Giving back to the soil what the veggies take out

I have been thinking about the veggie seeds that I  grow for immediate consumption.  I suppose they just take from the soil, then covert it into vitamins and other goodies that we in turn use when we eat them.  I have been reading a lot about how much more nutritious our home grown organic vegetables are than those sold in most grocery stores. There are all different ways that I continually add goodness back into the soil, because if the growing vegetables are taking it out, then I better be replacing it with something. I am cropping quite intensely and also want to try to produce food year round.  I know outright of a few things I do to amend the soil, but wonder if there is something else I am missing.  If I want to take so much out of the soil how do I know I am putting enough back?
Generally in this area of the tropics vegetables are grown in the "winter" or dry season, and the ground is left fallow for the wet season.  I want to grow year round, and if the wet season crop is not for eating then it better be feeding the soil.
Perrenials:
I have a few perrenials in the veggie patch.  2 Asparagus were planted as two year crowns two years ago and then I have two other plants grown from seeds planted two years ago.  I am still playing around with when to harvest and how to mulch and whether to cut the plants back entirely.  They never totally die down in this climate.  Other perrenials include galangal, lemongrass, ginger, mushroom plant, basil, sawtooth coriander, mother of herbs.  Some of these are cut right back in the winter to allow part of the perrenial beds to be used for other crops.
Nitrogen fixing plants:
Certain beans and legumes fix nitrogen into the soil, and they do this better if the seed is coated with an innoculant.  The first time I planted pigeon peas I got the seeds with an innoculant, I think I need to do that again. The innoculant needs to be fresh and formulated to a specific seed. Pinto peanuts are another plant grown in this area to fix nitrogen when it is slashed back into the soil, therefore also adding many other different nutrients.  Plants that are grown merely to amend the soil are also known as green manures.
Rotation of crops:
I know that solanacous plants  (tomatoes, eggplants etc)  should not be grown in the same location year after year.  Lucky gardeners with large gardens can have a nice little rotation going, but I  don't have that much room.  I was planning to grow tomatoes again in the center bed next year, and then this eggplant volunteered right in the middle of the bed, and has been going strong all winter.  I let it be because I love eggplant, but I realize I am flouting my own rule.  Opening up two beds along the back fence has allowed more beds, but funnily enough tomatoes just have not grown well there this year. I grew marvelous cherry tomatoes in the center bed the first year I was here and am anxious to grow them there again next winter.
Soil amendments:
I normally add some kind of manure based pellets once or twice a year, at the beginning of each planting season.  I also pick up seaweed and spread it as mulch once or twice a year, especially around the asparagus.  I am continually making compost, and add a large amount just before planting each season.  I have also used seaweed, comfrey, fish emulsion, and weed tea as foliar feeds throughout the year. Sulphate of potash and trace elements have also been added this year.  My soil continuously shows up as 7 on my trusty little ph meter.  Either I have very consistent soil or else my trusty little meter is broken.
sorry - no photos this time, just my thoughts.