There are many different types of fertilizer and it is important to know the difference between them. Key nutrients are Nitrogen (N), Phosphorus (P), and potassium (K). You will need to test your soil with a kit to determine the existing levels present in order to select an appropriate fertilizer. If your soil has equal amounts you want a 1:1:1 ratio fertilizer. If your soil tests otherwise, you need a fertilizer that has a specific ratio that matches your soil demands. Next choice is going with organic or synthetic fertilizer. Organic is environmentally friendly but takes longer to dissolve.