Definition

Total N-Stock refers to the total amount of nitrogen (N) present in the soil, expressed in kilograms per hectare. This stock is substantial, typically ranging from 1,000 kg to over 20,000 kg N per hectare. More than 95% of this nitrogen is bound within soil organic matter rather than being immediately available to plants.

Importance

Nitrogen is a key nutrient for plant growth and soil fertility. The total N-stock represents the soil’s long-term nutrient reservoir. While most of this nitrogen is in organic form, a portion becomes plant-available mineral nitrogen through the process of mineralisation, which generally occurs between April and late August. This gradual release supports crop growth during the main growing season.

Factors influencing N-Stock

• Soil Organic Matter Content: Higher organic matter means a larger nitrogen reserve.
• Soil type and texture: Clay-rich soils often store more nitrogen than sandy soils.
• Management practices: Crop rotation, organic amendments, and cover crops can increase N-stock over time.

Target values and interpretation

The scale of N content in your soil sample indicates how close the sample is to its target value. This target is not universal; it varies for each soil type and reflects the soil’s potential. Using soil-specific targets avoids unrealistic expectations and ensures accurate interpretation of nitrogen reserves.

Role in soil ecosystems

Total N-stock acts as a buffer for nutrient supply, reducing dependency on synthetic fertilisers. It supports sustainable agriculture by maintaining soil fertility and promoting healthy crop growth over the long term.

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