The mulch isn't the problem but already planted seedlings are.

Are your seedlings planted in rows or scatter-sown? When row planted you would just rake the mulch back from the plants and then do what is called side-dressing of the row in a 4" deep trench about 3-4" out from the row of seedlings. Cover with soil and then rake the mulch back into place. If scatter sown that is impossible so all you can do is dig some pockets for it in among them - depends on the plant spacing. Using one of the many liquid forms of N would work better in that case.

If you dilute it in water it needs to be well diluted and you still need to keep it from direct contact with the plants. And keep in mind that tested N levels all depends on the soil temp. The cooler the soil the lower in N it tests so as the soil warms the soil nitrogen levels will rise too. Don't over do it. Better to add frequently in small amounts at a time rather than over lead it.

Dave

You can just put sodium nitrate on the soil surface and water it it. It contains no form of nitrate that can volatilize or evaporate. Sodium nitrate is not a very good source of nitrogen because it adds unwanted sodium. You're better off using calcium nitrate or ammonium sulfate.

I agree about sprinkling it on the soil surface. That makes the application more gradual than liquid feed. Mixing granules with water and doing a liquid feed could end up hitting the roots with too much nitrate all at once.

Sodium nitrate dissolved in water doesn't liberate ammonia gas. So the nitrogen stays in your soil as NO3- ion.

What is the evidence that your soil is low in nitrogen? Wood chips in compost is not indicative of that. If the wood chips didn't compost, they didn't necessarily use up the nitrogen in the compost.

Thanks for the info, I have a test kit and did the test many times and every time it indicated depleted levels of nitrogen (what is weird is I kept a small amount of the dry compost in a bag in my home when I got it and when I tested that it had a surplus of nitrogen? but the same compost in my garden always indicates depleted)

Also last year I got my compost from the same place and used it somewhere else in my garden and I had a Surplus of nitrogen according to the test and all my plants where dark green but this year there was more wood chips in the compost and i'm assuming that is why it is depleted of nitrogen.

If you are using one of the common home test kits then they are notoriously inaccurate, especially when it comes to N and pH readings. A common recommendation is to never make any big corrections based on their results. Far too often it only makes things even worse, not better. For a few dollars more you can contact your local county ag extension office and get a professional test done.

Dave