Hey guys! New here, but huge fan of the game. Always wanted to do an ecology/permaculture farming sim, (still haven't found a good one), and from the very beginning thought DF is a perfect start. I am irl a former-computer engineering student-turned-professional horticulturist and practical ecologist. I know agriculture is something on the development horizon, so hopefully I'm not too late here. There is already so much care that goes into world formation geology, it seems natural to continue that into dynamic game-play.
In one sense, I'm bumping this
http://www.bay12forums.com/smf/index.php?topic=76007.0 pretty exhaustive thread, but also wanted to bring my own spin, which will probably include some points already made, but may also offer a good marriage of intuitive simplicity and fun/challenging complexity.
I think a big part of the crux of soil and ecology and its translation into human understandable/programmable language is the overwhelming complexity that unfolds when you approach the subject from a reductive/scientific pov. Here, I think it would help to focus on the basic foundational, modular/symbolic concepts upon which all living processes (plant and dwarf alike) are modeled.
There are four ingredients to living processes: mineral, air, water, and carbon (the old Greeks called it fire, a simple model of synergetic carbon reduction/oxidation; combustion and respiration are ecologically very similar). Balance is an important concept (in fertile soil: 25% air, 25% water, 45% mineral, 5-10% carbon). Mineral is heavy/slow and air is insubstantial/fleeting, but water and carbon cycle endlessly through atmospheric and terrestrial phases, and in transition, they are extremely manipulable.
DF already does pretty well with the mechanics of water and its seasonal flux, though there are some tweaks that could be implemented with how it soaks into and is held in soil.
I think carbon would be a good place to start with adding a new mechanic around soil fertility modifiers to soil tiles (similar to the 1-7 depth-scale of water?). The roots of plants are really the primary builders of soil carbon; as they grow and die and regrow through the seasons, they leave behind carbon-rich air/water channels in the soil. In this way, disturbance associated with annual cropping systems depletes soil-carbon, while long-term/stable perennial cropping systems build soil-carbon. This type of soil-carbon would probably be part of world-generation. I would love to see an agricultural option that allows perennial guild/community style planting zones that could be built up around pre-existing fruit/nut trees, though I understand the current system of annual cropping has an attractive mechanizable aspect for many (hence our modern reliance on industrial fertilizers and machinery).
And then of course there are the possible fun sub-mechanics surrounding the translation/cycling of "waste" (refuse, corpses…) into "resource". Some waste is rich in carbon (wood and other dry/brown vegetation), while some waste is rich in nitrogen (green vegetation and especially animal products). Carbon and nitrogen have a kind of twin-sibling relationship. Too much nitrogen causes carbon to be quickly respirated (depleted) from the soil, and leads to collapse of soil-life when the artificially-applied nitrogen is eaten up and washed out of the soil (think like the binge-crash of sugar or hard-drugs), while too much carbon ties up plant-available nitrogen and/or leads to water-saturation/anaerobic conditions. In this way, there should be an appropriate sense of time and place regarding the manipulation of these resources.
Ideally, we "complex" these valuable resources by 1) facilitating interaction, and simultaneously 2) slowing/buffering the flow through the system. Terracing linked up to a drainage/water-source is a perfect example of complexing water. Planting nurse-logs/corpses in the ground, "chop-and-drop"/chip/leaf mulches are examples of complexing carbon into the soil system.
Mostly, the focus should be on the interactions of water and carbon, as these really lie at the heart of healthy soil and plants.
Gotta run,
Thanks again for a really fun game.
-B