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Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe |
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Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe |
Comparing Cost of Fertilizers based on Nitrogen
Nitrogen is the most important element � because it is required in the greatest amount (1-4%) Since it is a major consideration, calculate cost. To calculate the cost, use the formula:
Nitrogen cost ($/kg) = cost of fertilizer ($) x 1/ %N x 1/pack mass (kg fertilizer)
The first one is done for you. Complete the remainder of the table.
| Fertilizer Costs | |||||
| Brand |
Type |
N-P-K | Pkg Price ($) | Pkg Wt (kg) | Nitrogen cost ($/kg) |
| RaPid Gro | S | 23-29-17 | 1.99 | 0.227 | 38.10 |
| Peter's Houseplant | S | 15-13-7 | 1.19 | 0.071 | |
| Jobe's Spikes | C | 10-10-4 | 1.49 | 0.015 | |
| Miracle-Gro | S | 15-30-15 | 2.19 | 0.227 | |
| Osmocote | C | 14-14-14 | 4.95 | 0.553 | |
| Schultz Instant Liquid | L | 10-15-10 | 4.99 | 0.397 | |
S= soluble, L = liquid O = organic C = controlled
This exercise is adapted from Hershey, D (1990) Sleuthing the nutrients that make your houseplants grow. Science Activities 27: 17 � 20.
Last updated: 01/11/2005 / � Copyright by SG Saupe / URL:http://www.employees.csbsju.edu/ssaupe/index.html