Page 182 - Calculating Agriculture Cover 20191124 STUDENT - A

15-10 Metric Measurements CH 15]

(b) Calculate the Dry Matter in the baled hay. Remember that the weight of DM never changes

(Total Weight % – Moisture %)
DM weight = Total weight x —————————————
100%
(100% – Moisture %)
DM weight = Total weight x ————————
100%

(100% – 13%)
DM weight = 1.09 tonnes x —————
100%
87%
DM weight = 1.09 tonnes x ——
100%
Dividing by 100% converts the percentage to a decimal
DM weight = 1.09 tonnes x 0.87

DM weight = 0.95 tonnes

(c) Calculate the weight of the forage at harvest with 80% moisture, The Dry Matter
weight does not change. The Percent DM does change.

Dm#
——————— = Total Weight (dm + moisture at cutting)
(100% - Dm%) / 100%

0.95 t
—————— = Total Weight (dm + moisture at cutting)
(100% - 80%) / 100%

0.95 t
———— = Total Weight (dm + moisture at cutting)
(20%) / 100%

0.95 t
——— = Total Weight (dm + moisture at cutting)
0.20

4.75 t = Total Weight (dm + moisture at cutting)

Refer to Page 9-27 & 9-28
None of these carriers have 100% nutrient content, and some of them contain more than one of
the three major nutrients. Hence, the quantity of these carriers to be used in mixing fertilizer becomes
an issue of consideration and arithmetic calculation.

Example A: The three main plant nutrients in commercial fertilizers are nitrogen, phosphate
and potash. The amounts of each vary to meet the needs of a particular soil and
crop. An 8-10-4 fertilizer contains (by weight) 8% nitrogen (N), 10% available
phosphate (P 20 5), and 4% available potash (K 20). Determine the number of kg of
nitrogen in 1,000 kg. of 8-10-4 fertilizer; also determine the kg of Phosphorus (P),
and kg of potassium (K).
Solution: N — 1,000 x 0.08 = 80kg Nitrogen
P — 1,000 x 0.10 = 100kg Phosphate
K — 1,000 x 0.04 = 40kg Potassium

Example B: How many kg of plant nutrients are in a tonne of 15-12-4 fertilizer?

Solution: Calculate the pounds of each and then add them together. (Add the %’s of each
together and then multiply)

1,000kg / tonne x (0.15 + 0.12 + 0.04) =
1,000kg / tonne x (0.31) = 310 kg nutrients

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