Saturday, December 29, 2012

Reducing Hay and Silage Harvesting Losses

Hay and silage account for half the cost of most livestock farms. Too often, valuable feed is lost: 1) in the field, 2) during storage, and 3) at feeding. In years when feed supplies are tight, it is especially critical to minimize these losses. This blog entry is the first of a three-part series, and will focus on strategies to reduce the losses during the field operations of hay and silage making. Mowing, conditioning, drying, and harvesting operations all contribute to field losses of forage.  

Mowers and Conditioners

Work at Michigan State University and the University of Wisconsin have shown that rotary disc mowers tend to have 3-4% higher field losses than sickle cutterbar mowers. This is due to greater respiration (plant breakdown) losses for the rotary cutterbars (4.2-4.8%) compared to sickle bars (0.3%), Rotz and Sprott (1984). Additionally higher losses occur in the baler when rotary disc mowers (2.1-2.2%) are used compared to sickle cutterbars (1.5%), Koegel et al. (1985). Rotary disc mowers allow for faster harvest than sickle cutterbars which typically operate at 6-8 mph. Rotary disc mowers can more easily harvest lodged fields than sickle cutterbars, but more forage will be left in the field with rotary disc mowers. For more detailed discussion of adjustments to the both types of harvesters to minimize losses see Machinery Designs and Adjustments for Minimized Field Losses.

Figure 1: Rotary Disc and Sickle Cutterbar Mowers

Properly adjusting conditioners have a greater impact on field losses than the type of conditioner. Shattered leaves and over-conditioned (bruised) alfalfa stems are the primary sources of field losses from conditioners. When using a roll conditioner, the clearance between rolls and the pressure should be reduced for low-yielding harvests and the clearance and pressure should be increased for larger harvests. The timing of the inter-meshing rolls also needs to be adjusted to prevent over-conditioning (dark green discoloration on stems) and reduce leaf shatter. Impeller conditioners should only be used for making grass hay. Even if the impeller speed is reduced, alfalfa and clover crops will have high leaf losses. When trying to make silage there is no need for any conditioner in the mower provided the haylage is laid in a wide swath (>70% of cutterbar width) and properly tedded. Conditioning only helps to dry out the stems once the stomata on the leaves are closed. Spend the money instead on a wider mower and tedder/merger to increase the amount of haylage that can be cut and dried quickly. When making wide swaths for silage drying remove the deflector shields or place them all the way up with metal bars attached to spread the swath back out wide. For more discussion on drying hay and haylage see Reducing the Drying the Time of Hay and Silage in the Field
The hood height can be lowered to provide more aggressive conditioning or raised to reduce the conditioning action on impeller units for pure grass crops. Few, if any, differences in field DM losses have been shown between molded rubber (5.2%), tire cord (5.4%), rubber and steel (5.8%), and two steel conditioning rollers (5.9%), Shinners et al. (1990).

Figure 2: Flail Impeller Conditioner and Roll Conditioner

Rakes, Tedders, Mergers, and Inverters

Pickup height, tractor speed, and forage moisture are the most important factors influencing field losses during field operations of rakes, tedders, and mergers. Rake height needs to be adjusted to pick up the forage while minimizing the rocks and dirt that end up in the forage. Side rakes, tedders, and mergers do not have to touch the ground in order to turn the windrow/swath, but wheel rakes need to touch the ground in order to work properly. Faster tractor speeds increase the amount of leaves lost in alfalfa, but a compromise between working fast enough to get the job done and not losing valuable feed needs to be struck when doing these operations. Losses from tedding operations can be minimized by tedding when the forage crop is 60% moisture or greater, while raking, merging, and inverting should be done when the forage crop is at least 40% moisture.

Figure 3: Side Rake, Wheel Rake, Tedder, and Merger

Balers and Silage Harvesters

Similar to tedding, raking, merging, and inverting, the most important factors influencing field losses when making bales or silage are the crop moisture, pick-up height, and ground speed. Leaf losses increase as crop moisture goes down, Figure 4. 

Figure 4: Hay Leaf Losses Increase as Hay Moisture Decreases

Round bales should be made at a uniform density, about 10 pounds/ft3. Adjustments may be needed throughout the baling process and will vary depending the type of baler used. Making uniform bales will make for easier handling, storage, marketing, and cost calculation. When round baling narrow windrows (less than half the pick-up width), picking up on one side of the windrow for 10-12 seconds and then quickly crossing over to the other side of the windrow (pattern a) makes more uniform round bales than constantly swerving across the windrow (pattern b) or driving straight down the windrow (pattern c), Figure 5. 

Figure 5: Round Baler Pick-Up Strategies Effect Bale Shape in Narrow Windrows

Making wide windrows or swaths that are equal to the baler pick-up width will also result in more uniform bales, and enables driving directly down the windrow. Matching the ground speed to PTO speed will result in quickly formed bales which minimizes leaf loss. If harvesting full windrows that are equal to the pick-up width, ground speeds of 4-6 mph usually result in uniform bales. Using a round baler with a variable or expanding chamber instead of a fixed chamber will also result in more uniform bales and lower leaf loss (3.75-4.25% vs. 3.5-8.0%), Prairie Agricultural Machinery Institute.

Silage losses in the field are most often due to leaf loss of alfalfa, exposure to rain, improperly adjusted equipment, and delayed harvest operations. Similar to baling hay, silage harvester ground speed should be adjusted to match pick-up with PTO speed, but minimize leaf losses. Silage bleaching occurs when rain falls on the silage, which reduces many of the digestible nutrients and results in white windrows. Field DM losses of 22%-44% of silage can occur with only 1 to 1.6 inches of rainfall a day or two after cutting, Rankin and Undersander (2000).

Bottom Line
1. Properly adjusted and maintained equipment go a long way to reducing field losses of hay and silage.

2. Optimizing the speed of field operations and conducting these operations at the appropriate crop moisture levels reduce field losses of forage. 


Drying Rates, Losses and Fuel Requirements for Mowing and Conditioning Alfalfa
Rotz, C. A. and D. J. Sprott, Michigan State University, 1984. Transactions of the ASAE, 27(3)715-720.

Forage Growers Guide to Round Baling
Prairie Agricultural Machinery Institute.

Machinery Designs and Adjustments for Minimized Field Losses
Ronald T. Schuler, Extension Agricultural Engineer, Biological Systems Engineering Department, University of Wisconsin-Madison.

Management Tips for Round Bale Hay Harvesting, Moving, and Storage 

Robert Grisso, Extension Engineer, Biological Systems Engineering, Virginia Tech
Ray Smith, Forage Specialist, Crop and Soil Environmental Sciences, Virginia Tech
John Cundiff, Professor, Biological Systems Engineering, Virginia Tech

Quantification of Mechanical Losses
Koegel, R. G., R. J. Straub and R. P. Walgenbach, University of Wisconsin, 1985. Transactions of the ASAE, 28(4)1047-1051.

Rain Damage to Forage During Hay and Silage Making
Mike Rankin and Dan Undersander, University of Wisconsin, 2000. Focus on Forage.Vol. 2: No. 4.

Leaf Loss and Drying Rate of Alfalfa as Affected by Conditioning Roll Type
Shinners, K. J., R. G. Koegel and R. J. Straub, University of Wisconsin,  1990. ASAE aper 901048. St. Joseph, MI, 14 pp.

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