I know there is a lot of sites where you can find facebook application cheats, but farmville is a hard one to find so i'll post these farmville cheats/hacks that i know.

here are the things we need:

1. Firefox
2. CheatEngine (CE) 5.5 download
3. Flash player 9 go here to download

Settings we will use in CE: setting on CE, check HEX, on value type choose ARRAY OF BYTES (AOB) that's it.

INSTANT HARVEST (YEHEY NO MORE WAITING! LOLZ)

instruction:

1.sign in to facebook and open farmville
2.open CE click the computer icon then target firefox
3.on CE tick HEX then AOB
4.paste this on value: d2 24 00 0d ?? 00 00 d0 60 ?? ?? 2c ?? ?? 2c ?? ?? 62 ?? 62 ?? 56 02 46 ?? ?? 03 4f ?? ?? 01 5d ?? ?? 62 ?? 4f ?? ?? 01 5d ?? ?? 60 ?? ?? 4f ?? ?? 01 5e ?? ?? 60 ?? ?? 46 ?? ?? 00 68 then click FIRST SCAN
5.on left side of CE 1 address returned, double click on it, it should now be on the bottom part of CE
6.ok heres the trick part read it carefully!
on the bottom of CE double click the VALUE of the adress we just put there so the value is same as the value on step 5 now here are the only value we will edit

NOTE:

erase
the first 4 values which are (d2 24 00 0d) then replace it with the
value (10) now on the last part put any of these between the value (00
68)
2D 03 A1 <- 2-4 Hour Plants. (TIME OF SEED TO BE HARVESTED)
2D 53 A0 <- 6-11 Hour Plants.. (TIME OF SEED TO BE HARVESTED) 2D 47
A0 <- 3-4days up(TIME OF SEED TO BE HARVESTED) 

ok heres an example: scanned value:

d2 24 00 0d 18 00 00 d0 60 00 00 2c a1 20 2c 4e 2d 00 68

editted value:

10 18 00 00 d0 60 00 00 2c a1 20 2c 4e 2d 00 2D 03 A1 68

now try to harvest a 3 to 4 days to harest seed and when your done next thing you know it is ready to harvest!