"Harvesting and storing forage crops at the proper moisture is necessary to minimize forage losses and to maintain maximum nutritonal value. But it is difficult to determine the moisture concentration of forage crops prior to ensiling or baling."--First page.Barry J. Steevens, Ron Belyea and Richard Crawford (Department of Dairy Science)New 1/86/6

Belyea, Ron

Crawford, Richard

Steevens, Barry J.

English

University of Missouri: MOspace

J~M 21 ,gsG Using a microwave oven to determine moisture in forages Barry J. Steevens, Ron Belyea and Richard Crawford Department of Dairy Science Harvesting and storing forage crops at the proper moisture is necessary to minimize forage losses and to maintain maximum nutritional value. But it is dif-ficult to determine the moisture concentration of forage crops prior to ensiling or baling. Ways to measure moisture A common way to measure moisture is the hand-squeeze method. You squeeze the forage into a ball for 30 seconds and then guess the moisture level. This method is very deceptive and lacks precision. Another way to determine moisture-drying forage in an oven-is time consuming and impractical. Three other methods use specific equipment: the Delmhorst* moisture tester, the Koster* tester, and the microwave oven. The Delmhorst moisture tester is a convenient hand-held device that estimates moisture as a mea-sure of electrical resistance. It is designed to estimate moisture in the range of 13 to 40 percent. Consider-able variation in readings can exist, as moisture percentage in a bale of hay will vary from wafer to wafer. When using a Delmhorst moisture probe, you should use a second, more accurate method to gain experience and a frame of reference in estimating moisture percentage. The Koster moisture tester is a portable, forced air electric drying unit. You use a small scale that comes with the heater to weigh forage into a mesh-bottom basket. You put the basket into the drying device and dry the forage until stable readings occur, which takes about a half hour. You then take dry matter/ moisture readings directly from the scale. This meth-od gives accurate estimates of forage moisture, but you need to be near an electrical outlet to use it. You can take it to the field if a portable generator is available. *Delmhorst, Koster: Mention of trade names does not imply endorsement. Figure 1 . Weigh forage sample using a scale measured in grams. A microwave oven dries forage in a mm1mum amount of time and can provide accurate forage moisture determinations. The following describes how you can use a microwave oven for moisture testing. Collecting forage samples As with all forage analyses, obtaining a representa-tive sample is an important, but difficult, step. Select three to five locations in the field where the windrow is uniformly thick. With a sharp shears, cut 6-inch cross-sections from windrows. If the for-age is dry, try not to lose leaves. Chop the forage into pieces 1 to 2 inches long. Mix samples in a clean pail and subsample for drying. For baled hays, sample with a Penn State bale corer or another appropriate device. (See UMC Guide 3950, "Sampling feedstuff for chemical analysis.) Damp hay baled with preservatives results in excess friction and heats the core borer. This dries the sample while it is still in the bale corer and underesti-mates moisture significantly. 3151 Archive version - chck for updatesSelecting equipment You need a microwave oven with a power range of 50 to 1,000 watts and a small scale (postal, kitchen, or dietetic) that weighs in grams. Postal scales are less expensive but they measure in ounces. Results with postal scales are less accurate than scales that mea-sure in grams unless you use large samples (1-2 pounds) . Determining moisture content Moisture determination requires weighing a wet for-age sample on a scale, drying it in a microwave oven to a constant weight, and calculating the moisture concentration. The following steps illustrate the pro-cedure. 1. Weigh an empty paper dish and record its weight as weight A (see item 4) . You may substitute other microwave-safe containers such as a brown paper bag or containers that are porous so water can evaporate. Do not use metal. The weight of the container will not change much during drying, but you must know it. 2. Place a representative sample of forage in the paper dish. The sample should weigh 100 grams or 1-2 pounds if using postal scales. Record the weight of the dish plus the forage sample as B (see item 4). 3. Dry the sample gradually in the microwave oven. Warning: do not leave drying samples un-attended. Place a small glass of water, three-fourths full, in the back corner of the microwave. Keep water level fairly constant during microwave use. Micro-wave manufacturers say this prevents damage to the oven. Begin by drying the sample for 3 minutes. If the sample is fresh material (70 to 80 percent moisture) you may start with 5 minutes; if you think the sample has less than 35 percent moisture, start with only 2 minutes. Use the oven's higher heating or power Table 1 . Approximate total drying time for forage samples. Forage Time (minutes) Hay lage 4-15 High moisture corn grain 10-15 Corn silage and fresh material 8-20 3151 Figure 2. To protect the oven, place a container of water in it while drying the sample. levels for wetter materials. As the forage dries, lower the heat level. Check for dryness after the initial heating and stir the sample again inside the container to retard loss and to dry layers. Repeat the 3-minute drying time for very wet samples. Check and stir the sample again. At this point, you should be able to feel a loss of moisture. Continue drying for intervals of 1 to 2 minutes until the sample feels almost completely dry, stirring be-tween intervals. Weigh the sample to determine weight loss. Now, dry the sample for approximately 30 seconds and reweigh. Repeat the 30-second drying intervals until the weight of the dish plus sample ceases to change. Record this as weight C (see item 4) . Different forages require different drying times. Shelled corn may take as long as 15 minutes; haylage, 5 minutes or less. Experience will tell you how much drying time your samples require. To prevent burn-ing, check samples at frequent intervals as they approach dryness. A sample may feel dry, yet contain as much as 10 percent moisture . The only way to ensure a sample is 100 percent dry is to check the weight after each 30-second drying interval. If the weight is still chang-ing, moisture is still being driven off. If the weight is constant after three 30-second drying intervals, stop. All the moisture is gone and the sample is 100 percent dry. Do not dry further as carbohydrate will be volatized and moisture will be over-estimated. Stop before charring occurs. A trial run to gain experience in using microwave is recommended. Total drying times (Table 1) are approximate. For example, if your sample initially doesn't change much during 1 ½ minutes of drying, leave it for 2½ minutes at a time . Take care to prevent charring or burning of forage sample. Attend drying procedures at all times as a fire is always a potential risk if over drying and charring occurs. Do not send these samples for forage testing. Fiber and protein concen-trations could be altered and heat damage and pro-tein binding are possible. 4. Calculate percent moisture: (A) Weight of empty paper plate or bag. (B) Weight of wet sample + paper plate or bag. (C) Weight of dry sample + paper plate or bag. Subtract plate or bag weight (A) from both wet weighing (B) and dry weighing (C). Line 1: B-A Line 2: C-A Percent moisture = Line 1 - Line 2 x 100 Line 1 Example of moisture calculation 3151 (A) Bag weight = 10 grams (B) Wet sample weight + bag = 90 grams (C) Dry sample weight + bag = 70 grams Line 1: 90-10 = 80 grams (wet sample) Line 2: 70-10 = 60 grams (dry sample) 80-60 x 100 = 25 percent moisture 80 ■ Issued in furtherance of Cooperative Extension Work Acts of May 8 and June 30, 1914 in cooperation with the United States Department of Agriculture. John W. Oren, Director, Cooperative Extension Service, University of Missouri and Lincoln University, Columbia, Missouri 65211 . ■ An equal opportunity institution. 3151 New 1/86/6M 

Using a microwave oven to determine moisture in forages

https://mospace.umsystem.edu/xmlui/bitstream/10355/72784/1/g3151-1986.pdf

Using a microwave oven to determine moisture in forages

Abstract

Similar works

Full text

Available Versions

University of Missouri: MOspace