OK,
It took me a little while to figure out what you are all saying, but since i am still getting my head around agricraft i thought i would go with the approach of making giant
mushrooms with bonemeal. Since I have a skeleton powered spawner running i have tons of bonemeal. (I will still go into Agricraft, as it looks fun).
SO i spent a while chopping them up and planting new ones.
I am not sure how to breed things with Agricraft, so will read up on this, but i guess what you are saying is to get 10/10/10 mushroom seeds, plant them in a dark room
with those crop sticks and then use an MFR harvester?
-Wuffle!
That seems to be the consensus, and what I would recommend personally.
Agricraft is great, and pretty simple, there are just a couple of things to get the hang of and you'll be away. You'll need a seed analyser and a journal (dead easy to make). The idea behind Agricraft is that, unlike vanilla crops, you have to grow its crops on cropsticks. Seeds are planted on single crop sticks (4 sticks sticking up out of the ground vertically), and when mature (WAILA is your friend for telling you this) they can then spread to an adjacent block of land that has cross-cropsticks (cross-crops) planted on. These are what you get when you apply cropsticks twice - once for the vertical, a second time applies 4 horizontal sticks. Depending on the configs, they may only need one adjacent mature plant to spread or they may need more (default is 2 I believe).
Now to the plants: in vanilla minecraft, there is one basic type of seed - wheat seeds. Well, two, if you count nether wart, and that's relevant later. Agricraft adds 2 others: carrot seeds, and potato seeds. These can be obtained from breaking grass. To start working with the seeds, you need to analyse them with the seed analyser. Once you've done that you'll find they now have numbers attached: 1/1/1. Seeds obtained in this way will always be bottom level. The figures are for Gain, Growth and Strength (the order may be wrong there) - basically: Gain is how much you get when harvested, Growth is how fast they grow, and Strength is resistance to weeds (and chance of success at planting clippings).
To increase these values, you need to breed the same plants together (usually - again, depends on configs I think). So if you have three blocks of farmland, the two on either end with cropsticks and the centre empty, you would plant a 1/1/1 wheat seed at either end, then wait for them to mature (or bonemeal them up!), then plant cross-cropsticks in the centre block. When this spreads to the centre, you'll notice the cross-crops now appear to be normal cropsticks and there is an unidentified wheat plant in the centre. If you break this and analyse the seeds, there should be a small increase in at least one of the stats.
Why did I say wait until they were mature?
Weeds. I mentioned them before, and they are the bane of your existence. They have a chance to appear on cross-crops (and cropsticks I believe) that have no plant on them. So you'll need to keep an eye on your centre block and make sure it is wheat and not weeds when the cross-crops disappear. If you do get weeds, break the cropsticks and replace them to get rid of the weeds. You can use the rake, but I rarely bother. Weeds can spread and overrun an entire field of crops if unnoticed - a high Strength stat increases the time this takes, but there is no immunity to weeds.
One thing worth mentioning is that (again in the default configs) if you have 4 mature plants around a cross-crops (diagonals don't count), the stat increase you will observe when it spreads to the centre will be higher than if you use 2.
Coming back to the plants at last: the idea behind Agricraft is that EVERY plant bar those 4 (wheat, carrots, potatoes and nether wart) can be bred from those starting plants. So, sugarcane seeds (that's right, even sugarcane can be bred!) are bred from wheat seeds and carrot seeds. This works similarly to the improving of stats - adjacent plants can spread to cross-crops - but instead of improving stats, they produce a whole new plant which, unlike breeding the same plant, only takes some of the stats of its parent (so two 10/10/10 plants usually produce a 5/5/5 crossbreed).
One more thing to consider is soils - most seeds can be grown on farmland (tilled soil, hydrated of course) but certain things require the expected "soil" under the cross-crops - so sugarcane and cactus both require sand, mushrooms require mycelium, nether wart requires soul sand. The ore crops have other requirements I won't go into here.
EDIT: D'oh! took me so long to write this, someone else did a better job, more succinctly!
