The organic gardener's mantra is: feed the soil, the soil will feed your plants.
If you continually replenish soil humus by adding compost (or another source of humus such as well-rotted manure), and if you choose plants that are well suited to your soil type, climate, and your growing conditions, you will have fewer problems in the garden.
What is humus exactly?
Quite simply, it's the stuff that makes soil come alive. Basically, it consists of the decayed remains of once living materials, most commonly plant residues and animal manures.
You can make humus in your backyard by composting plant remains, kitchen scraps and fall leaves, or you can buy composted manure or compost at garden centres.