Liquid Fertilizer 101 (Ratio, Quantity, Tips Included)

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Hey there, lawn enthusiasts! Have you ever wondered how much liquid fertilizer you should use to keep your lawn lush and green? Well, worry no more! We’re going to take you through the ins and outs of liquid fertilizer application, with plenty of data to make sure you’re well-informed. Let’s dive into the world of lawn care, from a beginner’s perspective, but with all the details you need to become a pro.

To determine the appropriate amount of liquid fertilizer for your lawn, follow the manufacturer’s recommendations and base your calculations on the Nitrogen-Phosphorus-Potassium (N-P-K) ratio present in the fertilizer. A general rule of thumb is to apply 1.9 pounds of nitrogen (from 18N, 3P, 6K) per 1,000 square feet of lawn every 4-6 weeks during the growing season.

There are do’s and dont’s in using liquid fertilizers for your lawn. This guide answers everything about liquid fertilizers’ quantity and usage levels that can make your lawn lushy and healthier!

Understanding the N-P-K Ratio

Before we get into the nitty-gritty of liquid fertilizer application, it’s essential to understand the N-P-K ratio. This ratio represents the percentage of nitrogen (N), phosphorus (P), and potassium (K) present in the fertilizer. Check out my articles about why plants need nitrogen, phosphorus and potassium.

For example, a 20-5-10 fertilizer has 20% nitrogen, 5% phosphorus, and 10% potassium. These three elements are crucial for healthy lawn growth, with nitrogen being the key player in promoting lush green grass.

If you’re a beginner, I’d recommend checking the NPK ratio on the label first before you head on to apply it. There are different proportions and you shouldn’t get this wrong!

How to Calculate the Amount of Liquid Fertilizer

Now that you’re familiar with the N-P-K ratio, let’s look at how to calculate the correct amount of liquid fertilizer for your lawn.

  1. Measure your lawn: Start by measuring the square footage of your lawn. You can do this by multiplying the length and width of your lawn (in feet) or by using an online lawn size calculator.
  2. Determine the nitrogen requirement: Most lawns require 1.9 pounds of nitrogen per 1,000 square feet every 4-6 weeks during the growing season. Calculate the total amount of nitrogen your lawn needs by multiplying its size (in square feet) by 0.001. I’ve also written an in-depth article about how much fertilizer is needed for a healthy lawn.
  3. Calculate the fertilizer amount: Divide the required nitrogen amount by the percentage of nitrogen in the fertilizer (expressed as a decimal). For example, if you’re using a 20-5-10 fertilizer and need 1 pound of nitrogen, you’d divide 1 by 0.20, resulting in 5 pounds of fertilizer.
  4. Convert to liquid measurements: Liquid fertilizers are usually sold in gallons, so convert the weight of the fertilizer to gallons by following the manufacturer’s instructions or using an online converter.

Having said that, here’s a common guide explaining the quantity for each type of grass.

Type of GrassQuantity (in lb Nitrogen per 1000 sqft)
Conventional (unknown)1.9

Tip: If you’re looking for grass types that don’t go dormant in winter, check out my article here.

Tips for Applying Liquid Fertilizer

So, you’ve bought a liquid fertilizer from the shop. What’s the next step? Before you rush to apply it, here are a few tips that has helped me personally in achieving the desired outcomes.

  • Read the label: Always read the manufacturer’s instructions carefully and follow their recommendations.
  • Choose the right equipment: Use a hose-end sprayer, backpack sprayer, or a dedicated liquid fertilizer spreader to ensure even application.
  • Time it right: The best time to apply liquid fertilizer is in the early morning or late afternoon when temperatures are cooler and the sun is less intense.
  • Water after application: Water your lawn after applying liquid fertilizer to help the nutrients penetrate the soil and prevent the grass from burning.


Can I over-fertilize my lawn with liquid fertilizer?

Over-fertilizing can lead to fertilizer burn (here is why), excessive growth, and a weakened lawn. Always follow the manufacturer’s recommendations and avoid applying more than 0.25-1.9 pounds of nitrogen per 1,000 square feet (depending on the grass type) every 4-6 weeks during the growing season.

Is liquid fertilizer better than granular fertilizer?

Both liquid and granular fertilizers have their advantages. Liquid fertilizers are fast-acting and easy to apply, while granular fertilizers release nutrients more slowly and can provide long-lasting results. The choice between the two depends on your specific lawn needs, personal preferences, and budget.

When should I start applying liquid fertilizer to my lawn?

Begin applying liquid fertilizer in early spring as your lawn starts to green up and actively grow. Continue to fertilize every 4-6 weeks during the growing season, with the last application in early fall before the grass goes dormant.

Can I use liquid fertilizer on newly seeded lawns?

Yes, but it’s essential to choose a starter fertilizer with a higher phosphorus content to promote root growth. Be cautious not to over-apply, as excessive fertilizer can harm delicate new grass.

Are organic liquid fertilizers a good option for my lawn?

Organic liquid fertilizers, derived from natural sources like fish emulsion or seaweed, can be a great option for those seeking a more environmentally friendly solution. They typically have lower nutrient concentrations, so you may need to apply them more frequently. However, organic options can improve soil health and promote beneficial microorganisms.


Applying the right amount of liquid fertilizer to your lawn is crucial for a healthy, lush, and green landscape. Always follow the manufacturer’s recommendations and use the N-P-K ratio to calculate the correct fertilizer amount for your lawn’s size. Remember to measure your lawn, determine the nitrogen requirement, calculate the fertilizer amount, and convert to liquid measurements. Finally, choose the right equipment, time your application wisely, and water your lawn after fertilizing.

Ready to take your lawn care skills to the next level? Keep exploring my blog for more tips, tricks, and expert advice. Happy fertilizing!

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I am always happy to share all my knowledge about how to keep your garden in good condition and make it special.

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