situation A (Normal)

 

Top soil

75% Field capacity (FC)

Sub soil

100% Field capacity (FC)

Situation B(Very Dry)

 

Top soil

25% Field capacity (FC)

Sub soil

25% Field capacity (FC)

Rooting depth

40 inches

 

Table 2. Hybrid-Maize model input factors that varied by location

 

ISU Research and Demonstration Farm (Location)

Factor

NW

North

NE

WC

Central

SW

SE

Year

1988

1997

1988

1988

1986

1997

1988

 

 

 

 

 

 

 

 

Top Soil

SiClLo

Lo

Lo

SiLo

ClLo

SiClLo

SiClLo

Sub Soil

SiClLo

Lo

Lo

SiLo

ClLo

SiClLo

SiClLo

 

 

 

 

 

 

 

 

Hybrid GDU§

2500

2500

2500

2600

2600

2600

2600

† Year when automated weather data collection began
‡ Si = Silt, Cl = Clay, Lo = Loam.
§ GDU = Growing Degree Units; 2500 = about 105 RM; 2600 = about 110 RM.

Given the two soil moisture scenarios at planting, the model allows us to estimate the effects of changing plant populations, as well as other factors, on simulated yield. The model predicts corn growth based on temperature, solar radiation, and precipitation actually recorded in the automated weather database for each research and development farm. It does not account for factors like insect feeding, diseases, weed competition, nutrient deficiency, hail, wind damage, etc.

For this comparison, I used a single ‘generic’ hybrid at each location: NW, N, and NE locations: 2500 GDD (about 105 days RM); West Central, Central, SW, and SE locations, 2600 GDD (110 days). For the analysis in this article, I compared final plant populations of 27,000, 32,000 and 37,000 ppa at each location with each of the two soil moisture scenarios at planting.

 

Simulation Results 

Wet soils at planting

Probabilities for different plant population responses with different soil moisture conditions at planting are shown in Table 3.  At Kanawha and Ames for example, if we start the season with a wet soil profile, responses in all the previous years (16 and 27 years of weather history in the database for Kanawha and Ames, respectively) would always favor planting 37,000 ppa over 32,000 ppa.  Likewise, the lowest population, 27,000 ppa, always yielded less than the middle population, 32,000 ppa, when soils were wet at planting at both of these locations.

Table 3. Years where simulated yields of specified plant populations were greater than that of the other specified plant population as affected by whether soils were dry or wet at planting.

R & D Farm

(Location, years of weather data)

Wet at Planting

Very Dry at
Planting

37k > 32k

32K > 27k

37k > 32k

32k > 27k

Probability of Plant Population Differences (%)

NW (Sutherland, 25yr)

92

84*

60

60

N (Kanawha, 16yr)

100

100

63

56*

NE (Nashua, 25yr)

92

92

72

76*

WC (Castana, 25yr)

84

84

56

60*

Central (Ames, 27yr)

100

100

85

89*

SW (Lewis, 16yr)

94

94

81

81

SE (Crawfordsville, 25yr)

96

88

56

52

* Indicates situations where the 27,000 plant population resulted in greater yields than the 37,000 plant population in 2012. See figures linked in the endnote for more information.

 

For another example, at Sutherland in NW Iowa, 37,000 ppa out-yielded 32,000 ppa in 23 of the 25 years, 92 percent, when soils were wet at planting. The lowest population, 27,000 ppa, increased yields over 32,000 ppa in only four of the 25 years, 16 percent. However, in 2012, simulated yields with 27,000 ppa were greater than those of 37,000 ppa by an estimated 6 bu/acre (noted by the asterisks in Table 3). In most cases, if soils are wet at planting, staying with higher seeding rates would improve yields at all locations.

 

Very dry soils at planting

If we start the growing season with very dry soil profiles, optimism for high yields plummets along with probabilities of yield increases with high plant populations (Table 3). To illustrate this, look at the responses at Castana in WC Iowa. If we start with a very dry soil at planting, yields with 37,000 ppa are greater than those of 32,000 ppa just over half the time, 56 percent.  Likewise, 32,000 ppa outperforms 27,000 ppa 60 percent of the time. In a year like 2012, 27,000 ppa would out-yield corn at 37,000 ppa by an estimated 9 bu/acre. That was true at Kanawha, Nashua and Ames as well. If soils are dry at planting, higher plant populations may reduce yields compared to lower plant populations.

Similar to modeled data in January 2012 ICM News, these modeled yields show that higher plant populations improve the chances for higher yields in high-yielding years (see figures linked in the endnote).  In lower-yielding years, yields resulting from different plant populations are more similar; thus, seed costs associated with higher populations may not be offset by yield increases in lower yielding years when the soil is dry at planting. But the probabilities of greater returns from higher seeding rates in better years would seem to counterbalance those concerns.

 

Summary

We all know that many things can happen between now and planting. Normal seeding rate/ plant population recommendations are based on full soil profiles at planting (typical plant population responses). If 2013 soil moisture conditions do not improve,  that is soils are dry at planting, be conservative on seeding rates changes. Although planting to achieve high plant populations is a good approach in most years, 2013 may be the year to not push seeding rates to higher levels especially in drought-prone soils. Meanwhile, as before, let’s hope for complete recharge of our soil in the weeks remaining before planting!

 

Endnote

This article summarizes portions of a 2013 Crop Advantage Series talk presented in January 2013.  Detailed summary graphics for each location modeled are available.

 

Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. He can be contacted by e-mail at relmore@iastate.edu or (515) 294-6655.



This article was published originally on 2/18/2013 The information contained within the article may or may not be up to date depending on when you are accessing the information.


Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.