Fertilizer maths

Awrighty. Now that some of the seedlings have a set or two of leaves, it’s time to start supplementing their soilless growing mix with fertilizers. I’m using a mix of fish and kelp fertilizer and as per the advice of my garden gurus, I’ll be feeding them every other watering or so, at one third the strength. The danger with young seedlings is overfertilizing, which burns and kills them, not under so I want to be quite careful and dilute the liquids properly.

To do that I had to pull out my very rusty and basic math skillz, and work with ratios. Isn’t gardening fun?

fish-fertilizerThe fish fertilizer is some potent stuff – the label says mix about 1 tbsp to a gallon. I needed to figure out how much that would be in 2 cups of water that I was using to water the seedlings.

So… 1 gallon = 16 cups
15 ml = 16 cups
X = 2 cups

Takes ya back to high school don’t it? Solving for the x, I got about 1.9 ml. Since I wanted the fertilizer at about 1/3 strengh, it worked out to be about 0.5ml for 2 cups of water. By the way both fertilizers look like brown sludge, and the fish one smells exactly like what it is. Mmmm.

kelp-fertilizerThe kelp fertilizer is a bit more forgiving, allowing 1.5 oz to a gallon. Using the exact same formula as above, I ended up with 1.5 ml of fertilizer per 2 cups of water. I rounded up and down freely by the way, since the quantities we’re talking about are so small.

I’m shooting to fertilize them at this very weak dilution about once a week or every other time I water. The seedlings are thirsty and at this stage I check them daily and water about every three-four days.

Of course I had some help doing this. Thanks Tweaks, couldn’t have done it without ya!

tweaks-the-helper