I would say more effective than wood chips. No need for an N underneath. Wood chips probably really don't need any as long as they aren't mixed in the soil, breaking down mixed in the soil is where it eats up the N. There is quite a mixture of leaves including Oak and Walnut, but they are mixed in and don't believe they are that many in one spot to cause any problems. I haven't noticed any in mine anyway.
I can't help but think being they are from the previous year and starting to break down, they act as a weak compost tea every time it rains. I have made compost tea and added to certain plants to see if it made a difference, and it definitely does. So I just let Mother Nature do it for me. Unlike wood chips they are pretty well broken down into fine compost the following Spring and plow down nicely to add organic matter to the soil.
I put them down probably close to 6" deep and you may get an occasional weed pop up through but usually an old Bull Pea vine, that's about it.