Correct Option: C

Plants, on average, capture only about 0.1 percent of the solar energy reaching Earth. However, it does not mean that the other 99.9 percent is a “vast untapped reservoir” awaiting man’s exploitation. All biological systems, including crops, follow the second law of thermodynamics when solar energy (a highenergy form) is converted into chemical energy. Plants utilize this chemical energy in the process of building their own tissue. Some of the energy being changed from light to chemical energy is lost as heat that dissipates into the surrounding environment. In agricultural ecosystems, an estimated 15 million kcal of solar energy (net production) is fixed per ha per crop season. Even so, this amounts to only about 0.1 percent of the total solar energy reaching each ha during the year and equals about 3500 kg/ha of dry biomass. The amount of biomass varies with the crop and ranges from 200 kg/ha for low production crops under arid conditions to 15,000 kg/ha for corn and sugarcane.