Oh, sorry it's 3 astrals and 2 nats, I thought it was something else. So for supercompost, you just pay 610 gp and get 25 farming xp. With fertile soil, you pay 925 gp, get 18 farming xp, and 87 magic xp. If you train magic by String Jewelry, that's saving you 348gp. If you train it by Ice Burst/Barrage, that's saving you 522gp. If you train it by Alching, it saves you 261gp. All of these also save you time, which isn't a lot, but should be taken into consideration. If the average person makes 500k per hour, you can average 138gp per second. String Jewelry trainers would save ~1-2 seconds, bursts would save ~3 seconds, and alchers would save ~4 seconds. That's 138, 414, and 552 respectively. So far, supercompost costs 610 gp with no benefits, which fertile soil costs 925gp but comes with either 486, 936, or 813 "cash back" through the magic xp and the time saved. So fertile soil is by far the best option. EDIT: I forgot Plankmake! If you train by Plankmake, fertile soil would save you 50gp and 2 seconds, which totals to 326 gp, still making it the better option. Also remember that if you make more than 500k per hour, the difference will be even more in fertile soil's favor. Then again, if you make less, it'll favor supercompost more. Also, if you don't care about magic xp, it'll be even more in supercompost's favor.