Issue: Janua1y 12, 2002

Terminology - workable soil

Question:

What exactly is meant by 'as soon as ground can be worked in spring'?

Answer:

Thanks for this question. Jgon can sometimes get us in trouble, but it can also be a teaching point. For you, in Las Cruces, the phrase "when the ground can be worked in the spring" probably has no meaning. It refers to soil being too cold -- the water in the soil frozen -- or too wet, which is an important consideration for gardeners with clay soils in moister environments. Frozen soil is difficult or impossible to "work," ie. to turn it with a shovel or rototiller. I have tried using a pick on frozen soil, but it's a lot easier to wait until the soil thaws. Shady areas of the garden on the north side of my house in Albuquerque are very unworkable right now. Clay soils present unique problems because of their ability to hold water. If the soil is a wet clay it is not good for the soil to turn it. When it is dry it is also difficult to work. In your area, dry soil is more often the problem, and can be remedied by irrigating and then waiting for a few days. In moister climates, clay is often too wet in the spring to be easily turned. Clay has a very narrow moisture range when it can be successfully rototilled or turned with a shovel. Addition of organic matter helps with the moisture problem, but the soil is still difficult to work when frozen. So, for you, this term is of little relevance, but for other parts of New Mexico and much of the U.S., soil workability is an important consideration

How much water?

Question:

How can I tell if I have enough rain or snow so that I don't need to irrigate in the winter? I don't want to waste water, but I don't want my plants injured either.

Answer:

The only way to know for sure is to probe the soil by digging or using a soil probe to determine the depth of moist soil. However, there are some general guidelines you can use. Sandy soil moistens more deeply than silt or clay even with the same amount of moisture. Silt also moistens more deeply than clay. For example, one inch of rainfall (roughly 10 inches of snow) will moisten sandy soil to a depth of one foot, while moistening silt to six inches and clay to three inches. If the rain comes rapidly and runs off onto surrounding land or the street, then the soil will moisten less deeply. Snow may sit on the soil and slowly sublimate, or evaporate. In this case, you again have less soil moistened. In colder areas of our state, snow often sits on frozen soil, which cannot absorb moisture, so even more may be lost without benefiting the soil if the ground is frozen.

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For more gardening information, visit the NMSU Extension Horticulture page: desertblooms@nmsu.edu.

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, office: 505-865-7340, ext. 113.