What is the most important gardening principle? Soil preparation! The most basic element in your garden is soil. Ninety percent of successful gardening is getting the soil healthy. Our job as gardeners is to prepare and optimize the soil’s condition
What is the most important gardening principle? Soil preparation! The most basic element in your garden is soil. Ninety percent of successful gardening is getting the soil healthy. Our job as gardeners is to prepare and optimize the soil’s condition so we can produce healthy plants.
Soil is composed of inorganic particles — silt, sand, and clay — as well as air, water, and organic matter. Soil quality depends on the proper balance of these components and the activities of the present microorganisms, fungi and earthworms.
Alkalinity and acidity of the soil is measured on the pH scale, which ranges from 0 (pure acid) to 14 (pure alkaline). From the neutral point of 7 the numbers increase or decrease exponentially: thus a pH of 5 is 10 times more acidic than a pH of 6. In Hawai‘i, gardeners should be able to grow most plants if the garden soil has a pH range between 5.5 to 7, provided the soil nutrients are available.
For a quick pH test you can use litmus paper, sold at most pharmacies, or you can submit soil samples to the University of Hawai‘i Cooperative Extension Service for analysis for a modest fee. To take a soil sample, dig a hole in the garden 6 to 8 inches deep. Take a slice of soil from top to bottom of the hole, remove any plant material, then put the soil in a clean container. Take several more samples from random spots in your garden. Mix the soil together in the container, then take two cups of soil and place it in a clean zip lock bag for analysis. Ideally, you want to test your soil for pH and available nutrients so you can add any soil amendments before you plant your seeds or plants. The soil analysis will tell you if you need to add lime or any nutrients.
Your soil’s texture is important. Texture is the amount of silt, sand, and clay in the soil, while structure refers to how these components clump together. Sandy soil provides aeration and drainage but does not hold much water and nutrients. Clay soils hold water and nutrients longer but may not provide adequate drainage.
Rub a pinch of moist soil between your thumb and forefinger. Too much sand makes a gritty feel. Smooth and slick means silty. Too much clay feels sticky and rolls up easily into balls. Ideal “loamy” soil has a mealy feel and should contain up to 50 percent sand, between 25 and 50 percent silt, and up to 25 percent clay.
Gardeners can improve the soil by adding well rotted compost. The addition of compost will help to hold moisture and nutrients in sandy soil and increase aeration and drainage in clay soils. Spread a 2-inch-thick layer of compost over the garden area, add any recommended fertilizer and mix it in with 6 to 8 inches of soil.
• Tom Peterson is a Kaua‘i master gardener and Richard Ebesu is the Kaua‘i master gardener program coordinator with the University of Hawai‘i College of Tropical Agriculture and Human Resources Cooperative Extension Service.
