CMEG Crop Management Extension Group

Field Crop News

Website Address: http://fcn.agronomy.psu.edu/

July 23, 2007    Vol. 07:21

IN THIS ISSUE:

Estimating the Potential Grain Yield from Corn Silage Yields — Greg Roth, Grain Production Specialist

One method of assessing silage value is to estimate the grain yield potential of the crop at harvest and then compare the costs and returns for harvesting for grain compared to the returns from harvesting for silage. Unfortunately, few corn plots are harvested for both grain and silage. My colleague, Dr. Joe Lauer, at the University of Wisconsin, has studied this relationship carefully and summarized his findings in an on-line factsheet.

Based on 1858 observations, Joe has developed a relationship between forage dry matter yield and grain yield at harvest. The equation for the relationship is Grain Yield= -78.9+44.0(FY)-1.66(FY)2 , where FY is the forage yield in DM tons/acre.

Using this relationship, I calculated the bushels/ton for 4, 6, 8, and 10 ton DM yields (70, 125, 167, and 195 bushel corn equivalents). To express these in terms of wet silage at harvest, I then corrected for DM since the potential bushels/ton is a function of the DM of the silage. At 67.5 % moisture, the estimated bushels/ton were 5.7, 6.8, 6.8, and 6.3, respectively, for the four yield categories. At 62.5% moisture, the estimates were 7.0, 8.4, 8.3 and 7.8 bushels/ ton of harvested silage.

The bottom line is that on average, both the moisture content of the silage and the yield potential can affect the estimated potential yield bushels/ton. The data appears to suggest that at low yield levels, grain content could be less than average, presumably due to lack of grain fill. At high yield levels, there is also a trend for lower grain contents. Their research has shown considerable variation from year to year, depending on grain fill conditions and early season stress.

We have initiated some research with Dr. Lauer last year on this issue to compare these numbers for Pennsylvania, but don’t have a sufficient data set to make any firm conclusions at this point. The data do seem to be consistent with some of the “rules of thumb” encountered in the industry of 6.5 to 8 bushels per ton. It is important to note that these numbers are not the same as the bushels of grain in a ton of harvested silage, since there is some grain fill that can occur following silage harvest.

Drought Stress, Nitrates, Prussic Acid and Sorghum-sudangrass Hybrids and Corn — Jeff Graybill, Lancaster County Educator

With the spotty summer rainfall patterns we have been experiencing this season, many areas of the state have or may undergo significant drought stress. This may prompt concerns about handling crops.

There are two critical management issues to be aware of when producing a sorghum-sudangrass. The first is the presence of prussic acid (a cyanogenic compound) which can interfere with oxygen transport in the blood system. Ruminants are more susceptible than monogastric animals. The youngest shoots and new growth will have the highest potential for this toxin. It also can accumulate rapidly after a frost in the plant. Therefore, proper management would be:

  1. Do not harvest or graze until you have at least 20 inches of growth, some publications will list a minimum of 30 inches (especially for grazing).
  2. Field curing can reduce prussic acid levels by 50–70%. Thus, a conditioned and field wilted crop will have significantly less toxin than a direct grazed one.
  3. Frosted fields (over 20-30″) should not be harvested or grazed for 5 days and until the forage material has dried out on the surface. This will allow much of the toxin to dissipate.
  4. Frosted fields less than 20″ should be allowed to re-grow for two weeks before harvesting or grazing.

Nitrate accumulation in the forage is the second management issue to be aware of. Both corn and other forage species like sorghum-sudangrass will accumulate nitrogen in the form of nitrates in the lower stem. Extended periods of drought are conducive to this accumulation within the plant. Also, the first few days after a significant rain can flood the plant with soil nitrate which will then be slowly metabolized into proteins. Try to avoid harvesting drought stressed fields for a few days after a significant rainfall. Another option is to harvest the crop with 8″ or more stubble. This will leave some yield in the field but also a significant amount of the accumulated nitrate.

Sorghum-sudangrass, corn, and other similar species will “luxury” consume excess nitrates in the soil as well; this means that excessive N fertility can also cause high levels of forage nitrate. Therefore, farms with an accumulative amount of nitrates should be especially watchful of nitrate levels in their forages species. In other words, if you have elevated nitrates in well water, use high amounts of manures and/or nitrogen fertilizers, etc, the nitrate levels your animals are consuming needs to be closely watched. Drought stress in a situation like this will be more likely to elevate nitrates to potentially dangerous levels.

One positive note is that the ensiling process does tend to lower the nitrate content of forages. The fall, as you are routinely testing your forages, consider the potential for nitrates in this years crop and request a nitrate test in addition to the standard forage analysis.

