Crop Alert 3-26-2014

This article was originally written for and distributed to farmers and other members of the agricultural industry in western New York.

A PDF file of this article is available here.

Bill Verbeten and Mike Stanyard, Regional Agronomists Cornell Cooperative Extension

Reducing Small Grain Nitrogen Losses

Snow continues to fall across northwestern NY, but spring may finally decide to show up in the next couple of weeks. With daytime highs predicted to be between 40-50 °F and nighttime lows in the 20-30 °F range the next couple of weeks many farmers will be starting their first nitrogen applications on small grain fields. However remember that the risk of losing nitrogen is higher with these early applications under saturated and frozen field conditions. Farmers in Kentucky have already had high nitrogen losses this season due to applying nitrogen too soon on their small grains. A number of practices can reduce the chances of losing early season nitrogen. NH₃ volatilization is much higher in liquid urea fertilizers than dry urea fertilizers. Adding a urease inhibitor will also reduced NH₃ volatilization. Agrotain-treated urea has performed well in recent years in our region. NH₃ volatilization will also be worse on the limestone soils of our region  (i.e. the Niagara Escarpment) due to the higher pH of the soil solution. NH₃ losses will also be higher on muck and sand soils. Ammonium sulfate (AMS) has lower hygroscopicity (does not absorb water as quickly) as other dry fertilizers and has also been used successfully for earlier nitrogen applications on small grains. There is also a high chance that the small grains will respond to the sulfur since our fields no longer get sulfur for free as a result of pollution from coal fired power plants. Many farmers will throw a handful of Agrotain-treated urea or AMS out on their lawns or a nearby small grain field and wait until that area greens up before getting into their fields. Using a combination of these two dry fertilizers is also common. Small grain fields throughout the region are looking a pretty rough right now, Figure 1.

Figure 1: Small Grain Field with Some WInter Damage

Source: Bill Verbeten

Limit any early nitrogen applications to 25-50 lb./acre of nitrogen as there has not been widespread evaluations of most small grain fields for tiller counts or for winter injury in 2014. Once green-up occurs in small grain fields, applications of liquid nitrogen through stream bars will likely give better results than dry fertilizers. At minimum hold off until the snow melts from these latest storms (more coming Saturday for most folks) before getting nitrogen on small grain fields. Be mindful not to rut up these fields—try to apply nitrogen early in the morning or later in the day when the ground will better support traffic.

Frost Seeding Forages

Farmers will also begin to frost seed forages soon in our region. The temperatures in the forecast for the next couple of weeks will create freeze-thaw cycles that will help establish some crops. This will not occur on sandy soils, since the clay particles in clay and loamy soils are responsible for this action. Red clover is the most common forage frost seeded and it is often very successful even when broadcasting into small grain fields, pastures, or hay fields. When frost seeding other legumes (Ladino & Alsike clover, birdsfoot trefoil, and alfalfa) establishment is more variable when broadcasted and is generally better with a no-till drill. Rolling the soil may also improve seed to soil contact. All grasses should be frost seeded with a no-till drill. If they are not drilled, establishment of grasses will be in small patches instead of uniform rows. Generally orchardgrass and perennial ryegrass will establish better than other grasses when frost seeded. Seeding rates for frost seeding are listed in Table 1.

Table 1. Frost Seeding Rates

Sources: Ohio State, Iowa State, University of Minnesota

Replanting/Planting Questions

Many questions are coming in about preparing for possible replant situations if winter small grains or haylage fields have severe winter damage. Be sure to actually evaluate small grain fields and alfalfa stands in the coming weeks prior to purchasing more seed. See the small grain and alfalfa articles on this topic.

Do not plant winter small grains in the spring: Almost all winter small grains (some spelt varieties are the exception) will produce no grain if planted in the spring. They require vernalization (exposure to cold after germination) over the winter in order to produce grain. When planted in the spring, winter small grains will only have vegetative growth and will die within a few months. Planting corn, soybeans, or a spring small grain will be a better option, but be sure to kill the remaining winter small grain plants prior to planting.

