Increasing Manure Value With Calibration

Knowing the nutrient content of manure isn’t enough. It is important to know how to get the intended rate on the field with the equipment at hand and to ensure that manure is uniformly applied. Advances in technology such as guidance systems, GPS and flow meters can improve uniformity. However, just as most people wouldn’t take a sprayer to the field to apply herbicides without calibrating, neither should manure application equipment be used without fine-tuning.

Solid Manure

Solid manure is often applied at higher rates than producers expect. Uniform application is difficult with solid application equipment due to variation in manure moisture content and composition. Dry pack manure is often “clumpy”, while dry broiler litter is light and moves easily with the wind. With traditional box spreaders, driving wheel to wheel gives best uniformity. The following methods should be used to determine application rates and uniformity. 

Solid Manure Method 1 - Calibrating Application Using Scale (portable or elevator)

Application rate = [lbs (or kg) Loaded spreader weight – lbs (or kg) Empty spreader weight] ÷ acres (or ha) covered per load

Solid Manure Method 2 - Calibrating Application Using Plastic Sheet

Using a 48 inch (122 cm) x 40 inch (88 cm) sheet (plastic feedbag)				Example: Extrapolating area of plastic sheet to acre equivalents (1 ac = 0.405 ha)
lbs (kg) manure/sheet		Application Rate tons/ac (tonnes/ha)
1	(0.45)	1.6	(3.6)	40” x 48” =3.3’ x 4’ = 13.33 sq ft
2	(0.9)	3.3	(7.5)
3	(1.4)	4.9	(11.1)	13.33 sq ft /43,560 sq. ft per acre = .0003061 acres
4	(1.8)	6.5	(14.7)
5	(2.3)	8.2	(18.6)	2 lbs/.0003061 = 6,536 lbs
7	(3.2)	11.4	(25.9)
10	(4.5)	16.3	(37.0)
15	(6.8)	24.5	(55.6)	6,536 lbs / 2000 lbs/ton = 3.27 tons/acre
20	(9.1)	32.7	(74.1)

Liquid Manure

It easy to calculate how much liquid manure was applied to a field by knowing the tank volume and dividing the number of loads by the acreage covered by those loads. Uniformity of application is a bigger issue with liquid manure. Type of tanker, tanker setup and speed all influence application rate. Something as simple as hitting a tree limb with a manure tanker splash plate can change the spread pattern and uniformity. Spread pattern uniformity is most easily seen when spreading part of a load on a small snow-covered area or cement pad. Calibrating uniformity at the time of application can be done with relative ease by placing straight-walled jars or cans (Photo 1) across the spread width of the tanker, and calculating the rate using the following methods.

Photo # 1

Liquid Manure Method 1 - Calibrating Application by Jar Weight

Using a 3⅛” (7.9 cm) diameter jar (with lid) (ie lab sample jar)				Example: Extrapolating area of jar to acre equivalents 1 Imp gal/ac = 11.23 litres/ha
Manure Wt = Total weight - jar weight lbs (kg)		Application Rate (Imp gal/acre)(litres/a)
0.025	(0.055)	2,050	(23,023	3⅛” = 3.125 inch diameter / 2 = 1.56” radius
0.033	(0.073)	2,700	(30,323)
0.04	(0.098)	3,275	(36,781)	1.56 inches / 12 in./ft = 0.13 ft
0.05	(0.10)	4,100	(46,046)
0.066	(0.15)	5,450	(61,207)	area of circle = πr2 3.1417 x .13 x .13 = .053 ft2 .053 / 43560 ft2/ac = .000001219 acre
0.075	(0.17)	6,150	(69,069)
0.10	(0.22)	8,200	(92,092)
0.125	(0.28)	10,250	(115,115)	One gallon weighs about 10 lbs If filled jar weight – weight of jar = .05 lb .05 lb / 10 lb/gal = .005 gal
0.15	(0.33)	12,300	(138,138)
0.20	(0.44)	16,400	(184,183)
0.25	(0.55)	20,500	(230,229)	.005 gal / 0.000001219 acre = 4,100 gal/ac
0.30	(0.66)	24,600	(276,275)

 

Liquid Manure Method 2 - Calibration Using A Straight-Walled Pail

Depth of Manure In Pail		Application Rate	Application Rate
Inches	(mm)	(Imperial gallons/acre)	(litres/ha)
1/10	(2.5)	2,265	25,440
1/8	(3.2)	2,825	31,730
1/4	(6.4)	5,650	63,450
1/3	(8.5)	7,550	84,790
3/8	(9.5)	8,500	95,460
1/2	(12.7)	11,325	127,200
5/8	(15.9)	14,150	158,910
3/4	(19.1)	17,000	190,960
1 inch	(25.4)	22,650	254,440

1 Imp gallon = 4.545 litres, 1 US gallon = 3.785 litres, 1 Imp gallon = 1.20 US gallon

The owner’s manual of many solid manure spreaders has often referred to spreader capacity in bushel weights. Table 1 below shows the approximate bushel weight comparison of different manure types. There is however a large difference between semi-solid cattle manure and dry poultry litter. Liquid manure is assumed to weigh close to 10 lbs/gal. To measure the actual density of manure being applied, follow the formula given for measuring manure density.

Table 1 - Approximate Densities of Different Types of Manure

Manure Type	lbs per Cubic Foot	lbs per Bushel	Kg per m3
Liquid	62.4	80	1000
Simi-solid	60	76	961
Thick solid	50	64	801
Light solid	35	45	560
Dry poultry	25	31	400

1 bushel = 1.25 ft³, 1 lb/ft³ = 35.31 kg/m³

Measuring Density Using Weight and Volume

Example:

Using a 1 kg coffee tin.

Container is .52 ft diameter (.26 ft radius); height is .53 ft

Volume = πr² x height = 3.1416 x .26² x .53 = .1126 ft³

Container filled with compost weighs 3.31 lbs

If:3.31 lbs / .1126ft³ = x /1 ft^3, then x = 29.4 lbs per ft³