Root depth for maize

[yuki-nmi]

Root depth is 10cm for mais and grassland, 30cm for arable land and nature ('root_depth.R'). The root depth influences the conversion of SOM (%) to D_OC (kgC/ha), and D_OC is the input parameter for D_NLV. Due to the difference in root depth, NLV is much higher for arable land than maize when the SOM level is the same.
Consequently, the indicator for N (I_C_N) is often very low for maize (median 0.52 for whole NL) compared to arable land (median 0.9). Furthermore, indicator for N retention (I_E_NSW and I_E_NGW) are often high for maize (median 0.98 and 0.96) irrespective of their high leaching fraction. This sounds like an artefact.

Action needed: Re-consideration of root depth for mais in 'root_depth.R'. It should be deeper, e.g. 25 cm (measurement depth for maize field)??

[yuki-nmi]

An additional note: in the factsheet of 'stikstoflevering', it is stated that the depth of bouwland (for conversion of SOM to D_OC) is 25 cm. Thus, either the factsheet or the R script needs to be updated.

[gerardhros]

the NLV calculation for grass is an empirical function calibrated on long-term experiments. Its different from the function for arable land, that is based on a model estimation or C decomposition. So, SOM should only have impact on non-grassland soils.
Indeed, depth for maize should be 25 cm, comparable to all arable crops.