Damaged haylage fields: If haylage fields are severely damaged plant oats or another spring small grain as early as possible. Harvesting these silages in late-May to mid-June will have at least 2 ton DM/acre of silage. Forage oats will yield about 25% more silage DM and mature later than grain oat varieties. For more information on spring small grain silage management see this University of Wisconsin factsheet. Once the soil gets to 70 °F BMR sorghums and BMR sorghum-sudangrasses can be planted for one or two harvests after the spring small grain silage harvest. For less damaged haylage stands planting a forage grass prior to May can also make up some of the potential yield losses.

Spring small grain planting delays: Previous work in NY has shown between 1/2 to 1 bu loss in yield for every day spring small grain planting is delayed after April 15th. Long term yields of spring barley and wheat generally are 50-60 bu/acre while oats approach 80 bu/acre in the Cornell variety trials. Be sure to know how many bushels of these spring small grains are needed to cover the costs of putting them in the ground prior to attempting a late planting.

Long season vs. shorter season corn and soybeans: While many farmers are already locked into their corn relative maturities and soybean maturity groups for 2014, it may be worth switching to shorter season varieties if possible on some acres. We will likely have a colder than normal spring due to the Great Lakes having record levels of ice coverage this year.  This may cut our growing season short on the front end by delaying most planting operations and reducing temperatures. Early maturity corn grain, corn silage, and soybean varieties will also have a better chance of drying down sooner than later maturity varieties. Many factors influence crop yield potential and while some general trends exist, growing a shorter season corn or soybean variety does not necessarily mean that there is lower yield potential.

Crop Alert 3-7-2014

This article was originally written for and distributed to farmers and other members of the agricultural industry in western New York.

A PDF file of this article is available here.

Bill Verbeten and Mike Stanyard, Regional Agronomists Cornell Cooperative Extension

Evaluating Alfalfa and Small Grains for Winter Injury

The combination of extremely cold weather and bare ground across northwestern NY has many farmers and consultants concerned about winter injury to their alfalfa (Figure 1) and small grain (Figure 2) crops. As the snow melts in the next couple of weeks it will be important to get out into the field and check on these crops. A detailed discussion of the factors that influence the chances of winter injury are available online for alfalfa and small grains.

Figure 1: Winter Damages Alfalfa

 Source: Alfalfa Management Guide, page 15.

Figure 2: Dead, Damaged, & Healthy Crowns of Winter Wheat

Source: Washington State University

Handy Bt Trait Table

Not sure about which insects your Bt trait is rated to control? Have questions about what refuge requirement is appropriate for your Bt corn variety? Wondering what herbicide tolerances are associated with different Bt hybrids? Check out the "Handy Bt Trait Table" authored by Chris DiFonzo of Michigan State University and Eileen Cullen of the University of Wisconsin.

Early Season Small Grain Nitrogen Management

Wheat Early season applications of nitrogen on small grains will begin in the coming weeks across northwestern NY. The amount of nitrogen fertilizer needed for high grain yields depend on tiller counts in wheat fields. Wheat fields with lower tiller counts will require higher nitrogen rates early in the season (Table 1), while fields with higher tiller counts should have more of their nitrogen applied later in the season just prior to the first node appearing at Feekes 5.0-6.0 Figure 3). Fields with higher levels of soil OM, manure applications, and a proceeding crop of soybeans will require less nitrogen. See Mike’s March 2014 Ag Focus article for more information on “Early Season Wheat Management Tips.”

Table 1: Early Wheat Nitrogen Using Tiller Count                

Figure 3: Winter Wheat  Stages for Second Nitrogen Application

 Source: Growth Stages of Wheat

Small Grain Silage In 2013 a large scale study of nitrogen rates

on 44 NY farm locations growing small grain (mostly winter triticale) silage found that about 1/3 of the fields did not respond to increasing levels of nitrogen fertilizer. Preliminary analyses indicate that soils with high levels of active organic matter (probably from manure) are increasing soil nitrogen supply. Small grain silage fields with recent manure histories should receive 20-30 lb./acre of nitrogen at green-up to ensure early season nitrogen availability. Just over 40% of the fields had yield responses at high nitrogen rates (~75 to 120 lb./acre) in the 2013 trial. However with the current prices of nitrogen ($0.80 to $1.20 per lb. of N) it will likely not be profitable to apply more than 50-60 lb./acre of nitrogen to small grain silage fields. In the 2013 trial, winter triticale silage crude protein by ~1% for every 18-20 lb./acre of nitrogen applied (Figure 4). Most of the fields tested in the 2013 trial had CP in the ranges depicted by the green lines in Figure 4, with the black line being the overall average. Nitrogen addition can increase crude protein levels to nearly 20% but typically high N fertilizer rates (and high fertilizer costs) are needed to achieve these levels. Agrotain-treated urea performed very well in the 2013 trial and on commercial fields, especially when applied early in the spring.

