What are synthetic fertilizers primarily used for?

Synthetic fertilizers are primarily used in agriculture to enhance crop yield. These fertilizers are formulated to provide essential nutrients to plants, such as nitrogen, phosphorus, and potassium, which are critical for healthy growth and development. By supplying these nutrients in a readily available form, synthetic fertilizers help to increase the productivity of crops, leading to higher yields per acre.

The other options relate to different environmental or agricultural practices but do not accurately describe the primary function of synthetic fertilizers. For example, while it is important to purify drinking water, synthetic fertilizers do not serve that purpose. Providing minerals for groundwater is more associated with natural processes and soil management rather than the direct application of synthetic fertilizers. Similarly, reducing soil erosion involves different agricultural practices, such as planting cover crops or creating barriers, rather than the use of fertilizers. Thus, the role of synthetic fertilizers is specifically tied to improving the efficiency of agriculture and maximizing food production.