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Eastern MN & Western WI Walking Your Fields newsletter-June
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Eastern MN & Western WI Walking Your Fields newsletter-June

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This June issue of Walking Your Fields newsletter contains articles about: corn stand evaluation, planting date impact on soybeans, nitrogen loss after rain, and early weed control in corn. ...

This June issue of Walking Your Fields newsletter contains articles about: corn stand evaluation, planting date impact on soybeans, nitrogen loss after rain, and early weed control in corn.

Articles are written by DuPont Pioneer agronomists in Minnesota and Wisconsin and are distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

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Eastern MN & Western WI Walking Your Fields newsletter-June Eastern MN & Western WI Walking Your Fields newsletter-June Document Transcript

  • A late spring and wet conditions have delayed soybean planting in some areas. This article addresses how later planting affects soybean development and maturity. Soybeans are ‘day length sensitive’ plants. This means flowering and maturity are triggered by the length of the night or dark period. When adapted maturity varieties are planted before the middle of June, the flowering is trig- gered by shorter days (actually longer nights) after June 21. For each three to five day delay in planting, flow- ering and maturity are delayed only about one day. That means that if you plant the same variety on May 10 and June 10 (30 days later), the flowering and maturity of the later planting is delayed about six to ten days. This happens regardless of the maturity of the variety. Soybean Development. Flowering usually begins six to eight weeks after seedling emergence and continues for three to four weeks. However, flowering will occur earlier if soybeans are planted late. Warm temperatures acceler- ate development, especially flowering. A full season soy- bean variety will normally flower in the first ten days of July. If there is a hot period in mid June, it can flower up to two weeks earlier. When this happens, and if there is good weather for the rest of the season, higher yields result because of the extended reproductive period. The soybean plant may flower ten days earlier, but it won’t necessarily mature ten days earlier because of day length controls. Generally, yield increases as the length of the flowering to maturity stage increases. Warm weather in August or early September does not hasten maturity much, un- less it causes water deficit stress. Sometimes, temper- ature is blamed for stress, because hot temperatures often accompany drought. A cool fall does not delay ma- turity much either, although yields may be reduced if the cool weather is accompa- nied by heavy rain, causing disease. The flowering peri- od is influenced more by temperature, but maturity is more strongly influenced by photoperiod. The rapid shortening of days starting in mid August drives the soy- bean to maturity; temperature has only a small influence on maturity. The average yield of corn in the U.S. and Canada has tripled over the last half-century. Yield gains have result- ed from improved hybrid genetics, more precise soil fertil- ity practices, better weed control, and advances in other production methods. Among these factors, genetic im- provements have contributed the most to yield gains, adding from 1.0 to 1.5 bu/acre each year. To accomplish these increases, corn breeders have selected for superior tolerance to drought and other stresses, and yield stability across diverse growing environments. A key result of en- hanced stress tolerance is adaptability of hybrids to high- er plant populations. Optimum economic returns often require plant populations of 35,000 plants/acres or more, depending on the hybrid and environment. Obtaining the- se higher plant populations is essential, especially at higher yield levels. It is important to evaluate stands shortly after emergence. Corn stands can be reduced by many issues such as cold or wet soils, insect feeding, poor seedbed, and equipment issues. Shortly after emergence is the best time to evalu- ate stands and the effectiveness of planter equipment, residue management, and seedbed preparation. Jerome Lensing Product Agronomist Ryan Bates Field Agronomist Brian Buck Field Agronomist June 10, 2013 - Issue 3 Planting Date Impact on Soybean Development and Maturity Photo: Pat Branick, DuPont Pioneer Photo:TomDoerge,DuPontPioneer Evaluate Corn Stands: Identify Areas for Improvement Continued on pg 2 WALKING YOUR FIELDS® newsletter is brought to you by your local account manager for DuPont Pioneer. It is sent to customers throughout the growing season, courtesy of your Pioneer sales professional. The DuPont Oval Logo is a registered trademark of DuPont. PIONEER® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents. ®, TM, SM Trademarks and service marks of Pioneer. © 2013 PHII.
