Table of Contents

• Fertilization
• Cation exchange capacity
• Enhanced efficiency nitrogen fertilizers
  • Controlled-release nitrogen fertilizer
  • Nitrification inhibition
• Height of litter layer

Fertilization

If surface water is present at fertilization, and defined fertilizer depth equals zero, fertilizer is equally added in surfacebulk layers.

Fertilizer application can be placed hetereogeneously, e.g., crop-specific in multi-cropping systems. The amount of fertilizer that is placed at a specific location is implemented as fraction of total fertilized nitrogen. For now, different N-species (e.g., NH4, NO3, DON) are not distinguished but only considered as total N.

Author

David Kraus

Date

Dec, 2017

Cation exchange capacity

Authors

• Khaledian [34]
• David Kraus (implementation into LandscapeDNDC)

Cation exchange capacity (CEC) describes the capacity of soils to hold positively charged ions such as:

• Calcium \((Ca^{2+})\)
• Magnesium \((Mg^{2+})\)
• Potassium \((K^{+})\)
• Sodium \((Na^{+})\)
• Hydrogen \((H^{+})\)
• Aluminium \((Al^{3+})\)
• Iron \((Fe^{2+})\)
• Manganese \((Mn^{2+})\)
• Zinc \((Zn^{2+})\)

E.g., clay and soil organic matter (SOM) are negatively charged and are major contributors to total soil CEC. The CEC of SOM depends on the soil pH value (increasing with pH). The CEC of soil can be expressed in mol positive charge per soil mass \(\left ( \frac{cmol_c}{kg} \right) \). Sandy soil with low SOM have low CEC \( \left( < 3 \frac{cmol_c}{kg} \right) \)), while clayey and SOM-enriched soils have high CEC \( \left( > 20 \frac{cmol_c}{kg} \right )\).

The ecosystem type specific pedotransfer functions of soil CEC are taken from [34].

• Arable ecosystems \( 41.025 + 1.091 * clay + 0.512 * silt + 0.159 * sand - 10.087 * ph + 0.494 * som \)
• Grassland ecosystems \( -64.880 + 1.365 * clay + 0.992 * silt + 0.864 * sand - 2.453 * ph + 0.282 * som \)
• Forest ecosystems \( 10.973 + 0.427 * clay - 0.379 * silt - 0.436 * sand + 4.313 * ph + 6.963e-2 * som \)

Enhanced efficiency nitrogen fertilizers

Authors

• David Kraus (implementation into LandscapeDNDC)

Controlled-release nitrogen fertilizer

The cumulative fraction of N release [0-1] is given by:

Nitrification inhibition

\[ 1 - (1 - \beta_3) \cdot min \left( e^{- \beta_1 T_{cum} + \beta_2 cwf + \beta_0}, 1\right) \]

Height of litter layer

Authors

• Ruediger Grote
• David Kraus

Update litter height depending on soil organic matter and bulk density.