A major challenge, facing the farmers in Africa in their daily work, is getting access to nitrogen to support plant growth. Professor Ken Giller, at Wageningen University in the Netherlands, works on this issue. Access to nitrogen is a double-edged sword in terms of sustainable development. Too much on your soils is a bad thing, as it causes contamination of groundwater, eutrophication of freshwater and estuarine ecosystems, atmospheric pollution and soil acidification as well as soil degradation. On the flip side, too little nitrogen results in low production yields, soil nutrient mining and soil degradation. All of these consequences lead to poor human nutrition. Generally, farming in the Northern Hemisphere is characterized by a high availability of nitrogen in its farming, while Sub-Saharan Africa has too little. These imbalances are not just due to differences in access to artificial fertilizers, but also enhanced by export and import. When plants such as soya grow, for example in South America, they bind nitrogen from the atmosphere, so now the nitrogen is contained in the crops that are exported to Europe. These crops are eaten by livestock in intensive farming. After digestion of these crops, the nitrogen is now found in the manure, which is released to the environment. Sub-Saharan Africa does not import nitrogen in a comparable way, and their staple crops such as maize, do not have the same ability to bind nitrogen from the atmosphere as soybeans. For this reason, Ken Giller has specialized in putting the plants that can fix nitrogen to use for small-scale farmers in Africa. These plants are called legumes. Basically, all of my career I've worked on nitrogen fixing legumes, really the peas and beans. And these have a number of real advantages for smallholders in the tropics, particularly in Africa, so they're important foods, they provide protein, minerals, particularly for people in their diets. They are very good in terms of the fact that they fix nitrogen from the air. We'll talk about that further in a minute, because they have this symbiosis with bacteria in the soil, and it means that they can actually capture nitrogen in the air, nitrogen that's all around us, and convert it into a form of protein, which is good for us to eat. Legumes come in many shapes and forms. We have the grain legumes of peas and beans, such as I've got in my hand here, but they come as forage plants - creeping forage plants - and we have some on the floor nearby, that I can show you. They come as trees, which can also be used as as forages and some of them even have have edible fruits as well. But the common thing of all these plants is, that they have very nitrogen rich leaves and nitrogen rich seed, which actually gives them this real benefit then, for use for smallholder farmers. The legumes can both be utilized for human feed and for animal fodder. So this is creeping peanut plant, it's called Arachis Pintoi, and it's from Latin America, but it's grown throughout the tropics in different places, because it provides this beautiful nitrogen rich forage for livestock. That means that, whereas in intensive animal production systems for pigs or for dairy in Europe, we have a lot of concentrate, which contains a lot of protein, often on soya meal that comes from the Southern Hemisphere from Brazil. In these plants, you can actually fix the nitrogen in their nodules below ground and they can be eaten directly by livestock. The culture of legumes carries with it enormous potential for the challenged farmers in Sub-Saharan Africa. However, realizing this potential is dependent on people learning about how the processes of the legumes work. So I'm holding here a petri dish, which has got a root system in it. On that root system are lots of small nodules. These nodules are formed when the roots is triggered by a bacterium in soil, we call that Rhizobium and the bacteria actually invades the nodule. It's right in the center of the nodule, in the plant cells, that bacterium gets carbon - sugars, energy from the plant and it uses that energy to take nitrogen, nitrogen gas, that diffuses into the nodule. It converts that into ammonia, into proteins, which then gives legumes this fixed nitrogen. So they're not dependent on nitrogen from the soil. Most soils contain the bacteria for the given legume, because the legumes have been grown there for many years. But when we take new legumes into a new area and particularly, we're doing this with soybean in Africa, you often have to introduce the bacterium. Now, this is a packet of inoculum, which is produced by a company in Malawi. It's something we've helped with through our different projects. Basically, you grow a culture of bacteria in a flask, in a laboratory, you inoculate that into a a bag of peat. That then grows into the peat and when we want to sow the seed in the field, you break open the bag, you mix that with the seed you sow that in the soil, and that carries the bacterium with it, that can then form the nodules on the plant to fix nitrogen for the crop. Ken Giller is of course not suggesting, that Sub-Saharan Africa does not need increased access to nitrogen fertilizers. However, when such fertilizers are used in combination with the culture of legumes, smallholder farmers can boost their production with less amounts of fertilizers. In addition, to the nitrogen that goes directly into the grain, and can be consumed or used as feed, the legumes leave behind nitrogen in the soil, which improves soil fertility for other crops. We've done a lot of work on this in Africa, particularly. Legumes are often grown with maize. Maize is really the major cereal in Africa, providing energy for the majority of the population in many different parts, and if we grow a legume and then we grow maize afterwards, we'll often find that the legume leaves enough nitrogen in the soil, to actually give us another half a ton of maize in the next crop. Now that might not sound a lot in terms of yield, but you have to realize that in very poor soils, farmers are only often producing half a ton to one ton of maize per hectare. Growing a legume can often increase that by 50% or even 100%. So it's adding nitrogen back to the soil. But before I get too enthusiastic just about nitrogen fixation, of course a yield of maize of one and a half to two tonnes, is really not what farmers are looking for. They need a yield that's really double that, to produce enough returns to their investment in labour. That means that efficient use of nitrogen fertilizers is also important in Africa.
