Using urine as a fertiliser for plants and trees has a centuries-old history. It is a renewable organic resource with the perfect combination of plant-growing nutrients that also saves water and chemicals when kept out of the sewage stream. Urine provides ideal amounts of nitrogen, phosphorus, and potassium: the three nutrients required by all growing plants.
Collect urine daily. Keep a tight-lidded plastic container in the bathroom and use instead of flushing urine down the toilet. Fresh urine does not smell and does not carry bacteria. In fact, it is almost sterile. Keep the urine lidded tightly and change out containers frequently.
Use urine daily. As urine ages (more than about 24 hours), it begins to break down and create higher ammonia levels which are not good for plants and which make the urine smell bad. Fresh urine generally does not smell. Any odours from strong foods like garlic or asparagus will not harm the plants. Take the collected urine out of the house at least once per day to fertilise plants.
Mix urine in the ratio of one part urine to ten parts water. This dilutes the urine's nitrogen content enough to use on tender plants. Using urine full strength will burn tender plant leaves. Use the diluted urine on plants immediately and do not store, either full strength or diluted.
Water around the roots of plants with the diluted urine fertiliser. Fertiliser in general may burn tender plant leaves so try not to splash on leaves or fruits. The dilution will allow you to water daily and it can be used in container plants and hanging baskets as well. Water until the soil surrounding the plants' roots is saturated but do not allow plant roots to sit in puddled water.
Check the growth of the fertilised plants regularly. If the leaves begin to take on a yellowish tinge and the plant looks like it is struggling, dilute the urine fertiliser further to prevent the plant from receiving more nitrogen than it needs. If fruiting plants grow lush vegetation but no fruit, cut back on the amount of urine fertiliser they are receiving.
Use any leftover urine to keep predators out of your garden. This works especially well with male urine, which contains hormones that other animals take as being a signal to stay away. Pour small amounts of undiluted urine around the perimeter of the area to be protected. This will have to be repeated after every rain shower as the rain will dilute the urine.
Some sources recommend ending urine fertilisation on vegetable and fruit plants two weeks before harvest, but it is unnecessary, as long as vegetables and fruit are thoroughly rinsed before eating.