Jadam JMS temperature

This is from the book — Close the lid and leave under the sun for culturing. Place it in the same environmental condition as the crops. Leave it at ambient temperature. It takes 1-3 days till completion. It is faster, and there are more foam in summer. If water temperature drops below 18°C (64.4°F), use an electric heater to keep at 20°C (68°F) and wrap the container with insulation. (If you use cold underground water, take out the water and leave for a day for it to warm before use.) —

I think this is really dependent on volume of JMS we are making ….in the book he says 500L (132g) is the volume that he is doing and to warm that much water up sitting in the sun after it has gotten really cold is not easy so by putting a heater in there to keep it warm on cold nights so that the temp does not drop so much is important to brewing a good batch of microbes ….but if we are making a smaller batch ie: in my case i make 3 gallons (11L) of JMS for my garden cause it gets mixed at a 10-1 ratio with water so in the end i have 30 gallons (113L) to drench my garden with …so in that case i dont use a heater cause the sun warms up that small volume of water just fine after a cold night  … in early spring or late fall it will take up to 5-6 days to be ready instead of 3-4 as it does in the summer …i would think that up to about a 55 gallon (208L) drum sitting out in the sun would not need a heater and would heat just fine in the sun and even better if it was black in color for a bit more passive solar heating