Whether a fertilizer is organic meaning from animal waste or whether it is chemically synthesized either through concentration of the animal wast or from other sources there are only 3 main components that you need to understand.
The Three main components of Fertilizer are Nitrogen, Phosphate and Potassium.
Each of the three components have their place and depending on how you are using the product you will want to get different levels of each component in your mix.
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Nitrogen is normally thought of as the food the plant eats and for that reason if you were to use it on vegetables or lawns you will see a darkening of the plant and it will grow faster. Lawns will turn darker green and will grow faster. Tomatoes can be effected negatively by too much nitrogen in their early stages by causing stem growth instead of fruit growth but if the plant is hungry and weak it will help.
Most people stop right there and think that a product is good if their grass turns dark green or if their tomato plants grow a foot in a week. However that is not the only thing you need to worry about especially in your vegetable garden.
The last two components Phosphate and Potassium are necessary for Vegetable and Flowers but also lawns. They help the plant fight off disease and they promote root growth.
If a plant has good roots it will do better in the hot sun. It will be able to survive through the winter in the case of Trees, fruit plants and bushes and it will produce better yields of food in the end.
If you look at a container of Vegetable Fertilizer you are likely to see all three components listed.
The first number is the amount of nitrogen (N),
the second number is the amount of phosphate (P2O5)
and the third number is the amount of potash (Potassium) (K2O).
If you look at lawn food you will normally see the first and sometimes the third but often not the second.
For example General Purpose Garden Fertilizer is normally a mix containing 10-10-10.
An organic manure fertilizer will often be much weaker and rated 5-2-0 which is really weak fertilizer.
A strong commercial Lawn Fertilizer is 30-0-4
in my vegetable garden I use a weak 10-10-10 general purpose
however if you are growing
roses 18-24-16
or tomatoes 18-18-21
When selecting Fertilizers for my yard I tend to use a Weed and Feed Fertilizer for my lawn it kills the weeds while helping the grass and I don’t have to do the lawn twice
However if you have crabgrass the only way to get rid of it is very very very early in spring use crabgrass preventer.
It stops the growth of all seed in your lawn and crabgrass is first to seed because it dies every year.
but that means you can’t plant regular grass for 3 months if you use crabgrass preventer.
It is also important that you do not over fertilize your plants and lawn or you could cause delayed fruit growth or burn their roots.
Most products have directions. Read and Understand them before you apply the product.
Final Note
So, now you better understand the chemical mixtures in your fertilizer bag. All three components are necessary for all growing plants however if you are treating the lawn in the early spring you want to include a Weed Preventer.
If you are treating a garden at the beginning of the season a good amount of 10-10-10 will prepare the soil and then later on when your tomatoes begin to grow over about 3 feet tall and get flowers you can start to help them grow better fruit by using a fertilizer that you dissolve in water that has much stronger components.
If your lawn had a hard time last winter or barely survived the hot summer and you want to give it a month or two of growth to prepare it for winter then you can use a commercial grade fertilizer that has a higher nitrogen and potassium.
If you want to prepare the roots of your plant for the hot summer use more phosphate and it will help the roots grow and reduce the effects of drought.