Grass Seed or Fertilizer First? (What do you Put down First)

Starting a new lawn grass from seed requires careful preparations to encourage even germination and proper growth. Grass seeds need a starter fertilizer to boost their initial growth. So, what do you put down first, grass seed or fertilizer?

You should put down fertilizer first before putting down grass seed. Fertilizing soil before planting makes nutrients readily available for the incoming grass seed and seedlings. This promotes faster growth and establishment of the grass.

Grass Seed or Fertilizer First?

It’s essential to fertilize the soil before planting grass seeds to establish healthy germination and proper growth. Adding nutrients into the soil will ensure newly germinated seedlings have what they need to grow properly.

There are various recommendations to follow for better results before fertilizing and sowing grass seed.

1. Conduct a soil test

Before doing anything on the site, conduct a soil test to determine the pH and nutritional condition of the soil. Performing a soil test will tell the inadequate nutrients and the proportions required. You do not want your new lawn to miss out on critical nutrients such as nitrogen and phosphorus in its initial growth stage.

2. Clear and till the earth

Clear the site to remove small bushes, dead plants, sticks, stones and other debris. Use a hoe to till the land up to a depth of 6 inches. Break up the large clods of soil and grade the area to ensure it slopes away from your compound’s buildings. Be sure the area is even by filling dips with soil. The soil should be loose to allow easy penetration of roots.

3. Amend the Soil

Add organic materials into the soil to improve fertility, drainage and aeration. Apply at least a 2-inch layer of well-rotted compost on the surface of the soil and in-cooperate it into the soil for about 6 inches. Be sure not to use fresh compost or manure that may introduce weeds and diseases into your garden.

4. Correct the Soil pH

Adjust soil pH as needed by adding lime or sulphur. Most grass varieties thrive and establish well in soil with a pH of 6.0 to 6.8. If the pH is high or low, follow the recommendations provided by the soil test results. If the pH is too high, apply sulphur to bring it down within recommended range. On the other hand, apply lime if the pH is too low.

5. Fertilize the Area

Apply starter fertilizer before planting the seed. If you conducted a soil test, apply according to the recommendations provided. Select the best fertilizer that suits your soil’s nutritional needs.

Generally, you can apply 1 pound of starter fertilizer per 1,000 square feet. Use slow-release fertilizer since it releases nutrients slowly and longer than plants require. Choose a fertilizer that doesn’t contain herbicides. It can prevent grass seeds from germinating.

6. Rake and Sow Grass Seed

Rake the area to obtain smooth and fine soil particles. Remove sticks, rocks and other debris that may have remained in the soil. Apply grass seed on the soil surface as recommended on the package. Use an empty lawn roller to firm the soil gently. Alternatively, you can cover the seeded area with a layer of mulch. Lastly, water your seeded lawn.

How long after fertilizer can you put down grass seed?

You can plant grass seed immediately after fertilizing the area. The initial fertilizer will help to feed the grass seed as they germinate. Since you’re regularly watering to keep the soil moist during germination, nutrients may leach out of the soil relatively fast.

Therefore, you must fertilize your seeded lawn with the second round of starter fertilizer after 4 weeks of seeding. The fertilizer will continue to boost the germination and growth of seedlings. Application rate should be according to recommendations provided on the package.

You must wait longer before planting grass seed if you’re using a fertilizer product containing herbicides. Such products are ideal for killing weeds while promoting growth for an established lawn and should not be used on a seeded lawn.

Weed-and-feed products should never be applied immediately before or after seeding. They contain herbicides that kill grass seedlings or prevent germination from taking place.

If you applied fertilizer containing herbicides, wait 8 weeks before planting the grass seed. You should also wait for the same period of time before using these products on your new lawn grass.

Also read: When to fertilize new sod for best results.

Will Fertilizer Kill Grass Seed?

Yes, regular fertilizer instead of a lawn starter can kill grass seed. Regular fertilizers don’t contain enough phosphorus needed by newly germinated grass. Instead, it will suffocate grass seedlings with unnecessary nitrogen and potassium in the initial growth stage.

The best time to fertilize new grass seed should be 4 to 6 weeks after germinating. You should use a well-balanced, slow-release granular fertilizer formulated for new lawns.

Some regular fertilizers contain pre-emergent herbicides to control crabgrass and other weeds before germinating a lawn. They’re ideal for an established lawn. Such fertilizers can disrupt seed from germinating when used on seeded lawns.

Herbicides, or pre-emergents, are made to prevent germinating seeds from establishing roots. However, these herbicides cannot distinguish between harmful weeds and desirable seeded lawns. Although they are aimed at killing broad leave weeds, they can injure immature grass seedlings.

Be sure to follow the manufacturer’s instructions when using fertilizers containing herbicides. Generally, you should refrain from applying fertilizers containing herbicides 6 to 10 weeks before or after planting new grass seed.

It’s also important to conduct a soil test before applying fertilizer to determine the inadequate nutrients and the quantities required. Generally, starter fertilizers should be applied at 0.5 – 1 lb. nitrogen per 1,000 square feet of lawn.

Applying excess nitrogen fertilizer can result in lawn fertilizer burns or the killing of your newly germinated grass seedlings.

Final Thoughts

It’s recommended to apply fertilizer first before sowing grass seed. It’s also important to conduct a soil test to select a suitable starter fertilizer. The results will indicate pH and the level of nitrogen, phosphorus and potassium the soil needs for the healthy growth and establishment of your new lawn grass.

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