  • Stand counts. Take several sample counts to represent the field or area under consideration. For ease of calcula- tion, a sample size of 1/1000th of an acre is recommend- ed (Table 1). Measure off the distance appropriate for your row width, count the number of live plants and multi- ply by 1000 to obtain a reasonable estimate of plants/ acre. Stand counts should be taken randomly across the entire area of the field. The accuracy of your stand esti- mate will improve with the number of locations sampled within the damaged area. Stand uniformity. Evaluate whether plants are evenly distributed or if the stand is uneven. Gaps and doubles indicate an equipment or seedbed problem and re- duce yield. Identify Problems and Plan for Solutions. After you have evaluated stands and uniformity, make every effort to identify the causes of any observed problems. Were metering devices working properly? Were row cleaners set properly and working effectively? Was plant- ing depth proper and consistent? Was residue managed effectively? Were monitors effective in identifying meter- ing device or other equipment problems when they oc- curred? Was pre-plant tillage uniform and did it create a quality seedbed? Continuously improve your planting op- eration by making sure to implement solutions to any problems observed. Heavy spring rainfall causes concerns about nitrogen (N) losses in corn fields and raises questions about the need for supplemental N applications. There are two types of N loss: 1) Leaching—movement with water below the root zone, and 2) Denitrification—loss to the atmosphere. In general, leaching losses are more likely on sandy soils where water can move through the profile quickly. Denitri- fication is more likely on medium and fine textured soils that are not well drained. The exact extent of N losses through leaching and/or denitrification following the heavy rains is difficult to determine. Both of these loss process- es occur through the nitrate form of N, so the potential for significant loss is determined by the amount of the N sup- ply that was in the nitrate form when the excess rainfall occurred. Losses depend on many factors such as the time of N application, the forms of N applied or expected to provide N for the crop, soil characteristics, and soil moisture. Where fertilizer N was applied before planting, the timing of the application and the form of N used are important in determining the risk of loss. Keeping in mind that losses occur through the nitrate form of N, the timing of nitrate formation is an important consideration. Fall-applied ferti- lizer N has a high risk for loss following excess rainfall because most or all of the N would be in the nitrate form by mid-May. For spring preplant applications, ammonium forms of N such as anhydrous ammonia or urea are con- verted to nitrate-N in about four to six weeks. Urea usual- ly is converted to nitrate more rapidly than anhydrous am- monia. Nitrogen solutions (28% UAN) contain half of the N as urea and the remainder as ammonium nitrate. Es- sentially, this fertilizer contains 75 percent of the N as ammonium and 25 percent as nitrate when it is applied. Denitrification losses can occur within a few days, if the soil remains saturated or flooded and nitrate-N is present. Warm temperatures and extended periods of saturated conditions favor high losses. Work in Illinois suggests that four to five percent of the nitrate-N present can be lost each day the soil remains saturated. Table 2 from the University of Nebraska provides some estimates of deni- trification losses at various temperatures and times of saturated soil conditions. Options for applying supplemental N when it is needed include traditional side-dressing with anhydrous ammonia or N solutions. Where the entire crop N requirement has not yet been applied, side-dress or other post-emergence applications should contain the balance of the crop N re- quirement plus 25-50 percent of the N that was already applied. Urea-ammonium nitrate solutions (28%) can also Table 1. Row lengths equal to 1/1000th of an acre. Row Width Length of Row 38 inches 13 ft. 9 in. 36 inches 14 ft. 6 in. 30 inches 17 ft. 5 in. 22 inches 23 ft. 9 in. 20 inches 26 ft. 2 in. 15 inches 34 ft. 10 in. Photo:TomDoerge,DuPontPioneer N Loss Following Excessive Rainfall Continued from pg 1 Table 2. Estimated denitrification N losses influ- enced by soil temperature and days saturated. Soil Temp (°F) Days Saturated N Loss (% of applied) 55-60 5 10 10 25 3 60 75-80 5 75 7 85 9 95 Source: Shapiro, University of Nebraska.
