Beneficial? Well it can't hurt but it won't make much difference. Better to spend the money on lots and lots of quality compost and composted manure.

A mistake? Yes, unfortunately it was. No more than 50% of the bed should be top soil is the standard recommendation so now you have to correct the mistake and spend more money to do that. Pull up all the discussions here about how to build/fill raised beds - there are many of them - for all the details.

Dave

Top Soil in this country formed under thousands of years of grasslands dying every winter, and the dying material and root growth breaking down into rich humus. Or in the case of wooded uplands, fallen trees and leaves breaking down into organic matter.

Without knowing specifics or fertilizer types used, I would say that you are starting to deplete your soil fertility. Fruit intensive crops will, through the course of producing, use Nitrogen, Phosphorous, and Potassium in order to produce high yields. They will also use micro nutrients, that is other minerals needed in much smaller ammounts, like iron, copper, manganese, cobalt, moly, and a couple of others. When you grow vegetables, which humans have bred to produce far more fruit per plant than nature ever intended, they will need more nutrients in the soil to produce them.

Most of the nutrients that plants require can be found in other plants, so taking weeds and composting them would be beneficial. Animal manure like horse or cattle is even better, as they eat plant material and only absorb a fraction of what they ingest, making their manure prized garden gold for use in vegetable gardens. Be sure to hold off on adding fresh manure onto growing plants, the N content in fresh manure will be too high for most plants to tolerate. Animals are essentially giant nutrient factories for plants.

In gardening, you also have to note your pH levels. pH is a function of the concentration of positively charged hydrogen in your soil. Most micro nutrients have a negative charge, so when the pH is high, when there are a lot of positively charged hydrogen ions in your soil, nutrients like iron (which are negatively charged) will bond with the hydrogen and become unavailable to your plants. The best pH range for plants is in the neighborhood of pH 6.2-6.5. At that pH plant growth is fastest, and nutrient uptake is maximized.

With that kind of background I can assume two things, just shooting in the dark: Your soils probably need to be fertilized, and your pH might need to be lowered. Top Soil from most midwestern states formed under limestone, and they tend to be slightly alkaline, a higher pH. Top Soil from out east, especially in the south is more acidic. There's no way to know what you've got unless you test it. Your local county Farm Service Agency or county Natural Resources Conservation Service will have a list of places that offer soil testing for very modest fees. I recommend against do it yourself kits, as they require you to add a special dye to a soil/water suspension, and have you judge the shade of the color of the suspension against a color chart - very subjective.

I have no way of knowing what your issue is, because I don't know the particulars of your situation. Organic sources of fertilizer work slowly, and require microbial activity to release nutrients. Inorganic sources of fertilizer work quickly and efficiently, and they can lower a soil's pH over time.

It's hard to know the correct advice to give to you without knowing what you like to grow and if you have fertilized. Itzy is correct in her assertion that compost is always a good thing to add to soils. I could go into another paragraph about organic matter, but I won't.

~Chris

Dave

Some people with clay sometimes raise a garden, no boards or other tricks, just raise it, to get better drainage.
I have done this in a small area for a few things but do not treat it any differently than I do the hundreds of square feet at ground level.

Then in the spring, adding a fair ammount of the fertilizer to the beds. If your pH is right, you'll only have to fertilize at the beginning of the year, and the soils should retain the nutrients well into August.

If you add a lot of organic matter to the soil in the spring it will start to break down in the soil, and the soil bacteria that break it down will tie up some N while they break it down, you might have to add some more Nitrogen during the growing season. Adding organic matter in the fall and letting the soil microbes work on it through the winter should give it plenty of time to avoid Nitrogen tie up next year.

As for how much to add, it's a judgement call. A little bit of granular goes a long way, and eyeballing it should be sufficient for what you want. Just spread a moderate ammount, or if you are that worried, measure out the weight according to what your soil test says to add. For Potassium and Phosphorous, if you add a little too much of it, that's ok, as any extra P and K that isn't used by your plants will stay in the soil until next year. Any extra N will be eaten by Nitrobacter by the time next spring rolls around, so you won't get any carryover.

If you do add organic matter to the soil this fall, it would help to add *some* nitrogen to the soils to help in the breakdown process, because the bacteria that break down organic matter require N to do the job. The neat thing is that they release the N that they use back into the soil when they are done breaking down the organic matter.