Smart Farming Solutions

If you look at a bag of fertilizer, you will see labels with headings such as: 10-10-10; 16-8-8; 6-0-6. What this means is the percent concentration of nitrogen (N), phosphorous (P) and potassium (K) in that order. A bag of 10-10-10 has 10% nitrogen, 10% phosphorous and 10% potassium; the rest is filler such as lime rock, sand or sludge. Every nutrient adds to cost. For example a 50 lbs bag of 16-0-8 should cost less than a 16-8-8 because it does not have any phosphorous. To complicate matters, every manufacturer uses a slightly different composition from others and has a different coverage rate. Nitrogen is the most expensive component, so one way to compare apples with apples is to take similar compositions and compute the cost of nitrogen per pound. Example: You are looking at two 50 lbs bags of fertilizer. One is a 16-4-8 for $26.97 the other is a 20-5-11 for $29.99. In the first case multiply 0.16 (16%) nitrogen by 50 lbs = 8lbs of nitrogen. Divide $26.97 by 8 = $3.37 per pound of nitrogen. In the second case: $29.99/ (0.20x50) = $2.99 per pound of nitrogen. This means you are getting more bang for the buck with the second bag. Now divide your cost for nitrogen by the advertised coverage rate and you get your cost per square foot.
Liquid fertilizers are absorbed by the plants through leaves 10 times more efficiently than through roots. As a result, much less liquid fertilizer is needed to compensate for a deficiency. When comparing prices of fertilizers between liquid and dry, once again consider the coverage per pound of nitrogen, phosphate or potassium (based on which ever has the greatest concentration).
Slow release fertilizers are more desirable than dry or liquid fast release fertilizers. However, their costs are significantly higher. The choice depends on your time. Fast release fertilizers are most effective when applied in small quantities frequently.
Also consider the ingredients. For example, plants can absorb nitrogen in ammonium or nitrate form. However, the use of only one form can be detrimental to plant growth. So an ammonium nitrate combination is more desirable. Better yet, a calcium nitrate, potassium nitrate, ammonium phosphate and ammonium sulfate combination provide the essential macronutrients. Stay away from any muriate of potash, (potassium chloride), due to the potential salt damage from the chloride.
Finally, if buying dry fertilizers, strive for organic inert material. If you buy a 10-10-10, 70% of the bag is inert material such as sand, gypsum, lime rock or organic waste. Unless you are growing vegetables, which may come in contact with the soil, strive for organic inert fillers.
Remember that cheap fertilizers can cause more harm than good. In the end, you get what you pay for.