How to Fertilize Strawberries and Potatoes Naturally

Test the soil pH level before adding fertilizer or planting strawberries and potatoes; a community extension service can usually assist you with this for free or a slight fee. Strawberries need a pH level of 5.0 to 6.5; however, they can produce in soil with pH levels up to 7.5. Potatoes like this middle range, too, preferring a 5.3 to 6.0 pH level. They are flexible across a wide range of pH levels, however, if other conditions such as sun and water are optimal.

Add limestone -- known as lime -- to raise the pH level in your soil if it is too low. Add sulphur or an organic fertilizer containing urea, or ammonium sulfate or nitrate to lower the pH level. Purchase either product at a garden center and mix it into the top 6 to 7 inches of the soil with a hoe or garden tiller for nutrients to reach the plant roots when you apply them.

Mix a desired compost into the soil with a hoe or garden tiller; this can be aged farm manure for the strawberries or a mixture of decomposed kitchen and garden material for either strawberries or potatoes. If the soil pH needs modification, wait a week before adding compost. If the soil pH falls into the desired range for strawberries and potatoes, add the compost when you're tilling the garden to begin preparing the soil. As the compost adheres to the surrounding soil, it adds vital nutrients for organic fertilization of the plants.

Plant the strawberries and potatoes when the soil has warmed to at least 50 degrees in the spring; make sure to plant them in different spots rather than planting them as companions. Water thoroughly but do not add fertilizer yet if you added compost to the soil.

Place compost around both types of plants approximately a week after planting for natural fertilization; it will break down slowly. As compost will not "burn" plants, you can place it around them to provide mulching benefits, as well.

Spray potatoes with a liquid seaweed or fish-emulsion natural fertilizer once blooms appear and cease when blooms end. Application in the morning when plants are wet with dew and temperatures are lower allows the fertilizer to absorb quickly and easily. Get this type of organic fertilizer at a garden center.

Fertilize strawberry plants after berries have been harvested by covering the plants with an additional 2 inches of compost. You can add a water-soluble natural fertilizer then, as well -- such as one providing seawood or fish nutrients.