Central Minnesota’s Walking Your Fields newsletter-June


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This issue of Walking Your Fields newsletter contains articles about: nitrogen losses, herbicide applications and timings, planting date impact and stand evaluations.

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

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Central Minnesota’s Walking Your Fields newsletter-June

  1. 1. Is The Drought Over? For many of you a defi- nite, “Yes” is the reply. One grower recently said he would welcome back a “little drought,” so he could complete his 2013 field planting operations. Rainfall patterns have been extremely spotty across the state with some areas still on the dry side. The planting window has been extremely compressed with only a few good working days in May. Large planters helped many growers cover a lot of acres when they had the opportunity. This issue of Walking Your Fields® news- letter will center around stand evaluation, replant deci- sions, weed control and nitrogen management. You can access a wide variety of agronomy topics on www.Pioneer.com and select the “AGRONOMY” tab, also follow us on www.Twitter.com/PioneerMN. Now is the time to inspect fields for any planting errors and/or where waterlogged parts of fields may have drowned out. Pioneer® brand hybrids are treated with four different fungicides which should pay dividends this spring with improved stands and better overall plant health. Corn stands can be reduced by many issues such as cold or wet soils, insect feeding, poor seedbed and equipment issues. Check with your Pioneer Sales Repre- sentative for details regarding our replant program. Stand Evaluation & Re-plant Decisions: Re-planting should involve a careful study of the field in question and an analysis of its yield potential. Follow these steps: 1. Determine cause of reduced stand. Insect, disease, environmental, etc. If you do not resolve the underly- ing cause, such as Pythium or Black Cutworm, etc., a second re-planting might become necessary. 2. Determine stand density and condition of the stand. 3. Estimate yield potential of reduced stand in question. 4. Estimate cost to re-plant and find out if replacement seed is available. 5. Will re-planting pay for itself? Sometimes it‟s better to leave the reduced stand; especially the later in to the season it gets. Re-planting costs time and money, and it should be done only if the need is justified and backed up by sound deci- sions and economics. To determine a plant stand for row crops, take several sample counts to represent the field or area under con- sideration. For ease of calculation, a sample size of 1/1000 of an acre is recommended (Table 1). Measure distance appropriate for your row width, count number of live plants, multiply by 1000 to obtain a reasonable esti- mate of plants per acre. Jim Boersma Field Agronomist Dave Pfarr Field Agronomist Clyde Tiffany Field Agronomist June 10, 2013 - Issue 3 WALKING YOUR FIELDS® newsletter is brought to you by your local DuPont Pioneer account manager . It is sent to customers several times throughout the grow- ing season, courtesy of your Pioneer sales professional. The DuPont Oval Logo and Harmony® are registered trademarks 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. Spring of 2013 Will Be Long Remembered Evaluating Stands & Replant Decisions Table 1. Row Length 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. Table 2. Soybean Stand Reduction Loss Chart 38" 30” 15” 7.5” Plants Per Acre Potential YieldNo. of plants in 10' of row 131 103 52 26 180,000 100 116 92 46 23 160,000 100 102 80 40 20 140,000 100 87 69 34 17 120,000 99 80 63 32 16 110,000 97 73 57 29 14 100,000 94 65 52 26 13 90,000 90 58 46 23 11 80,000 86 51 40 20 10 70,000 82
  2. 2. Heavy spring rainfall causes concerns about nitrogen (N) losses in corn fields and raises questions about the need for supplemental N applications. In general, leaching losses are more likely on sandy soils where water can move through the profile quickly. Deni- trification 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 diffi- cult to determine. Both of these losses occur with the nitrate forms of N, so the potential for significant loss is determined by the amount of the N supply that was in the nitrate form when the excess rainfall occurred. Losses depend on many factors such as:  When the N was applied (spring vs. fall)  The forms of N applied or expected to provide N for the crop  Soil characteristics  The duration of time soils remained in a wet or satu- rated condition like the above photo 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 most Nitrogen losses occur when in the nitrate form, the timing of nitrate formation is an important consideration in evalu- ating potential losses. Fall-applied fertilizer N has a high- er risk for loss following excess rainfall because most or all of the N would be in the nitrate form by mid-May. For spring pre-plant applications, ammonium forms of N such as anhydrous ammonia or urea are converted to nitrate-N in about four to six weeks. Urea usually is converted to nitrate more rapidly than anhydrous ammonia. Nitrogen solutions (28% UAN) contain half of the N as urea and the remainder as ammonium nitrate. Essentially, this ferti- lizer contains 75 percent of the N as ammonium and 25 percent as nitrate when it is applied. Options for applying supplemental Nitrogen when it is needed include: 1. Traditional side-dressing with anhydrous ammonia or 28/32% N solutions. Where the entire crop N require- ment has not yet been applied, side-dress or other post-emergence applications should contain the bal- ance of the crop N requirement plus 25-50 percent of the N that was already applied. 