Are burning crop residues and grass good for soil health and fertility? Views from a farmer and an agricultural researcher

Soil health

Notes to broadcasters

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Crop residues are the remains that are left over after the plant or crop has been put to use – for household food, for fodder, for sale, etc. In western Kenya, farmers usually spread these residues along their farm boundaries. Some residues may be used for making composted manure or laid on the floor of a cattle shed to mix with dung to produce manure fertilizer for crops.

In western Kenya, farmers have long known that burning crop residues is a bad habit. However, bean crop residues are often burned. The ash is often cooked with vegetables such as cowpeas to make them softer for eating. Farmers normally burn these bean residues in their homes. Apart from beans, only a few farmers burn crop residues, except when there are so many residues that they may take a long time to decompose. The practice of burning crop residues has its positive effects. What we must note is that its positive effects are very short-term, as the script will show.

In this script, a smallholder farmer and an agricultural researcher give different opinions on whether burning crop residues and grasses is a good idea. The farmer sees that burning residues makes her farming work easier. Burning controls weeds and pests, and improves yields in the season after burning. On the other hand, the agricultural researcher says that, over the long-term, burning destroys the soil. It causes increased soil erosion; it kills beneficial soil organisms, and eventually causes lower yields.

This is a complicated subject. Some researchers say that, in humid environments like western Kenya, it is not as harmful to burn residues as it would be in dryer environments. In dry environments, burning residues can reduce soil fertility quite quickly.

For some farmers, it may be easier and cheaper to burn residues and grass, even if it is not a good long-term strategy. Farmers may not have the labour or resources to grow cover crops, or dig residues into their fields, or adopt other practices that are better for long-term soil fertility and soil conservation than burning. They do not have enough labour to cut bush and pull weeds by hand. So they burn their fields and they see immediate gains.

However, broadcasters should help farmers understand that cover crops, incorporating residues, and other soil-building practices – including the residue and agroforestry practices suggested by the agricultural researcher in this script – are a good long-term investment, and will help them achieve good yields over the long-term. It’s important to note that not all these practices work in every climate. For example, farmers in dryer areas may not have sufficient mulch or crop residues to use some of these practices. Or all the residues may be needed to feed livestock.

This script is based on actual interviews. You could use this script as inspiration to research and write a script on a similar topic in your area. Or you might choose to produce this script on your station, using voice actors to represent the speakers. If so, please make sure to tell your audience at the beginning of the program that the voices are those of actors, not the original people involved in the interviews.

Script

Characters

Host
Farmer: Josephine Atieno
Agricultural researcher: Lena Oringa

Thematic music to introduce the program

Host:
Welcome, listener, to your favourite program on soil health. Today, the program will focus on burning crop residues and grass. We will hear the perspective of a farmer who has experienced the benefits of the practice. We will also hear the perspective of an agricultural researcher on the practice of burning crop residues and grass.

For a moment, listener, think of a farming practice that people feel negative about. You might take the risk as a farmer to test the practice on a small piece of land. This may convince you of its benefits as well as it negative effects. So it’s not a bad idea to try it out. But first, talk to farmers and researchers. Find out the reasons why they say that the practice might be positive or negative.

Today’s guests are Mama Josephine, a farmer, and an agricultural researcher, Mrs. Lena Oringa. This is what they will talk about today on your favorite radio station…. Stay tuned. I am your presenter, (presenter’s name).

Musical break

Host:
Welcome back, listeners. Talking to women farmers makes me happy because women make up the majority of farmers in the local community. Women farmers are so important to help feed the community. I was able to talk to a women farmer who burns crop residues on her farm. Fortunately, today Josephine is here with us to talk about the practice. Welcome, Josephine.

Josephine:
Thank you.

Host:
So, Josephine, we will get it from the horse’s mouth today. Can you please share with our listeners your experience with burning crop residues and grass?

Josephine:
Thank you again. I have been a small-scale farmer since I got married more than twenty years ago. Before I was involved with women’s groups, I did not have good farming ideas. But coming together with women farmers enlightened me. Since then, I have been exploring different techniques. I have learned from trainings on farmer innovation to always be innovative.

In this area, our soils are infertile because of damage from human activities. I tried techniques to improve the depleted soils so I could get good crop yields. I planted trees to control erosion, and I did improved fallows instead of leaving the land naturally fallow. Burning crop residues is something I learned about just by trying it and seeing what happened. It’s an old tradition. Whenever the extension officers from the Ministry of Agriculture visited, they would condemn this practice. And so I believed it was not a good thing to do. But I always believe the saying “necessity is the mother of invention.” Those who are in need will always find solutions through trial and error.

Host:
Mama Josephine, would you tell the listeners how you used the residues before you tried burning them?

Josephine:
I always used residues to make compost. I spread the compost on the farm to help the soils. And I would lay some crop residues at the farm boundary. I didn’t know that burning residues and grass had benefits, as well as the disadvantage of killing some important soil insects. In everything I did on the farm, I was keen to know how well the practice worked. So I tried burning the residues and grass on the farm. I can testify there are some positive results.

Host:
What exactly were the benefits you saw on your farm?

Josephine:
Burning reduces pest invasions after planting. I believe the reason is that the weeds that may have attracted the pests are killed. Weed seeds are also destroyed and do not rejuvenate. The ashes from the residues are rich in potassium and calcium; this adds value to the soil and benefits the crop. Since I do not use fertilizer, this is a way to give the soil what it lacks.

