Tilling or plowing is a common agriculture practice that has been proven to have a profound impact on the nitrogen cycle. Tilling breaks up hard soils to ease the planting and germination of crops, and it also introduces more oxygen into the soil

Question

Many fertilizers contain N in the form of ammonia because ammonia is readily absorbed and used by plants, while N in the form of nitrate is more mobile and is more easily lost from the soil. Based on your knowledge of microbial transformations of inorganic nitrogen species, what impact would you predict extensive tilling to have on the fate of ammonium-based nitrogen fertilizer?
What will be an ideal response?

Answer 1

Answer: Ammonia-oxidizing and nitrite-oxidizing bacteria are found in soils and together convert ammonia to nitrate. Nitrate can be lost from the soil via leaching or denitrification. Losing nitrate from the soil represents a loss of total N from the soil, decreasing soil fertility. Introduction of more oxygen into soil through tilling would most likely increase the rate of the nitrification, resulting in increased N loss from the soil. Reduced tilling may help retain fertilizer and natural N in a soil and increase soil fertility.