Fertilizer is the greatest thing that ever happened to your lawn, and one of the simplest and cleanest yard chores you can do. Anyone can agree with that statement in general -- it's when fertilizing gets specific that homeowners feel uncertain, even fearful they will actually harm their turf. The answers to the questions below give you enough specific information to fertilize with confidence, then sit back and enjoy the results.

Complete fertilizers contain three essential nutrients: Nitrogen (N), Phosphorous (P) and Potassium (K). The number on the bag of fertilizer indicates the percentage of each of these vital plant nutrients contained in the bag. For example, turf food (20-5-10) contains by weight, 20 per cent nitrogen, 5 per cent phosphorous and 10 per cent potassium. The remaining percentage is a carrier that is necessary for distribution and small quantities of micro and macro nutrients. Many high quality lawn and garden fertilizers found in Landscape Ontario member garden centres will contain slow release properties for non-burning and long lasting results.

Q. How much fertilizer does my lawn need?

A. Turf grass fertilizers usually contain nitrogen, phosphorous and potassium in ratios close to 4-1-2 (such as 20-5-10 or 21-6-12). There are many brands available but are all quite similar in this regard.

Your lawn needs a one-half kilogram of nitrogen for 100 square metres with each application. Check the manufacturer's recommendations on the bag for the actual coverage. Fertilizers are applied generally in early spring, late spring, summer and fall for a total of 2 kg. of nitrogen per 100 square metres in the growing season.

Q. How many bags of fertilizer will be needed?

A. The numbers on the bag are percentages, so a bag of 20-5-10 contains 20 per cent nitrogen. An 18 kg. bag will therefore contain 3.6 kilograms of nitrogen (18 divided by five). In applying half a kilo per 100 square meters this 18 kg. bag will be sufficient to cover 720 square metres. Note: Most manufacturers provides the coverage information on the packaging. Use this information as concentrations of micro and macro nutrients can vary substantially.

Q. Do I water after applying fertilizer?

A. Yes, dry granular fertilizers can be watered in to begin to dissolve them and take nutrients down to the roots. If Mother Nature helps, with rain, that makes it even easier. However, it is not essential for this to be done immediately after application.

Q. Is that the same with Weed and Feed?

A. No. The active ingredient that kills the weed has to stick to the foliage. Generally Weed and Feed fertilizers are applied when the grass is dry, and when it is expected to be dry for a little while. It is important to note that most Weed and Feed fertilizers should not be applied when the temperature is above 24 degrees Celsius. Read the instructions on the label for the best technique.

Q. How do I store fertilizers? Will they keep?

A. Unused fertilizers will not lose their effectiveness; but keep them in a cool dry place such as on a shelf or at least off the floor in the garage. Close any open bags. Moisture will do no actual harm but will make the product difficult to spread properly.

Q. How do I apply lawn fertilizer?

A. While there are many ways to spread fertilizers, a cyclone type broadcast spreader will offer some of the most even distribution.

Q. Can I burn the grass if I use too much?

A. Yes you can. Most lawn fertilizers are very safe, with a proportion of their nitrogen in a slow-release form. Nevertheless, too much in one spot can burn the grass. It is a good practice to calculate the amount of fertilizer needed and apply only half that amount walking with the spreader in one direction and then apply the remaining half at right angles across the lawn (see illustration below).

Q. How much fertilizer do I apply to flower and vegetable beds?

A. A typical formulation for flowers and vegetables is 4-12-8 or similar. One kilogram of such a balanced formula per 10 square metres, should be worked into the soil at planting time.

Q. Should I fertilize again through the summer?

A. Yes. Another application of one kilogram per 10 square metres of a balanced fertilizer should be applied close to each plant as a side dressing. Do this four to six weeks after planting and, in the case of tomatoes, after the first flower cluster has set fruit.