The Case of the Missing Corn Plant(s)

By Daniel Hudson, UVM Extension Agronomist

For the most part, the corn crop is off to a slow start in the Northeast and beyond.   It is good to finally see fields with tidy rows of corn plants making the most of sunny days and warmer temperatures. At this time of year, it is not uncommon to get calls about missing corn plants. If you have missing plants or an uneven stand, investigating the matter sooner than later will increase the likelihood that you will find useful indicators of the cause of the problem.

picture from: William Wiebold, University of Missouri

picture from: William Wiebold, University of Missouri

Several years ago I was attending a seminar and a corn farmer was giving a presentation having to do with certain practices on his farm. One of the slides showed a nice picture of his corn field with the plants each about ten inches tall. The farmer glanced at the slide, probably to remind himself of what he was supposed to say next. Clearly off script, he did a double-take, half-crouched and pointed at a gap in the row of corn in the picture on the screen and said, “All I want to know is what happened to that corn plant!” The inference was, ‘I paid about a 4/10 of a penny each for those seeds, a BUNCH of money for the equipment and field operations that were necessary to put it in the ground, and I was careful….it had better come up and keep growing!’

Sparse plant populations are disturbing and cause a fair amount of anxiety for different farmers each year, especially when things are behind schedule as they have been in 2014. Reasons for plants being missing can include planter problems, cool/variable soil temperatures, compaction, pathogens (damping off diseases), wire worms, cutworms, seedcorn maggots, and sometimes injury from excessive rates of seed-placed fertilizer.

Corkscrewing

If you dig where a missing plant is supposed to be and find an unemerged seedling with a mesocotyl (the part between the coleoptile and the seed) that changed direction more than once underground, the phenomenon is commonly known as ‘corkscrewing.’ In some cases, the seedling even ‘leafs out’ below the soil surface. While the leaf occasionally makes it to daylight anyway, the seedling often dies underground. Bob Nielson of Purdue notes several potential factors that can contribute to corkscrewing:

picture by Daniel Hudson, University of Vermont

picture by Daniel Hudson, University of Vermont

• Compacted soils
• Variable soil temperatures, where the top layer of soil is very warm during the day, but drops dramatically during very cool nights.
• Herbicide injury (seedling growth inhibitors such as acetochlor) in certain soil conditions
• Kernel position in the soil

In one field where I observed corkscrewed corn seedlings last week, torrential rain after planting had caused an extremely dense layer of soil to form over the seeds. While the plant takes gravity into account when deciding which direction to send different plant parts, large fluctuations in daily soil surface temperatures also likely ‘confused’ the coleoptile about which way was actually up. It is not clear how extreme or prolonged these temperature differences need to be for this to happen.

Damping off diseases

picture from: William Wiebold, University of Missouri

picture from: William Wiebold, University of Missouri

Damping off diseases can afflict corn seedlings before or after emergence. If you dig up the top two inches of soil in a gap where a corn plant ought to be, you will often find that it is not simply a ‘skip’ due to the corn planter. You will often find a seedling that is dead, dying, or still in the process of emerging. If you find a seeding that is in the process of emerging and the mesocotyl and seminal roots are a nice white color and crisp, you probably just need to wait longer. This is not to discount the reality of the yield losses that uneven emergence can cause. However, if the aforementioned tissue is brown and/or mushy, the seedling probably succumbed to one of several pathogens, which is not uncommon when soils are cool and moist for long periods of time. Damping off can also occur when pathogens attack the mesocotyl (pictured). If an emerged seedling (V6 or younger) looks sickly and the exhumed mesocotyl is brown or deteriorating, the issue is post-emergence damping off. This is because young corn seedlings rely on nutrients coming from the seed and seminal roots (via the mesocotyl). After V6 the nodal root system begins to be the primary source of nutrients for the plant.

Insects

If you find a small white maggot living in/on the seed, it is very likely a seedcorn maggot. seedcorn maggotThis happens most frequently in situations where seed is planted without an insecticide and organic material (manure, cover crop, etc) has been incorporated within the past month or so. The fly of the seedcorn maggot is attracted to the scent of decaying organic matter. The eggs hatch within a few days of deposition and the resulting maggots feed for up to two weeks before pupating. In systems where insecticide is not used and in fields with challenging soils this problem can be minimized by waiting to plant until soils are very warm (rapid emergence and plant development) and/or waiting for several weeks after substantial amounts of organic material have been applied or incorporated. For non-organic farmers, an appropriate insecticidal seed treatment is almost always very helpful.

If you find a small white maggot living in/on the seed, it is very likely a seedcorn maggot. This happens most frequently in situations where seed is planted without an insecticide and organic material (manure, cover crop, etc) has been incorporated within the past month or so. The fly of the seedcorn maggot is attracted to the scent of decaying organic matter. The eggs hatch within a few days of deposition and the resulting maggots feed for up to two weeks before pupating. In systems where insecticide is not used and in fields with challenging soils this problem can be minimized by waiting to plant until soils are very warm (rapid emergence and plant development) and/or waiting for several weeks after substantial amounts of organic material have been applied or incorporated. For non-organic farmers, an appropriate insecticidal seed treatment is almost always very helpful.

In a corn field with missing plants and along with plants that came up and then died (generally before V6) wireworms are likely culprits. The most telling indicator of wireworms is the presence of a hole in the crown of the plant, just below the soil line. This generally only happens when the corn plants are still small and the growing point is still below the soil surface. Wireworms are also most common in situations where a sod or cover crop has been terminated. These pests are effectively controlled by soil-applied insecticides unless plant development is so slow that the insecticide loses efficacy.

