Most gardeners know building a deep rich soil is the key to success when it comes to growing flowers and vegetables.

Likewise, anyone who has tried to dig a hole in Lawrence quickly realized we have compacted clay rather than fertile loam for soil. For years, gardeners have been adding organic material to local soils to help create tillable productive gardens. However, are we adding too much? Here is the scoop when it comes to shoveling the horse poop.

There is an abundance of organic materials in the autumn season. Fallen leaves, frosted plant parts, and mowed grass clippings are all available for the taking. Either directly applied to an area before tilling, or composting first then working them under, the question remains “How much is too much?” Standard organic materials can be added in fairly large quantities without many problems developing. It helps if the materials are partially composted or finely shredded so that they can begin the process of decomposition rapidly. Generally, a four- to six-inch layer of material should be worked in each year.

Where we can run into trouble is when we begin adding organic materials that have a high nutrient concentration. Usually this comes in the form of fresh animal manures. Horse, sheep, cow, and other animal manures have the potential of adding too much of the “good stuff.” High nutrient levels or an imbalance of nutrients can cause plant problems next year. In addition, high levels of nutrients can leach into groundwater or be carried off in surface waters creating water quality issues.

Finally, some concentrated manures contain levels of salt that can be toxic for certain flower and vegetable plants. The salt problems become even more noticeable in dry seasons when natural leaching of salts through the soil is slowed down and salts accumulate in the garden.

As a general rule, use caution when applying concentrated manure without a soil test. It is not a good idea to apply more than a one- to two-inch layer of manure at any one time. It is better to add manure that has composted or been exposed to the elements for several months. This allows many of the nutrients to leach out making the material less damaging. Also, be careful about multiple year applications. It might be better to wait two or three years between applications especially if a soil test indicates there is adequate soil nutrition. This gives time for salts to leach out and plants to use the nutrients available in the soil.

For general soil improvement in terms of looseness and work ability of the soil, applications of composted yard waste such as leaves, grass clippings, and similar materials work much better than applications of animal manures, especially fresh concentrated ones.

:quot; Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.