More formal than 种地 ('work the land,' colloquial). 耕作 emphasizes the technical process of preparing soil - plowing, harrowing, weeding - and is the standard term in agricultural writing (耕作制度 'cropping system,' 免耕 'no-till farming').
memory
耕 = 耒 (lěi, ancient plow radical) + 井 - the radical 耒 shows a wooden plow handle, planting the field-character 井 right next to it. Once you spot 耒 you'll recognize all the farming verbs: 耕 (plow), 耘 (weed), 耨 (hoe).
