Since Monterey Foli-Cal is a fertilizer, there should not be any issues applying it together with another product, unless the product label for the other product prohibits such applications.
According to the Monterey Foli-Cal Product Label: "Foliar sprays of FOLI-CAL are intended to complement good soil fertility by supplying nutrients directly to the foliage, roots and fruit of crops during critical growth stages. " It is mostly intended to be used as a full coverage spray on the foliage and fruit to allow for faster absorption and results. You should be safe to use it as a drench, but since the manufacturer does not state use instructions for this on the label, we couldn't advise on what rate to apply the product.
Application rates for Monterey Foli-Cal vary depending on the target area you are applying to. See label for complete application instructions
Vegetables and ornamentals: 3 fl. oz. in 2 gallons of water
Trees and vines: 6 fl. oz. in 4 gallons of water
Turf and lawns: 3 fl. oz. in 2 gallons of water
hydroponics: 8 fl. oz. in 25 gallons of water