Garden Soil Amendments

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As you may know, your local county extension office often supplies soil testing kits for the home grower. You should have your garden soil tested annually so that you know what kind of amendments to add to your soil to make it the best possible soil.

Your plants need nutrients and sometimes the dirt just doesn’t have enough in it to supply your garden, especially if you’ve heavy feeders such as corn.


A simple soil amendment formula is 2 parts lime, 2 parts gypsum and 1/2 part blood meal. This simple mixture fertilizes and enriches the soil improving soil quality. Here’s how it works:

Mined Soil Additives
Dolomite Lime
Your growing garden absorbs nutrients from the soil which in turn lowers the pH of the ground, to a more acidic level. A soil that is too acidic, below 5, is toxic to most plants, especially those crops that grow well in alkaline soil with pH levels between 7 and up. Adding lime into the soil during your plants’ growth cycle or after harvest increases pH to suitable, optimum levels between 5.5-7 ranges. For most gardens, a pH of 6.5 is just about right, since most plants thrive between 6-7 pH levels.

The main active component of lime is calcium carbonate, along with varying levels of magnesium oxide, magnesium carbonate, and calcium. Lime increases the pH level of soil or brings it up to the neutral levels. Lime is also a source of magnesium and calcium for your plants. It also enhances water penetration in acidic soil and boosts the capacity of plants to absorb major nutrients, including potassium, phosphorus, and nitrogen.

Farmers have been adding gypsum to their fields for centuries. Early 18th & 19th century farmers amended to reduce sodium levels. High salt concentration results in plants having too much sodium, boron, and chlorine, which accumulates in their stems and leaves and is toxic for plants. The toxicity often shows up as browning of the leaf edges.

High salt levels also produce an effect called osmosis, which prevent plants from absorbing water. In response, plants use their organic and sugar components just to absorb water, resulting in reduced growth and lower crop yield.

Gypsum or calcium sulfate is also soluble, making its sulfur and calcium content readily available for plant absorption. Like lime, its calcium content helps amend high acid levels in soil. It also helps break down heavy clay, increasing water absorption of the ground.

Organic Soil Additives
Blood Meal
Blood is simply dried animal blood and is an excellent organic source of nitrogen. It’s fast acting and helps increase the levels of nitrogen in the soil immediately but should be used in moderation to keep from burning your plants with too much nitrogen.

Blood meal can be used to deter some animals, including deer, squirrels, and moles, which are believed to dislike the smell of blood. On the other hand, blood meal can attract possums, raccoons, dogs, and other omnivorous and carnivorous animals. Ever planted a row of tulips amended with blood meal only to discover at the end that every single hole was dug up by your dog? It’s very attractive to dogs.

hand dirt
hand dirt

As useful as these soil amendments are it’s best to have your garden soil tested before you start amending. Your county ag agency can help you, or point you in the right direction, for soil testing of nutrients as well as ph levels. Be sure to follow recommended instructions when applying because more is not always better.