Figure 4: Response of Winter Triticale Crude Protein to Nitrogen Fertilizer

Malting Barley Apply lower rates of nitrogen (20-60 lb./acre) to malting barley fields to keep the CP ≤12% and the kernel plumpness high. Use lower rates for varieties that tend to lodge more easily (i.e. Conlon), manured fields, and crops following a legume. Apply nitrogen as early as possible. Typically early season nitrogen increases small grain yields, while later nitrogen increases small grain CP. A one-page growing malting barley fact sheet and a summary of available spring malting barley varieties are available online. For additional information see the Malting Barley page on our website.

Evaluating Alfalfa for Winter Injury

This article was originally written for and distributed to farmers and other members of the agricultural industry in western New York.

A PDF file of this article is available here.

Appropriate varietal selection, fertility, planting dates, and harvest management greatly increase the winter survival of alfalfa. The extreme cold and lack of snow cover in northwestern NY during the 2013-14 winter have put alfalfa fields at greater risk of damage this year.

Effects of Management
The risk of winterkill goes up with increasing winter-hardiness ratings. In NY alfalfa varieties should have a winter-hardiness rating of 1 or 2. Winter-hardiness ratings are different than fall dormancy ratings (how tall alfalfa grows after September 1^st). In the past a lower fall dormancy rating also meant a variety had increased winter survival. However breeders have separated out the winter-hardiness & fall dormancy traits in recent years. Having higher fall dormancy ratings will lead to increased fall and early spring growth along with faster regrowth between cuttings. Proper pH and fertility (especially potassium) are critical for alfalfa to survive the winter. Alfalfa needs at least 6 weeks of growth to develop a crown, requiring an August or early September planting date in our region. Taking a late fall cutting, leaving less than 6 inches of fall stubble, harvesting less than every 30 days in the growing season, and having an older stand all increase the chances of winterkill. A scorecard for evaluating the risk of winterkill to alfalfa is available on page 54 of the Alfalfa Management Guide available at www.nwnyteam.org.

With the shallow soils in much of northwestern NY, perennial grass species like tall fescue, orchardgrass, reed canarygrass, and timothy are often planted with alfalfa. Having these grasses in the mix reduces the risk of yield loss from winterkill because they will survive if the alfalfa is damaged. However if too much fall growth was left in the field these grasses can be damaged by snow mold similar to small grains.

Effects of Weather
The weather conditions that put small grain stands at risk for winterkill also are hard on alfalfa. Alfalfa stands without 6 inches of snow cover, prolonged temperatures below 5°-15°F, and temperature spikes over 40°F during the winter will likely have some damage. The crowns of alfalfa are shallower than small grains and are consequently more vulnerable to freezing and heaving damage. In addition to these conditions, the excessive soil moisture from the fall of 2013 makes damage from ice sheeting a greater risk this year in alfalfa fields in our region. Damage plants will resemble those on the right in Figure 1.

Figure 1: Winter Damaged Alfalfa

Source: Alfalfa Management Guide, page 15.

Evaluating Alfalfa Stands

A number of signs can indicate winter damage to alfalfa stands. Fields that remain brown longer than others are probably damaged. If the alfalfa plant only has shoots growing on one side of the crown, the buds were injured over the winter. Damage to buds can also result in uneven shoot growth in the same plant. However the best way to evaluate alfalfa is to dig up 4-6 inches of roots. If the roots have a grey water-soaked appearance, look brown and stringy, and/or can easily have water squeezed out the plants then winterkill has occurred.

Contact your crop consultant, myself, or Mike Stanyard if you have a question about alfalfa stand evaluation.