The types of plants that you are growing will have a bearing on the characteristics you require from a soil, but there are some general guidelines to follow. Using plant species that are adapted to the soil will help minimize maintenance and water required.
Plant growth and ease of maintenance are improved immensely by high quality soils. Landscape soil quality can be improved by keeping it clean during construction, tillage to reduce compaction, and amending with fertilizers and organic matter. To amend soils correctly requires an understanding of the following characteristics.
Soil texture: This refers to the percentages of sand, silt, and clay in a soil. Sandy soils drain quickly and retain little water or nutrients. Clay soils consist of much smaller particles and have less drainage, but better nutrient retention than sandy soils. Soils with appropriate balances of sand, silt, and clay are described as loamy. Loam soils, or close relatives such as clay loams or silt loams, are the best soils for plant growth.
Soil structure: Structure refers to the degree to which small soil particles clump together, forming both large and small pores throughout the soil. This clumping aids water and air movement in the soil because water and air can move freely through the large pores. At the same time, the smaller pores within the aggregates hold water for plant use.
Soil organic matter: Organic matter is beneficial in soil because it decomposes to provide plant nutrients. Organic matter also improves water infiltration, drainage and retention in the soil, largely due to its ability to improve soil structure. Manure, compost, leaves, and grass clippings are sources of soil organic matter.
Nutrient status: The nutrient status of the soil refers to the amount of nutrients such a nitrogen, phosphorus, and potassium in the soil. These nutrients and several others are essential for proper plant growth. If nutrients are limited then plant growth suffers because of deficiencies. On the other hand, excessive levels of nutrients or other compounds, such as sodium chloride, can result in salty soils. Saline soils are difficult for plants to grow in because high levels of salts make it hard for plant roots to absorb water.
Soil pH: This refers to the acidity or alkalinity of the soil. It is important because the soil pH affects the availability of mineral nutrients to plants. For example, Utah soils have high levels of iron, an essential mineral. However, due to the high pH of these soils, the iron present is not readily available for plant growth.
The most effective way to determine a soil's characteristics is to have a soil test done. Soil testing is done by commercial laboratories, or through agencies such as the Soil Testing Laboratory at Utah State University . Instructions and sampling kits for soil tests are available at county Cooperative Extension offices.
Plant selection is a fun part of the design process for most people and selecting the right plant for the right place is essential for creating a water-efficient landscape. Visit local water-wise demonstration gardens to get ideas for plant combinations and mature sizes. The following water-wise plant lists were created for arid Utah landscapes.
Fit and Function: Choose plants based on height, width, shape, color, and form that will best help accomplish the design goals. Plants can be used to conserve energy or water, block undesirable views or noise (dense plant material), control erosion on steep slopes (lower growing groundcovers) and attract birds, butterflies and bees. There are many resources for water-wise plant lists and tree selection that are searchable by desired characteristics and water use.
Choose Adapted Plants: Use plant species that are adapted to the landscape environment—the soil, water, temperature, light, and pest conditions—to help minimize maintenance and water requirements. This does not necessarily mean that water-wise landscapes are composed entirely of native plants. In fact, some native plants, such as Aspen, do not generally do well at the altitudes and water levels in most gardens as they are adapted to high elevations and wet-meadow situations. There are many plants from other dry regions around the world that are well-adapted to suit the low-water requirements of our region.
Hydrozones: Grouping plants according to their water needs allows for more efficient irrigation as plants are less likely to be over or under-watered. Also, remember that smaller plants tend to have lower water requirements than larger plants.
Seasonal Interest: Think about the timing of the foliage, bloom and seed head displays of the planting material to ensure interest year round. Try to Incorporate spring, summer and fall interest in each planting group so that no place in the landscape looks bare.
Hardiness Zone: Use plants that will survive in our climate. Plant hardiness zones in Utah range from 4-9. The hardiness zones were established by the USDA and are based on the minimum, annual survival temperatures for plants. Plants for hardiness Zone 4 can survive -20 to -30 °F, Zone 5 can survive -10 to -20 °F, Zone 6 can survive 0 to -10 °F and Zone 7 can survive 0 to 10 °F. However, micro-environments created by the plant’s surroundings can also influence its hardiness for the region. Contact your local Utah State University County Extension Agent or go to the USDA Plant Hardiness Website to learn the hardiness zone of your area.
Lawns have many benefits including cooling effects, erosion control, water filtration and water infiltration. Lawns can withstand trampling and play that no other plant can handle. Lawns also need a lot less water than they are given.
At times it has seemed that water-wise landscaping might not allow for the use of turfgrasses at all. In fact, water-wise landscaping recognizes turfgrass as an integral component of the landscape.
