Wisconsin Walking Your Fields newsletter-June


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This issue of Walking Your Fields newsletter contains articles about: late planted forage options, nitrogen management, glyphosate restrictions, cover crop options and soybean planting date.

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

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Wisconsin Walking Your Fields newsletter-June

  1. 1. Corn Silage. When looking at crop species options for producing late–summer or fall forage, corn for silage still yields more during June and July planting dates as com- pared to crops like sorghum-sudangrass, soybeans, alfal- fa, and small grains. Research at the University of Wis- consin shows corn silage is the best choice for emergen- cy planting at any date and location in Wisconsin. Despite little or no grain yield on late-planted corn, it can achieve relatively high quality as compared with other alternative forage crops. Typically, planting an early-season hybrid shows a quality advantage (Milk/T) over a full-season hybrid when planting is delayed into June. However, when planting is delayed to mid-June or July, early- season and full-season hybrids produce similar silage yields and quality as starch differences are small since grain development is limited no matter the maturity uti- lized. Warm-season Grasses. Although lower yielding, warm season grasses, such as sorghum-sudangrass, may be options for growers who are interested in planting a crop that can be harvested earlier than corn silage for emer- gency forage. Warm soil and growing conditions are re- quired for these crops to succeed. In addition, harvest may only be a few weeks ahead of when corn silage is harvested, with the first harvestable crop about six weeks after planting. 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 when the N was applied, the forms of N applied or expected to provide N for the crop, soil characteristics and soil mois- ture. 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. Keep in mind that losses oc- cur through the nitrate form of N, and the timing of nitrate formation is an important consideration in evaluating po- tential losses. Fall-applied fertilizer 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 pre -plant applications, ammonium forms of N such as anhy- drous ammonia or urea are converted to nitrate-N in about four to six weeks. Urea usually is converted to ni- trate more rapidly than anhydrous ammonia. Nitrogen solutions (28% UAN) contain half of the N as urea and the remainder as ammonium nitrate. Essentially, when this fertilizer is applied, it contains 75 percent of the N as ammonium and 25 percent as nitrate. 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. Arnie Imholte Field Agronomist Matt Pauli Product Agronomist Aaron Prestemon Field Agronomist June 10, 2013 - Issue 3 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. Late Planted Forage Options Nitrogen Management (Source: Portions of this article were taken from ‘Evaluating Nitrogen Losses Following Excessive Rainfall,’ Dr. Larry G. Bundy, U of WI Extension Service.) Table 1. Estimated denitrification N losses influenced by soil temperature and days saturated. Soil Temp (°F) Days Saturated N Loss (% of applied) 5 10 55-60 10 25 75-80 3 60 5 75 7 85 9 95 Source: Shapiro, University of Nebraska.
  2. 2. Glyphosate on Corn Corn can be damaged by spraying glyphosate too late in the growing season. Ears appear to have aborted kernels or scattered pollination. It can be easy to diagnose when only part of the field has been sprayed. There is a distinct line and difference between sprayed and unsprayed por- tions of the field.  Corn may be sprayed broadcast or over the top with glyphosate until it reaches V8 stage or 30 inches in height (whichever comes first).  Corn can be sprayed be- tween 30 and 48 inches with a ground rig employing drop nozzles that direct the spray to the base of the corn plants and avoids di- rect application of spray solution into the whorl of the corn plant. It is ex- tremely important to follow the specified label for your glyphosate product. Glyphosate on Soybeans Spraying soybeans with glyphosate can occur through R2 stage. Reproductive phases are as follows:  R1--Plants have at least one flower on any node.  R2--Plants have at least one flower open on one of the two uppermost nodes (Four days after R1).  R3--A 3/16 inch pod at one of the four uppermost nodes (Ten days after R2). After you see the first flower, you have approximately two weeks to spray glyphosate to stay on label. This recom- mendation is a clarification of previous definitions of spraying glyphosate on soybeans throughout flowering. Cover crops can serve growers in a number of important ways. It’s important that crop selection decisions be made after taking into account the needs and limitations of the acres considered for cover crop establishment. Erosion and weed management are two popular goals that cover crop growers hope to achieve, but perhaps nitrogen man- agement or forage availability are important to you as well. In any case, there are a range of species and man- agement levels that will fit some situations better than others. A useful tool to help you select a cover crop based on your needs is provided by the Midwest Cover Crops Council. Decision Tool: http://bit.ly/uEe85I. Some important questions need to be address when considering late-spring or summer planting of cover crops to acres intended for row crops.  