More clarification: in 2005 we planted two rows of raspberries (20 ft across, Prelude and August Red) in the middle of our 150 foot long garden in full sun. So it was our garden soil. We put in rotted manure and such as recommended by the place we bought them (Fedco in Maine), and mulched with sawdust. We top dressed them two years later. They did marvelously for three years, then one row started declining. No signs of disease but in the spring just fewer and fewer plants. In 2011 the first row was down to about 10% so we took it out this year. In 2011 the 2nd row started declining and it down to maybe 30% this year so it will be taken out next year. I can't quite imagine that the PH would change dramatically, would it? They did great for three years. If the mulch gets worked in and it gets weedy, would that make a difference? In the woods, raspberries grow with grass and such around them. The canes that are out there are bearing very well, but there are not that many... We live in western NYS where there is a good bit of rain. If it doesn't rain for a long period, we have soaker hoses laying around them that we can use. The confusing part is that the canes that are there bear well, we still get good berries, but just not many. We cannot see signs of disease on them. I have a call in to the Cornell Cooperative Extension that I trust will be returned...