Forage Tidbits

Mike Rankin
Crops and Soils Agent
University of Wisconsin - Extension

Wheel Traffic on Alfalfa Will Reduce Yields

        It's sort of one of those things we all know but hate to talk about because it's hard to fix the problem.  Time and time again we see in alfalfa fields the detrimental effects of wheel traffic from harvesting equipment, manure spreaders, or pickup trucks.  In severe situations, alfalfa plants can be killed or at least stunted to half of the size of normal plants.

        First-year results from a University of Wisconsin study showed that total season yields were reduced from 13 to 37 percent in alfalfa field plots where tractor wheel traffic was imposed following harvest with a plot harvester.  Percent yield reductions for some individual cuttings were even greater.

        The bottom line here is to minimize unnecessary heavy wheel traffic to every extent possible (especially when soils are wet).  It's probably not necessary to use a 200 HP tractor to run a wheel rake.  The operation that may be most damaging is spreading manure on alfalfa fields after harvest.  It's often done after new growth has been initiated and these operations involve a lot of axel weight from both the fully loaded spreaders and the large tractors needed to pull them.

Packing Capacity Must Equal Harvest Capacity

        On farms that harvest large acreages of alfalfa or corn silage, there has been a rapidly upward trend toward increasing harvesting capacity over the past five years.  However, this increased ability to harvest must be matched with the increased ability to pack the forage.  If it doesn't, spoilage and dry matter losses in the bunker will skyrocket.

        If you're looking for a "quick and dirty" method to determine how much packing capacity is needed, simply take the known filling rate (wet tons delivered to the bunker in one hour) and multiply it by 800.  For example, if 80 tons per hour is delivered to the bunker, you need 64,000 pounds of packing capacity (total weight of packing vehicles).  Conversely, you can figure what your maximum delivery load needs to be by dividing the weight of the packing tractor(s) by 800.  If this number is lower than the actual delivery rate, it then becomes a question of either increasing packing capacity or decreasing delivery rate.

Text Box: Checking Silage Density in the Bunker If you are interested in knowing how silage density on your farm stacks up against what is recommended, the UW Extension office is equipped to probe bunkers on site. Contact Irv Possin for details.


What's the Yield Penalty for Late-planted Silage Corn?

        Although the optimum planting date for corn is during early May, that horse is already out of the barn for year 2001.  This year there may be no choice but to harvest late planted corn for silage.  Although there is nothing wrong with this strategy, there will clearly be a yield penalty and feed inventory strategies will need to be adjusted accordingly.

        University of Wisconsin researchers have been doing corn silage date of planting studies for over ten years.  Looking at this data, and speaking in terms of round numbers, it appears that we lose about 0.1 tons of dry matter per day (roughly 0.25 tons of 65% moisture silage) as planting date is delayed from the middle of May to the middle of June.  The loss is somewhat less during the last half of May but somewhat greater during the first half of June.

        As a reminder, be sure to evaluate hybrid maturity against planting date as we push into the latter part of May.  It's unlikely that full season silage hybrids (105 to 110 day RM) will reach something close to optimum whole plant moisture before the first frost.  

 

Inoculants for Hay Crop Silage

        The fundamental reason to invest in silage inoculants is to insure there are enough lactic acid producing bacteria (LAB) for optimum silage preservation.  This is not to say there may not be sufficient numbers already on the wilted crop.  Factors that promote the growth of naturally occurring LAB to sufficient levels on alfalfa include long wilting periods (>2 to 3 days), low silage moistures (<60%), and high average wilting air temperatures.  Based on this, we would expect the greatest economic return from using alfalfa silage inoculants on first and fall cuttings (low average wilting temperatures), fast dry-down summer harvest conditions (<1 day wilting period), and where silage is harvested for bunker silos at higher moistures (65 – 70%).

Here are some general thoughts and recommendations for the use of silage inoculants on hay crops:

  •       Based on current research and inoculant price, using inoculants “across the board” on all crops ensiled will likely result in a worst case scenario of  “breakeven” but likely will be better.  Returns could be highest by limiting applications to situations and crops where naturally occurring LAB are not already present in the crop at sufficient levels.

  •       The likelihood of positive fermentation and production benefits is highest with alfalfa and grass silage and somewhat lower with corn silage.

  •       When using inoculants, apply at a minimum rate of 90 billion live lactic acid bacteria per ton of crop.  Store inoculants in a cool, dry environment to maintain viability.  There are no positive research results from inoculating silage with dead bacteria.

  •       If possible, purchase inoculants that are labeled for the crop you are ensiling and from a reputable company with a history of inoculant testing and research.  Read the product label and look at the types of bacteria being applied.  They should include one or more Lactobacillus species.

  •       LAB do not “swim” around the silo.  Inoculants must to be applied uniformly to the crop.  This is best accomplished when applied in a liquid form at the chopper.

  •       Lastly, and perhaps most importantly, silage inoculants will not cover-up for otherwise poor silage harvest and storage management.

For more information contact Mike Rankin

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