Agriculture effluent is like the water that comes out of the bath tub after you take a bath, but for farms.
When farmers use water on their crops or animals, the water has stuff in it like dirt, poop, pee, and sometimes chemicals. This water is called effluent.
Just like your parents might drain the bath water to make sure it doesn't flood the bathroom, farmers have to find a way to get rid of their effluent so it doesn't hurt the environment or make people sick.
Sometimes farmers will treat the effluent to make it cleaner before they get rid of it, or they may use it to water other plants or crops. It's important that farmers are careful with their effluent because it can pollute rivers and lakes, harm fish and other animals, and make people sick if they drink water that's not clean.