Tuesday, November 20, 2012

Reducing the Drying Time of Hay and Silage in the Field

Harvesting high quality hay and hay silage has been a challenge in a number of hay growing regions because of the unpredictability of rainfall. Rain falling on hay that is laying down in the field causes a number of problems. Soluble nutrients are lost, reducing feeding value and fermentation potential. Wet hay may also undergo spontaneously combustion. Forages can be ensiled or baled at a wide range of moisture contents (Figure 1). Whether making silage, hay, or baleage, some field drying will be necessary.  A number of practices can reduce the amount of time that cut forages are exposed in the field.

Figure 1: Forage Harvesting Methods and Associated Field and Storage Losses

Adapted from Grass Silage Jerry Cherney & Debbie J.R. Cherney, Cornell University

Wide Swaths
Cutting implements that lay hay down in windrows that are 70% or more of the cutting width dramatically reduce drying time. The wide rows maximize the amount of area hay exposed to the sun and allow air to move underneath the swath. This maximizes the drying rate in Phase I (Figure 2) of the dry-down process. This is very important because the plants will continue to respire and use nutrients while the stomata (holes in the leaves) stay open. The outer 0.75 inch of the swath/windrow dries quickly, and having wide, shallow swaths essentially allows all of the forage to dry rapidly compared to a small percentage on the outside of a traditional deeper windrow.

Figure 2: Sequence of Drying Forages

Field experiments in the Midwest and Northeast have shown that alfalfa cut in the morning and laid down in wide rows dries down to about 65% moisture about 5-7 hours later and is ready to be chopped for silage that same day during good drying conditions (warm, windy, sunny day). Adjustments can usually be made to the mower to increase the swath width. If swath width cannot be increased to at least 70% of the cut width farmers can use a tedder immediately after cutting, weld metal bars or bolt metal deflectors (Figure 3) to the back of the mower to spread out the feed, or find a neighbor or custom operator who has the equipment to spread the forage out. Cutting with a simple sicklebar mower (without conditioning attachments) also lays the silage or hay out wide to allow for quick drying. 

Figure 3: Farmer Mower Modifications to Increase Swath Width

In the past there was a large concern about driving on windrows because of the risk of leaf loss. While this would be a concern on very dry hay, few leaves are lost when a wide swath is driven on during the initial drying stages (Phase I and Phase II, Figure 2) unless extremely wet and muddy field conditions exist at the time of harvest. No detectable difference in forage quality has been found in the areas driven over compared to the other parts of the swath.

There are two types of conditioners available to farmers:  roller crimpers and flail impellers.
Roller crimpers are made out of rubber or steel. They are used to crush the stems of alfalfa to increase the dry down rate in Phases II and III (Figure 2). If alfalfa is being made into hay then it should be conditioned with a roller crimper. If the alfalfa is made into silage it does not need to be conditioned if laid down in a wide row. Narrow windrows (less than 70% cut width) should be conditioned whether the alfalfa is made into silage or hay if the windrows are not spread out soon after cutting. Before harvesting, the rollers must be properly adjusted in order to crush the stems. Check your machine's owner's manual or refer to Mower-conditioner Adjustments for Rapid Forage Drying in the Field for more information. Various crimper designs are available, but no consistent differences have been shown between the various designs in the dry down time.

Flail impellers are used primarily for grass hay or entangled forages. The deflector must be properly adjusted to ensure that the grass surfaces are cut by the flails. Impellers are not very effective tools to condition alfalfa.

Tedding, Raking, Inverting, & Merging
Raking and tedding are two of the most well known practices to increase the dry down rate of hay in the field. They can, however greatly increase the ash content and leaf loss of the hay if done improperly. Lower leaf loss occurs if the hay is tedded or raked between 40-65% moisture (i.e. with the morning dew on). If a farmer lays down a wide swath when making hay they could ted/rake the next morning, while a farmer with narrow windrows would typically have to wait an additional day or two to reach this moisture content. Tedders and rakes should also be adjusted to minimize the amount of ash (dirt) they pick up off the ground. Inverters and mergers are used to flip and merge swaths and windrows. Inverters tend to pick up less ash than rakes or tedders. Mergers are used before chopping or bailing to merge multiple windrows (swaths) into one bigger windrow. Some drying occurs when the windrows are flipped, but not as much as wide swathing or conditioning operations.

Dessiccants are drying agents that can be sprayed on forages which can reduce the time needed for hay to dry. They are most often applied at cutting. The most effective products have potassium or sodium-carbonate based solutions. These treatments are most effective on alfalfa cut in the summer months. The major drawback to using desiccants is the large volume of water required to apply the products to the hay.

Preservatives are applied at baling to ensure the quality of hay, often at a slightly higher moisture content (20-25%). When rain is coming, applying a preservative can allow baling at these higher moisture contents.  The most effective preservatives on the market are made from proprionic acid. Other organic acids (acetic acid, etc.) can work as well, but proprionic acid-based products are the most reliable. They are generally applied at 1-2% of hay weight.

Many products are available to inoculate silage and baleage. These products do not increase the drying rate of forages or make up for poor field handling, but can preserve or increase forage quality if applied correctly. Many products on the market have not been independently tested so farmers should take some time before the season to evaluate which of the available products have truly shown consistent results outside of company trials.  Most of the products contain at least one of three types of bacteria: homolactic, heterolactic, or propionibacteria. 

Homolactic bacteria ferment sugars to lactic acid which improves initial fermentation by quickly dropping pH. Enterococcus faecium and several Pediococci species have been shown to be effective in modifying initial fermentation. 

Heterolactic bacteria convert moderate amounts of lactic acid to acetic acid after initial fermentation and improve aerobic stability during feedout. Lactobacillus plantarum (once thought to be a homolactic bacterium) and Lactobacillus buchneri are the only heterolactic bacteria consistently shown to increase the aerobic stability of silage during feed out. 

Propionibacteria theoretically convert lactic acid to acetic and proprionic acids in the bunk, but currently no species or strains have been shown to actually increase aerobic stability in the field.  For a more in depth discussion of silage inoculants and situations in which to use them refer to, Help in Choosing an Effective Silage Inoculant.

Bottom Line
1. Drying forages occurs much more quickly in wide, thin swaths than thick, narrow windrows. Silage can be made the same day as cutting if the forage is spread wide. Inoculants can enhance, but not save silage

2. Hay and silage making often require using multiple management practices (wide swaths, conditioning, raking, tedding, desiccants, preservatives, inoculants, etc.) and a little bit of luck in the humid regions of the U.S. in order to make high quality hay and silage.

Disc Mowers vs Sicklebar Mowers
No difference in drying rate is noticeable between disc and sicklebar/cutterbar mowers. 
Tom Kilcer, Advanced Ag Systems, Kinderhook, New York

Drying Forage for Hay and Haylage

C. Alan Rotz, Agricultural Engineer USDA-ARS, Penn State University

Jerry Cherney & Debbie J.R. Cherney, Cornell University

Help in Choosing an Effective Silage Inoculant

Limin Kung, Jr, University of Delaware

Mower-conditioner Adjustments for Rapid Forage Drying in the Field
Ronald T. Schuler, Agricultural Engineer, Wisconsin Extension

Jimmy C. Henning and Howell N. Wheaton, University of Missouri Extension

Jerry Cherney, Tom Kilcer, Debbie J.R. Cherney, Cornell University