05-11-30 N Re Allocation

A new switch "N ReAllocation" was introduced, which provides an option ("on") to calculate a withdrawal of nitrogen from the plant storage pools as a response to low C:N ratios. When this option is chosen, the actual C:N ratios in the plant storage organs are not allowed to be less than the minimum C:N ratios of each organ respectively (the latter are specified by the user). Carbon losses that would result in a lowering of the C:N ratio below these thresholds are instead met by a corresponding allocation of nitrogen to the mobile nitrogen pool. Nitrogen demand by the plant is first met by utilising the nitrogen in the mobile pool, and secondly by withdrawing nitrogen from the soil.