You Drive Up to it until the Sprayer ist next to the tank. Then you press CTRL and choose the fertilizer from the menu and press Start.

Up the top left just next to the mission box should be an option to click, I think it's [Filltype], Hold left ctrl, select that and filltype and click fill.

I can buy fertilizer for the sprayer but my balance is zero money... Due to crashes I uninstalled Cattle and Crops online installer through Programs and Features,delete all files in C drive etc,etc,after that install it again,updated and it's ok,it works smoothly,but...my balance is zero money,so i can't buy nothing.neither fill up the sprayer cause i must pay for the fertilizer...Any ideas guys?

@AchillesSibir Open the console and use the command 'goldencrops' to get money again. The bug probably occured while saving or smth.

@AchillesSibir
What you can do:

1. Open the console ingame with the " ^ " key
2. type in "cmd", this gives you all available console commands
3. type in "goldencrops" and your account should be cool again

@TheCoCe @Memphis Thanks for the command guys,it worked...10 millions euro