Answer:
decreased soil nitrogen due to the harvesting of crops.
Step-by-step explanation:
Nitrogen is an element that is very important for all organisms because is a key element to build proteins. Nitrogen is acquired by plants through a process called assimilation. This nitrogen is build up in the soil by different processes and bacteria are the main organisms responsible for it. When plants, let's say corn, are grown in a field they take the nitrogen from the soil and incorporated into their biomass, when they are harvest, this nitrogen is exported out of the soil because we ship it no consumers. Normally organisms die and the decomposition process returns the nitrogen to the soil again.