June 2, 2012

1 - The difference in potting soil, garden soil, and compost.

2 - Drip irrigation system and some plants are wilting.

Yard and Garden June 2, 2012

Q. #1

At my local garden store I noticed that there were bags of potting soil, garden soil, and compost. They looked pretty much the same, but upon reading the labels, I noticed that the garden soil said it was not for use in pots as a potting soil. What is the difference?

no name

A. #1

It is a good thing that you were paying attention to the labels. Reading labels is an important practice for gardeners, especially when using pest control products. However, as you noted, it is wise to read the labels on even bags of soil amendments. Many of these products are composted materials. The composition of the product depends on what was composted and how well that material has decomposed. Some products contain fertilizers or organic materials such as manure that can provide nutrients to plants; some are just composted organic materials. Both will provide nutrients, but some types will provide nutrients at an optimal level and rate for container plants, others work better in the garden when mixed with native garden soil. Some bagged potting soils may contain sphagnum moss while others contain other materials. These differences in composition will alter their performance and effectiveness for various uses. There are even specialized potting media (called media because they contain no mineral soil) intended for specific purposes. Some are made for cacti, some for flowering houseplants, some for African violets or orchids. Some are specially formulated to provide the best results for starting seedlings. Other materials may be used in this manner, but they will not perform as well as those made specifically for seedling growth. These products are formulated to perform best when used in the manner recommended on the label.

Q. #2

My garden is irrigated by means of drip irrigation and I have noticed that some plants are wilting when other plants are not wilting. Is there a problem with my irrigation system?

James N.

A. #2

There may be insects feeding on the roots of some plants and not others. Look for insects. Check for diseases as well. Overwatering can increase disease problems. Finally, check your irrigation system to see that it is functioning properly. To check your irrigation system, place small cans under each emitter in your drip system (you can do this one, or a few at a time, or all at once if you have enough cans). Run your irrigation system and measure the water collected in each can. If there are differences between the cans, is this due to the fact that you are using emitters rated to provide different amounts of water, or because some emitters are clogged. If you determine that some emitters are clogged, you should replace them. Use replacement emitters that provide the same quantity of water (gallons per hour) as the one you are replacing, unless you need to increase water provided to individual plants. Be careful that you do not alter the efficiency of your irrigation system by trying to put too many high volume emitters in a system that cannot carry enough water. If you are not certain what volume emitters you can use, check with your local irrigation company to help you calculate the capacity of your system and each branch of your irrigation system.

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.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

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