[GpsFrontier]

Hello twd000,
This is part 1 of the reply, I had to break it into two posts because it was too long to fit in one post.

What is the reason for placing different crops in different systems? Are the nutrient solutions that different? I assumed since I was planning to grow leafy green things, not fruiting things, that they could be grown in the same system?

While nutrient differences are one reason, there are many other reasons. You can physically grow anything together with anything, in any type of solution you want. But it's inevitable that some plants will suffer, and you may be wasting a lot of useful space because of it. I'm not saying it's impossible to grow them all in one system, just that if you want healthy plants not only is doing so not practical, but can waste a lot of useful space because it's designed for some plants, but not all of them. While the main thing that specifically defines a specific hydroponic system is the reservoir, there is a lot more to a hydroponic system than a reservoir to consider. There are also 6 types of hydroponic systems, and some systems are better choices for some plants than others, especially when you consider the number of plants. That's why I said I would split what you plan to grow into at least two systems, and depending on how many plants of each possibly more.

So often new growers try to do things backwards. They pick a hydroponic system that they think would be easy to build, build it, and start growing plants in it. Only to find out shortly later that they made the wrong choice in type of systems, designing it, and/or the plants outgrew the system before they can even harvest anything from it. Bottom line they tried to do to much, and skimped the planning because there were either things they didn't know about to consider, or just didn't think it was necessary. So having to go back to the drawing board and start over becomes their first lesson they learn the hard way.

For me my first lesson I learned the hard way was the importance of the water temperature. Because I didn't know it was important to consider the water temps, and the time of year, that ended my growing season for the summer. I sent that summer researching economical ways to to keep the nutrient solution temps down. One of the biggest drawbacks to trying to grow everything in the same system that new growers don't consider is that their all connected. In other words if you have a problem with pathogens or disease affecting one plant, that will also affect all of your plants. You can wipe out all your crops in one fail swoop, because you didn't separate them. Its all about the benefits and compromise. I'm currently in the middle of writing an article (more like handbook) on the subject I've titled "Comprehensive Guide to building your own hydroponic systems and getting the most out of your space and budget" that's already over 7,000 words and 13 standard printed pages, and I still have a lot more to do.

Reading elsewhere online, it sounds like people are able to get nearly continual harvest (cut-and-come-again) from leafy greens, so there is little need to stagger planting at different growth stages. If I only harvest outer leaves for each night's salad, can the main plant survive and thrive?

Yes, with some pants you can just cut off what you need right now, and leave the plant to grow more. I have even done that exact thing because I didn't need a whole head of lettuce. I just needed enough for dinner that night, and I'm only one person (not a family of four). But just cutting off what you need at the moment, doesn't reduce how much you need to harvest/eat. It also wont increase how fast the plants grow the foliage, or reduce the number of plants you need to grow to get that foliage.

In fact there is a reason that the lettuce you buy at the store is the center head, and not the outer leaves. That's because the outer leaves are tougher, and usually more bitter. The center leaves (head) is more tender and sweeter. So again just cutting and eating the outer leaves will affect the quality of product you wind up eating. The older the plant gets, the tougher it will get. I'm not saying that you cant just cut off what you need, and leave the plant to continue growing. Just that considering that your trying to feed a family of four, doing so has little if any benefit.

Now there are some crops that you don't typically harvest the whole plant, and just cut off what you need and leave the plant. Like Spinach, micro greens, herbs, etc. etc. Even so you do want to rotate these plants on occasion because the older the plant gets, the tougher it will get. These type you may want to rotate every 6 months rather than harvesting from the same plant for years. Again just another reason to separate the plants into different systems (long term plats and short term plants).

Just to clarify using different systems has nothing to do with "stagger planting at different growth stages" except for the prorogation system, and the prorogation system has a much more important function. That is saving space and nutrients, thus money and allowing you to be much more productive in the same amount of space. As an example. if you eat and consume 3 heads worth of Romain lettuce each week. You would still need to be growing 24 plants. But if you only harvest the outer leaves, you need 24 full grown Romain lettuce. If you harvested the full heads, and rotated seedlings in to replace the heads you harvested. The main system would only need to hold 12 full plants, and you have the other 12 plants in the prorogation system. Essentially cutting the size of the main system in 1/2. The prorogation system takes up far less space, and can be used to raise all your crop seedlings. In short making you about twice as productive in the same space.

Your comments on organic vs. conventional nutrients make sense to me. If that is the case, what is the benefit of the worm tea, if the plants get 100% of nutrition from the conventional nutrients?

The point of compost teas is beneficial microbes, fungi, bacteria, and acids. The compost tea brewer takes these beneficial microbes, fungi, bacteria found in abundance in the quality compost and multiplies them by the millions. It's an absolute great insouciant for soil grown plants as well. While some water soluble nutrients are extracted from the compost, the oxygen rich environment provides a great environment for the beneficial microbes, fungi, bacteria to breed and multiply. In soil these "beneficials" turn the organic material into raw chemical elements/nutrients the plants absorb.

Now there is no soil in hydroponics, so your asking what does that have to do with hydroponics. These "beneficials" have another very important function. To combat pathogens. They are important for combating pathogens in soil as well. As for hydroponics, no mater how sterile your hydroponic system is, or how you take care of your nutrient solution, there is always the a possibility of pathogens. Pathogens can enter your system from any number of ways, including from the air, and given the right conditions can take over. I found that out when they were doing some sewer maintenance on our street and were kicking up a lot of dust. That dust got into my hydroponic system and introduced soil born pathogens to my hydroponic system.

Think of it like a war (beneficials are the good side, and pathogens are the bad side), the side with the most troops typically wins. If the pathogens get a foothold they can bread and multiply uncontrollably. When they out number the beneficials, the pathogens take over and cause damage and disease to the plants. The point to inoculating the hydroponic system with beneficials is to keep it a one sided fight, but favoring the good side. Along with combating pathogens, some of the beneficial fungi and bacteria also help the plant absorb and use the nutrients, as well as can have other benefits to the plants roots.

Now beneficials can't live floating around in water very long, so they need some kind of bio-filter to attach to to live and breed (basically takes the place of soil in nature). In hydroponics, the growing media becomes the bio filter. Naturally some growing medias are better as a bio filter than others, and the more of it the more space there is for the beneficial to perpetuate breading and multiplying. The beneficials feed on pathogens, sugars, and some of the nutrients in the water. Beneficial microbes is a fairly complicated subject, but there is a lot of information on it.