The relative sizes of the different mineral particles in a *soil
that affects its aeration, capillarity, porosity, water absorption, and ease of cultivation. Gravel and stones are defined as being larger than 2 mm in diameter. On the same scale sand particles are 0.05-2.0 mm, silt 0.002-0.05 mm, and anything smaller than 0.002 mm is termed clay. Thus a sandy soil with larger particles has larger spaces and is well aerated and drained but dry. A clay soil is badly drained and becomes waterlogged. However clay particles tend to group together and also chemically attract other substances such as *humus
. The clay-humus complex is chemically active and thus capable of holding plant nutrients in the soil, maintaining fertility. Cultivation affects soil texture, e.g. ploughing, harrowing, and rolling will break down large aggregates into smaller particles. Over cultivation, however, can lead to soil erosion.