9. Input To & Output From Soil

Input to soil

C input

From crop residues: Organic C content in crop residues incorporated into soil is described in Residue removal & incorporation.
From manure: C inputs from manure application and grazing excretions are estimated based on manure N content and manure C:N ratio. As a safety check to prevent unrealistic high values, C input from grazing excretions is capped at 2500 kg C ha^–1 year^–1.
From compost & sludge: C inputs from compost and sludge are described in 8. Compost & Sludge.

N input

External N input sources to soil include mineral N fertilisers, manure application, grazing excretion (grassland only), compost, sludge, atmospheric deposition, and biological N fixation. The total amount of N input varies depending on crop and region.

Equation 9.1

where:

is the total N content in mineral fertilisers applied to the field (see Distribution of mineral N fertilisers]).

is the total N content in manure applied to the field (see Distribution of animal manure).

is the total N content in urine and feces excreted during grazing (only for grasslands; see Distribution of grazing excretions).

is the total N content in compost applied to the field (see Nutrient content in compost).

is the total N content in sludge applied to the field (see Nutrient content in sludge).

is the total atmospheric NH₃ and NO_x depositions to the field, which are part of default Miterra input derived from regional deposition maps.

is the biologically fixated N, as calculated in Biological N fixation.

N_fix should only include fixation by arable crops and grasslands. N fixated by soybeans and pulses are added indirectly as part of crop residues.

P input

From atmospheric deposition: At present the deposition map is not updated to the input data yet. Currently, P deposition of 1 kg P ha^–1 year^–1 is assumed.
From mineral fertilisers: P input from mineral fertilisers are calculated based on the application rate of each type of fertiliser, and the P content in the fertiliser.
From manure: P content in applied manure and grazing excretions are estimated based on N content and N:P ratios of the manure.
From compost & sludge: P inputs from compost and sludge are described in 8. Compost & Sludge.

Input of other elements

Other elements include Ca, Mg, K, Na, Cl, S, Cd, Cu, and Zn. Not all elements are accounted for in each input source.

From atmospheric deposition

Atmospheric depositions of Ca, Mg, K, Na, S, Cd, Cu, and Zn are available as part of Miterra default database.

From mineral fertilisers

Element inputs from mineral fertilisers are calculated based on the application rate of each type of fertiliser, and the composition of the fertiliser.

From manure

Input of other elements to soil from manure is estimated based on the total manure N applied, and the corresponding N:X ratio in manure, where X may be Ca, Mg, K, Na, Cl, S, Cd, Cu, or Zn.

Equation 9.2

where

	is the content of element X in applied manure (kg X ha^–1);
	is the N content in applied manure (kg N ha^–1); and
	is the N:X ratio of applied manure.

From compost & sludge

Input of K are calculated for compost and sludge, as described in 8. Compost & Sludge.

Output from soil

C output

Emission of CO₂ is the only C output pathway from soil, which is modelled by RothCN (see Decomposition of organic carbon).

N output

N output pathways include:

Harvest of crop products (see Harvested products);
Removal of crop residues (see Residue removal & incorporation);
Emissions to the environment in the forms of N gases, surface runoff, and leaching (see 10. N Losses from Soil).

P output

P output pathways include:

Harvest of crop products (see Harvested products);
Removal of crop residues (see Residue removal & incorporation);
Loss to water via surface runoff and leaching (see Runoff and leaching).

Output of other elements

Output pathways for other elements include:

Harvest of crop products (see Harvested products);
Removal of crop residues (see Removal and incorporation of other elements);
Loss to water via surface runoff and leaching.
- For S, see Runoff & leaching.
- For heavy metal elements (Cd, Cu & Zn), see Runoff & leaching.
- For Ca, Mg, K, and Na, see Runoff and leaching.