08/17/2026
Tank mixes in the field are one of the most complex tasks a grower can undertake. There are many factors to understand to create a proper tank mix; pH and buffers, chelation vs. complexation, the importance of the order of addition, and the proper selection of utility products. Let’s focus on these factors since understanding these can save you time, money, and unnecessary cleaning.
pH and Buffers
Most tank mixes are stable in acidic conditions, with pH less than 7 (usually between pH 4 - 5). Alkaline conditions (pH greater than 7) can lead to settling and fallout issues. Adding a buffer to a tank mix can help keep the pH in the desired acidic range without the concern of large fluctuations in pH and the potential for subsequent issues. The most common buffers are organic acid-based (i.e. acetates and citrates) and species such as phosphates and sulfates, These buffers can “absorb” the hydrogen ion responsible for pH and acidity, keeping them from reacting and causing the pH of the tank mix to rise. However, not all buffers are great in a broad spectrum of tank mixes; phosphates and sulfates should not be used with unprotected calcium or hard water and acetates have a very limited capacity to “absorb” hydrogen ions compared to other buffers.
Chelation vs. Complexation
Chelation occurs when a chelant (i.e. EDTA or EDDHA) forms a chemical bond with a micronutrient to form a compound that can keep said micronutrient from reacting with other chemistries long-term. Complexation occurs when a complexing agent (i.e. citric acid, sodium glucoheptonate, etc.) forms a loose chemical association with a micronutrient that can keep it from reacting with other chemistries on a limited basis. For example, manganese EDTA complexes can be placed in a tank mix with virtually any chemistry under a broad pH range (pH 5-12) and not cause any tank mix issues; however, EDTA is a strong chelant and does not release the manganese ion for a long period in the soil (after at least 30 days) and does not allow for much foliar absorption. On the other hand, manganese complexed with citric acid can be placed in a tank mix with most chemistries if the pH of the tank mix does not exceed 7.5-8, and the manganese ion can be easily released from the citrate in the soil and made plant-usable, as well as the fact that foliar absorption of citrate micronutrients is well documented.
The Importance of the Order of Addition
The order in which chemistries are added to a tank mix can greatly affect the success or failure of the final mix. Improper mixing of chemistries, or adding multiple chemistries simultaneously can cause large fluctuations in pH that can result in unexpected chemical side reactions, settling, or fallout. Always read the label of the chemistries you are using before you begin a mix. If you are unsure when a certain product should be added perform a jar test to determine when it should be added. As a rule of thumb, you should always follow your WALES or DALES after adding water. Doing so will help to keep the pH of a tank mix stable, with little chance of large fluctuations in pH:
1 Wettable Powders or Dry Flowables, then
2 Agitate, then
3 Liquids, then
4 EC formulations, and finally
5 Surfactants.