reduce alfalfa drying time with chemical agents

AE48

Reduce Alfalfa Drying Time With Chemical Agents 1Richard P. Cromwell and O. Charles Ruelke2

1. This document is AE-48, one of a series of the Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date Reviewed: April 2000. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.

2. Richard P. Cromwell, Associate Professor, Agricultural and Biological Engineering Department, and O. Charles Ruelke, Former Professor, Agronomy Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences/University of Florida/Christine Taylor Waddill, Dean.

Introduction

Potassium carbonate has historically been used to increase the drying rate when making raisins. It appears to be quite effective in reducing the drying time of alfalfa as well. Research conducted at the University of Florida and other universities indicates that potassium carbonate in a spray solution applied to alfalfa can reduce the required drying time in the range of 30 to 50%. Alfalfa that normally would require 3 to 4 days to dry to the 15 to 18% moisture level needed for storage might be baled after 1.5 to 2 days.

Until the advent of 'Florida 77' alfalfa, hay producers in Florida could not readily grow alfalfa because available varieties had been developed farther north and would not persist under Florida conditions. Florida 77 has demonstrated its ability to yield at an economical level for 3 to 4 years. Florida farmers now have the opportunity to produce a very high quality hay. Protein levels in the low 20% range are not uncommon for alfalfa hay. However, getting the large stemmed alfalfa crop dried to a safe storage moisture level (15 to 18%) is definitely a problem during the humid summer months. Applying potassium carbonate to the crop should increase chances for getting the hay harvested. However, it should be noted that drying time of treated alfalfa will

be about the same as for bermuda grass hay, and experienced hay producers have had bermuda hay rained on regardless of how careful they have been to avoid summer showers.

The ill effects of rain falling on a drying alfalfa crop are far greater than for bermuda grass. Alfalfa leaves are knocked off by rain; and, if the crop has to be scattered out of a windrow with a tedder after a shower, leaf loss will be very high. Unfortunately, leaves are the high quality part of the alfalfa plant.

Applying the Chemical

Potassium carbonate should be applied at the rate of 5 pounds per ton of dry hay. Therefore, a field that yields 1.4 tons per acre should have 7 pounds per acre applied. In order to estimate hay yield, weigh the amount of fresh cut material harvested from a 3 feet x 3 feet area, and multiply the amount in pounds by 0.73. This will give an estimate of the yield in tons per acre. In order to improve the estimate, harvest the green material from 3 randomly chosen locations in the field and average the results. When harvesting the material from the plots, leave a stubble of at least 3 inches because this is the recommended stubble height for alfalfa.

Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

Reduce Alfalfa Drying Time With Chemical Agents 2

Example 1 : A 3 feet x 3 feet area yields 1.8 pounds of green alfalfa. What would the hay yield per acre be, and how much potassium carbonate should be applied per acre?

Hay yield = 0.73 x Green weight from 3'x3' area

= 0.73 x 1.8 = 1.31 tons per acre

Potassium Carbonate to apply = 1.31 x 5 = 6.55 pounds per acre

If sample plots are not harvested to estimate the yield, apply 6.0 to 7.0 pounds per acre to an alfalfa field with a reasonably good stand.

Potassium carbonate should be applied in 25 to 30 gallons of spray per acre to insure good coverage. Care must be taken to apply most of the spray onto the alfalfa stems rather than the leaves. The major reason for high harvesting losses in alfalfa hay is that the leaves are over dried by the time the stems have dried, and the leaves shatter when the hay is baled. Applying a chemical drying agent to the leaves worsens an already bad situation. A means for increasing the amount of chemical applied to the stems is described later in this publication.

Equipment for Cutting and Spraying Chemical

Figure 1 shows a mower-conditioner equipped with a sprayer for applying a chemical. The sprayer pump is driven by the conditioner roll shaft. The sprayer pump begins spraying when the tractor PTO is engaged. Details about the equipment are given below:

Figure 1 .

Mower-Conditioner: Conditioning alfalfa increases the drying rate more effectively than it does for most grasses. An alfalfa hay producer should definitely use some type of mower-conditioner.

