Question
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I was present when the contractor installed the drainfield and is plenty deep. We have not recieve much rain for about a month, but have been watering. I didn't know if the starter fertilizer used during seeding was enough to carry my new lawn into the summer months. The new grass everywhere except over the old trench for my new drainfield is doing very well. So, you think there is no need to apply anymore fertilizers till fall? The starter fertilizer was spread early in March. Thanks again for your advice!
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Followup To
Question -
In February I had to install a new drainfield in my backyard. This spring I reseeded with starter fertilizer and my yard is coming back to life. However, where the contractor cut trenches to lay new drainpipes, the new grass is starting to turn yellowish compared to the rest of the yard. Any suggestions? Also, is it too late to apply a fertilizer before summer and should I. I live in the eastern part of Maryland. Thanks in advance!
Answer -
One application of fertilizer in early spring is more than enough. Most of the fertilizer should be applied in fall.

I recommend that you fertilize in late spring, early fall and late fall. The late spring timing should be after first flush growth, e.g. in May. if you fertilized earlier than do not repeat in May.

The 2nd application should be in early september after the heat of summer disapates. last application of the year should be in late fall, after the grass has stopped growing. if you mow weekly in late fall, then wait until you have not had to mow two weeks in a row (due to grass has stopped growing) and then fertilize. usually this happens after first frost; typically between halloween and thanksgiving. as long as the grass is green and not been exposed to a really deep freeze, the green leaves will conduct photosynthesis and this time (with no top growth) is the optimal time to fertilize.

The yellowing may be due to one of two reasons:
new grass need more water than a mature lawn. I recommend watering at least once weekly (water deeply).

another reason could be that the drainage pipes are placed too shallowly. if you do not cover with atleast 8-10" of soil, the grass may yellow due to lack of water. the drainage is simply too good and it pulls needed moisture away from the grass roots.

I would test with a screw driver/spike how deep the drainage pipes have been placed. if necerssary contact the contractor for him to redo the pipe system and lowering it.

Finally, newly planted grass has less capacity to store fertilizer nutrients. therefore it is not uncommon for newly planted grass to turn yellow if given too little fertilizer. typically it turns light green and then yellow. However, it can also be due to watering as explained above, and if it is, adding more fertilizer will just kill the lawn.

I would check moisture of the soil under the turf and the dept of the drainage pipes. if soil moisture is present and drainage pipe placed deep enough then try a light application of fertilizer. water in immediately.

If the soil is rather dry or the soil profile on top of the pipes is too shallow, then I would not fertilize, but contact the installer.

Answer
If the soil is not dry, then apply an application of fertilizer now. then repeat same in fall.

when you water, make sure you water deeply and infrequently rather than frequently and shallowly. e.g. it is better to water once per week for 2 hours than 15 minutes daily. during this first year of establishment it is ok to water twice per week, but still make it deeply.

It is probably a lack of fertilizer which is giving you the problems.