WHEREVER PLANTS ARE GROWN, soil nutrients are disappearing. As farmers know, continually removing nutrients results in declining harvests. In nature, vegetation returns to the ground along with the droppings of animals that have eaten the plants. By leaving grass clippings on the lawn and using fallen leaves as mulch, you mimic nature's recycling patterns. The same is true if you compost garden wastes. Since I want a healthy, beautiful garden, I try to replace what I remove, and perhaps add extra to beef up soil that wasn't ideal to begin with. The three chief nutrients are N, P and K: nitrogen, phosphorus and potassium. In a nutshell, N promotes growth and greenery, P encourages a plant's life cycle, and K promotes strength and disease resistance. Any commercial fertilizer should have the ingredients on the label, including the percentages of those three main nutrients. Since I don't know exactly what nutrients I've removed from my garden, I have to approximate what to apply, staying conservative to prevent soil and plant damage. I've also done soil tests in the past. These provide an overview of your soil's general condition. Nitrogen has dramatic results; you'll soon know if you use too much. When a commercial company took care of our lawn (something my better half insisted upon), they overdid the nitrogen and burned the grass under one of my tree lilacs. The grass browned and the lilac shot up. It was soon twice as big as its companions down the row, a mass of vertical branches. It also stopped blooming for three years, until the excess nitrogen was finally assimilated into the soil. Now that it's been heavily pruned, it more or less resembles its comrades again. If you have good, well rotted compost, it can gently fertilize while helping condition the soil. Well rotted manure is similar, but is apt to contain a higher percentage of nitrogen, so you need to take more care with it. Purchased compost and manure list the analysis on the label, but if you're mixing the components yourself and using material from a local farm, it's guesswork. Watch for signs of overfertilizing, especially lush, weak growth. Symptoms of underfertilizing are smallish plants, fruits and vegetables, and often blotchy, discoloured or misshapen foliage. During the growing season, you can topdress by spreading compost or rotted manure between plants, to be soaked in with irrigation or rain. Green manures - crops such as alfalfa, clover or rye grass plowed into the soil - can dramatically increase tilth while adding nutrients as efficiently as animal manure. If you garden organically, there are other soil additives such as blood meal, chiefly supplying nitrogen, and bone meal, chiefly phosphates. Among the potassium alternatives are alfalfa meal and kelp meal. Since I'm a gardener, not a farmer, I can afford to have a fertilizing regime that is more art than science. If my tomatoes are undersized or my grass isn't bright green, it won't affect my livelihood. Thus, I combine mostly organic fertilizers with some chemical boosters when they're needed, mainly on the tomatoes. What I keep in mind is that too much fertilizer, or the wrong fertilizer, can do serious damage to plants, soil and the environment. We can all be extravagant when it comes to colour and design in our gardens, but it's wise to be cautious with fertilizers. - JENNIFER BENNETT Jennifer Bennett welcomes feedback at jenben@istar.ca or via acreagelife.editors@producer.com.