Sustainable Agriculture May 2009
A cure for sick soil
Dr Robert Abaidoo: Soil microbiologist
Summary:
For crop farmers, the growth of fungus in their crops is often a problem - causing poor plant health and reducing yields. But some types of fungus are useful. Mycorrhiza fungi, for example, form associations with plant roots, which allow the plants to take up more nutrients and give them greater resistance to disease. Mycorrhiza can also improve soil aeration and structure. In Nigeria, scientists are now trying to use them to rehabilitate soils that have been damaged by oil spills.
Suggested introduction:
Spills of oil from leaky pipelines can cover large areas, robbing farmers of vital land for cultivation. Such spills have been reported in several African countries, including Kenya, South Africa, Cameroon and Gabon. But the most serious instances are found in Nigeria, in the Niger Delta.
Now, scientists at IITA, the International Institute of Tropical Agriculture, are finding ways to clean up these polluted soils, and they are using some unusual tools to do the cleaning.
Ismaila Senghore and Salu Mangeh Koroma met with soil microbiologist Dr Robert Abaidoo to learn more. Dr Abaidoo is a specialist in micro-organisms - the bacteria, viruses and fungi that live in soil and are vital to its health. He wanted to show how fungi - or mycorrhiza - can help to heal sick soil. But first Ismaila began by asking him to explain what exactly a micro-organism is.
Tape in:
A micro-organism generally is...
Tape out:
...available to the plants
Closing Announcement:
Microbiologist Dr Robert Abaidoo, telling Ismaila Senghore and Salu Mangeh Koroma about the amazing importance of the tiniest creatures, the micro-organisms that live in the soil.
Making the most of it:
Find out about research going on to heal a sick soil near you, whether it is exhausted, eroded or polluted.
Discover what other life in the soil is useful to farmers.
What are the techniques to keep soil life - and crops healthy?
Further information:
Dr Robert Abaidoo,
Soil microbiologist,
IITA, Ibadan, Nigeria
Email: r.abaidoo@cgiar.org
Transcript
Abaidoo
A micro-organism generally is any organism that is beyond the resolution of your normal eye, and you might need a microscope to be able to see them. One gram of soil can contain a trillion micro-organisms.
Senghore
That's wonderful!
Abaidoo
Yes, that shows how tiny they are.
Senghore
Now are they always present in any sample of soil, or do they differ in different soils?
Abaidoo
Well, the diversity you have in the soil, the numbers you have in the soil determine the health of the soil. In a highly degraded soil, the microbial components will be lower than in an un-degraded soil.
Koroma
And you have brought me here to a place where you have samples of soil and you have things growing in it. What do you do here exactly?
Abaidoo
One of our problems in African soils is availability of phosphorous. Our soils are tropical in nature. They have certain chemical compounds that fix phosphorous, which means that phosphorous no longer becomes available for plant uptake. So even though it is there, we say it is not available, because plants cannot access it. Now in the soil there are micro-organisms we collectively call mycorrhiza. In this case we are dealing with vesicular-arbuscular mycorrhiza, which for short we call VAM. They are fungal in nature, and they form an association with the plant roots and help the plant to take up nutrients. Nutrients that are not easily available. They also impart disease resistance to the roots. They also contribute to soil structure formation, and therefore improve soil aeration.
Koroma
I'm in a big hall in the International Institute of Tropical Agriculture in Ibadan. Presently I'm looking at some big tables that contain some pots. You have some plants in them. Mr Robert, can you tell us what is going on here?
Abaidoo
Just closest to you, you have soil that you would describe as highly degraded, because they have come from an oil spill area in the Niger Delta of Nigeria. And what we are doing currently is examining whether we can use mycorrhiza, VAM mycorrhiza, to rehabilitate.
Koroma
Yes, as I look through the pots I see what you are trying to say. The plants here are a bit different. Some are green and some have some kind of yellow description. So, what can you say about that?
Abaidoo
The plants that appear to you greener are the plants that are growing on a healthier soil, or a less degraded soil. Those plants that look pale, that are very close to you, are those that are growing on highly degraded soil.
Koroma
Are many soils like this in Africa?
Abaidoo
Yes, many soils in Africa are described as degraded, either physically degraded, chemically degraded, or biologically degraded.
Koroma
So what do you do to treat, so that you can upgrade this?
Abaidoo
There are many approaches that we can adopt. As a soil microbiologist, what I'm interested in is how to use micro-organisms to rehabilitate soils, to increase nutrients' availability to crops.
Koroma
Is that what you are doing here, exactly?
Abaidoo
Exactly, this is what we are doing here. We have added mycorrhiza fungi, that is vesicular-arbuscular mycorrhiza, which you can simply call VAM. When I add mycorrhiza, I am expecting that nutrient uptake will improve. Plants that are grown or are inoculated with the mycorrhiza will appear to be growing better than the plants without the addition of the mycorrhiza.
Koroma
Can you tell us what do you mean by nutrients?
Abaidoo
Nutrients, in the same way we take in food nutrients to grow, plants need soil nutrients to grow. So if I add mycorrhiza, at the end of the growth period I expect the mycorrhiza-treated plants to look bigger, nicer, greener, than the plants that have not received the mycorrhiza.
Koroma
I got to understand that you spoke about polluted soil, especially in the Niger Delta. So how are you going to help farmers to regain what they have lost?
Abaidoo
As we showed you in the lab, we can multiply these mycorrhiza species and apply them in these degraded soils. But I must say that it is also a very difficult task, because of the sheer enormity of inoculum that you have to use. I remember in China, they had to inoculate large areas with cassava mycorrhiza, so that they could grow cassava in those areas. So it is not an impossible task. But I would just say that it's enormous.
Koroma
As we are talking about sustainable agriculture in Africa, what advice do you have for farmers listening?
Abaidoo
The advice I would give to farmers is that farming practices should be friendly to microbial life in the soil. Because these micro-organisms contribute to the health of the soil, and also contribute to making nutrients available to the plants. End of track.
