Plants, just like people need food. If you have good healthy soil with lots of compost in it, your plants will have lots of nutrients to bring up through the roots. But you can also add extra food for plants by adding fertilizer. This is when you add something extra to the soil around the plant, or spray it on the leaves. Wee, also called urine, is quite high in nitrogen and citrus trees love a high nitrogen fertilizer. It’s a good idea to water it first then have a good wee and then water it again.