AP Human Geography Agriculture Practice Test 2026 - Free Practice Questions and Study Guide

Adding nutrients to soil to boost plant growth is what fertilizers do. Fertilizers supply essential elements like nitrogen, phosphorus, and potassium that crops need to grow well and produce higher yields. When the question specifies a chemical added to soil to increase fertility, it points to fertilizer, typically in inorganic or synthetic forms, though organic fertilizers are also used to bring nutrients back into the soil. Pesticides are for pest control, monocropping describes growing the same crop repeatedly, and subsistence farming is about farming to meet basic household needs rather than enhancing soil chemistry. So the best answer is fertilizer.