Soil Types

It pays to know what type of soil you are working with.

Soils are classified and named by the USDA-Soil Conservation Service Surveys into individual soil series. In the Coachella Valley there are only 5 distinct soils of horticultural significance but their soil-water characteristics vary drastically. Note that the water holding capacity may vary as much as 6 times across the 5 major soil types within the Coachella Valley while the permeability rate can vary by a factor of 33. For this reason, it is important that local landscapers be aware of the soil type that makes up their site.

In many instances, irrigation problems can be attributed to the soil that is receiving water, rather than the irrigations system hardware that is delivering it. Furthermore, many of the solutions to these variations in water holding capacity, permeability rate and rooting depth can be found in creative scheduling techniques made possible by computer controlled irrigation system.
Carsitas Soil
Carsitas
  • Soil permeability rate: 6-20"
  • Available water holding capacity: 0.4-0.8"
  • Drainage characteristics: high
  • Stratification layers present: rare
Carsitas soils are characterized by gravelly sand in the first foot below the surface, with more gravelly courses sand up to 5 feet underground. This soil dominates (>50%) in Desert Hot Springs and is significantly present (10-50%) in Palm Springs, Cathedral City, Rancho Mirage, Palm Desert and La Quinta. The Carsitas foothill soils are the youngest in the Coachella valley and have had very little time to develop the fines necessary to increase water holding capacity. As a result they hold very little water and daily split irrigations are often necessary during the peak evapotranspiration rates of summer. These soils are also easily leached and are subject to nitrate fertilizer percolation losses. Infiltration, permeability and drainage rates are very high. Runoff is almost impossible.

Myoma
  • Soil permeability rate: 6-20"
  • Available water holding capacity: 0.7-1.1"
  • Drainage characteristics: moderate
  • Stratification layers present: unlikely
Myoma soils are characterized by layers of fine sand and very fine sand in the first 5 feet below the surface. This soil dominates (>50%) in Palm Springs, Cathedral City, Rancho Mirage, Palm Desert and Bermuda Dunes. It is significantly present (10-50%) in Indian Wells and La Quinta. The wind-blown soil is the most common in the western valley, which is not surprising considering that the wind played a major role in its genesis. This is a very nice turfgrass soil. Its infiltration, permeability and drainage rates are moderate and its water holding capacity is almost an inch per foot.

Coachella
  • Soil permeability rate: 2-6"
  • Available water holding capacity: 0.4-1.8"
  • Drainage characteristics: moderate
  • Stratification layers present: possible
Coachella soils are characterized by layers of fine sand and silt lenses in the first 5 feet below the surface. This soil does not dominate (>50%) in any area but is significantly present (10-50%) in Rancho Mirage, Palm Desert, Indian Wells, La Quinta and Bermuda Dunes. The Coachella soils have been worked by water as well as wind. They can usually be found near the old stream bed of the Whitewater River flood course. This is probably the best soil in the Coachella Valley because it is an ideal mix of available water holding capacity, permeability and drainage. Stratifications are often present, but they are usually thin and deep, posing a problem to deep-rooted trees.  However, a deep, back hoed planting hole will usually solve this problem because the backfill will have shattered and mixed up the restricting layer.

Gilman
  • Soil permeability rate: 0.6-2"
  • Available water holding capacity: 0.8-2.5"
  • Drainage characteristics: slow
  • Stratification layers present: likely
Gilman soils are characterized by layers of fine sandy loam, silt loam and loamy sand in the first 5 feet below the surface. This soil dominates (>50%) in Coachella. It is significantly present (10-50%) in Palm Desert, Indian Wells, La Quinta and Indio. This can be a difficult soil. Its strong point is a high water holding capacity, but getting water into and through it can be difficult, especially on slopes and in areas compacted by heavy equipment or golf carts. Stratifications are also common further complicating matters.

Indio
  • Soil permeability rate: 0.6-2"
  • Available water holding capacity: 1.6-2.4"
  • Drainage characteristics: restrictive
  • Stratification layers present: likely
Indio soils are characterized by layers of loamy fine sand, very fine sandy loam and silt loam, in the first 5 feet below the surface. This soil does not dominate (>50%) in any area but is significantly present (10-50%) in Palm Desert, La Quinta, Indio and Coachella. This is the toughest landscape soil in the Coachella Valley and requires careful management. Its water holding capacity is excellent, but infiltration, permeability and drainage is restrictive. Trees have a hard time becoming established on this soil unless carefully irrigated. Compaction is always a potential threat and stratification is common.