Hi Colin,

I’m certainly not an expert in humic substances but my understanding is that they are extremely heterogenous materials (very complex surface chemistry with both positive and negative charges and very high CEC) so they will bind to whatever existing organic matter or clay that is in your soil, and will also chelate a number of soil minerals, forming larger molecular structures that are more likely to bind to soil surfaces. In your case with a sandy soil and low organic matter the conditions are less than ideal but I suspect the answer is yes, you would still see a greater ability of the soil to hold nutrients and would benefit from a humate application.