Producing high quality forage includes watching for and managing for prussic acid and nitrates in sorghum-sudangrass hybrids and similar species.

Roundup Ready Alfalfa: Final Administrative Order — Marvin Hall, PSU Forage Specialist

Recently, the USDA issued mandatory practices around the production and use of Roundup Ready Alfalfa. This is an update from the preliminary order this past spring. For more information on this order, go to: http://fcn.agronomy.psu.edu/2007/rr_alfalfa_final_ruling.pdf.

Crop Insurance and Market Information — John Berry, Lehigh County Educator and Gene Gantz, PA Department of Agriculture

Crop Insurance:

There are many acres of crops, in many areas of the commonwealth, that are seriously drought stressed. Thankfully, many producers took advantage of some excellent crop insurance protection for this season. Growers with crop revenue insurance protection will use $4.06/bu. for their corn and $8.09 for soybeans on the insurance guarantee bushels they selected.

Whatever crop insurance product used; if current conditions continue, harvest will likely be earlier than normal for stressed crops, especially corn silage, and since the silage harvesting window is pretty narrow, insurance loss adjusting could get backlogged. Additionally, USDA has toughened the loss adjustment rules for 2007. Producers who want to harvest damaged crops must have a loss adjuster appraisal to determine the grain yield before beginning to harvest, or have an adjuster select samples rows from which the yield will be appraised at a later date. GROWERS CAN NOT PROCEED WITH HARVESTING UNTIL THE ADJUSTER GIVES WRITTEN AUTHORITY.

Please remember, producers should never destroy a damaged crop (including salvage harvesting as silage) before an adjuster determines the amount of loss or provides written authority to leave pre-selected sample rows for later yield determination. For these reasons, it is being recommended that producers notify their insurance agent about a month before they intend to begin harvest.

Markets:

On one hand, we have a very bearish factor of a huge supply of old crop soybeans (600 million bushels) left over from the 2006 crop. On the other hand, carry-over supplies of new crop 2007 soybeans could be 60% lower (245 million bushels) than just a year ago, thanks to 11 million fewer acres of soybeans in 2007. When we add the increasingly speculative nature of this volatile market and local market conditions — it can become difficult to follow our marketing strategy. Remember the primary rule of marketing… “with every sales decision you make, you will give up something to get something else in return”. If you make a sale today you give up the chance for a higher price, but in return you get protection against prices falling. If you make no sale at all and sit on the sidelines for the time being, you give up the chance to establish a profitable price as well as run the risk of prices falling, but in return you may be able to sell your beans for a higher price later on. Just make sure you understand all the ramifications of any sales decision before you make the decision. Once you have made your choice, then you must be able to live with it and not look back. Profit is the name of the game.

PDA Weekly Grain Market Reports:

http://www.agriculture.state.pa.us/agriculture/cwp/browse.asp?A=391 Our local basis is seasonally average for corn and seasonally positive for beans.

If the corn and soybean acres planted in Iowa return a trend yield in 2007; there is not enough commercial and on-farm storage in the state to hold it all. If grain demand continues into 2008 and additional crops are harvested — Now what happens to storage?

Link to some points about energy efficiency of ethanol production: http://www.extension.iastate.edu/agdm/articles/hof/HofJuly07.html.

I watch three pieces of information to get a personal perspective on what is happening and what might happen with commodity marketing. A key indicator for me is the historical record of past market conditions. Sometimes the historical record can illustrate where prices are in relation to “normal.” One source for free historical charts is: http://www.tfc-charts.com/menu.html.

Sprayer Retrofit Meeting-August 16 — Andrew Frankenfield, Montgomery County Educator

A Sprayer Retrofit Twilight Meeting will be held Thursday, August 16, 2007 in Montgomery County, Pennsylvania. Come out and see a 45 foot boom sprayer retrofitted with quadnozzle bodies set up to use 4 different tips, depending on the application, without removing any nozzles. Core credits will be given. Sponsored by Penn State Extension and the Southeast Crops Conference Partners.>

To register, go to: http://fcn.agronomy.psu.edu/2007/sprayer_retrofit_meeting.pdf.

Come Visit the Crop and Soil Sciences Tent at Ag Progress Days, August 14–16, 2007

An invitation is extended to everyone to visit the Crop and Soil Sciences Tent. Bring your questions, problematic weeds and walk the corn maze. For more information about Ag Progress Days: http://apd.cas.psu.edu/.

Contributors: Department of Crops and Soil Sciences: Douglas Beegle, Ronald Hoover, Gregory Roth. Extension Educators: Kevin Fry (Armstrong), Andrew Frankenfield (Montgomery), Jeff Graybill (Lancaster), John Rowehl (Cumberland).

Editor: Mena Hautau (Berks)

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