While missing corn plants, thin stands, and uneven emergence can be very expensive and discouraging, learning to identify the cause of the problem this year can pay dividends in the future. If you need help identifying the cause of a sparse or uneven stand, do not hesitate to contact your local Extension Agronomist.

 

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Maximizing Your Return to Fertilizer Investment

Daniel Hudson, UVM Extension Agronomist

  • The pre-sidedress nitrate test (PSNT) works well in a ‘normal year’ but consistently over-recommended sidedress N by about 30-50 pounds per acre on the fields studied in 2013.
  • Adapt-N modeled N-dynamics fairly well on the farms we studied in 2013, but recommended rates seemed to be 20-30 pounds low and sometimes a little lower.
  • The accuracy of the sidedress-nitrogen recommendation generated by Adapt N can be no better than the quality of the data entered into the program by the farmer (e.g., manure rates/analysis, soil organic matter levels, etc).
  • While Cornell maintains control over the evolution of the tool, Adapt-N has been licensed to Agronomic Technology Group.   Depending on your scale, Adapt-N will cost about $2-3/acre this year.
  • Technology has not yet eliminated the need for common sense!

Farms adopt technologies when they clearly see that it will more than pay them back in the short- and medium-term. Why do dairy farmers take forage quality samples and monitor milk production? Because they know that data can help them come up with a ration that will support excellent lactation and healthy cows at a low cost. Relationships between mixer wagon IIfeed intake (ingredients, amount, etc.) and lactation are generally understood and can be modeled quite well with computer programs used by ruminant nutritionists. Even without computer models, practical experience leads farmers to comments like, ‘when I added feed ingredient X at Y pounds per animal per day, milk production went up Z pounds per cow per day, when I took that ingredient out, production went back down again.’ While there are probably many approaches to it, failing to optimize the ration amounts to wasting money or leaving money on the table. Similar principles apply for improving herd genetics, improving cow comfort, etc. USDA-NASS statistics show the net effect of improving bulk tanknutrition, genetics, and adopting better practices and products: milk production per cow in the U.S. has risen from about 11,000 lb/cow/yr in 1976 to nearly 22,000 in 2013!

We also know that choosing better corn hybrids and forage varieties pays, but can optimizing soil fertility pay a farmer back in an analogous manner? Can interacting factors that affect soil fertility dynamics and crop yield even be modeled? ‘Yes’ on both counts, but there is a significant lag time between the time you put the fertilizer on the field and the time you cover the bunker silo for the last time during the harvest season, so the cause-effect relationship may be less apparent. ‘Was this terrific yield really the result of the fertilizer I put on, or was it the amount of manure that I put on? Maybe we just had good precipitation patterns? Or was it the snake oil fertilizer additive I bought?’

Providing crops with adequate plant-available nitrogen is very important to dairy farmers because it has a profound effect on crop yields and quality. While all plant available nutrients can change forms and become more or less available, nitrogen is particularly difficult to manage. Plant-available nitrogen in a given undisturbed field can increase as organic matter decomposes (mineralization), and can decrease via leaching, volatilization, denitrification, or immobilization. To make matters worse, each of these factors are affected by management: tillage, manure incorporation, levels of soil organic matter, timing of manure application, temperature, etc.PSNT2

In the early-1990s the pre-sidedress nitrate test (PSNT) came into use as a direct nitrate measurement that was used to predict the need for sidedress nitrogen on corn (i.e., how much more N you need to apply to attain your realistic yield goal). It is a snapshot of the soil nitrate (NO3-) concentration at the time the samples are collected. The sidedress-N recommendation is based on research that correlates soil nitrate concentrations at the time corn is 8-12” tall with the total amount of plant-available nitrogen that will be released by soil organic matter over the course of the growing season. It is like saying, ‘I measured four cords of wood in the shed in October, and that should get me through an average winter.’ But what if winter is not average? It might be REALLY

from University of Wisconsin

cold; winter might drag on and on; someone might help themselves to my wood; the shed could burn down; or the wood might be greener than average. Similarly, the PSNT gives good recommendations in a normal year but may not accurately predict the optimal sidedress nitrogen rate when conditions are abnormal.

While the PSNT typically offsets the cost of sample processing and labor (by far), it suffers a low adoption rate probably because it:

  • needs to be done during an otherwise busy time of year (starting when the corn is about 6” tall).
  • takes a significant amount of time to do properly because fields need to be subdivided and sampled according to soil type, features of the land, and management history.
  • requires that samples be taken to a depth of 12”, which can be challenging in stony soils.
  • does not always demonstrate a payoff within a week. When fertilizer costs are reduced, the payoff is immediate. Yield benefits are not experienced until harvest and sometime are attributed to other factors.

How does the PSNT compare with Adapt-N?

The PSNT works well in a ‘normal year’ but consistently over-recommended sidedress N by about 30-50 pounds per acre on the studied fields in 2013. This is not surprising because heavy rain just before the tests were collected leached much of the existing nitrate from the top 12” of soil. The logic of the PSNT says, ‘low soil nitrate concentrations now N rec summary(~V6 corn) means that soil nitrate concentrations will continue to be low and therefore lots of sidedress-N is necessary to meet yield goals.’ In 2013 sidedress-N recommendations from the PSNT were often over 100 lb of actual N per acre.

