CROPS WATCH: How to avoid ‘making gravy’ in a spray tank mix

As spring crops have been, and are still being sown, late this year, we have yet to find out the consequences of delayed planting. One result will be a short growing season – most likely leading to short spraying windows.

New tank mixes may occur as a result, as farmers apply broad-leaved herbicides, wild oat sprays, fungicides and trace elements together. John Mulhare, TerraChem agronomist, describes a simple test to see if products will mix in the tank in the latest installment of CROPS WATCH.

The simple method takes just a few minutes and could mean that you avoid “making gravy” in an expensive tank of spray.


Before the farmers get to the tank mix stage, John’s advice is to spray aphicide early (GS14 for best results). After this, herbicide and fungicide sprays may run together and this is where his trick comes in.

John’s tank mix test

  • Get yourself a conical flask, like John has in the video, or even just a jam jar – as long as it has a lid;
  • Pour some water into the jar;
  • Pour a dollop of each spray, that will go into the tank mix, into the jar or flask;
  • Give the jar a shake or a swirl.

The results

This method will test the physical compatibility of products in the sprayer. Ideally the spray will mix well in the jar.

There are three main results that may happen that will not be good for the sprayer:
  • The mix looks like a “cottage cheese effect”. It’s lumpy and you will see it instantly;
  • The mix flocculates, everything falls out of suspension and falls to the bottom;
  • The mix forms sticky lumps. This is the worst result, while the other two may come out of the sprayer in some shape or form a sticky mix will not.

John was keen to add that while this method tests a tank mix in the sprayer, no chemical company can say what sort of an effect a tank mix will have on the crop and the phytotoxicity reactions that may occur.

A lot of chemical on a crop can cause stress and we need to be aware of that.

It is also very hard for a chemical company to stand over anything greater than a four-way mix and in many situations only a two-way mix will be approved.

It is important to note that the correct personal protective equipment (PPE) should be used when carrying out this test.