Article 6-4 The Most Important 2 Weeks
By Steve Berlow
When asked to write my first article for Maximum Yield Magazine, I immediately thought of all the great things I could write about that could help the hobbyist hydroponics grower. Having spent over 10 years helping hobbyist hydroponics growers in Australia, there was so much that I could write about, but was there a single topic that would have an immediate impact for obtaining significantly better results. To help me, I consulted my very good, and often consulted friend, Jack (Daniels!). Jack helps me at times with many things, from arguments with the wife through to helping me decide what to write about for you now. After much pondering and consulting with my good friend Jack, (about three or four times!), it dawned on me that there was indeed a topic that I could write about, one that would make a significant and dramatic impact on the results of almost every grower out there.
So what is this vital and often (almost always) overlooked topic that could make such a dramatic difference to what we grow. Well, let me start by saying that this is a two edged topic, one is the timing and the other is the application, both are equally important and both are forever intertwined. Ok, let's look at timing. What if I said that you, as a hydroponics hobby grower, were probably not capitalizing on the two most important weeks of your plants life. You're probably thinking I'm a little crazy but the truth is, if your not concentrating on this very critical phase of your plants life then it could be you that are a little crazy because you're missing out on so much extra development and yield! This is the time that you can make a significant difference to the final results that can be achieved just by spending a little time and effort during these critical first few weeks. So how can this be? How can significant results be achieved when, after two weeks, the plants are still so small? They do all their major growing and development during flowering or fruiting, right? That's correct in part, plants do undergo significant growth and development during this period, which is typically called the exponential growth and or development phase. If you look at figure one you will see all vigorously growing plants typically undergo what is called a sigmoid or "S" shaped growth curve or pattern. "A" is the lag phase, which, for most, will equate to the first seven to 10 days of growth. "B" is called the exponential growth or development phase, which, typically, lasts for approximately four to five weeks and this is the stage that most people spend most of their time and money on because they can visually see the biggest results. "C", the final stage, is what is called the equilibrium phase. This phase is when the plant has done most of its growing and development. This growth and development is calculated as total biomass of all plant parts. Now we know a little more about how plants grow and develop, let's look at what happens when we concentrate a little more on the "lag" or first stage of the plants development. This is where a little can make a lot of difference in the end. Now, have a look at figure two where the blue line indicates a typical regime in nurturing our plants and the red line indicates where we have done something so simple and yet so effective. By spending a little time and money (typically less than $50) we have increased our base biomass index by approximately 35%. Now, this may seem like a lot but when we look closely it's not really. It's the difference between having a plant that's around nine inches high X nine inches wide and having one that's around 10 inches high by 10 inches wide at the end of your second week. Doesn't seem like a lot, does it? Now, have a look at the end points of both lines in figure two. That's right, there's now a 300% difference in biomass! Before we start having a party and running out to the nearest hydroponics store, we need to understand that this is a 300% increase in total bio mass that can equal, in some cases, a 20% + increase in yield of desirable plant parts, e.g. flowers or fruits. This scenario is in line with foliar nutrition based experiments conducted by Dr. Hillier at Washington State University who demonstrated an average four-year yield increase in potato crops of over 30% (3). Ok, now you can have a party and run off to the nearest hydroponics store! Hydroponic storeowners take note; get ready for rush of excited customers!
Now we know that spending a little more time and effort on our plants during the lag phase can make a huge difference. We now have to concentrate on what we have to do, or the methodology to get our plants that little bit bigger during this period.
The easiest and most effective way to do this is through foliar spraying. By foliar spraying our plants with selected nutrients etc. during this period, we can get that increase in early biomass that we are looking for. So what do we spray and how? Before we go wildly spraying our plants, we need to look at a very import partner to our foliar spraying program, "Wetting and Delivery Agents". These little guys will almost single handedly determine the percentage of success of your foliar spraying regime. So why do we need a wetting and delivery agent? Simply put, without it, only a small amount of what you spray on your plants will actually get inside to where it's needed! Just to complicate matters further there are several types of wetting and delivery agents on the market, some good and some that can quickly lead to problems if used incorrectly. Basically there are two types of agents that you may come across in your hydroponics store; Agents that use alcohol ethoxylates and silicates (a very common type) and ones that use matrix keys and plasma membrane stabilizers (not so common but worth getting your hands on, ask your retailer to get you one if you don't want to use the other type). Agents that use alcohol ethoxylates typically dissolve small holes in the protective waxy layer that surrounds the leaf to allow foliar delivered agents to get in, then use silicates to try and protect the leaf whilst the plant rebuilds the waxy layer. The big drawback to this is that if you use a little too much agent in your foliar spray then you can very quickly burn your plants and slow down your growth (the exact opposite of what we want to do!). As well, these agents quite often don't let all the elements in depending on their electrical charge (anion or cation). The other type, or matrix keyed and plasma membrane stabilized, is in my opinion a superior choice due to two main factors. Firstly, because it uses matrix keying to get past the waxy layer, it won't burn your plants, even at ridiculously high doses or dilution rates. Secondly, the plasma membrane stabilizers allow all the elements to get inside your plants quickly and effectively. Now we know about our important foliar spraying partners, we can now look at what to spray on our plants.
In it's most "simplest" form you can spray a one third to a one half strength nutrient solution on your plants, which will allow for a quicker growth pattern during our "lag" phase growth period. However, there are some excellent specialized foliar sprays on the market that will allow you to get significantly better results than just spraying a diluted nutrient solution on your plants. Some foliar sprays are designed to enhance the branching characteristics and growth rates of your plants whilst others concentrate on early flowering or fruiting support. There are even foliar sprays that contain their own wetting and delivery agents! With all this choice, look to your hydroponic store owner for help in directing you to one that will suit your needs and remember that the advice given here in this article will also help you make the right choice for your needs.
Well guys (and gals) that's it for my first article in Maximum Yield. I hope you gained some important information and skills from reading this and enjoyed reading it as much as I enjoyed writing it. Now my good friend Jack is calling me, (again!) so I must go and think about what to write for my next article.
"S" curves used in this simulation have the form y = x / (x + exp(cA - cB * x)) where cA and cB areparameters that set the shape of the curve. Depending on these parameters, an "S" curve can look like the figure one , or be reversed.
- A review of Plant Mod 2.1
by William D. Batchelor
Agricultural and Biosystems Engineering
Iowa State University
Ames, IA 50011
- Patterns of Growth & Development
University of Western Australia
- Dr Larry K Hillier; FOLIAR FERTILIZATION BUMPS POTATO YIELDS IN NORTHWEST www.fluidfertilizer.com/PastArt/pdf/10P28-30.pdf