Cornell soil scientists have developed a program (Adapt-N) that models nitrogen behavior in agronomic soils. This model includes as many of the relevant variables as they have data to support as well as historical and real-time weather data from each site studied. The whats new with adapt Nprogram had a good sense whether more or less N was needed, but also seemed to generally under-recommend N by 20-30 lb/ac and sometimes more. With our approach, it was impossible to determine if this was due to weaknesses in the model itself or imperfections in the information that we were feeding into the program (manure analysis, soil organic matter levels, etc).  Recommendations given by any model cannot be better than the data that is fed into the model: garbage in, garbage out. That being the case, neither the PSNT nor Adapt-N should be used without common sense. If either tool generates a recommendation that is significantly outside of what you consider to be reasonable or normal for the conditions in a given field, other measurements should be taken and/or the data you entered into the program should be reconsidered.

Overall, I believe that Adapt-N will be much better than the PSNT for predicting the need for sidedress N for several practical reasons:

  • Adapt N accounts for most major variables known to affect soil nitrogen behavior, whereas the PSNT only considers the nitrate concentration.
  • Adapt-N is not blind to the past and therefore has the ability to model the behavior of
    Lagoon I

    photo by Daniel Hudson

    soil N under unusual environmental conditions whereas the PSNT only gives a snapshot of a particular moment in time.

  • Adapt-N uses historical and real-time data to model how much plant-available nitrogen is in the ‘pipeline’ and anticipate when it will become available to the crop; the PSNT measures how much nitrate is in the ‘leaky bucket’ right now.
  • If managed well Adapt-N can/will continue to improve its accuracy over time, while the PSNT will never change.
  • Assuming that Adapt-N recommendations are as good as or better than the PSNT,
    from Cornell.edu

    from Cornell.edu

    Adapt-N is more adoptable. Data can be entered into the Adapt-N program at any time: early in the spring, at night, on rainy days, etc. Farmers that have nutrient management plans already have much of the data they need to make the program work! The PSNT samples can only be collected during an otherwise very busy time of year.

  • Adapt-N allows the user to subdivide fields up into more appropriate management zones with very little extra effort or cost. In contrast, if I am using the PSNT and decide to split a 15 acre field into 3 management zones (which is often appropriate), I have just tripled the amount of time and cost required to test that field.

Up until this year, Adapt-N was available at no cost. While Cornell maintains control over the evolution of the tool, Adapt-N has been licensed to Agronomic Technology Group.   adapt N training webinarDepending on your scale, Adapt-N will cost about $2-3/acre this year.  A recorded webinar explaining the new user interface and fee structure can be found here.

Finally, it is important to mention highlighting the limitations of the PSNT is not a criticism of the tool or the scientists who developed it. Those who create tools are usually more aware of its limitations than anyone else! The PSNT was developed using a valid and rigorous process, and continues to be a good tool in a normal year. Many farmers have made/saved money by using it, and many more should have.   The PSNT can still be used in the traditional manner or be used to corroborate the data that Adapt-N generates for those occasions when the farmer is looking for assurance that the tool is working.

Between the two tools, no one should find themselves in a situation where they have no idea how much sidedress N to apply to their 2014 corn crop. Depending on your scale, proper use of these tools (together with common sense) could easily improve your bottom line by tens of thousands of dollars per year, both by increasing yield and by avoiding sidedress-nitrogen applications where they are not needed.

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Managing for High Yielding, High-Quality, Low-Cost Crops

Daniel Hudson, UVM Extension Agronomist

Feed is, by far, the greatest expense for dairy farms. The 2012 Northeast Dairy Farm Summary published by Yankee Farm Credit showed that on average, feed represented over 37% of total farm expenses, and labor was a distant second at just over 15%. The primary influences that the dairy farmer has over this cost are in the areas of:oesterle chopping

  • Forage yield and quality
  • Crop yield and quality
  • Management of stored feed (preventing losses of quality and quantity between the field and the mouth of the cow).

This is why every farmer benefits from careful management in their cropping system. Land is the farmer’s foundational resource, whether rented or owned. Value is added to the land by growing crops. Value is then added to the crops by running them through the digestive tract of the cow — at least when milk prices are good.

Most dairy farmers would be astonished if they heard a fellow dairy farmer say, “I know that my cows don’t lactate much, limp a lot, and the milk has an extremely high somatic cell count, but I am a crops guy – cows aren’t really my ‘thing.’” What? Unthinkable! If you are not a ‘cow-person,’ hire someone who is! If your cows have fundamental problems, it does not matter how well other things are going.

Interestingly, if a dairy farmer said, “my crop yields are awful, forage quality a perpetual problem, and my feed costs are through the roof,” much less shock would be expressed. I am not saying that dairy farmers are bad at growing crops, but that there are many who could make a lot more money by devoting more attention to the crops. Here are some economically profound facts about crop production in dairy systems:IMG_0211

  1. A tall fescue variety trial conducted at Cornell showed a 30% difference in yield between the high and low yielding cultivars. Choose your forage varieties carefully.
  2. Corn that has its nitrogen needs met can yield twice as much as corn that does not.
  3. The yield of two different corn hybrids of similar maturity can differ by more than 30%.
  4. Under common conditions, grass that had its nitrogen needs met can have protein levels that are 4% higher than in grass that did not. Assuming a 4 ton/ac forage yield, this protein difference would equate to the amount of protein found in 684 pounds of soybean meal, which currently has a value of $163 (CBOT price, more at the farm gate).
  5. Depending on severity, inadequate phosphorus or potassium fertility can reduce crop yields by more than 50%.

    oregon state bunker silo

    From: Oregon State University

All of these facts have implications for risk management (inventory), profitability (grain bill, purchased feed), and efficiency.

Here are some pieces of low-hanging fruit that I believe can help the bottom line of the average dairy farmer in the 2014 cropping season.

