Medicine is top at £31,383 on average, dentistry at £29,664 and botany (plant sciences) at £28,591.
According to the survey: "Only a handful of students take this subject, but their expertise is in high demand from employers in a number of areas.
"A number of plant science graduates pursue careers in industrial and academic research so go on to further study after graduation." The guide recommends careers as a plant geneticist, soil scientist or project coordinator.