Rule n°10 : Crop planting decision rule Title Time step for examining the rule Limits of time step for applying the rule Options To crop or not to crop year Year 1 to tree harvest Y/N State variables required for the rule Net margin of crop in alleys for last year (NM crop ) Cost of weed control in tree rows (C weed ) Net margin from cropped area with no crop (Nm nocrop ) Likely consequences known by the manager Increased profitability of agroforestry system, if crop rotation is ended when the rotation becomes uneconomic. Effect on the tree, effect on future options for growing crops (weed control), cost of managing the uncropped alley… State variables required for the rule Crop yield over time, past expected yield over time, past climate conditions (to mitigate expected-actual yield discrepancies) Tree diameter over time, canopy width, lowest branches and machines, recent history of pruning (intention to prune or thin the stand), Decision criterion Economic management rule: IF NM crop - C weed > NM nocrop THEN Crop ELSE Not Crop Questions and comments This rule needs to be elaborated In the case of dry farming, water saving fallow should be considered as a crop, not as the end of the cropping system. Therefore, the rotation will be imposed with a fallow period, and the decision to crop will not be examined during fallow years. Alternately, the decision to crop could depend on the water content of the soil at a given date. But this would mean that the fallow water use can be modelled. We therefore need a fallow module in the crop model.
Rule n°11 : Choice of the crop rule Title Time step for examining the rule What crop to plant next year Year Limits of time step for applying the rule 1-n Options Keep the basic rotation as defined in the initial setting Change to a more shade tolerant rotation (including a permanent pasture) Avoid a crop sensible to slugs problems where the trees are too big Information needed about the current state of the system (state variables) Likely consequences known by the manager State variables required for the rule Decision criterion Questions and comments When light demanding crop yield falls below a threshold To be effective, the crop model should be realistic about the impact of the tree environment on the crop growth. This should probably left as a strategic rule. But a shift from a light demanding rotation to a shade tolerant rotation could be included as a tactical rule. Additional rule on fallow in dry systems by Gerado Moreno Title Ploughed fallow or unploughed fallow Or Fallow or crop next year Time step for examining the rule Limits of time step for applying the rule Year 1-end of crop Options State variables required for the rule Likely consequences known by the manager Soil moisture content at time of crop sowing Cost of ploughing Reduction of the grazing area Effect on future crop production