1)Plants require micro and macro nutrients. Ideal concentrations exist for micro and macro nutrients for specific species of plants at specific stages of growth. Furthermore, even within species (varieties) there is variation as to the ideal concentration for ideal growth.
2)Nutrients adsorb and absorb to growing mediums in different ways. In example, perlite is a good cation-exchange medium. Perlite is composed of silicate, which by nature is anionic, whereas potassium is cationic and you can get the picture (opposites attract). In analogy, a chemistry cation/anion exchange chromatography column. You can see why "flushing" or rinsing your medium is important?
Many have studied various concentrations in various growing mediums and many standards have been put forth. For example, Nutrient Solution Formulation for Hydroponic (Perlite, Rockwool, NFT) Tomatoes in Florida http://edis.ifas.ufl.edu/cv216
4)Nutrient strengths can be calculated from the nutrient label's analysis via the mass of nutrient you add into solution. Or nutrients can be measured/quantified via conductivity (i.e. TDS) or more quite intimately with colorimetric methods or ion-selective electrodes (ISEs). Conductivity can not give you an individual nutrient concentration like a colorimeter or ISE can. TDS is just a total concentration of dissolved solutes in comparison to a sodium chloride solution (the calibrator). Colorimeters and ISEs cost mucho dinero whereas a conductivity meter around a $100. If one wanted to really hit the mark on nutrient strengths one should feel inclined to purchase a nutrient analyzer.
http://www.hannainst...ode=HI 83225-01 $500-$1000.
5) Nutrient deficiencies can be diagnosed morphologically (by looking at it) or by way of quantification with an analyzer or ISE. Quantifying something is always nice as this leaves little room for ambiguity. A sap press allows one to press out a sap sample for analysis. In analogy, getting your blood taken at the doctor's office, Again, all of this instrumentation costs $$$$.
Now for my present gardening dilemmas. I don't have a nutrient analyzer or any ISEs. Though, I very much intend to purchase some. I do have conductivity and pH probes though. Therefore, that leaves me to diagnosing deficiencies via morphological methods mostly. I have read that nitrogen concentrations can be pushed quite high so long as phosphorous, magnesium, and potassium levels are pushed in harmony as well. So when I'm looking at some morphological anomaly, I'm not just thinking about reducing my total nutrient strength, I'm also thinking about increasing or decreasing another nutrient to find the equilibrium.
Take Basil here for example:
Take notice of the downward cupping of the leaves and the inter-veinal chlorosis (yellowing). The inter-veinal chlorosis, from my readings, implies a less than suitable magnesium concentration. The cupping? From my experiments, I'm leaning towards linking the upward and downward cupping from insufficient and excess concentrations of nitrogen, respectively. What does it all mean? Trial and error is a son-of-a-bitch. I haven't collected enough data yet and need help from an agricultural pro.
The morphology stuff I have googled, thus far, has been less than adequate. My local library is inadequate in the agriculture field. I feel a "shout out" is in order. What are some key morphological features to look for when diagnosing plant nutrient anomalies?
Edited by homobrassinolide, 17 March 2011 - 09:24 PM.