In addition, as an herbaceous plant, turfgrass is often one of the first plants in the landscape to exhibit signs of drought stress. These facts coupled with a “more is always better” attitude toward landscape irrigation, predispose turfgrass areas to over-irrigation.
Turfgrass has some very specific benefits in the landscape. For example, it is the only landscape plant material that can withstand the stresses of traffic and mowing that are commonly applied to it.
One can trample it, tear it, mow it, and it grows back! It is also the most practical surface for many types of outdoor recreation. And mowed lawns are a standard component of many urban fire control strategies.
Yard Clean Up CalgaryTurfgrass also provides many other environmental benefits. One such benefit is a reduction in the amount of surface runoff water. This is a key component to protecting water quality.
An average golf course, for example, can absorb 4 million gallons of water during a 1-inch rainstorm. A golf course or turf area can absorb far more than one inch of rain water without runoff, assuming it's not coming down too quickly. This is because a dense turf area can reduce runoff to virtually nothing. And when compared to a non-turf area (like a garden or agricultural field), grass areas can reduce runoff-induced soil erosion by up to 600 times (Whiting, et al., 2005).
Turfgrass also reduces environmental pollutants. It traps dust and pollen and controls wind erosion of soil. Turfgrass also moderates temperature levels, which can reduce the amount of energy used for home cooling in the summer months.
Turfgrass can be a practical and beautiful component of a water-wise landscape. As a design component, turfgrass invites participation in the landscape while providing unity and simplicity (Welsh, 2001).
Only use turfgrass in areas where it is functional. These areas may include play areas, areas receiving traffic, and areas needing temperature, noise, or dust mitigation. If the only time a turf area receives traffic is when it's mowed, perhaps a lower maintenance plant would work in that location.
Consider choosing turfgrass species with lower water requirements. In Utah, certain varieties of different turfgrass species perform better. These may be found in the bulletin Turfgrass Cultivars. This bulletin also discusses the characteristics and applications of commonly used turfgrass species in Utah. Another good resource is the Turfgrass Water Conservation Alliance (TWCA).
Consider using non-irrigated turfgrass areas. If the turfgrass is not performing a functional role, does it really need to be irrigated? Many turfgrasses can withstand considerable drought stress by entering dormancy (turning brown). When conditions improve, they will green up again.
Do not plant turfgrass in narrow, small, or oddly shaped areas that are difficult to irrigate efficiently. In these types of locations, there are many other plants that are more practical choices.
Hydrozoning in a water-wise landscape certainly applies to turfgrasses as well as other plants. Plan and design irrigation systems so that turfgrass areas are irrigated separately from other landscape plants. Also, become familiar with the actual water requirements of the turfgrass and don't exceed them.
Use cultural practices that will improve turfgrass water use efficiency. For example, mowing at a height of 2 ½ or 3 inches will encourage deeper rooting and improved heat and drought tolerance. Proper fertilization will also support healthy turfgrass and allow it to withstand the stresses of heat and drought better. Returning grass clippings when mowing also helps to reduce evaporation of water from the soil surface.
Mulch can provide many benefits in water-wise landscapes. Mulch covers the soil and prevents crusting, compaction, and water evaporation, while also providing an important visual design aspect. Choosing the right mulch for the situation is dependent on plant selection, watering regime and site use.
Mulch can provide many benefits in water-wise landscapes. Mulch covers the soil and prevents crusting, compaction, and water evaporation. In fact, mulching around trees, shrubs, and in flower beds can result in a ten-fold reduction in evaporative water loss from soil.
Reducing soil water loss means more water is available to plants and less water needs to be provided. Mulch also reduces the number of weeds in a water-wise landscape by preventing light-induced germination of weed seeds. With fewer weeds, less cultivation is required, which can prevent damage to plant roots, soil structure, and soil organisms. In addition, mulch moderates soil temperature and protects plant roots.
In winter, moderation of soil temperature can prevent plants from heaving out of the ground due to freezing and thawing. Mulch also can be an important visual design element in a water-wise landscape, and it is used along walkways, in plant borders, and for color and structure in a landscape or garden.
Organic mulches include materials such as wood or bark chips, shredded bark, nut shells, pine needles, or other discarded plant parts. These materials have the potential to enhance soil structure, increase soil fertility, prevent compaction, and increase soil organic matter as they break down and are incorporated into the soil.
Mulch is a great way to recycle yard waste, such as pruned woody plant materials, fallen leaves and needles, and even grass clippings. To ensure adequate water infiltration and aeration and to slow decomposition, make sure mulch particles are larger than the underlying soil particles (usually larger than a half inch in diameter).