Frankster
Never trust a doctor who's plants have died.
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I've got the master kit; and I've done some periodic test; and nitrates are certainly the ones that are in play yes. I don't really use it that much; because I go more by pH and what the plants are speaking to me. But I keep it around incase I come up with any ideas; and for periodic tracking purpose.
Both nitrate ions and ammonium ions can be taken up by plants (some prefer one to the other). These ions provide nitrogen for the plant to make its own amino acids for protein synthesis; creating chlorophyll... Plants can absorb nitrogen either in the nitrate form (NO3-) or the ammonium form (NH4+). The total uptake of nitrogen usually consists of a combination of these two forms.
The ratio of ammonium-to-nitrate affects both plants and the soil or grow medium. For optimal uptake and growth, each plant species requires a different ammonium-to-nitrate ratio. The correct ratio also varies with temperature, growth stage, pH in the root zone and soil/grow medium properties.
To understand how temperature affects plants’ abilities to metabolize the different forms of nitrogen, first we need to understand the different ways these two nutrient forms are metabolized by plants. When plants metabolize ammonium, more oxygen is consumed than with nitrate.
Ammonium is metabolized in the roots, where it reacts with sugars. These sugars have to be delivered from their production site in the leaves down to the roots. On the other hand, nitrate is transported up to the leaves, where it is reduced to ammonium and then reacts with sugars.
At higher temperatures, plants’ respiration is increased, consuming sugars faster and making them less available for ammonium metabolism in the roots. At the same time, at high temperatures, the oxygen solubility in water is decreased, making it less available as well. Therefore, at higher temperatures, applying less ammonium is advisable.
At lower temperatures, ammonium nutrition is a more appropriate choice, because oxygen and sugars are more available at the root level. In addition, since transport of nitrate to the leaves is restricted at low temperatures, basing a fertilization program on this form of nitrogen will delay plant growth.
Electrical balance in the root cells must be maintained, so for each positively charged ion that is taken up, a positively charged ion is released and the same is true for negatively charged ions. When the plant takes up ammonium, it releases a proton. An increase in protons around the roots decreases the pH. Alternatively, when the plant takes up nitrate it releases bicarbonate (HCO3-), which increases the pH around the roots. Therefore, we can safely conclude that nitrate uptake increases pH around the roots while uptake of ammonium decreases it.
This phenomenon is especially important in soilless media, where the roots may easily affect the grow medium’s pH because their volume is relatively large compared with the medium’s volume. To prevent the grow medium’s pH from rapidly changing, we should keep an appropriate ammonium-to-nitrate ratio, according to the cultivar, temperature and the growing stage.
Under certain conditions, the pH may not respond as expected due to nitrification (conversion of ammonium into nitrate by bacteria in the soil). Nitrification is a rapid process, and the added ammonium may be quickly converted and absorbed as nitrate, increasing pH in the root zone instead of decreasing it.
Other Nutrients
Ammonium is a cation (positively charged ion), so it competes with other cations such as potassium, calcium and magnesium for uptake by the roots. An unbalanced fertilization program, with ammonium content that is too high, might result in calcium and magnesium deficiencies, while potassium uptake is less affected by the competition.
Ie. some of the fans get sun wrinkles somewhat like an old farmer.... ie. UV damage.
