Other trees effecting sap production?

[Jerome]

I have one tree along my driveway that use to produce twice as much sap and a higher (by taste) sugar content. Years ago we planted a black walnut about 30 feet away an arborist told me that it would effect the maple. For the last couple of years I have noticed that this tree is not a very good producer anymore, is it the walnut or just a cycle trees go through.
Thanks

[Marcus]

Years ago my wife's grandfather planted walnut and sugar maple trees alternating everyone. I am know tapping those trees. Last year i only tapped a couple and they produce great. This year i did not think they did as well.
Marcus Yoder

[Loch Muller]

Walnut is known to be alleopathic, which may be part of why your maple doesn't run like it used to. I've got a similar tree that used to run great but mine has been out grown by a Norway spruce just south of it so the maple is in the shade now. There's an easy fix for that, just haven't got to it yet.