Some nutrients promote growth, such as nitrogen (N), while iron (Fe) is an important nutrient for photosynthesis. That is why plants will grow poorly if the soil they are in is not supplied with fresh nutrients.
We can add nutrients directly to the soil or to the plant by applying fertilizer.
You can buy fertilizer at garden centers, for example synthetic - or organic fertilizers. If it is no longer possible to buy fertilizer, you can make it at home. Garden waste can be mixed directly into beds, or you can make fertilizer from, for example, urine or nettles. If you have livestock, such as chickens, their droppings can be used to make organic fertilizer as they contain high levels of nitrogen.