Friday, March 7, 2014

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

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

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.

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