Can You Put Down Grass Seed and Fertilizer at the Same Time?

There are no shortcuts when it comes to seeding and fertilizing your lawn. You may think that doing them simultaneously saves your time, only to realize during the grass germination that you made a serious mistake. Here are the implications of putting down grass seed and fertilizer at the same time.

To put down grass seed and fertilizer simultaneously, test the soil for nutrient and pH deficiencies. Till the seeding area with fertilizer to a depth of 4 to 6 inches. Spread two to eight pounds of grass seed for every 1000 square feet and roll them in contact with the soil. Finally, water them for 3 to 4 inches per week. 

Although many people do not calculate the planting area, we will see how essential it is for correct seed and fertilizer application. You will also know how you can put grass seed and fertilizer simultaneously. In the end, I give you the best fertilizer for grass seed. For dark green, thick, and healthy lawns, follow these recommendations.

Do I need starter fertilizer for grass seed?

Starter fertilizer provides readily available nutrients to grass seeds. However, it is recommended to apply the starter fertilizer before seeding. Grass seeds require a lot of phosphorus to stimulate root growth and enhance grass vigor. Therefore, the phosphorus in starter fertilizer is essential for a lush and thick lawn.

It is important to have a soil test before applying starter fertilizer. The examination reveals your lawn’s soil pH, minerals, and nutrients. But if you did not test your soil, experts recommend between 0.5 and 1 pound of nitrogen per 1000 square feet as anything beyond 1 pound can burn the young grass seedlings.

A starter fertilizer with an N-P-K ratio of 10-6-4 or 15-10-10 is acceptable for promoting the early growth and development of grass seeds. However, if you use manure-based compost that is amended to a layer of one or two inches into the soil, starter fertilizer becomes unnecessary. They have significant amounts of phosphorus and nitrogen.

Can you spread grass seed and fertilizer at the same time?

I do not recommend spreading grass seed and fertilizer at the same time. This can create an uneven distribution of the materials and result in burns and patches on your lawn. Although it ensures the availability of vital nutrients to jumpstart seed growth, there is no need to take that shortcut.

Instead, fertilize the area with starter fertilizer at a depth of 4 to 6 inches to allow Pottasium and Phosphorus to move fast enough in the soil. Unlike Nitrogen, the two elements do not get in the soil adequately when the starter fertilizer is applied at the soil surface. Nitrogen can disappear without impacting the grass seeds when tilled at those depths.

After fertilizing, you can spread between 2 and 8 pounds of grass seeds per 1000sq ft. In other words, apply starter fertilizer before or at the planting time. Four or six weeks after the grass has germinated, apply regular fertilizer that is predominantly Nitrogen.

Two pounds of Nitrogen fertilizer will ensure dark green, healthy, and attractive grass. Whether using cold season or warm season grass seeds, you will need around 4 or 6 pounds of fertilizer per year.

How to apply grass seed and fertilizer

According to Penn State Extension, spreading grass and fertilizer requires careful planning. You should consider factors such as the type of grass seed, planting season, and the available tools for doing the work. For example, you may need an aerator to loosen compact soil, a seed spreader, and a lawn roller.

Instead of a specific grass seed, you can use a standard mixture of perennial ryegrass and Kentucky bluegrass for durability in high-traffic lawns. The best month to plant cool-season grass like Fescue is September or mid-August. On the other hand, plant warm-season grasses like Bermuda grass in late spring to summer.

But how do you apply grass seed and fertilizer?

For the best outcome, follow these steps.

1. Test the soil

Soil testing is essential to estimate your soil’s pH and nutrient content. Without the test, you may destabilize your lawn and get patchy and burned areas on the lawn. Since it takes up to four weeks for the soil test results to come out, you should take the soil sample early to avoid missing the recommended planting times. 

2. Determine the seeding area

You must not just go for the fertilizer and grass seed without knowing the total area you should plant it. Although aerial google maps of your property can help you estimate the area to be seeded, physical measurements can also work. Divide your lawn into regular shapes with lengths and widths and do the calculation.

Without this knowledge, you may end up applying too much or too little seeds and fertilizer on the lawn. That may encourage patches and burns of the grass.

3. Till the area or loosen compact soil

You may want to apply grass seed and fertilizer to a new lawn or renovate worn-out ones. You cannot just spread them on an unworked area. There is a need to loosen the soil by tilling or loosening compact areas using an aerator. Tilling exposes weeds to the surface and makes it easier to remove them while aerating will promote deep roots and healthy green grass.

4. Add fertilizer

Not only should you use granule fertilizer, but it should also be a slow-release fertilizer.  Lawn professionals suggest that granular fertilizers are easier to apply than spray fertilizers. Similarly, slow-release fertilizers allow you longer periods between applications. That is, between six to eight weeks.

That is about 4 or 5 applications yearly. Generally, the best starter fertilizer should contain nitrogen and phosphorus and be highly water-soluble. Spread two kilograms of fertilizer for every 100 square meters of lawn. The third or fourth application can be organic materials like manure.

5. Apply grass seed

As we have already seen, you need between 2 and eight pounds of grass seed for every 1000 square feet of lawn. Adjust your spreader accordingly, so you do not put more or less than the recommended amount. Most importantly. Look at the grass seed label to adjust the spreader or apply the seeds.

I recommend using a broadcast spreader instead of a drop spreader. You can hire or buy one from a grass seed store near you. Not only are they affordable, but they also disperse fertilizers and seeds at a wider distance, reducing the chances of grass stripes and overlaps. Spread the seeds along the perimeter first before working in the middle.

6. Roll and water the lawn

If it is a new lawn, a roller eliminates low spots and the soil clods that were removed during aeration. Furthermore, the lawn roller will help keep the seeds in contact with the soil and speed up germination. Most importantly, water the grass seeds and seedlings 3 to 4 inches per week.

If there are no rains, you will have to water up to 4 times a day. Mulching can help keep moisture, warmth and provide organic nutrients to encourage seed germination. It will take between five and ten days for the grass to grow, and the fertilizers will ensure a growth rate of about ⅔ cm every week.

Best fertilizer for grass seed

The best fertilizer for grass seed must be high in phosphorus and nitrogen. If you need something that will improve seeding results, then you should use the Scotts 21814 Turf Builder Starter Food for New Grass. It has an N-P-K ratio of 24-25-4, indicating significant amounts of Nitrogen and phosphorus.

Therefore, it gives your seeds a 35% quicker growth and up to 70% grass thickness. The fertilizer is available in different sizes and can cover between 1000 and 14000 square feet. Most importantly, you can use the Scotts 21814 Turf Builder Starter Food on all grass types.