Were pre-emergence herbicides used? If so, what are the planting restrictions? The University of Wisconsin has information about plant-back restrictions for some common corn and soybean herbicides (http:// bit.ly/15jhiwc).  Will the cover crop be used to scavenge applied nitro- gen or is it meant to be a nitrogen source? Grasses and other non-legumes tend to utilize applied nitrogen and provide a harvestable crop, but this may limit crop insurance options. Legumes, on the other hand will produce good nitrogen credits for next year’s crop. When a harvestable forage cover crop is used, delay- ing harvest past November 1 may still allow the pro- ducer to take advantage of crop insurance for prevent- ed planting. Grasses that will be potentially useful with a June planting date include warm-season species such as sudan, mil- lets, or sorghum. Oats are a good option as well; they tend to establish quickly for good soil coverage. Clovers, sweetclover and cowpea are legume options that will es- tablish and also provide a nitrogen source for the follow- ing year. Of course, mixes are available that provide some benefits of both types of crops. For June planting, consider an oat/clover mix over some- thing with ryegrass or brassica (canola, rapeseed, tur- nips) components as these prefer cooler spring weather for establishment. Using cover crops on ‘prevented planting’ acres may af- fect crop insurance, so check with your RMA crop insur- ance provider or advisor and make sure you understand any implications of cover crop usage. A couple good USDA resources include: http://1.usa.gov/17S1i6G and http://1.usa.gov/10LMilP. Restrictions on Spraying Glyphosate Ear on left shows irregular kernel set resulting from a late glyphosate application. Ear on right is from unsprayed plant in same field. Photo: Clyde Tiffany, DuPont Pioneer. Cover Crops/Fallow Ground Table 2. Green manure N credits for commonly used legumes in Wisconsin Crop < 6” growth >6” growth ---- lb N/ac to credit ---- Alalfa 40 60-1001 Clover, red 40 50-801 Clover, sweet 40 80-1201 Vetch 40 40-901,2 1 Use the upper end of the range for spring seeded green manures that are plowed under the following spring. Use the lower end of the rand for fall seedings. 2 If top growth is more than 12 inches before tillage, credit 110-160 lb N/ac. Source: University of Wisconsin
  3. 3. 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. How- ever, flowering will occur earlier if soybeans are planted late. Warm temperatures accelerate development, espe- cially flowering. A full season soybean variety will normal- ly flower in the first ten days of July. If there is a hot peri- od 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, 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, but 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 SUMMARY POINTS  Soybeans are able to adjust their final maturity to com- pensate for late planting. Delayed planting will delay the onset of flowering by only a matter of days, even when planting is delayed for weeks. Harvest dates will only be delayed by about one day for each three to five day delay in planting.  Normal maturity soybean varieties should be planted at least until about June 10. Earlier varieties would be induced to flower before sufficient vegetative growth is achieved to produce top yields. Reduced vegetative growth can lower yields by limiting the number of available flowering sites.  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.  Maturity is strongly influenced by photoperiod (day length). Warmer or cooler than normal temperatures do not greatly influence maturity. The rapid shortening of days starting in mid-August drives the soybean to maturity; temperature has a small influence. Planting Date Impact on Soybeans Photo: Pat Branick, DuPont Pioneer Photo: Tom Doerge, DuPont Pioneer
  4. 4. WALKINGYOURFIELDS® KD Imholte, Prestemon, Pauli 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 @PioneerWI In this issue:  Late Planted Forage Options  Nitrogen Management  Glyphosate Restrictions  Cover Crop Options  Soybean Planting Date This Walking Your Fields® newsletter is brought to you courtesy of your Pioneer Sales Representative and DuPont Pioneer Account Manager. Aaron Cole Account Manager Julia Engler Account Manager Tim Mansell Account Manager Eric Pille Account Manager Roy Berrey Account Manager Joel Stieber Account Manager Matt Wichman Account Manager Kyle Nilsestuen Account Manager Alan Patterson Dairy Specialist Jim Serwe Account Manager