Are you irrigating the sod? If so, how often and for how long?

You're either watering too much or your water table is rising. You should only be watering enough to moisten (not saturate) the sod. Usually this takes three short waterings per day. We often talk about doing it 3x for 10 minutes each time but some sprinkler systems can put out a full 1/2 inch in 10 minutes. That is far too much moisture for starting new sod or seed. Mine takes 4 hours to put out 1/2 inch. You'll have to measure yours with a cat food or tuna can to see how fast it is putting out 1 inch.

When your grass knits to the underlying soil, then you can back off on watering. You can tell when the grass is knit in by trying to lift the sod. If it does not lift up, it is ready to back off on watering. When I say back off, you should be watering something like once per month this time of year. One inch, once a month, all at one time, is all you need. This practice will develop a deep root structure and help to prevent weeds. Weeds love a wet surface. If the soil gets dry and hard before a month is up, pay no attention to that. It is only the grass that is important. If the grass starts to look dry before a month is up, then water it again. The worst thing you can do is divide the one inch up by 30 and water it every day for just a minute or two. It is far better to water deeply and infrequently.

You do not need to fertilize in March or April. If you do you will have grass exploding out of the ground. It will mean you have to mow 2-3 times per week to keep up with it. Spring time grass growth is amazing whether you fertilize or not. If you fertilize in early spring you are wasting your money. Wait until after the big flush of growth stops and then fertilize. Memorial Day is a good rule of thumb for most people in the north.

If you want to fertilize with organic fertilizer, you can do that in late winter. The organic works differently and usually will not increase the growth that much. I would suggest something simple like alfalfa pellets (rabbit chow) at a rate of 20 pounds per 1,000 square feet. I fertilize my lawn with organics about 3 weeks prior to our normal last frost date. The lawn is not yet growing but by the time the organics go to work, the grass is usually just starting up.

Why use natural fertilizers instead of synthetic lawn fertilizers? Because they are better for your grass, the environment, and they are proven to work better than synthetics!Cut your grass correctly and to the recommended cutting height.