45% conversion to crop is actually amazing and way higher than I thought it would be. You'd never be able to get it to 100% just based on thermodynamics alone.

45% conversion to crop is actually amazing and way higher than I thought it would be. You'd never be able to get it to 100% just based on thermodynamics alone. It takes a lot of energy to move nutrients from an area of low concentration (the soil) to an area of high concentration (the plant). Just making up number here, but if a plant needed 10 grams of nitrogen, but the soil contained only 50 mg at any given time (but was constantly replenished), plant growth and yield would suffer considerably - despite the fact that a sufficient supply is available over time. You need to have an excess supply of nutrients available to maximize growth. It's similar to water - many plants will die in soil that has a low level of moisture. The water is there, the plant just doesn't have the capacity to actually pull in enough to sustain life.