Farming weeds

The classic definition of a weed is a plant out of place. Johnsongrass, I was taught in the state of New York (and all ag schools, being state schools, teach chiefly their states' ag), was a weed; then I went to Texas and found it a forage. So if you're farming weeds, I suppose they really aren't weeds anymore: you must have decided that whatever's in your field IS in place, no matter what it does or how it got there. In a way this is like rangeland management: you're accepting the plants that are there, seldom doing much to help them grow but never doing anything to drive them right out of business, moving your livestock along before they overgraze the area. Only here I'm not talking about raising animals but the plants themselves. Animals make sense where land can't be practically tilled, where the few plants that can survive on it can't be turned into row crops, where the only way to harvest such riches as there are is with things that can walk around great expanses of stony terrain and turn pulp into protein. But can the plants alone be made to make sense in such circumstances?

Maybe, if

it is simply impractical to till or sow - you have to grow what arrives in your field
things do arrive, regularly
it is, on the other hand, practical to fertilize and harvest - you've got to be getting something from your land, and when you do, you must be replacing it with something else (the only way anything is "sustainable")
if these encouragements encourage weeds also, you don't care - that's the whole idea!

I had imagined (really, fantasized) many alternatives to the above, in most cases postulating that the farmer of weeds wasn't harvesting: that what was being done was stewarding a purposely messy preserve, where useful parasites or insects or birds or suites of DNA and RNA could occasionally move out or be found out - carefully collected while the field was otherwise left in convenient peace. But that was all just too vague, even for my tastes. So I went back to the idea of almost-real farming: kudzu, say, would invade your land, and you'd decide not to inquire too closely as to how it got there (or worry, ha-ha, about whether it was going to come back next year) and just basically mine it. What you'd be mining it for would probably be just cellulose, the only thing you can count on all vascular plants to produce in large quantities.

So, the "lightweight agronomic calculator" here calculates as follows:

you state that there are n species of interest, and for each, you state
1. how long its life cycle is
2. what its peak biomass production per viable seed is
3. how many viable seed arrive from off-field, and how many viable seed each plant can produce
you start a timer
biomass is read out periodically, and when you feel like it, you harvest
at the end of a year (or let's say a "growing season"), you see how you did: total biomass harvested versus number of harvests

It is assumed you always provide adequate water and fertilizer, and that the weeds don't compete among themselves, and that incoming viable seed count is constant. Enormous stretches, I know. The assumptions - or fantasies - are documented in the source code.

Not this webpage's source code, though. The model is capacious, so I've put it on its own page.