Loamy Sand Soil

What makes a soil loamy sand

Loamy sand is the step between sand and sandy loam. The Soil Survey Manual defines it as 70 to 90% sand, with the silt percentage plus 1.5 times the clay at 15 or more, and the silt plus twice the clay under 30.^[1] On the triangle: 15 ≤ silt + 1.5 × clay and silt + 2 × clay < 30.

Those two sums do the sorting. The first lifts a soil out of pure sand: there is enough silt and clay to bind the grains a little. The second caps the fines, because once silt plus twice the clay reaches 30 the soil counts as sandy loam instead.^[1]

The margin is thin. Our texture classifier calls an 88/8/4 sand/silt/clay mix sand; move two points from sand to clay (86/8/6) and it becomes loamy sand, and by 75/15/10 it is already sandy loam. By feel, moist loamy sand forms a ball when you squeeze it but won’t push out into a ribbon.^[2]

Loamy sand vs sandy loam

The two names use the same words in reverse order, and the classes share a border on the triangle, but they are not interchangeable. Loamy sand is the sandier one and won’t ribbon. Sandy loam carries more silt and clay (silt plus twice the clay of 30 or more), makes a short, gritty ribbon, and holds noticeably more water, as the sandy loam page shows. Here are the three sandy classes side by side in USDA’s survey.^[1][2]

Excessively drained includes somewhat excessively drained. Shares are of each class’s acres with a recorded value.

How loamy sand handles water

Water goes through it fast. Loamy sand topsoils hold a median 1.1 inches of plant-available water per foot, less than every class except sand, and water moves through them at 92 µm/s, about 13 inches an hour, the same median as pure sand. Organic matter is low too, a median 1.3%.^[3]

Drainage is the other side of that. 33.1% of loamy-sand acres are excessively or somewhat excessively drained and another 44.3% are well drained.^[4] 50.8% sit in hydrologic soil group A, where water soaks in freely and runoff stays low even when the soil is wet, a share second only to sand.^[5]

It is not always dry ground, though. 14.1% of the class is somewhat poorly to very poorly drained, and 12.3% carries a dual group such as A/D, where the first letter applies only once the land is drained.^[5] On a wet loamy sand, sort out the drainage before you choose plants.

On the usual dry ground, water little and often. Purdue’s advice for lawns on sandy soil is to irrigate more often and in smaller amounts than on heavier soils;^[6] the full routine is in the sandy-soil lawn guide.

Loamy coarse sand, loamy fine sand and loamy very fine sand

The grades run from very coarse sand (2.0 to 1.0 mm across) down to very fine sand (0.10 to 0.05 mm); the full table is on the sand page.^[1]

The grade changes how easily the soil washes or blows away. Minnesota’s stormwater manual rates fine and very fine sands as highly erosive and medium to coarse sands as less so.^[7] The full erodibility ladder is on the silt page.

Is loamy sand good for gardens and crops?

Better than pure sand, by USDA’s land-capability ratings: 53% of rated loamy-sand acres fall in Classes I–IV, the classes suited to cultivation, against 42% for pure sand.^[8] Where the land falls short, the recorded reason is most often erosion (subclass e, 48%) or a root-zone limit (s, 28%), and 10.6% is mapped prime farmland.^[3][9]

For a garden bed the fix is organic matter. Colorado State University recommends well-decomposed compost or aged manure on sandy soils to help them hold water and nutrients.^[10] How much to add is on how to improve sandy soil, and the plants that take dry, sandy ground as it is are on plants for sandy soil. Test pH as well: 56.1% of loamy-sand acres are acid in the survey (see how to raise or lower soil pH).

Where loamy sand is found

Measured against each state’s own soil, the ranking changes: loamy sand covers 32% of Georgia’s classified acres, 20% of South Carolina’s and 19% of Michigan’s.^[3]

Most widespread loamy sand soil series

Of the 5 most widespread loamy-sand series, 4 are mapped mostly in Georgia. The largest, Tifton, is a very deep, well-drained soil of the Coastal Plain uplands that formed in loamy marine deposits.^[11]

Loamy sand, loam and clay compared

Loamy sand sits near the sand corner of the triangle and clay near the opposite one, with loam between. Colorado State University sums up the two ends: sandy soils drain quickly and don’t hold water and nutrients well, while clay soils hold a lot of both but drain slowly and get very hard when dry.^[2] The particles behind the three are on sand, silt and clay.

Digging and building on loamy sand

Shrink-swell is not a worry here: the median linear extensibility of loamy-sand topsoils is 1.4%, in USDA’s low class.^[12]

Trenches are another matter. OSHA lists loamy sand with sand and gravel as granular Type C soil, the least stable of its three excavation types, and a competent person still has to classify each trench on site.^[13] How the engineering systems differ from USDA texture is on the soil types hub.

Frequently asked questions

What is loamy sand?

A USDA texture class of 70–90% sand with just enough silt and clay to hold a ball when moist. It drains fast and holds about 1.1 inches of water per foot of soil.^[1][2][3]

What is the difference between loamy sand and sandy loam?

Loamy sand is sandier and won’t ribbon. Sandy loam has more silt and clay, makes a short gritty ribbon, and holds more water: a median 1.6 inches per foot against 1.1.^[2][3]

Does loamy sand drain well?

Mostly. 77.4% of its acres are well drained or drier, but 14.1% is somewhat poorly to very poorly drained, so check a low spot before you plant for drought.^[3][4]

Is loamy sand good for a garden?

It works with compost and regular watering. 53% of its rated acres are in the land-capability classes suited to cultivation, well ahead of pure sand.^[10][3][8]

Where is loamy sand found?

Texas, Georgia and California have the most acres. As a share of a state’s own soil it peaks in Georgia, at 32%.^[3]