Landscape Guide: Soil Management Strategies

Introduction | Water Characteristics | Soil Management |
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Soils from the Ground Up

Nutrients, organic matter, and water in the soil are the raw materials that give life to the landscape. Yet soil fertility is not just a matter of nutrients, but also of chemical, physical and biological factors: soil texture, composition, structure, pH and living organisms.

Few soils are of only one texture, with most being combinations of particle types. The best soil, called loam, is a combination of sand, silt and clay. Its mixture of sizes permits penetration and drainage of water while retaining moisture.
The addition of organic matter brings more nutrients and stimulates microbial activity. Organic matter creates a stable, open structure that improves drainage and water retention; it lightens heavy soils and firms up light ones. It also helps create the optimum acid-alkaline balance in which the most nutrients become available to plants.

Successful landscapes are as dependent upon successful management as they are upon the necessary raw materials. And remember: Site management is the same whether using recycled water or potable water.

Evaluating Drainage

Begin the process of evaluating drainage by examining your site, both surface and underground. At its simplest, assessing soil drainage involves excavating a test hole four to six inches deep, filling it with water, allowing it to drain, filling it again and measuring the rate at which the water level drops with a ruler placed vertically inside the hole.

The drainage rate will be highly variable depending on soil type and moisture content, so the measurement is meaningful only if determined when the soil is completely saturated with water. The drainage rate should be no less than one-quarter inch per hour and should not exceed two inches per hour. Soils with drainage rates outside this range may require soil modifications for optimum growth.

Good drainage

Essentials for improving drainage

• Aerate the soil.
• Add organic matter to the soil.
• Add soil amendments such as gypsum (only if necessary).

Soil Amendments and Fertilizers

If there were a perfect soil, it would be a balanced mixture of five ingredients: solids, ranging from small stones down to the smallest clay particles; organic matter, mostly decayed vegetable and animal matter; a substantial population of living creatures; and considerable quantities of water and air.

Soil texture - the size of the particles - is relatively easy to describe and nearly impossible to alter. Sandy soils drain freely, are well aerated, and easy to cultivate. They dry out quickly, are often alkaline, and tend to be low in available nutrients. They warm up quickly and cool down equally fast.

The small particles of clay soils are generally rich in nutrients and hold water well. They drain poorly, tend to accumulate salts more quickly, and are often difficult to cultivate. They warm up slowly in the spring and retain warmth well.

Improving Your Soil

Determining the type of soil on your site will help guide your landscape management strategies, including soil preparation, planting, watering and feeding. Heavier soils, similar to those found in the greater San Jose area, work well with recycled water as long as changes in soil-chemical properties are evaluated regularly. Regular testing of your soil will help you manage your landscape on an ongoing basis and pro-actively, rather than waiting for a problem to develop. This strategy is true whether you are working with potable or recycled water.

Obtaining a soil analysis of your site - whether you are installing new landscape or renovating to accommodate recycled water - is highly recommended. The report should reveal many of your soil's horticultural properties - its pH, salinity, soil texture, fertility, and organic matter content. The report may also identify some features that might be improved or corrected. Local soil labs that perform these horticultural tests have current recycled water data and can tailor their analytical reports specifically to your landscape site.

Recycled water has a nutrient value that may help you save money on fertilizers. Among the nutrients supplied in greater amounts by recycled water are nitrogen, phosphorus and potassium, which are all beneficial in landscape management. If you still find it necessary to use additional fertilizers when irrigating with recycled water, use materials with a low salt index, or incorporate a natural organic material containing low levels of salt.

Maintaining Good Soil

• Test regularly.
• Add amendments as necessary.
• Utilize ongoing maintenance.

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