Spray Tank: One of the more economical tanks for this system is a 110-gallon poly tank. A tank of this capacity holds enough spray to cut approximately 4 acres between refills.

Spray Agitator: Potassium carbonate dissolves in water quite easily. The pressure regulator by-pass flow provides adequate agitation after the chemical has been stirred into solution with a paddle. A jet agitator tapped into the discharge side of the pump is desirable, but not necessary.

Spray Pump: A roller pump is the most economical pump. Since the maximum flow needed to supply the boom is about 2.5 gallons per minute (GPM) when applying 25 to 30 gallons per acre, the pump should deliver about 6 GPM when turned at the RPM of the shaft being used to drive it.

The sprayer pump is coupled to the stub end of the lower conditioner roll shaft in Figure 1. This shaft turns counter-clockwise (CCW) which is opposite to the direction of most PTO shafts. A roller pump to be mounted on a CCW rotating shaft should be specified when ordering a pump. Some roller pumps will operate on a CCW rotating shaft if the pump rotor is pulled out and reversed. However, pump manufacturers might not observe warranty commitments for pumps that have had the rotor reversed.

Spray Boom: A dry boom, where the boom serves as the support structure and the liquid is conveyed through a chemically resistant rubber hose, is the preferred boom type. The hose connects to hose barbs at the nozzle locations, which are secured with hose clamps. The pressure used for this application should be in the 20-40 psi range. Hose rated at 100 psi would allow an ample safety margin and should be relatively inexpensive.

The nozzle arrangements listed in Table 1 should deliver the approximate gallons per acre (GPA) if the cutting speed is 3 mph, the pressure is 30 psi, and the nozzles are not worn. These recommendations are given as "ball park" recommendations. The sprayer will have to be calibrated in the field to determine the actual GPA in order to know how much potassium carbonate to add to the tank.



Example 2 : A field calibration test showed the sprayer was delivering 28 gallons per acre. If the tank is normally filled with 100 gallons of water, how much potassium carbonate should be added? Assume that a yield check of the alfalfa dictated 7 pounds of chemical per acre.

Acres sprayed per tank = Tank Volume ÷ Application Rate

= 100 gal. ÷ 28 gal./acre = 3.57 acres/tank

Assume that a yield check of the alfalfa dictated seven pounds of chemical per acre.

Chemical per tank = acres/tank x pounds/acre

= 3.57 x 7 = 25 lbs.

Adjustable Push Bar : The push bar is shown mounted on the front of the mower-conditioner in Figure 1. lt is a very important part of the chemical treating system. This bar lays the alfalfa over so that the spray can be directed onto the stems. The bar can be a piece of pipe welded at the ends to a piece of channel that has either enlongated slots or a series of holes for bolting the push bar to the mower- conditioner. The advantage of an elongated slot is that the bar height can be adjusted more easily.

General Tips for Harvesting Alfalfa Hay

1. Leave a stubble height of at least 3 inches to allow for air circulation and reduce the stress on the plant.

2. Windrow the alfalfa when the moisture level is about 35% in order to reduce leaf loss. When the hay dries to this point, rake into a windrow when dew has set and the leaves are more pliable.

3. Harvest the alfalfa between 1/10 bloom (an average of 1 out of 10 plants have flowers) and before the new growth at the base of the stem is taller than the usual stubble height. When the plant is cut leaving a 3-inch stubble as recommended, the plant should be harvested before the new growth is taller than 3 inches.

4. Large roll bales of alfalfa do not shed water as well as rolls of grass hay. Alfalfa rolls should be placed in covered storage to avoid excessive spoilage.


Table 1.


Table 1. Spray Nozzles.

Nozzle Spacing (inches)

Distance of Boom from Crop (feet)

Approximate GPA at 30 psi

(3.0 mph)

Spraying Systems D2-13 Delavan DC2-13

6 1-2 23

Spraying Systems D2-13

Delavan DC2-13

12 1.5-2 27

Spraying Systems D2-13 Delavan DC2-13

18 1.5-2 28


reduce alfalfa drying time with chemical agents

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