code: public Float computeInitialConditions(String key, Map<String, String> fullCurrentSoil, Map<String, String> previousSoil) {
  		Float newValue = (parseFloat(fullCurrentSoil.get(key)) * parseFloat(fullCurrentSoil.get(SLLB)) + parseFloat(previousSoil.get(key)) * parseFloat(previousSoil.get(SLLB)));
  		newValue = newValue / (parseFloat(fullCurrentSoil.get(SLLB)) + parseFloat(previousSoil.get(SLLB)));
  		return newValue;
  	}
docs: Perform initial condition convertion, for icnh4 and icno3 it's important to take into account the deep of the layer
  for computing the aggregated value.
  @param key
  @param fullCurrentSoil
  @param previousSoil
  @return