Understanding soil texture: A key to successful gardening

Have you ever watered your garden and noticed the water takes a long time to drain or percolate through the soil? You might want to investigate your soil texture.

When it comes to gardening, soil texture is one of the most crucial factors to consider for ensuring a bountiful harvest. Soil texture is the relative proportion of sand, silt, and clay in the soil. This texture determines chemical and physical properties, most importantly how the soil holds air, water, and nutrients. The three main particles vary in size: sand (0.05mm to 2mm), silt (0.002mm to 0.05mm), and clay (less than 0.002mm). The pore space between these particles influences their ability to retain air, water, and nutrients to varying degrees.

The ideal soil texture

Sand has the largest particle size with angular and gritty edges, allowing for large pore spaces. This provides more air between particles and allows water and nutrients to percolate through easily. However, sand does not hold onto water and nutrients well, leading to quick drainage.

Silt is a medium-sized particle with a texture like flour. Its smaller particles allow for better water-holding capacity and nutrient retention because of cation exchange capacity (negatively charged sites). Silt provides moderate water retention and drainage, less than sand.

Clay is the smallest particle with a sticky texture. Due to its small size, large surface area, and high cation exchange capacity, clay holds water and nutrients much better than the other particles.

Knowing the soil texture is important because plants typically grow best in a balanced mix of sand, silt, and clay, known as loam, although productive soils can also be slightly heavy on one of the particles. When these particle sizes are balanced, the soil will provide the beneficial properties of all three, allowing for good moisture retention, drainage, and aeration.

Sandy soils require more frequent watering and fertilization and may need to be amended with compost, organic material, or clay to improve water and nutrient retention and reduce erosion.

Clayey soils need less frequent watering but can suffer from poor drainage, potentially depriving plants of air. Clay holds nutrients well, so fertilization can be less frequent, but small pore spaces can lead to compaction, restricting root growth.

Determining Soil Texture:

Soil texture can be determined through laboratory tests, the feel method, the jar test, and soil survey maps.

Jar Test Method:

• Gather several soil samples from your garden and mix them in a 5-gallon bucket.
• Fill a quart jar two-thirds full of water and add a tablespoon of dishwashing liquid.
• Gradually add soil until the water reaches the top.
• Close the jar tightly and shake well for 1 to 5 minutes.
• Let the jar settle for 30 minutes to 3 hours. Sand will settle at the bottom first, then silt, and finally clay at the top.
• Measure the total depth of the separated soil layers and each layer individually.
• Calculate the percentage of each layer by dividing the depth of each layer by the total depth. These percentages will help you understand how well your soil will drain and retain nutrients.

Using the ratios from the jar test determination of soil amendment applications can be inferred. If your soil has a high proportion of clay (>50%), adding compost or sand can improve drainage and pore space size. If your soil has a larger portion of sand (>50%), adding compost or clay can improve water retention and nutrient-holding capacity.