Soil erosion and poor production conditions in developing countries are a major problem for local primary care. It is therefore even more important to ensure a functioning and stable ecosystem from which agricultural plants profit, too. Trees have found a brilliant way to gather enough nutrients for their survival. They enter a symbiosis with special types of fungi, the so-called mycorrhiza. This leads to more resistance of the crops, especially against drought. There is a method that can be used with the simplest means to prove that mycorrhizae are found in tree roots and thus assure improvement of soil fertility.