Page 67 - Nutrient Management Planning Guide

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Field Assessment

Management Implications »

Coarse textured soils have a higher risk for nutrient leaching into ground water because of higher infiltration rates and lower water holding capacity than medium or fine textured soils. This risk increases when groundwater is present at relatively shallow depths. Yield potential may also be lower on coarse-textured soils because of reduced water holding capacity and nutrient retention capacity. Excessive tillage should be avoided on coarse textured soils because of higher wind erosion risks.

Fine textured soils on sloping land adjacent to surface water bodies are at higher risk for runoff transport of nutrients to water bodies. These soils may have better yield potential due to higher nutrient and water holding capacities compared to medium or coarse textured soils. However, they are susceptible to compaction from field traffic when wet, reducing water infiltration and increasing runoff potential. These risks should be considered when planning and conducting field operations.

Soil Structure

Soil structure describes how individual soil particles clump together or aggregate. It is the result of several factors including: soil texture, root growth, decomposition, soil organic matter, freeze-thaw processes and soil micro and macro-organism activity. These physical and biological forces fracture clods, bind particles together and create channels for water movement and root growth. Cultivation tends to break down soil aggregates and destroy soil structure.

Soil structure is best determined by visual assessment. The Canadian System of Soil Classification (1998) describes four basic types of soil structure: structureless, block-like, plate-like and prism-like (Figure 3.1.6).

The soils of western Canada are dominated by montmorillonite clays, which increase the CEC of the soil. Since cation exchange plays an important role in crop nutrition, soil texture then influences soil fertility.

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