Soil hasn't grown anything well for many years

We have lived in the same home for 18 years. There is a part of the backyard where we cannot get grass to grow. We have rototilled, added compost, tried fescue sod, and we have tried planting buffalograss seed. Even the weeds are stunted in this area. We have installed a sprinkler system, and the other parts of the lawn are doing fine. The neighbors say that a previous owner, over 18 years ago, used a chemical in the yard that killed the trees. Could that still be causing problems?

Without knowing what chemical was used, I would say that it is possible, but other factors could also be involved. So let's consider some of the other factors first before we get to the more difficult problem of chemical persistence in the soil.

Is this area lower than the rest of the yard so that it remains waterlogged after watering? Is it higher so that it sheds water and never gets moist enough? Is there a pocket of clay or sand in this area? Have you dug a hole in the area to see if there is construction material buried at that site? Sometimes construction debris, sheetrock, bricks, concrete, etc., will be buried at the construction site. All of the factors mentioned above can cause irrigation problems which could be responsible for your problems. It would also be wise to check the irrigation system for uniformity of water application by placing some empty cans in various places in the lawn when irrigating to measure the amount of water each area receives from the sprinklers. Does the problem area not receive the same quantity of water as the rest of the lawn? Any of these, if they cause a severe enough irrigation problem, could cause the symptoms you described.

Have you had the soil tested for mineral content? It is unlikely that an over-application of fertilizer 18 years ago would cause the problem that you described; however, there are micronutrients which, in excess, can cause problems. Some of these micronutrients can persist in the soil for long periods of time without leaching, unlike nitrogen fertilizer which washes from the soil easily. Boric acid, copper compounds, manganese or others substances such as these can cause problems. Any products containing these or some others which were dumped or spilled in large quantities in the area of your lawn where you have problems could explain the problems. If you have some idea as to which is the problem, you can have the soil tested for that compound. Testing for these nutrients at most soil testing laboratories is much less expensive than testing for herbicide residue or the residues of other materials.

Finally, these other materials mentioned above should be considered. There are some so-called soil sterilants, actually herbicides which persist in the soil for a long time, that can also cause the problems. Few of these should have lasted 18 years unless dumped on the soil at that location in extremely high concentrations. It is possible to have the soil tested, but you need to name the chemical for which the laboratory will be testing, and it is expensive.

An experiment you might wish to try is to dig soil from the surface, six inches down, and a foot down. Place the soil in a flower pot, perhaps adding some sand to allow better drainage if the soil has a lot of clay. Then plant beans, or another broadleafed plant, and corn, or another grass plant. Some herbicides are selective, killing only broadleafed plants or grass plants. Others, and the micronutrient factors mentioned above, will affect all plants. Most of the soil "sterilants" which might have been applied to the soil will also be non-selective. By doing this you can determine the depth of the problem in the soil, if it is selective, or if the problem is really in the soil. After you have done this, contact your local Cooperative Extension Service Agent again with the results of the experiment, with soil nutrient test information, and information about irrigation. Perhaps then the solution will be apparent, even if it involves removing the top six inches of soil in the area or diluting it with soil from another area.

Good luck.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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