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Texas AgriLife Extension Service Texas Water Development Board Texas Nursery and Landscape Association Texas AgriLife Extension Service Texas AgriLife Extension Service
A supplement to the Best Management Practices Manual produced by the Texas Water Conservation Task Force.

Soil Analysis and Improvement

Soil provides water and nutrient reservoir for plants. To grow a successful landscape it is important to know both the original status of the soil – its structure and nutrient content in order to determine what plants will do well. Soil classification takes into account particle size, from silts and clays with the smallest particles to sands and gravels with the largest particles. The smaller the soil particles, the greater the surface area, and the slower that water moves through the soil. There are also geochemical properties of different soils which can promote the growth of adapted plants. Customers should be encouraged to get there soil tested as a first step in preparing a water wise landscape.
Soil depth provides a greater space for storing water, and adding organic materials provides the proper environment for healthy roots for many plants (care should be taken to ensure that plant which have evolved in low-nutrient soils are not planted where excessive fertility may actually harm the plant). The first step in preparing a water wise landscape is getting soil tested to determine its depth, classification and nutrient levels. With that information soil amendments can be added to increase soil depth, and add organic material.

Compost is used to supply nutrients to plants and improve the water holding capacity of the soil through the introduction of organic material. Introduction of compost as a top dressing can assist in replacing nutrients in soils which have been depleted. Top dressing has the advantage of not destroying or damaging the roots of existing landscape plants.
Programmatic approaches include education and distribution of free or discount compost. Education can be offered in form of brochures, or workshops in conjunction with home and garden shows, or other garden or lawn care related events. Local cooperative extension officers may offer these services and may be willing to collaborate with a water conservation program to deliver an educational program involving soil improvement including compost.

Incentive approaches include offering free or discounted compost. Waste water treatment plants produce bio-solids which if properly managed, can be used to produce compost. Some utilities have marketed bio-solids based compost to farmers, gardeners, as commercial nursery and landscape businesses, as an additional revenue stream for the utility. Free or discounted samples can be used to both increase water conservation through soil improvement and to promote the utilities compost product. Some caution in using bio-solids is important to ensure that temperature in the composting operation are high enough to destroy fecal bacteria, and that the waste stream does not include large quantities of heavy metals, pesticides or other toxic chemical effluents. Properly composted materials generate sufficient heat (130 to 170 degrees Fahrenheit) to virtually eliminate human and plant pathogens. For example, the City of Austin produces “Dillo DirtTM,”3  through mulching of brush and plant material; combining with bio-solids from the water treatment plant(s); active composting for over a month; followed by curing for several months, and screening prior to sale.

Another important aspect of proper soil analysis and improvement is preparation for and increase in the landscape’s drought tolerance. Especially important is adequate levels of potassium in the lawn, especially for turfgrass plants. And during times of low water availability, customers should be reminded not to fertilize with high nitrogen fertilizers, as they stimulate leaf growth and water demands for the plants.4


"Compost is used to supply nutrients to plants and improve the water holding capacity of the soil..."

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Photo courtesy Carol Cammack, TCE
3Introduction to Dillo DirtTM, http://www.ci.austin.tx.us/water/dillo.htm
4McAfee, J., Chalmers, D., Havlak, R., County Extension Agent Turf News – Spring 2006, by Department of Soil and Crop Science, Vol. 1, No. 1 April 2006