  1. As inglorious as it sounds: have your soils tested. Notice that I did not say ‘take soil samples.’ While anybody can learn to properly collect soil samples, it is something that most farmers can and probably should delegate to another competent and trustworthy individual. This is mainly due to the extremely busy schedule that most dairy farmers keep. There are many certified crop advisors (CCA) in Vermont, Massachusetts, Quebec, and New York. Some of them are independent and charge for soil testing services, others work for seed/chemical/fertilizer vendors and may provide the service to their customers. Search online by state and/or expertise. If you search on the website it will be helpful to know that the codes for ‘agronomy’ and ‘soil fertility’ are A1 and U2, respectively (http://portal.sciencesocieties.org/BuyersGuide/ProfessionalSearch.aspx?Token= ).
  2. Manure testing. Failing to regularly and properly test manure is like failing to test the

    from University of Wisconsin Extension

    haylage that goes into your total mixed ration. Similar to making ration, you need to know the nutrient content of each of your soil fertility ‘ingredients’ if you want to reach your crop yield and quality goals.

  3. Knowledge should lead to action: follow the recommendations of your soil test report and account for the nutrients applied in the manure. Just recently a farmer told me that amending the soil in a field that he was renting nearly doubled the yield. I am sure that quality was profoundly affected as well.
  4. Choose corn hybrids and forage varieties with care. Look for independent variety trials that were conducted under conditions similar to your farm. This can be challenging, but variety trials are routinely conducted in Vermont, Wisconsin (corn, forage), Michigan, New York, Ontario (corn, forage), and Minnesota. Conditions vary at each location so it will take some work to narrow down some of the best candidates.
  5. When reseeding perennial forages, include red clover (or alfalfa if your soils are suitable) in the seeding mixture. In pure grass stands between 150 and 200 pounds of actual N over the course of the season is required to optimize yield. In stands that with 40-60% legume, 40-50 pounds of actual N prior to green-up in the spring should optimize forage yield[1].

Cash has been hard to come by for dairy farmers over the past few years, and many have had to make tough choices about where (not) to spend money. Now is a great time to implement these foundational agronomic practices that add value to each acre of land that you manage.

[1] Some recommendations indicate this range to be 20-60% legume.

Contact: Daniel.Hudson@uvm.edu

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Why is barnyardgrass so abundant in Vermont hay fields and pastures this year?

By Daniel Hudson, UVM Extension Agronomist

This year many farmers are wondering why barnyardgrass is present in unusual abundance in their hay fields and pastures.  This annual warm-season grass weed is physically similar to Japanese millet and is found throughout the world.  In North America it is found from Mexico to Alaska.  This discussion will cover:

  • Forage quality and palatability questions and concerns
  • Factors that contributed to the problem in 2013
  • Crop management implications

Physical description

The tallest plants in this picture (aside from trees) are barnyardgrass

The tallest plants in this picture (aside from trees) are barnyardgrass

Depending on growing conditions and the time of germination, mature barnyardgrass plants may be between 1 and 6.5 feet tall.  Larger plants with more dense tillering (thick clumps with many shoots) can be expected in areas of very high fertility and/or less frequent harvest.  Stems are coarse and may range from 0.15 to 0.5 inches in diameter.  Leaves are between 4 and 12 inches long, up to 0.6 inches wide, green in color and occasionally have a reddish hue.  Seed heads have a sparse panicle arrangement (i.e., shaped like a ‘Charlie Brown Christmas tree’), generally have between four and seven lateral branches, and may be reddish-purple and/or green in color.  Branches of the seedhead range from 0.75 to 2.5 inches long and have bristly seeds densely packed along the length.  Roots are dense and fibrous.

First things first: what about the forage quality and palatability?  In absolute terms, barnyardgrass is not very palatable as a pasture forage except in the vegetative stage.  As with most weeds, barnyardgrass wastes no time moving from the vegetative IMG_0427stages to the reproductive stage.  If low to moderate amounts of barnyardgrass are present in a perennial hay field that is harvested for haylage, palatability of the ensiled product will almost certainly not be affected.  Research published by Marten and Andersen (1975) compared the forage quality and palatability characteristics of 12 pasture weeds to oats.  At the time the oats were at the early-head stage, the barnyardgrass was still vegetative, and their forage quality parameters compare as follows:

Species

IVDMD %

ADF %

ADL %

CP %

Ca %

P %

K %

Mg %

Barnyardgrass 81 30 3.0 21 0.8 0.4 4.2 0.6
Oats 71 34 3.6 19 0.4 0.4 2.9 0.3

*Data from 1973

The point here is not that barnyardgrass is a superior forage species compared to oats or anything else, but to demonstrate that barnyardgrass will not harm the forage quality parameters listed above if harvested or grazed at a vegetative stage.   As with all grasses, if barnyardgrass  is allowed to progress to the reproductive stage the forage quality will suffer greatly.

The researchers in this study used sheep to measure palatability of the various weeds: barnyardgrass was palatable, common ragweed was sometimes unpalatable, and wild mustard was unpalatable.  The researchers also tested for alkaloids, compounds which are grazing dairy heiferknown to reduce palatability; none were found in any of the grasses tested.  The data from the mineral analysis was used to calculate Ca/P ratios, which can indicate if that feedstuff may predispose cows to milk fever.  The K/(Ca + Mg) ratios were calculated to determine if any of the forages might be prone to induce grass tetany to grazing livestock.   The ratios for barnyardgrass suggest that it is unlikely to induce milk fever or grass tetany.  Finally, the nitrate levels were checked for all species in the study.  Forages with nitrate levels above 0.35% can induce nitrate toxicity, and some have suggested that barnyardgrass might occasionally have this problem.  In this study, however, barnyardgrass had 0.09% nitrates, while oats had 0.10%.  Nitrate toxicity is much more likely to occur in barnyardgrass and other forages in drought situations.

