Making healthy plant food choices
Gardeners are very concerned with the elements they use to produce healthy lawns and garden crops. Continuing research has brought many new plant nutrition products into garden and nursery centres. These products usually serve one of two purposes: to improve soil quality (its ability to accept, store and recycle nutrients and water) or soil fertility.
Using what we've learned
Plants, like people, need nutrients to support life. Our needs for vitamins, proteins and carbohydrates can be compared to a plant's needs for:
- Nitrogen, which encourages green plant growth
- Phosphorus, which helps plants produce strong roots
- Potassium, which increases overall plant strength, disease resistance and hardiness.
- Other minor nutrients (like iron, magnesium, manganese, zinc and copper) which are important for balanced plant growth.
Today's choices
A century ago, we didn't understand the intricacies of the relationship between soil and plant growth. We couldn't test soil to determine its nutrient content, and the products available to maintain soil quality and fertility were limited. In the 1890s, Ontario farmers and gardeners were using crushed gypsum, bone dust, slaughterhouse waste and salt to treat their soils, but with no understanding of how or why those products would work. Through scientific discoveries made over the last century, we can now accurately predict the nutrient levels that plants need in order to maintain healthy growth, and through soil tests, we can determine the fertility levels of our soils.
Manure improves soil texture and organic matter, and organic matter is the 'stamina' of the soil, improving its ability to hold nutrients and water. Manure is often low (as a percentage of weight) in the essential nutrients that plants need. Composted manure (which has been cured in rows and reached an internal temperature of 60o Celsius to kill harmful organisms and weed seeds) is also an excellent soil conditioner.
Compost recycles organic matter from your kitchen and garden back into the soil. Using compost will improve the quality of your soil, but its plant nutrient content is limited, usually containing one per cent each of nitrogen, phosphorous and potash as a percentage of its weight.
Fertilizers are applied to improve a soil's fertility, and to ensure that the proper nutrients are available in the amounts necessary for the plants you are growing.
Organic fertilizers are available from many lawn and garden centres. The available plant nutrients in these formulations (again, as a percentage of product weight) is lower than in conventional fertilizer, and may be not be enough to support plants with high nutrient needs, such as corn and other garden vegetables. It takes longer for the soil microbes to break organic fertilizers down in a form usable for plants, and the microbes only become active at temperatures above 16o Celsius. It may take more than one growing season for plants to access the nutrients in an organic fertilizer.
Manufactured fertilizers are also made from very down-to-earth sources. The nitrogen in most commercial fertilizers sold in Canada is extracted from the atmosphere. The manufacturing process traps it in a form that we can apply. Beneficial soil bacteria make it available to plants and through the plants, the nitrogen is returned to the ecosystem.
The two other ingredients in fertilizer are phosphorus and potash. The phosphorus, the fossilized remains of ancient marine life, is mined in Florida and North Carolina, and the potash (which provides potassium) is mined from naturally-occurring mineral deposits in Saskatchewan and New Brunswick. These natural elements are processed in a form that makes the nutrients accessible and available to growing plants.
Many lawn fertilizers also offer the advantage of slow-release nitrogen, and the best granular lawn fertilizers have the highest percentages of nitrogen in a slow-release form. These formulations allow consistent nutrient release over a period of six weeks without risk of burning the plant.
No one source of fertilizer is no more "natural" than other, nor is it of any different value to the plant. An effective fertilizer will provide the essential plant nutrients of nitrogen, phosphorus and potassium, in a form that is easily available to the plant, and in the optimal proportion.
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