Agronomy 101

The key to a healthy prosperous garden is healthy soil. Agronomy is the study of crop and soil science and my Dad is an agronomist (aka “crop doctor”). To make sure my garden is successful in growing the seeds I have started from my Mom’s collection I need to make sure my garden has the vital nutrients the plants need to grow. The macronutrients (the nutrients I need the most of) are nitrogen, phosphorus, potassium, magnesium and calcium and then there are many other micronutrients (the nutrients I need but in smaller quantities).

If you’d like to get your soil tested the first step is locating a place that you can send your soil sample to for analysis. Look into your county extension service that is offered through your land grant school and/or your master gardeners program. This website is very helpful in locating a lab near you: https://gardeningproductsreview.com/state-by-state-list-soil-testing-labs-cooperative-extension-offices/

I was able to collect my samples and bring them to Iowa with me – I collected two samples; one from my established garden and the other from the site where I plan to expand my garden into. I wanted to compare my established garden where I have added manure & soil to the untouched heavily blackberry laden area (known as forest on the test results) I am going to clear for the Spring 2021 garden expansion.

The first test result to look at is the pH – the garden is currently 6.4 and the forest is 5.2. The soil pH should be between 6.2 and 7.0 pH. To raise the soil pH in the expansion area I need to add calcium – this is generally done by using crushed limestone that is finely ground. You can buy bags of crushed limestone which is sometimes called “barn lime” at your local hardware store or large home supply store. In a 10’x10′ (100 square feet) garden you would need to spread about 15-18 pounds to raise the pH to the desired level (between 6.2-7.0). The crushed limestone needs to be incorporated into the top 6″ of the garden.

To raise the nitrogen, phosphorus & potassium an 8-8-8 or 10-10-10 or 12-12-12 (Nitrogen-Phosphorus-K potassium) fertilizer can be applied at 1 lb. per 100 square ft. and can be incorporated into the top 6″ of soil. If you’d rather not use a fertilizer you can add composted manure at ~10 pounds per 100 square feet, and again, incorporate this into the top 6″ of soil.

After adding the nutrients it is recommended to let the soil rest for two weeks before planting – this will allow the fertilizer and/or manure time to break down and become incorporated into the soil. With nutrient rich soil your plants will supply you with a bountiful harvest.