I think that with this practice, those who use fertilizer can reduce the amount of fertilizer they use. I took a risk. Through trial and error, I reaped the benefits of what other farmers believe is a poor farming practice. I believe that farmers should adopt this practice to see positive results. Experimenting with the practice is the way to see and confirm the truth.

Host:
Listeners, you have heard one farmer’s perspective on the positive effects of burning crop residues and grass. We will hear what the agricultural researcher has to say in a short while.

Musical break

Host:
Welcome back, listeners. Now we will hear the perspective of an agricultural researcher. Farmers have felt strongly negative about burning residues and grass. According to farmers like Mama Josephine, they received this negative opinion from agricultural experts. Listeners, meet Lena Oringa. Welcome, Mrs. Oringa.

Agricultural researcher:
Thank you. After listening to Mama Josephine’s story, I feel a little bit challenged. I feel that today, this practice of burning crop residues and grass should not be encouraged. The nutrients that are released after burning are usually washed away or leached by rain, or eroded by wind. Soil declines in productivity after burning because its nutrients are depleted. Because of this, the ancient farmers who practiced slash and burn had to leave the land for five to 25, even up to 40 years before they could farm the land again. This is impossible today because of population growth, which leaves no time for land to lay idle to regain fertility.

So, for quite some time, this practice has been discouraged. I know that there are benefits. When we burn the residues, we kill pests. Some pests contribute to diseases so there’s a double benefit. Weeds are also killed.

Host:
If burning is not a good idea, what should farmers do to restore soil fertility in western Kenya?

Agricultural researcher:
I would encourage farmers to continue spreading crop residues on their farms. Farmer Josephine uses improved fallows, which should also be encouraged. Like Mama Josephine said, crop residues can either be composted or laid on the floor of the cattle shed to mix with dung. This will produce manure which is good for the crops and more sustainable than burning. Once the residues on the farms decompose, they release nutrients to the soil, making it fertile and available for the crops.

Farmers can also plant the tree known as Faidherbia albida, at 100 to 150 trees per hectare. This will provide nutrients equivalent to 300 kilograms of nitrogen per hectare every year, plus lots of phosphorus and magnesium. Planting Faidherbia at this density can double or triple yields.

Host:
What about weed control?

Agricultural researcher:
Spreading residues in the field stops weeds by a combination of shading and smothering. The residues also stop the sun from drying out the ground. This keeps water in the soil so it’s available for crops. Farmers can make holes in the residue layer and plant their crops. Or they can simply spread organic mulch by hand around plants after they emerge. The crops get nutrients from the decaying leaves. The trees’ roots absorb the excess nutrients which are returned to the ground when the trees are pruned.

Host:
Do you have any other comments about burning crop residues and grasses?

Researcher:
Though burning crop residues and grasses is an organic practice, it is not safe. Farmers must be cautious with this practice. Burning damages soil and eventually ruins it. When soil is left bare after burning, there can be a lot of soil erosion. Also, burning residues and grass releases a lot of carbon dioxide into the atmosphere, which contributes to global warming.

Host:
Mama Josephine said that burning reduces pest attacks. What do you say about that?

Researcher:
It’s true that burning kills pests and disease-causing organisms in the soil. But it kills the beneficial and important organisms too. This reduces the biological activity in the soil. Mulching improves the soil by attracting and feeding earthworms and other living organisms. The organisms “till” the soil, and their feces are among the best fertilizers and soil conditioners. So, spreading mulch or crop residues instead of burning them should be encouraged. It builds the soil, and improves its structure and fertility.

Musical break

Host:
Welcome back, listeners, and thanks to today’s guests, Josephine and Lena. Listeners, you have heard from the horse’s mouth. It is a matter of choice. In all the farming practices we choose as farmers, let us take precautions and understand better the level of the practice’s importance. If I were you, I would embrace mixed farming systems. Instead of growing one single crop, farmers can intercrop cereals and legumes, and even grow agroforestry crops. Because it’s a mixed system, it has a number of benefits, including reduction in weeds and pests. Minerals are added to the soil. Further, practices such as mulching help soil hold water and make nutrients available to plants. It stops water logging and improves soil pH.

We have heard that ash has short term positive effects but long term negative effects. Though ash is a natural product that contributes positively, we should be cautious when using it. This is just like snake poison. Snake poison is natural, but can we use it to kill bugs on our farm?

Listeners, we believe that wherever you are, you have learned that it is not always easy to tell if a particular farming practice is negative or positive. There can be differences of opinion. And some practices may have short term benefits but negative long term side effects. In such cases, I urge you to follow the advice we have heard from the researcher if we want to experience great results as farmers.

Thank you for staying tuned. I am your presenter (presenter’s name). Until we meet on the next program on soil health, bye.

Acknowledgements

Contributed by: Senior Writer Rachel Awuor, Ugunja Community Resource Centre, Kenya, a Farm Radio International broadcasting partner.
Reviewed by: Peter Gaichie Kimani, consultant to World Agroforestry Centre (ICRAF), Nairobi, Kenya

Information sources

Interview with Luke Musewe, Ugunja Divisional Agriculture Officer, 20th April 2010
Interview with Josephine Atieno, Farmer, 26th March, 2010