After Harvesting and Selling a Crop of Corn,a Farmer Collects

After harvesting and selling a crop of corn,a farmer collects the corn stalks and feeds them to her cows.Why should the farmer add fertilizer containing nitrogen and phosphorus to the field before growing another crop?

A) The Haber-Bosch process makes fertilizer with higher quality nitrogen and phosphorus than occurs naturally in soil.
B) Nitrogen and phosphorus move out of the air and into the soil very slowly,so fertilizer is needed for the next crop.
C) The nitrogen and phosphorus the plants took from the soil will not return to the field through decomposition.
D) The bacteria in the field use up the nitrogen and phosphorus remaining in the soil after the crop is harvested.
E) Soil weathering does not occur quickly enough to replace the nitrogen and phosphorus lost when the crop was harvested.