Page 69 - Nutrient Management Planning Guide

64

Field Assessment

Prism-like:

Soil particles are arranged on a vertical axis bounded by flat vertical surfaces.

Prismatic structure: Well-defined vertical columns of soil with sharp edges.

Columnar structure : Vertical columns of soil with rounded edges, and are flat-topped, round-topped, or irregular.

Sources: Canadian Soil Classification Group, 1998; Brady and Weil, 2000 Photos courtesy National Aeronautical and Space Administration (NASA)

Figure 3.1.6 Types, Kinds, and Classes of Soil Structure

Implications of Soil Structure for Nutrient »

Management

Poorly structured (e.g., structureless or platy) soils have physical properties that may limit crop production, increase runoff and increase the risk of water erosion. In contrast, well-structured (e.g., granular) soils with stable aggregates promote better root development, enhance nutrient uptake and improve productivity. These factors must be considered when identifying field management strategies.

Identifying both surface and subsurface soil characteristics is important for managing nutrient leaching and runoff risk. Fields may have soil layers of

varying thickness with unique texture and structure. This can have a big impact on water infiltration rate (Figure 3.1.7). Soils prone to rapid water infiltration pose a higher risk of nutrient leaching, while those with poor infiltration have a higher risk of nutrient transport through runoff. Fields may be at risk of both if they have a layer of fine textured over coarse textured soil. This could result in runoff during rapid rainfall events and deeper nutrient leaching because of poor subsoil water holding capacity.