Why is barnyardgrass so abundant this year?  As with most weed problems that happen suddenly over a wide geographic area, the cause is environmental.

Interacting factors likely included:

  • Dry weather until the last week of May likely delayed nitrogen mineralization which reduced the vigor of early-season forage growth.  This left more nitrogen in the soil than would ordinarily be there in early-June.  This delayed release held back early growth of the pasture grasses yet coincided nicely with the early growth-stages of barnyardgrass seedlings.
  • Record precipitation in late-May through June set the stage nicely for germination and rapid growth of barnyardgrass, which thrives in extremely wet soils, especially if nitrogen is abundant.
  • Warm-season grasses like barnyardgrass and corn like hot weather.  The temperatures in July and August favored rapid growth of warm-season plants.

For some farms, one or two of this year’s hay cuttings happened on wet soils.  In some cases, this led to compaction, which favored retention of surface water and reduced competition from the established perennial plants.  Some farmers may notice strips of barnyardgrass oriented in the same direction that the field is harvested.

Could my management practices have made this problem worse?  Maybe a little.  Given the many multifactorial decisions that need to be made each year, most IMG_0235farmers have to choose between the ‘lesser of two evils’ several times per year.  In this case the choice for many was between taking the first cutting when soils were still somewhat wet during a two day break in the rainy weather as opposed to delaying harvest until soil conditions improved.  In many cases, delaying the harvest would be the greater of the evils given the inevitable loss of forage quality that would affect the bottom-line for the rest of the year.  In pasture settings, barnyardgrass always has a competitive advantage around watering areas due to higher levels of compaction, abundant nutrients, moisture, and destruction (i.e., reduced competition) of the perennial pasture plants.  Given the geographic scope of the problem in the state, it is safe to say that fields with certain types of soils probably would have ended up with barnyardgrass this year under many management scenarios.

Will it show up again?  The seeds that produced the plants we see this year were already in the soil. References to research done on the subject of barnyardgrass seed viability in the soil suggest that most of the seed in the soil seed bank loses viability within three years, but some may survive 13 years or more.  Given that barnyardgrass is a prolific seed producer (it can produce 2,000 pounds of seed/ac in a severe infestation) it is reasonable to assume that past infestations made significant contributions to the soil seed bank and that we will probably see it again.

How can this weed be managed in the future?  Knowledge about the particular characteristics of a weed can help the manager make decisions about how to manage it in the future.  Barnyardgrass:

  • is a warm-season annual grass.  It will not be a factor for a timely first cutting, but the plants will grow rapidly thereafter.
  • seed production will be heaviest in August and September.  Plants will keep attempting to produce seed until cooler temperatures inhibit regrowth.
  • favors rich, moist soils and grows well in poorly drained soils.
  • is not tolerant of shading by other plants
  • thrives when nutrient (particularly nitrogen) levels are high in the soil
  • seeds float; moving water is a major mode of seed dispersal.
  • can be removed from corn and legume fields with herbicides, but there are no labeled herbicides that will remove it from a grass hay field or pasture.

Conclusion:

While barnyardgrass is not something that anyone would intentionally plant in their pastures and hayfields, the impact on haylage quality will be minimal unless infestations IMG_0224are very heavy; in a few cases the impact on forage quality may even be positive.  To minimize future problems, endeavor to harvest fields before the barnyardgrass produces viable seed.  Promoting dense and vigorous growth of your perennial forage species will increase your chances of out-competing barnyardgrass, which is quite intolerant of shade.   In pastures, degraded areas will probably continue to favor barnyardgrass until management is changed to so that compaction and physical damage to the perennial forages is corrected.  In certain situations where barnyardgrass is a major problem, rotating the field to corn will give the crop manager the option to use herbicides.

References:

Esser, L. L. Index of species information: Echinochola crus-galli.  From Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.  Online: http://www.fs.fed.us/database/feis/plants/graminoid/echcru/all.html.  Accessed: September 2013.

Lanini, W. T., and B.A. Wertz.  Weed Identification 12: Barnyardgrass.  Penn State Extension.  Online: http://extension.psu.edu/pests/weeds/weed-id/barnyardgrass  Accessed:  September 2013.

Marten, G. C., and R. N. Andersen.  1975.  Forage nutritive value and palatability of 12 common annual weeds.  Crop Sci. (Vol. 15): 821-827. Online: https://www.crops.org/publications/cs/pdfs/15/6/CS0150060821.  Accessed: September 2013.

Mitich, L.  Intriguing world of weeds: barnyardgrass.  Weed Sci. Soc. Amer.  Online: http://wssa.net/weed/intriguing-world-of-weeds/#x  Accessed: September 2013.

Sprague, C.  E-434: 2013 weed control guide.  Michigan State University.  Online: http://www.msuweeds.com/publications/weed-control-guide/.  Accessed: September 2013.

Weiss, W.P. and Shockey, W. L. Nitrate toxicity in drought-stressed plants.  West Virginia University Extension Service.  Online: http://www.wvu.edu/~agexten/forglvst/nitrate.htm.  Accessed: September 2013.

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Does Your Corn Have Northern Corn Leaf Blight?

By Daniel Hudson, University of Vermont Extension Agronomist

silage corn affected by northern corn leaf blight (NCLB)

Silage corn affected by northern corn leaf blight (NCLB)

The silver lining of most disasters is that they are often accompanied by opportunities to learn something new or at least be reminded of something already known.  The down side is that disasters are often very expensive in the short-term.  The disaster of the day is northern corn leaf blight (NCLB), a fungal disease that in some circumstances can decimate corn yield and silage quality.  Northern corn leaf blight has been observed at varying levels of severity in Vermont for the past several years.  This year some fields along the Connecticut River (and probably elsewhere) will probably suffer 30% yield losses from this disease.  Much of this loss will result from poor grain fill stemming from the reduction of photosynthetic area on the affected leaves, which will also have implications for silage quality.

