Which natural product has been largely replaced by a synthetic alternative?

The transition from animal manure to synthetic fertilizers exemplifies a significant shift in agricultural practices. Synthetic fertilizers, such as ammonium nitrate and urea, offer a more concentrated source of nutrients like nitrogen, phosphorus, and potassium. These fertilizers are produced through industrial processes, allowing for large-scale production and consistent availability compared to traditional animal manure, which can vary in nutrient content and availability depending on factors like animal husbandry practices and seasonal conditions.

Using synthetic fertilizers also facilitates farmers in adopting more efficient farming techniques, as they can apply precise amounts of necessary nutrients directly to crops. This change supports the need for higher crop yields and helps meet the demands of a growing global population. While animal manure still has a role in organic farming and provides benefits such as improving soil structure and promoting microbial activity, the widespread efficiency and effectiveness of synthetic fertilizers have made them a dominant choice in modern agriculture.

The other choices represent different shifts but do not exemplify the same level of replacement by synthetic alternatives as seen with fertilizers. For instance, wood continues to be used alongside other materials for construction, and while natural fibers and coal have been complemented by synthetic options and renewable energy sources, they have not been entirely replaced in the same manner as manure with synthetic fertilizers.