Caliche is a naturally occurring soil layer that poses unique challenges for gardeners and homeowners, particularly in certain regions. Understanding its nature and impact on plant growth is essential for establishing a thriving landscape where it is present.
Understanding Caliche
Caliche is a hardened layer of soil or sediment in which particles are cemented by precipitated minerals, primarily calcium carbonate. It often resembles concrete. It typically appears as a light-colored layer, ranging from white to light pink or reddish-brown, depending on the other minerals present.
The formation of caliche is a slow process that can take thousands of years. It occurs when calcium carbonate, dissolved by rainwater, leaches through upper soil layers and then precipitates in deeper horizons as water evaporates or is used by plants. This accumulation binds soil components like gravel, sand, and clay, creating a dense, cemented layer. Caliche can manifest as soft, thin layers, scattered lumps, or thick, hard beds.
Where Caliche Is Found
Caliche is commonly found worldwide in arid and semi-arid regions. These areas typically experience annual precipitation of less than 26 inches (65 centimeters) and mean annual temperatures exceeding 41°F (5°C). Such conditions lead to high evaporation rates, which are conducive to the accumulation and hardening of mineral deposits.
Significant deposits of caliche occur in the High Plains of the western United States, including Arizona, California, Nevada, New Mexico, and Texas. It is also prevalent in the Sonoran, Chihuahuan, and Mojave Deserts, as well as parts of Australia, eastern Saudi Arabia, and the Kalahari Desert in Africa.
Impacts of Caliche on Your Landscape
Caliche presents several challenges for gardening and landscaping. Its hardened, impermeable nature restricts water movement, leading to poor drainage. Water often pools on the surface or drains very slowly, which can suffocate plant roots due to inadequate aeration and lead to salt accumulation in the upper soil layers.
Caliche also impedes root growth, as plant roots struggle to penetrate the dense layer. This limits the available soil volume for roots to access water and nutrients, making plants susceptible to drought stress and reducing their overall vigor. Shallow root systems can also lead to poor anchoring, making trees and shrubs more vulnerable to strong winds.
Caliche layers often result in highly alkaline soil with a pH typically ranging from 7.5 to 8.5. This elevated pH can reduce the availability of essential micronutrients like iron, phosphorus, boron, and zinc, even if these nutrients are present in the soil. Plants may exhibit symptoms of nutrient deficiency, such as yellowing leaves with green veins, due to their inability to absorb these elements.
Managing Caliche in Your Garden
Managing caliche in your garden requires several strategies. One approach is to physically break up the caliche layer, which can be done with tools like a pickaxe or, for very hard layers, even a jackhammer. For planting trees and shrubs, it is beneficial to dig holes that penetrate completely through the caliche layer to ensure proper drainage and allow for deeper root development. If a complete breakthrough is not feasible, creating narrow drainage “chimneys” through the layer can help.
Amending the soil with organic matter is another effective strategy. Incorporating compost, mulches, or other organic materials helps to improve soil structure, enhance drainage, and buffer the alkaline nature of caliche. Organic matter also provides a more hospitable environment for plant roots and encourages beneficial microbial activity. Adding elemental sulfur can help acidify the soil and increase the availability of micronutrients that are often limited in high-pH conditions.
Creating raised garden beds provides an alternative solution, allowing you to establish a planting area with imported, well-draining topsoil and organic amendments above the caliche layer. Selecting plants tolerant of alkaline soils, shallower root systems, or arid conditions can lead to greater success. Examples include native wildflowers like Engelman’s daisy and shrubs like Algerita. Proper irrigation techniques are also important; avoid overwatering, which can exacerbate drainage issues, and ensure water reaches the root zone without causing waterlogging.