What is soil type and why is it important?
Understanding your lawn's general soil type is helpful when creating watering schedules to minimize runoff. Additionally, estimating the depth of the roots helps to understand the size of the soil moisture reservoir (or the "water tank" in which the Rachio controller can refill). Each zone can have a different sized water tank based upon the soil in that zone and what's growing in the zone.
What is the "water tank"?
The earth’s soil serves as water storage for vegetation. If you think of this storage as being similar to a sponge, it helps illustrate why soil type is an important factor in Rachio’s scheduling decisions, in particular Flex Daily and Smart Cycle features.
A Simple Illustration
Water & soil in action!
Similar to soil, a sponge can be too wet or too dry to use:
- When a sponge is "soaking wet" is it oversaturated and cannot absorb any additional water.
- When a sponge is "moist" it's perfect and works as expected.
- When a sponge is "dry", it becomes difficult to use and sometimes has trouble absorbing water.
In the case of your yard, soil can be too wet or too dry. Managing soil moisture is the key to a healthy yard.
- When your soil is too wet, it becomes Saturated and cannot absorb any additional water. Runoff is common when soil is saturated.
- When your soil is moist, it is at Field Capacity and has just the right amount of water and air, which creates the perfect growing conditions for plants.
- When your soil is too dry, plants become stressed. If the soil becomes too dry and approaches Permanent Wilting Point, plant cells rupture and the plant will die.
For Rachio to properly calculate the size of the water tank for each zone, you must enter the proper soil type and vegetation type for each zone.
Sand, Silt, and Clay
Texture refers to the size of the particles that make up the soil. The terms sand, silt, and clay refer to relative sizes of the soil particles.
- Sand, made up of larger particles, feels gritty.
- Silt, made up of moderately sized, has a smooth or floury texture.
- Clay, made up of smaller particles, feels sticky.
As mentioned earlier, there are three basic soil classes identified by Rachio; Clay, Sand, and Loam:
- Clay soil is generally heavy and is compact in nature. Plants have a harder time developing roots in clay soil. Clay soil tends to retain water, but this is not always desirable. A clay or heavy clay soil, will greatly benefit from the addition of organic material, and it’s almost impossible to add too much.
- Sandy soils are the opposite of clay and generally drain too fast, and so are unable to hold onto any nutrients long enough for a plant to use them. Organic matter helps to hold onto water and nutrients, and as with clay, it’s almost impossible to add too much.
- Loamy soil is a rich, dark and crumbly soil that will allow drainage, but still retain enough moisture to be beneficial. Loam is a good balance of sand, clay, silt and organic matter. If you grab a handful of loamy soil, it should not form a compact ball. It should remain loose and crumbly. Loam is the best type of soil for growing almost everything!
There is a wide spectrum of soil types in the United States, as illustrated below.
Soil Infiltration & Scheduling
The type of soil helps Rachio to understand how quickly the soil will absorb water. If your nozzles apply water faster than the soil can absorb it, Rachio's Smart Cycle feature will automate cycle soak within the schedule, eliminating runoff by filling up your zone's Water Tank slowly, over an extended time period.
Consider yourself a Lawn Geek?
Below are a few resources & interactive maps that can help ID your soil type:
How to test your soil
The first step to understanding your lawn lies in knowing what soil consists of - particles, water, & air. The ratios between these three help determine the Soil Type you need to enter into the Rachio App. The three basic types of soil are Clay, Loam, and Sand. The most reliable way to figure out your specific soil type is to perform one of the following tests. These require you to get your hands dirty.
The "Mason Jar Test"
- Spread soil on a newspaper to dry
- Remove all rocks, trash, roots, etc.
- Crush lumps and clods.
- Finely pulverize the soil.
- Fill a tall, slender jar (like a quart canning jar) one-quarter full of soil.
- Add water until the jar is three-quarters full
- Add non-foaming dishwasher detergent, about a teaspoon.
- Put on a tight fitting lid and shake hard for 10 to 15 minutes.
- This shaking breaks apart the soil aggregates and separates the soil into individual mineral particles.
- Set the jar where it will not be disturbed for 2-3 days.
- Soil particles will settle out according to size.
- After 1 minute, mark on the jar the depth of the sand.
- After 2 hours, mark on the jar the depth of the silt.
- When the water clears mark on the jar the clay level.
- This typically takes 1 to 3 days, but some soils may take weeks.
- Measure the thickness of the sand, silt, and clay layers.
- Thickness of sand deposit ____
- Thickness of silt deposit ____
- Thickness of clay deposit ____
- Thickness of total deposit ____
- Calculate the percentage of sand, silt, and clay.
- [clay thickness] / [total thickness] = ___ percent clay
- [silt thickness] / [total thickness] = ___ percent clay
- [sand thickness] / [total thickness] = ___ percent sand
- Turn to the Soil Texture Triangle and look up the soil texture class.
- Soil particles will settle out according to size.
The "Hands On Test"
Ribbon test – Squeeze a moistened ball of soil out between thumb and fingers.
- Ribbons less than 1”
- Feels gritty = coarse texture (sandy) soil
- Not gritty feeling = medium texture soil high in silt
- Ribbons 1-2”
- Feels gritty = medium texture soil
- Not gritty feeling = fine texture soil
- Ribbons greater than 2” = fine texture (clay-ey) soil