[[TOC]]

Agricultural productivity is determined not only by weather and soil conditions only, but to a very large extent also by management. Apart from cultivar choices, sowing dates and irrigation and intercrops, which don’t do anything but affect the carbon balance of agricultural areas and the soil water, we don’t cover any management option explicitly, i.e. fertilizers, pest control, sowing densities, tillage, etc.

However, as carbon and water dynamics are affected by management intensity, we have introduced a mechanism to scale agricultural production intensity in LPJmL via scaling 3 parameters: LAImax, alphaA, HI (harvest index)

Initial description is in Fader et al. (2010)

The three parameters LAImax, alphaA, and HI (harvest index) are directly coupled to each other and can only be scaled in combination. Country specific values are supplied for each CFT in a file in the par folder e.g. source:trunk/par/manage_laimax_alphaa_revision_1241_sc.par.

LAImax can range from 1 (lowest intensity) to 7 (highest intensity) and alphaA ranges from 0.4 to 1 accordingly and HI has a CFT specific range (for the response to water stress, which is now disabled as water stress affects root growth, not HI, see #277)[2], which can be reduced by up to 20%, assuming more robust but less productive varieties in production systems with low productivity[3].

LAImax values are stored in the structure Manage (source:trunk/include/manage.h) which is part of the structure Managed_land (source:trunk/inlude/landuse.h), which is part of the structure cell (source:trunk/include/cell.h)

LAImax values are read in
source:trunk/src/landuse/fscancountrypar.c

LAImax computation in
source:trunk/src/crop/phenology_crop.c
alphaA computation in
source:trunk/src/crop/alphaa_crop.c
HI computation in
source:trunk/src/crop/allocation_daily_crop.c

Management intensities are just based on a simple calibration (in integer steps of LAImax from 1 to 7) to best match FAO national yields and need to be re-assessed if model parts that affect crop productivity or inputs have been changed.
For this, there is a R-script supplied in the R directory (see also #291), for a description, see Scripts_for_post-processing#R-script-for-LAI-max-calibration
source:trunk/R/global_fao_vs_lpjml_calib.r
most recently, Tim supplied a script that prepares the confs and param.pars needed and that generates the new par/manage_laimax_*.par
source:turnk/R/cal_helper.R

The management par file to use needs to be specificed in source:trunk/param.conf#L23
In the configuration file lpjml.conf you need to #define WITH_LAIMAX_CFT

M. Fader, C. Müller

#110, Wiki, Crop functional types, #277

1. Fader M, Rost S, Müller C, Bondeau A and Gerten D 2010 Virtual water content of temperate cereals and maize: Present and potential future patterns Journal of Hydrology 384 218-31 http://dx.doi.org/10.1016/j.jhydrol.2009.12.011

2. Waha K, Müller C, Bondeau A, Dietrich J, Kurukulasuriya P, Heinke J and Lotze-Campen H 2013 Adaptation to climate change through the choice of cropping system and sowing date in sub-Saharan Africa Global Environmental Change 23 130-43 http://dx.doi.org/10.1016/j.gloenvcha.2012.11.001

3. Gosme M, Suffert F, & Jeuffroy MH (2010) Intensive versus low-input cropping systems: What is the optimal partitioning of agricultural area in order to reduce pesticide use while maintaining productivity? Agricultural Systems 103(2):110-116. http://dx.doi.org/10.1016/j.agsy.2009.11.002