Code:
farms city requires factions { england, russia, southern_european, normans, timurids, } and hidden_resource light
{
capability
{
farming_level 10 requires factions { england, russia, southern_european, normans, timurids, } and event_counter very_good_harvest 1 and event_counter harvest 1 and resource grain
farming_level 8 requires factions { england, russia, southern_european, normans, timurids, } and event_counter good_harvest 1 and event_counter harvest 1 and resource grain
farming_level 6 requires factions { england, russia, southern_european, normans, timurids, } and event_counter normal_harvest 1 and event_counter harvest 1 and resource grain
farming_level 4 requires factions { england, russia, southern_european, normans, timurids, } and event_counter bad_harvest 1 and event_counter harvest 1 and resource grain
farming_level 8 requires factions { england, russia, southern_european, normans, timurids, } and event_counter very_good_harvest 1 and event_counter harvest 1
farming_level 6 requires factions { england, russia, southern_european, normans, timurids, } and event_counter good_harvest 1 and event_counter harvest 1
farming_level 4 requires factions { england, russia, southern_european, normans, timurids, } and event_counter normal_harvest 1 and event_counter harvest 1
farming_level 2 requires factions { england, russia, southern_european, normans, timurids, } and event_counter bad_harvest 1 and event_counter harvest 1
farming_level 0 requires factions { england, russia, southern_european, normans, timurids, } and event_counter very_bad_harvest 1 and event_counter harvest 1
trade_base_income_bonus bonus 1 requires factions { england, russia, southern_european, normans, timurids, }
;population_growth_bonus bonus 1 requires factions { england, russia, southern_european, normans, timurids, }
;population_growth_bonus bonus -1 requires factions { england, russia, southern_european, } and event_counter very_bad_harvest 1
;population_growth_bonus bonus -1 requires factions { england, russia, southern_european, } and event_counter bad_harvest 1
}
material wooden
construction 4
cost 800
settlement_min village
upgrades
{
farms+1
}
}
That's it! It took me three months to find out about the last step, bit I am glad to now share my knowledge and experience on it.