IMG_0096.JPG (2)

Cigar-shaped lesions on the leaves of a plant infected by northern corn leaf blight.

Northern corn leaf blight is most easily recognized by the ½ – 1” wide by 1-7” long ‘cigar-shaped’ lesions that form on the leaves.  In severe infestations, the lesions can be  prolific enough that they eventually join at the edges and may turn the entire leaf a grayish brown color.  The earlier this foliar disease occurs in the growing season, the greater the yield (and quality) impact will be.  Yield losses can be as high as 50% if the disease becomes established prior to tasseling.  To make matters worse, fields with severe infestations are often more susceptible to stalk rot. The NCLB inoculum can be deposited on the growing crop from distant fields via rain or wind, but infection will be more severe if inoculum is present in the field.

Corn grain farmers have had NCLB on their radar for a long time because the pathogen overwinters in the abundant corn residue which is characteristic of that cropping system.  Corn silage systems typically have fewer problems with NCLB because of the scarcity of residue remaining after harvest.

Will this disease be a problem every year?  Probably not, but the potential for economic loss is large enough that local farmers should seriously consider selecting resistant cultivars, especially in fields with the primary risk factors.  The fields with the greatest risk of developing NCLB are those that have:

  • a recent history of NCLB
  • characteristics that favor extended leaf wetness (6 – 18 hours per day).  For example, river bottoms with frequent fog, sheltered areas with reduced air movement, shade.
  • infrequent crop rotation
  • no-till or reduced tillage
  • much corn residue remaining after harvest
  • weather conditions includes frequent rain, cloud cover, high humidity, and mild temperatures (64-81⁰F)
IMG_0101.JPG (2)

This 97-day corn hybrid has a NCLB resistance rating of ‘4’ (a rating of ‘9’ indicates the highest level of resistance)

Be aware that the scales used to rate disease resistance may vary among seed companies.  Pioneer and Mycogen, for example, have a scale of 1-9, with a rating of 9 indicating excellent resistance; DeKalb’s scale is opposite, and a rating of 9 indicates poor resistance.  The variety planted in a local river-bottom field with a severe NCLB infestation had a rating of ‘4’ on the Pioneer/Mycogen scale.

IMG_0102.JPG (2)

This 106-day hybrid was planted in the adjacent field and had a NCLB resistance rating of ‘6’ (a rating of ‘9’ indicates the highest level of resistance). The difference in condition between the fields is probably only partially due to genetics.

There are two forms of NCLB resistance that exist in commercial cultivars: partial and race-specific.  The ‘partial’ resistance gives the plants some degree of resistance to all races of NCLB.  In areas where NCLB is a common problem, producers and their seed representatives can work together to choose hybrids that are resistant to the local NCLB race that is known to be most problematic.  Yellow lesions often still appear on resistant varieties, but they are small and do not result in the production of spores.

Other management options include crop rotation and fungicides. Scouting for NCLB should occur just prior to tassel emergence.  If the disease is beginning to develop at that stage and the forecast and other risk factors indicate that an infestation is likely to occur, a fungicide application may reduce the impact of the disease.  When warranted, the greatest economic returns will be realized when fungicides are applied between tasseling and early silking.  There are no established economic thresholds for fungicide applications in corn.  In conventional tillage systems, rotation away from corn for one year greatly reduces the likelihood that NCLB will develop in the subsequent corn crop.  In no-till systems, a two-year break is advisable.

Northern corn leaf blight can be easily confused with other diseases such as Stewart’s bacterial wilt and Diplodia leaf streak.  Contact your local Extension agronomist or Certified Crop Advisor for assistance with a diagnosis.

Daniel Hudson can be contacted by e-mail at daniel.hudson@uvm.edu or by phone: 802-751-8307.

References:

Darby, H.  Northern Corn Leaf Blight.  Online:  http://www.uvm.edu/extension/cropsoil/northern-corn-leaf-blight  University of Vermont Extension.  Accessed September 2013.

Dillon, P. Northern Corn Leaf Blight (NCLB).  Online:  http://ohioline.osu.edu/ac-fact/pdf/0020.pdf  University of Kentucky Extension. Accessed September 2013.

Lipps, P.E., and D. Mills.  Extension Fact Sheet: Northern Corn Leaf Blight.  Online: http://www.extension.purdue.edu/extmedia/BP/BP-84-W.pdf  Ohio State University Extension. Accessed September 2013.

Wise, K. Diseases of Corn: Northern Corn Leaf Blight.  Online: http://www.uky.edu/Ag/IPM/scoutinfo/corn/disease/nclb/nclb1.htm  Purdue University Extension. Accessed September 2013.

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Can foliar diseases in forage grasses cause economic losses for livestock producers?

By Daniel Hudson, UVM Extension Agronomist

late blight on ripe tomato. From Cornell University

Most garden enthusiasts are familiar with fungal diseases in fruit and vegetable crops. These diseases can induce a range of experiences from mild gardener irritation to complete crop loss.  Late blight in tomatoes, powdery mildew in squash, leaf spot, phytophthora , and pythium, just to name a few.  The most frustrating diseases are those that spoil the quality of the product just before it is ready to harvest!  Spores for most plant pathogens can be found almost everywhere those plants grow!  Given the right conditions, they can devastate a crop.  While some species and varieties of plants have varying degrees of resistance to certain pathogens, no plant is entirely immune.

