banana
It's not a crop but oil is called back gold.
You have to give me a number of choices for me to tell you which one is indeed green gold.
cocoa is called black gold because tha is how they named it
Rubber
Where I come from (St. Lucia) they are called "green gold" because they were the main source of domestic product upon becoming independent. Now tourism plays a larger role but the name stuck.
purple, green, and gold
Rice
Gold mine and wind fall are 2 synonyms of "cash crop".
Wheat
Green manure is a crop (clover, field beans, etc) that are not harvested, but are ploughed into the soil to feed a later main crop.
If you are asking about the short (About 2') accessory, it's called a riding crop.
Blue and Gold make green