  • be applied as a surface band or as a broadcast spray over the growing crop. Dry N fertilizers such as urea or ammonium nitrate can also be broadcast applied to the crop. Leaf burning from solution or dry broadcast applica- tions should be expected. Applying the dry materials when foliage is dry will help to minimize burning. Basical- ly, broadcast N rates should be limited to 90 lbs. N/acre for corn with four to five leaves and to 60 lbs. N/ acre for corn at the 8-leaf stage. Under N deficient conditions, corn will respond to supplemental N applications through the tassel stage of development if the N can be applied. To help you assess potential fertilizer N losses, download the simple and reliable Supplemental Fertilizer N Work- sheet from the University of Minnesota. http:// www.joe.org/joe/2005june/tt4.php (Source: Schmitt and Randall, U of MN) (Source: Dr. Larry G. Bundy, U of WI Extension Service. ‘Evaluating Nitrogen Losses Following Excessive Rainfall.’) Application timing is everything when only using glypho- sate to control weeds in corn, as it has no soil residual activity. The weeds need to be emerged, but not too large that they compete with corn and reduce yields. Usually this control is accomplished with multiple applications of glyphosate, and/or by using glyphosate in combination with herbicides that provide residual weed control. Critical Weed-Free Period. The critical period of weed control is the interval when weed control is required to provide maximum yield. Weed competition before this period will not affect yield, if weeds are controlled by the start of the critical period. Weed competition after the criti- cal period will not affect yield. Figure 1 shows weeds removed in the first four weeks after planting, corn yield was 100 percent (solid line). When the crop was kept weed-free for at least seven weeks, corn yield was also 100 percent (dashed line). It is difficult to predict the critical period, because it de- pends upon the weeds (how competitive the different weed species are, their density, when they emerge), and the environment (soil moisture and nitrogen). Research conducted on weed interference in corn indicates that weeds should be controlled by at least the third week after planting, and weed emergence should subsequent- ly be prevented until about eight weeks after planting (or more accurately, 14-leaf or V12 corn). If a non-residual herbicide like glyphosate is applied three weeks after planting, a second herbicide application or cultivation will probably be required to keep later germinating weeds under control, or a residual herbicide will need to be add- ed to prevent further weed germination during this win- dow. Herbicide Systems. According to research by University of MN, Dr. Jeffrey Gunsolus, the longer the duration of weed competition, the greater the impact on yield. His research concluded:  The best economic return came from a pre- emergence application of acetochlor followed by a post-emergence application of glyphosate at the 5- inch weed stage.  A one-pass application of acetochlor plus glyphosate at the 1-inch weed stage can maximize yields.  One post-emergence application of glyphosate did not maximize yields or returns in his study (Gunsolus, 2005). Always read and follow label directions and safety pre- cautions. NCGA National Corn Yield Contest This NCGA contest has given participants the recogni- tion they deserve as well as an opportunity to learn from their peers.  June 15: Early entry deadline. Cost per entry $80.  July 12: Final deadline to have all entries submitted. Cost per entry $110 Do you have a nice looking field of Pioneer corn? Enter a Pioneer® brand hybrid in the yield contest and all entry fees and membership dues are paid by Pioneer directly to NCGA. Talk to your Pioneer Sales Representative about your entry. Online entries are available by following this link: https://membership.ncga.com/CornyieldContest/ Early Weed Control is Key in Corn Figure 1. Source: Reprinted with permission from Chris Boerboom, U of WI. ‘Timing Post-emergence Herbicides in Corn and Soybeans.’
  • WALKINGYOURFIELDS® KC Bates, Buck, Lensing DuPont Pioneer Sales & Marketing PO Box 466 Johnston, IA 50131 ADDRESS SERVICE REQUESTED PRESORTED FIRST-CLASS MAIL U.S. POSTAGE PAID PHI CUSTOMER INFO Follow your DuPont Pioneer Agronomists @PioneerMN or @PioneerWI This Walking Your Fields® newsletter is brought to you courtesy of your Pioneer Sales Representative and DuPont Pioneer Account Manager. Michael Blaine Account Manager Pat Branick Account Manager Tim Hasler Account Manager Jack Gust Account Manager Nate Johansen Account Manager Marty Lovrien Account Manager Bruce Marty Account Manager Josh Shofner Account Manager Fred Schliep Account Manager Joel Dorn Account Manager In this issue:  Planting Date Impact on Soybeans  Corn Stand Evaluation  Nitrogen Losses Following Excessive Rainfall  Early Weed Control in Corn  NCGA National Corn Yield Contest