Adjuvant Tip of the Month: September 2023

WATER QUALITY CAN MASK MALPRACTICES... BUT BEWARE!

Poor water quality can have a devastating effect on crop protection products (CPPs). Hard and brackish water are highly antagonistic to salt-sensitive herbicides like clethodim, glyphosate, glufosinate, certain phenoxies, certain sulfonylureas and various others. This often leads to poor weed control. Fortunately, there are premium-quality ammonium sulphate adjuvants to deal with this problem. Technology is so advanced that you can even determine the adjuvant rate with a water analysis report or an electrical conductivity measurement.

On the other hand, high pH exposes sensitive insecticides to alkaline hydrolysis in the spray tank, so we use buffers. Because water is frequently antagonistic to CPPs, it’s hard to believe that poor water can sometimes have a positive impact. This is because some water sources have a high buffering capacity and resist a pH change. We will discuss two instances where poor water has a positive impact.

Sulfonylureas

Sulfonylureas are often more effective in alkaline spray water. It is because they are more soluble, up to a point, with increased water pH. Therefore, if a grower excessively acidifies sulfonylurea spray mixtures, it will impact weed control negatively. However, if the water has a high buffering capacity, it will not reduce the pH as much. This will increase the sulfonylurea solubility and efficacy. This is one instance where poor water masks the effect of an incorrect adjuvant choice. However, if the grower makes the same mistake with another water source on his farm, he may not be as fortunate. With a low buffering capacity, water will be more acidified, the sulfonylurea less soluble, and weed control reduced.

Incompatibility and foaming

Another instance where highly buffered water will mask malpractice is with some tank mixtures. Glyphosate commonly combines with phenoxy herbicides. These mixtures are normally compatible but not at an extremely low pH. Flocculation will occur if a grower uses a buffer or any adjuvant that decreases the pH drastically. This will result in blocked sieves and nozzles with wasted time and money. If this grower makes the same mistake with highly buffered water, he could possibly get away with it because of a higher pH. Some CPPs and adjuvants also foam more in soft water so the correct tank mixing procedure to reduce foaming will be less important with hard water.

Villa’s stance

When malpractices occasionally work, it could possibly be the spray water’s influence. Highly buffered and hard water can mask problems like sulfonylurea solubility, physical incompatibility, and foaming. However, remember that water quality often changes over time and that water sources on the same farm could differ. It is always important to follow the correct label-recommended procedures. Never rely on water quality to rectify poor choices.

Contact your Villa marketing advisor for more information about adjuvants and water quality.