Calculating the PPM of Nitrogen in Your Fertilizer

How a lot fertilizer do you utilize? In North America, it’s common to answer with one thing like “1/8 tsp of a 20-6-12 fertilizer. The issue with this reply is that it’s troublesome to match the quantity to somebody utilizing, for instance, 1/4 tsp of 7-3-5 fertilizer.

Are both of those near the really helpful quantity of 100 ppm nitrogen?

You will need to examine apples with apples and one of the simplest ways to do that is to report and talk about fertilizer in ppm models. It’s straightforward to do, it is going to make gardening communication far more helpful and it will provide you with higher perception into your fertilizer use.

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Why Use PPM Values

Fertilizer is offered in a wide range of NPK values and it’s troublesome for many of us to mentally convert one method to a different. For instance, which dilution accommodates extra nitrogen 1/8 tsp of a 20-6-12 fertilizer added to a gallon of water or 1/4 tsp of a 7-3-5 fertilizer added to 2 quarts? How far more does it have?

Now strive answering the identical query utilizing ppm. Which dilution accommodates extra nitrogen, a 40 ppm combination or a 75 ppm combination? How far more does it have?

The second cause gardeners ought to use ppm is that it’s the normal in horticulture, laboratories, and analysis experiences. As soon as you know the way a lot nitrogen you utilize in ppm models, you may examine it to industrial operations and mimic their efficiency.

Right here is an instance. Industrial orchids are grown at 150 – 200 ppm nitrogen. How does your 1/8 tsp of a 20-6-12 fertilizer examine to that? Are you utilizing an excessive amount of nitrogen? Too little? These questions are a lot simpler to reply if your fertilizer ppm worth.

What’s ppm? Ppm is brief for components per million which is normally based mostly on weight. One ppm = one mg/l.

Calculating PPM Utilizing Imperial Models

The next values are used.

Tsp = variety of teaspoons (tsp) of fertilizer added to at least one gallon of water.

%N = the quantity of nitrogen in your fertilizer. That is the “N” worth in the NPK. The %N worth for an NPK of 20-6-12 is 20.

The ppm worth of your combined fertilizer resolution is = Tsp * %N * 15.

(“*” is a multiplication signal, “/” is a division signal).

Instance:

An answer made by including 1/8 tsp of a 20-6-12 fertilizer to 1 gal of water has 37.5 ppm of nitrogen.

ppm = 0.125 * 20 * 15 = 37.5

Word: you may work with fractions on this method or you may convert fractions to decimal numbers (1/8 = 0.125, 1/4 = 0.25, 1/2 = 0.5, 3/4 = 0.75)

Different Models: Use these values to transform your methodology of measurement to tsp after which use the above method.

• Tablespoon: tbs = 3 tsp
• As soon as: Oz = 6 tsp
• Cup: 1/8 cup = 6 tsp
• Mililiters: 5 ml = 1 tsp

Calculating PPM Utilizing Metric Models

The next values are used.

Wg = weight of fertilizer in grams. You may assume that 1 ml = 1 g

%N = the quantity of nitrogen in your fertilizer. That is the “N” worth within the NPK. The %N worth for an NPK of 20-6-12 is 20.

#L = variety of liters of water used to combine the fertilizer.

The ppm worth of your combined fertilizer resolution is = Wg * %N * 10 / #L.

Instance:

An answer made by including 5 grams of a 20-6-12 fertilizer to 10 liters of water accommodates 100 ppm of nitrogen.

ppm = 5 * 20 * 10 / 10 = 100

How A lot Fertilizer Ought to You Use?

I’ve checked out a number of horticultural suggestions and analysis papers that decide the optimum nitrogen degree for rising potted crops. The nitrogen ranges are within the vary of 100 to 200 ppm nitrogen. For max productiveness, the values are typically round 200 ppm.

Crops solely develop nicely at 200 ppm nitrogen if additionally they get glorious environmental situations such pretty much as good lighting and excellent watering. Dwelling tradition isn’t that good. Our houses normally don’t present sufficient mild for optimum progress and watering isn’t as exact.

A part of the explanation for these limitations is that houses use home windows or low-intensity lights in comparison with rising in a greenhouse. One other vital level is that almost all gardeners have a assortment of various crops that every one should develop beneath one set of situations. We don’t maximize the rising situation for every kind of plant in the way in which that manufacturing greenhouses do.

The MSU orchid assortment is grown at 125 ppm. This similar fertilizer is used for many of their massive assortment of houseplants.

For these causes, houseplants don’t want as excessive a degree of nitrogen as industrial services. I’d advocate owners use about 100 ppm of nitrogen.

Industrial Fertilizer Merchandise for Houseplants

What do industrial fertilizers recommend for houseplants? I used the options on the label and the above formulation to calculate the ppm nitrogen for every product.

You’ll discover a variety of ppm values. The FoxFarm 1.8 ppm primarily provides no nitrogen and may be very pricy. Something beneath 75 ppm is simply too low for actively rising crops.

Based mostly on the above desk, gardeners ‘ frequent suggestion to make use of 1/2 energy and even 1/4 energy of the really helpful label quantity is incorrect typically. That’s not sufficient nitrogen for crops to develop nicely.

Crops which have slowed down progress in winter or after flowering might be given much less nitrogen (30-50 ppm).

The Price of Fertilizer

There’s a big selection of fertilizer prices. My current assessment of this discovered {that a} pound of nitrogen can price anyplace from $33 to over $6,000. Something over $75/lb is a waste of your cash.