Most seasoned gardeners understand that early spring is probably the best time to get beds ready for the growing season ahead. The annual crops we grow need plenty of soil nutrients to produce in the short months of summer. They take a lot out of the soil in order to put on that fast growth. In many cases the soil then waits out winter with rain and snow melt washing even more nutrients away. So this window of time, after the snow has melted, but before the last frost date, is a good time to make some adjustments.
It's early March here on the coast and already our garden beds are dotted with weeds. Henbit and Western Bittercress germinate super early, or emerge from rhizomes missed in last season's weeding. Already, dandelions are in bloom and buttercup is emerging. Even if there is still snow on the ground where you live, expect the first wave of spring weeds to arrive early, bloom early, and begin to spread their seeds.
We keep a separate, dedicated composter for weeds pulled from the garden in order to minimize their seeds (and root segments!) getting spread accidentally. Composted weeds, or even freshly dug ones in most cases, make good organic matter when the planting is going to be deep. They're good for the bottom of the hole where transplanted trees and perennials are going to go, and they're great at holding moisture in xeriscaping schemes.
Generally speaking, most garden beds benefit from a mulch of organic matter in the form of well rotted manure or compost. A mulch is a thin layer that is applied to the surface of the soil and it serves several purposes. First and foremost, it will benefit the earthworms, invertebrates, fungi, and bacteria that live in organically cultivated soil. All those organisms break nutrients in the mulch down into forms that are accessible to plants.
Mulch also serves as a blanket, helping to conserve moisture in the soil. It tends to be very dark in colour, so a good heat sink for sunny spring days. This is particularly true in raised beds, which are already warmer for being above the ground, and for their improved drainage.
For perennial plants like ornamental shrubs and grasses, fruit trees, and so on, a simple mulch of organic matter around the base of the stem or trunk will give them a boost of nutrition for spring growing. Avoid piling mulch up against the stems themselves.
When planting perennials that are going to stay in their permanent spots for a long time (asparagus comes to mind), bed preparation is very important. Dig in loads of organic matter, straw, tree leaves, and manure deeply into the soil before transplanting. This would also be a good plan for the heaviest feeding annuals like the giant pumpkins.
In my small demo and food garden, I have nine raised beds that are four by eight feet each. Over time the soil level goes down due to compaction, decomposition, and from harvesting, so I like to add two to four bags of soil to each bed to top them up. After raking the soil approximately flat, I like to add a mulch of organic matter, and I usually alternate between Original Sea Soil or bagged mushroom manure. Two bags for each bed seems to be a good formula.
Minerals
Adding all that organic matter is good for the soil biology, and overall good for the garden. But plants also require minerals and micronutrients to grow well. One of the best ways to top up minerals in soil is to add Glacial Rock Dust. This product reintroduces a very wide range of minerals into the soil, and it makes a good companion product when adding organic matter. It cannot be over-applied, but for each 4 x 8' raised bed, I add a minimum of about four cups, or one pound. This is one product that I rake lightly into soil the simply because it is so dusty, so that it doesn't blow away.
Cover Crops
Some beds can be planted with seeds that shrug off cold weather. Early crops like peas, radish, spinach, and mustards can be direct sown even before the last average frost date. But other beds might be reserved for peppers, tomatoes, or melons, so rather than leave them empty until transplant time in early summer, it's good practice to plant a fast growing-cover crop like buckwheat or crimson clover. Allow these plants to grow to the preferred size, and then dig them over and turn them into the soil. Buckwheat is a personal favourite because it is so easy, and it breaks down so quickly. The soil becomes very dark and aromatic as a cover crop breaks down.
These pre-season rituals are utterly worth the time and expense, and will produce results you can see. Crops will be healthier, with less competition from weeds, and with richer soil to produce in.