MASTER GARDENER PROGRAM — MGs in the News
Published in The Oregonian Homes & Gardens of the Northwest staff • April 25, 2017, 7:56 PM
By WSU Extension Clark County Master Gardener, Jessica Weir
Vegetable gardeners often need to amend their soil each year, adding back the nutrients that were depleted during the previous growing season. Soil amendments can be either enriched fertilizer salts (man-made) or organic (derived of natural process).
Soil is more than just a combination of sand, silt and clay. Between the non-living particles are whole populations of tiny creatures; bacteria, fungi, worms and others. There can be billions of these creatures, collectively known as microbes, in a single teaspoon of fertile soil.
Microbes break down nutrients, like nitrogen, potassium and phosphorus, so that plant roots may easily absorb them. Choosing the right amendment makes a difference in the lives and effectiveness of microbes.
Amending with fertilizer salts changes the balance of soil microbes, and once that balance is altered, more fertilizer amendments will be needed. This puts the gardener on a treadmill of regularly adding fertilizers and searching for the right balance of nutrients.
Examples of organic amendments include composts, manures, natural fertilizers, and cover crops. These additions support and feed soil microbes, enabling them to do their work of making nutrients available. As microbes digest the amendments, the nutrients are available to plants roots slowly over time. Organic amendments also improve the workability of soil, adding more pore space to hold air and water.
Apply amendments and fertilizers conservatively; some release nutrition to roots quickly and others slow. Nutrients not used up by plants or microbes can contribute to nutrient pollution of groundwater that flows to rivers and oceans.
If you’re curious of what is available in your soil or want to know how much amending is needed, you may want to consider testing your soil. Dr. Linda Chalker-Scott, WSU extension expert, suggests testing before adding amendments to get “an idea of what the soil contains before more material is added.”
Those interested in soil testing, are invited to join Master Gardener and Soil Scientist, Martha Minnich for Soil Testing Demystified, a presentation on April 26, from 6-7:30 p.m. at the Vancouver Community Library.
Dr. Minnich will cover the complexities of soil testing and interpreting its results. She will cover the when, why and how to test your soils, translating results, basic plant nutrition and information on organic amendments and fertilizers.
Bring in test results, if you have them, for discussion of specific examples and be ready to work in groups as you are guided through breaking down this complex subject into easier to understand concepts.