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- Retaining soil mechanics 
- Fertilizer is removed at season change 
- Speed gro mechanics 
- Fertilizer can/cant be applied after planting 
- Harvest quality calculation 
- Season change kills crops not in greenhouse 
Work in progress
Which fertilizer is best? Short answer: Speed-gro. Longer answer: It depends. Do you have sprinklers? If not, you may need to consider [[Retaining Soil]]. It's value is not based on money, but rather on time. This makes it hard to objectively argue about, and you have to decide for yourself if this is the way you want to play. If you have sprinklers, you have no use of Retaining Soil, and are left with four options. The two different qualities of Fertilizer, and the two different qualities of Speed-gro. In short, Speed-gro gives you additional harvests in a month, while Fertilizer makes your existing harvest worth more. Use the Crop Calendars to figure out which level of Speed-gro is optimal for your current situation. If speed gro makes no difference - usually because you're planting late in the month - consider using Fertilizer. Explanation or "How much does basic fertiziler increase harvest yield" This depends on your farming level. Fertilizer increases the chance of your harvest being of silver or gold quality by the following amounts at farming level 10: dirt 46% 33% 21% basic 15% 44% 41% quality 10% 29% 61% Silver quality crops sell for 1.25 times the price of normal crops, and gold quality sells for 1.5 times the price of normal crops. If a crop has the base price P, then one harvested crop has the average price: dirt Average price = 0.46*P + 0.33*1.25*P + 0.21*1.5*P = 1.1875*P basic Average price = 0.15*P + 0.44*1.25*P + 0.41*1.5*P = 1.315*P quality Average price = 0.1*P + 0.33*1.29*P + 0.61*1.5*P = 1.3775*P Which means that basic fertilizer increases your profit by 10%, and quality fertiziler increases your profit by 16% 1.315/1.1875 = 1.107 1.3775/1.1875 = 1.16 By comparison, using speed gro to increase your number of harvests in a month from 5 to 6 will increase your profit by 6/5 = 1.2 = 20% The rule of thumb is, the fewer harvests you can fit in a month, the better it is to use speed-gro. The following table shows what the Gain in percent is when increasing the number of harvests is for specific numbers of harvest. From To Gain Better than Basic? Better than Quality? 4 5 25% Y Y 4 6 50% Y Y 5 6 20% Y Y 5 7 40% Y Y 6 7 16% Y N 6 8 33% Y Y 7 8 14% Y N 7 9 28% Y Y 8 9 12% Y N 8 10 25% Y Y 9 10 11% Y N 9 11 22% Y N 10 11 10% N N 10 12 20% Y Y 11 12 9% N N 11 13 18% Y Y 12 13 8% N N 12 14 16% Y Y What about greenhouse? Fertilizer will disappear in the greenhouse when winter comes (or earlier, it depends), which kind of makes this discussion moot. Use speed-gro if you need crops sooner. Use fertiziler if you need some extra money earlier. What about multi-harvest crops? Only the one of the crops in a multi-harvest will benefit from the fertiziler, all the others will be basic quality. This skews these numbers a bit, but not to the benefit of fertiziler. Obviously, all crops in a multi harvest benefit from speed-gro. What about the agriculturist skill? You get a 10% increase to the base price. It doesn't affect these ratios. What about the... You know what, I don't even care anymore.