The biggest investment that you can make in your garden is improving the soil. Even if you imported completely new topsoil, you will likely want to adjust the pH and add amendments to change the nutrient profile so that the vegetables and flowers you cultivate will thrive in optimum conditions. The following organic fertilizers and soil amendments are approved for organic growing. To adjust the PH in your soil or add depleted minerals to the soil this section will help you nurture the most valuable component of your organic garden....your soil.