For Release April 11, 2004

Does Soil Wear Out?

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

I regularly receive questions from home gardeners about their garden soil. Invariably the conversation comes around to the question, "Is my garden soil worn out?" I sort of have to laugh and yet it is a very serious question. Soil doesn't wear out. It may get tired or abused, but it doesn't wear out. Throughout the world there are examples of continuous cropping systems that have been going on in excess of 160 years. These fields are still very productive. So I don't really think that a few years of your garden is going to "wear out" a soil.

But there are things that can happen to soil over time. Nutrient levels, mainly nitrogen and phosphorus, can become exhausted or depleted so that plant growth becomes very poor. This was the classic problem with cotton production in the southern United States in the mid 19th century. Continuous cotton production quickly depleted the nutrients in the soil forcing farmers to move on to new land. This is why George Washington Carver's work with peanuts and other soil building legumes was so critical!

Soil pH and organic matter can certainly change over time, often to the detriment of the plants. Organic matter is the partially decayed plant material that is in the soil and is important to give soil its tilth. Even soils with high clay content can be very productive if they have good organic matter levels. Soil pH, the acidity or alkalinity of the soil, is very critical. Heavy applications of fertilizer and organic matter can lower, or acidify the soil, but this is not usually the case in most gardens.

Many of the gardeners bringing in soil samples this year are concerned because the garden just hasn't done well the past several years. Most of the soil analyses are not showing major problems which reinforce my belief that the biggest problems with gardens the past few years has been the weather. But to help counteract nasty old Mother Nature, there are several management factors to consider.

Soil testing is a good place to start. What we are finding is that most of the time the only low nutrient is nitrogen, so regular fertilization can take care of this. But occasionally we run across a garden soil that has very low levels of several nutrients and I'm surprised that anything is growing.

Probably 80% of the samples are coming back with soil pH that is above 7 (neutral) meaning that the soil is slightly to moderately alkaline. Given all the limestone under our soils, this is no surprise. Most vegetables in our gardens prefer a slightly acid soil. We need to add sulfur and till it into the ground prior to planting. But without a soil test, we won't know for sure and we won't know how much.

The next thing gardeners should do is to rotate their crops. Continuously planting the same crop in the same place can build up antagonistic organisms in the soil that will hinder plant growth. Try to get into a four year rotation so a crop is in the same spot in the garden only once every four years.

Learn the basics of when you plant what crops. Planting into soils and conditions that are too cold or too warm will insure problems. Plant the right crop at the right time. Then keep the plants healthy, water when necessary and keep the weeds away. Soil doesn't wear out, in fact with good management we can make soil better over the years. But soil is just the base building block upon which all of the other garden management must build. Make sure there aren't any weak blocks in your garden's foundation!

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