2. Urea-ammonium nitrate solutions (28%) can also be applied as a surface band or as a broadcast spray over the growing crop. 3. Dry N fertilizers such as urea or ammonium nitrate can also be broadcast applied to the crop. Leaf burn- ing from solution or dry broadcast applications should be expected. Applying the dry materials when foliage is dry will help to minimize burning. 4. 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. 5. Under N deficient conditions, corn will respond to supplemental N applications through the tassel stage of development if the N can be applied. (Source: Portions of this article are from Dr. Larry G. Bundy, U of WI Extension Service, „Evaluating Nitrogen Losses Following Excessive Rainfall.‟) The days of using a total post-emerge glyphosate pro- gram to control weeds in corn is becoming very question- able, as there are more and more documented glypho- sate resistant weeds appearing. As weed species be- come more tolerant to glyphosate, growers need to use more diversity in their weed control program. Usually this can be accomplished by using a pre-emerge herbicide followed by glyphosate, or glufosinate and/or by using glyphosate or glufosinate in combination with herbicides that provide residual broadleaf 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 critical 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 Saturated soils can cause denitrifica- tion. Photo: DuPont Pioneer Supplemental Nitrogen Management in Corn “The Party Is Over” Figure 1. Source: Reprinted with permission by Chris Boerboom, U of WI. „Timing Post-emergence Herbicides in Corn and Soybeans.‟
  3. 3. after planting, and weed emergence should subsequent- ly be prevented until about eight weeks after planting (or more accurately, 14-leaf or V12 corn). Giant ragweed is a very competitive weed species and needs to be con- trolled before it reaches 4 inches in height. Control Emerged, Tough-to-Kill Lambsquarters DuPont Crop Protection has a few products that are excellent choices for difficult to control weeds like lambsquarters and pigweed in soy- beans. The active ingredient rimsul- furon is an older chemistry but still is an excellent tank partner along with glyphosate and is highly effec- tive on this weed species. Speak with your local sales rep to learn how DuPont® brand Harmony® GT XP can help control large lambsquarters. As always, re- member to read and follow label directions and safety precautions. 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 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 hap- pens 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. How- ever, flowering will occur earlier if soybeans are planted late. Warm temperatures accelerate development, especially flowering. A full season soybean 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 weath- er for the rest of the sea- son, 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, unless it causes water deficit stress. Sometimes temperature is blamed for stress, be- cause hot temperatures often accompany drought. A cool fall does not delay maturity much either; although yields may be reduced if the cool weather is accompanied by heavy rain, causing disease. The flowering period is influ- enced more by temperature. Maturity is more strongly influenced by photoperiod. The rapid shortening of days starting in mid-August drives the soybean to maturity; temperature has only a small influence on maturity. Key Points  Soybean maturity is strongly influenced by day length. The rapid shortening of days in mid-August drives the soybean to maturity; temperature has a small influ- ence.  Soybeans adjust their final maturity to compensate for late planting. Delayed planting delays the onset of flowering by only a matter of days, even when planting is delayed for weeks.  Even normal maturity varieties may be shorter when planted in June. When the normal vegetative period of six to eight weeks is shortened, the effect on the soy- bean plant is usually reduction in height.  Warm temperatures will induce earlier flowering and a longer flowering period, cool temperatures will induce later flowering and a shorter flowering period. Planting Date Impact on Soybean Development & Maturity 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 Enter that 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. On-line entries are available by following this link: https://membership.ncga.com/CornyieldContest/ Photo:TomDoerge,DuPontPioneer Photo: DuPont Pioneer
  4. 4. WALKINGYOURFIELDS® KH Boersma, Tiffany, Pfarr 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 Chad Anderson Account Manager Troy Elfering Account Manager Jay Zielske Account Manager Scott Hanna Account Manager Mark Navara Account Manager Reid Olson Account Manager Brad Weber Account Manager Neil Hansen Account Manager This Walking Your Fields® newsletter is brought to you courtesy of your Pioneer Sales Representative and DuPont Pioneer Account Manager. In this issue:  Stand Evaluations  Nitrogen Losses & Alternatives  Herbicide Applications & Timing  Planting Date Impact