Fungal infection of fruit and vegetables can render a crop completely unmarketable, a fact that looms large in the minds of producers.  In field crops and forages, however, fungal pathogens often do not prevent harvest or marketing, but often compromise yield and quality in ways that are not immediately evident.  Until recently I had the impression that foliar disease on forages was not a ranking concern among livestock farmers or hay producers.  This is why I was very surprised when I recently heard a farmer state that mid-summer grass diseases (foliar) are the most significant agronomic problem on his farm!

What are these diseases?

Stripe rust. Picture from: Oregon State University

While some species and varieties are resistant to some fungal pathogens, all grasses and legumes are susceptible to some diseases.  For example, there are at least 30 fungal diseases that can affect orchardgrass.  Depending on the time of year, the primary ones we see are rusts (caused by species of Puccinia fungi), scald (species of Rhynchosporium), and leafspot/blotch (species of Drechslera).  All of these diseases are favored by prolonged periods of leaf wetness.

What are fungal pathogens really after?

Fungal pathogens ‘want’ to reproduce; to do this, they need a source of energy.  Fungal pathogens specialize in accessing the carbohydrates in the tissue of certain classes of plants but are ineffective at exploiting other types of plants.  As in the case of communicable diseases among people, there are certain conditions that favor the development of disease in plants.  In forage crops, fungal foliar disease is likely to develop if:

soil test report

soil test report showing potassium deficiency

  • the plant has been stressed by drought, nutrient deficiency, insect damage, another disease, or lack of sunshine.  Potassium deficiency is often connected with increased susceptibility to foliar disease.
  • the leaves of the plant are wet for prolonged periods of time.  This time of year the dew sets early, nights are getting longer, and the grass is wet late into the morning.  Heavy forage stands reduce air movement, which causes the leaves lower in the canopy to stay wet longer.  Prolonged leaf wetness allows pathogens more time per day to penetrate plant defenses.
  • there is a lot of inoculum around.  In perennial forage stands, there is a lot of inoculum (spores) around in the soil and decaying plant material.
  • the plants are over-mature.  Plants will prioritize sending mobile nutrients to parts of the plant that have more access to sunlight.  Lack of photosynthesis deeper in the canopy and self-induced nutrient deficiencies accompany senescence (death) of lower leaves.  As this happens, these leaves are often colonized by plant pathogens.

Is foliar disease really an economic problem for farmers in the Northeast? 

Yes, but is difficult to estimate the size of the problem in the region or on a particular farm.  While foliar diseases on grasses may not be the biggest agronomic problem for every farmer in the Northeast, it can affect an individual farm in important ways, several of which are interrelated:

  • Reduced forage quality
    IMG_0123

    Leafspot (drechslera spp.). Picture by Daniel Hudson, University of Vermont Extension.

    • Fungi are after the total nonstructural carbohydrates (TNC) in the plant.  In affected tissue, much of the TNC and proteins that are not consumed by the fungi will be consumed by opportunistic microbes.
    • USDA laboratory research published in 1978 found that orchardgrass plants that had been inoculated with the pathogen that causes stem rust had TNC levels that were 36% lower than uninoculated plants.  The report also suggested that the nonstructural carbohydrates from infected areas of the leaf are essentially gone.

      the rust colored patches are fungal uredia (fruiting bodies) on wheat. Source: USDA-APHIS

    • Other research shows that fiber digestibility below fungal uredia (the visible spore-producing areas on the leaf) are not digested in the rumen.
    • Higher fiber levels: losing nonstructural carbohydrates increases the proportion of fiber in the harvested product. Because ruminant feed intake is determined (limited) by fiber levels, livestock can eat fewer pounds of that higher-fiber product per day.
    • Reduced palatability
      • Refused pasture: this is what most graziers notice.  It is not uncommon for animals to refuse a large percentage of grass tissue in a pasture when it is diseased.  Reduced NSCs change the taste and smell of the forage, and there may be a bad taste besides associated with the spores or byproducts of microbial metabolism.

        photo by Daniel Hudson, UVM Extension

        Leaf scald (caused by Rhynchosporium spp.). Picture by Daniel Hudson, UVM Extension

      • Sorting hay: livestock will often sort or reduce intake of dry hay that had foliar disease prior to harvest.  Have you ever noticed many tan/brown blades of grass in an otherwise green bale of second cut hay?  They are likely the result of foliar disease.
      • Yield losses
        • Lost nonstructural carbohydrates results in total dry matter yield
        • Plants that are weakened by disease this year are more likely to be winter-killed or injured, which will reduce forage yield next year.

          A cow with low body condition score. Picture from Virginia Tech.

These problems are economically harmful to livestock producers.  Forage in the pasture that is rejected by the cows will not help the calves grow or the cows lactate.  Refused pasture forage translates to fewer animal grazing days per acre.  Dry hay that your livestock sort out rather than swallowing is a direct economic loss.  Hay or haylage with significant foliar disease prior to harvest will have lower NSC and higher fiber levels, which reduces intake and performance.  The only way to completely compensate for this is by feeding more grain.  If a farmer chooses not to compensate for the lower forage quality, animal performance will be compromised: slower growth, lower levels of  lactation, and/or loss of body condition.

If this is such a problem, why is it almost never discussed?

We are not collectively more aware of the costs associated with foliar diseases in forages because the the crops and livestock do not die outright, there is no bad smell associated with it, and it is not as visibly dramatic as many agronomic problems.  We are frustrated with poor performance, refused pasture, and the costs of supplementation, but often do not acknowledge the role that foliar disease can play in the process.

How can foliar disease problems be reduced in my forages?

