Bagged manures and composts are not always 100% fully composted or broken down. Many bagged products contain manures and compost that are still actively being broken down by soil microbes. This is important because we tend to assume these products are ready to be used in our garden beds and therefore we can immediately put plants into the freshly manured and amended beds.
Company's are allowed to label just about anything as manure, compost or compost and manure. They are not regulated for quantity of the said product being put in the bags. Nor are they regulated on how far along the products need to be in the natural process of composting or breaking down into the water soluble or usable forms of nitrogen, phosphorous or potassium that we want for our plants. To keep it simple, many of the bagged products need a lot more time to breakdown into what we call 100% composted or broken down materials.
If you put bagged manures on the top surface of your raised beds and work it in several inches, you may feel you have a great planting bed. When your tomato plants (for instance) get planted, you find they don't thrive and flourish. They stay small, look yellow or purple. They seem to be sickly looking and just sit there for weeks. The reason is that your bagged composts and manures are still breaking down.
The microbes that digest organic matter are competing for the nitrogen in the garden bed, against your plants. The nitrogen is being used in the process of 'further composting' the manures and organic matter you added into the bed. Eventually the microbes will break these amendments down and turn them into usable forms of N, P and K for your plants. However, you end up losing weeks and months of potential garden production. Basically, composting is happening in the top inches of your garden soil instead of finishing out in a compost bin.
The answer to dealing with this potential problem is explained in the video. The bottom line is to be aware of the products you add to the garden and know how well they are broken down. It is best to use these products and amend your garden beds 3-5 months before you plant. This way they are fully broken down and available to your spring plants. Most of the time we do the amending in late fall or early winter.
I also go over, in the video, how to fill a raised bed in 4 alternating layers of manure/compost and soil. This basic set up gets your beds off to a great start and you really will never have a need to turn the soil again. Year after year, you add manures, compost and mulches to the to 1 or 2 inches of the raised bed and let worms and Nature breakdown the material and pull the nutrients into your beds for your plants.