I have the following hypothesis: God's intervention is actively required for healthy plant growth.
Can anyone describe a method by which this hypothesis could be tested scientifically?
To test this hypothesis, you would have to have some clear definition for God and the means by which God would operate.
For example, does God produce sunlight? If so, then perhaps God is required, as we know that plants require sunlight. So it would become a question of the source of sunlight.
The supernatural though, could be tested. For example, if the waters of the ocean split, in a way that couldnt be caused by any natural phenomena that we are aware of, then one could argue that the source was supernatural.
If a map took a single loaf of bread and infinitely split it into millions of loaves, this would be a supernatural occurrence (as far as we know), as it would defy conservation of matter. And in recording this, one could at least observe the existence of the supernatural.
This could also be tested. A non supernatural being, like a you or me, could try breaking the loaf into millions of loaves, and if only a divine being, such as God, can do that, then you are performing tests to determine who has supernatural powers and who doesnt.
So there are ways of observing, testing, and operating with supernatural occurrences. But, it all comes down to the question of if these supernatural occurrences actually occur. We have never seen a person defy conservation of matter, so its hard to observe or test something when such a thing, as far as we are aware, doesnt happen.