Spreading poultry manure on pasture. Picture from University of Georgia.

  1. Address soil fertility problems.  Soil test reports will reveal if you have nutrient deficiencies.  Alleviating potassium deficiencies in particular will make plants less susceptible to fungal attack.  Keep in mind that the first cutting removes the vast majority of the potassium for the season.  If potassium levels are marginal in the spring, they will likely be critically low for subsequent cuttings that year and that can make disease problems worse in mid- to late-summer.
  2. Consider whether shortening your harvest interval might be appropriate, especially in conditions that favor the development of disease.  If you compare regrowth from a recently harvested hay field with a more mature regrowth, you will notice that older leaf tissue is more susceptible to infection by some of the most significant pathogens.  Timely harvest will often improve quality and remove potential inoculum.
  3. While it may not be practical in many cases, crop rotation can reduce the amount of inoculum in the soil for a short period of time.

    Ryegrass susceptible to crown rust (left) next to ryegrass resistant to crown rust (right). Picture from: http://www.afbini.gov.uk

  4. Learn to identify which diseases are plaguing your forages.  When you are reseeding, seek out plant varieties that are resistant to those diseases.  Seed companies usually indicate what diseases their varieties have resistance against.  Some university variety trials also rate disease resistance.
  5. Alfalfa and clover do not share many diseases with grass.  While it will not entirely stop the spread of disease in the stand, inclusion of these and other legumes in your pasture and hay fields may reduce the spread of inoculum by providing a physical impediment against the spread of spores from one grass plant to another.
  6. In pastures, graze the regrowth when it is ready – not after you have finally caught up with the part of the pasture that initially got away from you earlier in the grazing season.   Allowing the plants to get too large increases the likelihood of fungal infection.
  7. If you are ever trying to decide whether to take that last cutting that looks ‘almost big enough to harvest’, keep in mind that grass thatch from an unharvested hay field will be a source of inoculum the next year.  This fact alone is not enough to justify harvesting marginal-yield last cutting, but it is a factor that should be considered.
  8. If you notice that foliar disease is a problem for a particular species on certain soil types, think about what might be causing that plant to be stressed and whether you should plant different species on those soils.
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Be Careful When Considering ‘Fertilizer Enhancers’

By Daniel Hudson, UVM Agronomist

Some timely, serious, and even controversial questions have recently been raised about the efficacy and safety of various “fertilizer enhancers.”  Urease inhibitors are one such product, and they are a relevant subject for those who are planning on applying sidedress nitrogen to corn fields in the next few days.  The purpose here is not to promote a particular brand of urease inhibitor, but to strongly discourage farmers from expending resources on products that are not effective.  As it turns out, only two products are mentioned in this discussion.

A quick review for context:

‘Urease’ is an enzyme that is present in microbes, plants, and throughout the soil.  As the name suggests, urease functions to break down urea; the byproducts of the reaction are ammonia and carbon dioxide.  If urea or UAN (a mixture of urea and ammonium nitrate) fertilizer is applied to the soil surface and not quickly followed by enough rain to move it into the soil, MUCH of it can be lost by volatilization through the activity of urease.  Heat, soil moisture, and wind all promote volatilization.

If the urease molecules local to the droplet or granule of fertilizer are inhibited, these volatilization losses can be reduced.  At least one product that claims to be a urease inhibitor has been proven to work; at least one has been shown not to work as claimed.  A product that does not work costs you more than just the cost of the product – the urea portion of the fertilizer is still unprotected and vulnerable to volatilization losses.

What the research says…

Getting to the point, I will focus on only two products for which urease inhibiting claims are made.  Other products may exist. The trade names of these products are NutriSphere-N® and Agrotain Ultra®.  While this is certainly not an exhaustive review of the subject, the studies mentioned are representative of the conversation in the literature from independent researchers.

Research done at Cornell  concludes that the active ingredient of Agrotain® (NBPT) does effectively function as a urease inhibitor while the active ingredient of NutriSphere-N® does not.  After studying in the laboratory and in wheat and rice systems, researchers from ND, MS, and AR concluded that NutriSphere-N® “. . . has no urea volatilization inhibiting properties at recommended rates . . .” The one source of consistent positive yield results (of which I am aware) from NutriSphere-N® comes from a former faculty member from Kansas State University.  On pages 5 and 6 of a document called Nitrogen Extenders and Additives for Field Crops, those findings are described as ‘curious’ in light of the body of contradictory evidence.

Finally, a concern has been raised about the possibility that one of the ingredients of an Agrotain® product could pass through cows and into the milk supply.  This concern is based on a situation in New Zealand where an ingredient from one Agrotain® product (Agrotain Plus®) was found in dried milk products. The ingredient of concern, a nitrification inhibitor abbreviated ‘DCD’, is found in Agrotain Plus® but not in other Agrotain® products such as Agrotain Ultra® or ADII® (‘Agrotain® Dry’).  Again Agrotain Ultra® and ADII® contain the appropriate urease inhibitors to use with sidedress nitrogen on corn in the Northeast; they do not contain DCD and have not been found to pass through to the milk.

Disclaimer: the purpose of this article is not for UVM or myself to promote the Agrotain® brand.  The active ingredient found in Agrotain® (known as NBPT) is the only commercially available product in the U.S. that has been shown to actually function as a urease inhibitor.  As far as I know, there are no other brands of fertilizer enhancers that have NBPT as an ingredient.

More information:

Agrotain® labels: http://www.agrotain.com/agrotaininfocenter/labels/

NutriSphere-N® label: http://sfp.com/product-labels/Nutrisphere-N-for-Liquid-Nitrogen-Fertilizer-Label.pdf

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