August 18, 2012

1 - Increasing the soil quality of tomato gardens this fall and next spring in preparation for next year.

Yard and Garden August 18, 2012


My daughter and I cleared and sifted the soil in a small patch of our xeriscape rock backyard (3ft by 50ft), and we installed a drip irrigation system so that we could have a tomato garden. We worked peat moss and manure into the soil and made it ready to plant. We purchased and planted a variety of garden center tomato plants (sweet 100's, cherry, and beefmaster) in mid-spring of this year.

The tomato plants never really took off...they did not die, but they seemed stunted and only reached a height of about 18 inches (2 to 3 times their original when we purchased them). Only the sweet 100 plant seemed to do slightly better and have only yielded a small number of tomatoes (less than 50).

Do you have any suggestions for increasing the soil quality of our tomato garden this fall and next spring in preparation for next year?

Jaime and Grace G.

Albuquerque, NM


This has been a difficult year for gardens in much of New Mexico because of the heat and drought. You installed a drip irrigation system, but how much did you irrigate and how often. The goal will be to moisten the soil to a depth of 1 to 2 feet and replenish the moisture as needed. The frequency of irrigation will depend on the type of soil in which you are growing the tomatoes and other plants. Clay soils are difficult to moisten, but hold more water and need irrigation less often; sandy soils hold less water and must be irrigated more often. This water must be applied over a sufficiently large area of soil.

A single emitter at the base of the plant may be sufficient for the plant when first planted, but several emitters further out around the plants will allow development of a larger root system that can support a larger plant and crop.

Adequate nutrients are also necessary for good plant growth and production of a crop. If the soil had been covered by plastic and rocks for many years, the soil may not have been providing sufficient nutrients to the plants. You applied peatmoss and manure as soil amendments. The peatmoss helps the soil retain water, but provides few nutrients to the plants. Manure does provide nutrients, but slowly. Manure is a low-analysis fertilizer. That means it has only a low percentage of nutrients readily available to the plants. Over time the nutrients can accumulate to be sufficient. Be careful with manures. They often contain minerals that can cause salt burn. This will cause browning of the edges of the leaves and stunting of the plants. So, although manure is good, it can be overdone. Apply manure in the fall so that winter precipitation will leach the harmful, burning minerals from the manure.

A very good amendment to add to soil is well decomposed compost. This may be purchased in bags, in bulk, or made at home in a compost pile. Compost is superior to peat moss in that it is already well decomposed, while the peatmoss will decompose more after being added to the soil. Compost provides some nutrients (once again low analysis and slowly released). Compost also helps soil retain moisture, supports growth of beneficial soil organisms that were depleted under the rock landscape. Compost also improves the characteristics of the soil so that each year it becomes better. It does continue to decompose slowly in the soil and must be replaced annually.

A soil test will help you know more about the characteristics and nutrient content of your soil so that you can manage the garden better next year. Your local NMSU Extension Service agent can help you get a soil test and understand the results of the test.

Another management technique that often helps is the use of organic mulch over the soil to reduce water loss, maintain constant soil temperatures, and slowly improve the soil as it decomposes. Mulch may increase insect problems, so the proper material carefully managed is important. Mulch would probably have helped your garden this year.

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


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

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