The basic concept is that there are four things you have to get right if you're going to use fertilizer well. First, you have to pick the right source of fertilizer, and that may be manure if it's available, or you have to make a decision whether you're going to use ammonia, or ammonium nitrate, or ammonium sulphate for your nitrogen source, and the kind of sulphur you need, etc.
You have to decide what nutrients are in the soil, and how much of the nutrients the crop will use. You have to determine the absolute amount of fertilizer that you need to apply to provide a good diet for the plants and crops that you're growing. Then you have to put the fertilizer in the right place. Often, that means putting it under the soil, so it's not exposed to the elements, and is in proximity to the seed where the roots can use the fertilizer efficiently, and there's less chance of it being lost to the environment.
Finally, it's the timing. For example, it used to be a practice, and it still is in some places, to apply manure in the winter, or fertilizer in the winter. You run a great risk if you're applying nutrients on frozen soil that in the spring it will simply run off. In other areas, timing may relate to when you have heavy rains, and you don't want to be applying your fertilizer right before heavy rains, as again that's a loss. Some farmers split-apply their fertilizer. They put on a certain amount in the spring, but then they go in the middle of the year when the plant is growing vigorously and needs a boost, and give it additional fertilizer.
It's looking at all those things together, those four areas—the source, rate, time, and place—that give you a better chance at getting your fertilizer to be more efficient in the crops you're growing.
A big part of the program is also to not just look at the economics of your farm, but also to look at the environmental issues where you are. In Prince Edward Island, the issue is that nitrates have been getting into the groundwater from a number of different sources, so a lot of the focus there, and using the 4Rs, is to reduce losses of nitrates to the aquifer system.
In western Canada, a lot of the focus has been on greenhouse gas, nitrous oxide being lost to the air because of the different growing conditions. In the Great Lakes region, people are very worried about phosphorus getting into Lake Erie, so a lot of the effort is on using the 4Rs to reduce phosphorus losses.
Finally, then, society itself has issues like being able to grow sufficient food for the population, but also more local things like reducing conflict between farmers and city people. If we, as a group in agriculture, are able to demonstrate we're being responsible in our fertilizer use, perhaps we'll have a better relationship with people who live in towns and cities.
It's those three areas of sustainability—economic, environmental, and social—that are embedded in the whole planning process. It's really about making wiser decisions when you're using fertilizer, manure, or other sources of nutrients.