Addressing the challenges of soil erosion and degradation in Karatu, Tanzania

Good morning, listeners. In today’s program, we will discuss how soil erosion and degradation have destroyed arable land and affected agricultural production for small-scale farmers in the Karatu district of Tanzania. Karatu district is in Arusha region of northern Tanzania. We will also discuss the measures taken to address these problems and restore the degraded lands to productivity and restore the environment.

To help in our discussion and answer questions, we have with us Eliud Letungaa, an expert in land restoration involved in a project on regenerative agriculture in Karatu district run by MVIWA Arusha, a farmer-based organization.

Please give us a brief context of how soil erosion and degradation have affected small-scale farming in Karatu district.

We started this project in Karatu in 2017 and we have reached an estimated over 1,000 farmers. The terrain in Karatu is hilly and because of that, the farmland has gullies because of water runoff. The water runoff is rapid because the clay soil consists of the smallest soil particles and once it gets soaked with water, the top soil it easily washed away. The clay soils become more prone to erosion by water or strong winds when they are not fertile enough. Other causes of erosion in Karatu district include human activities such as brick making for buildings which involves digging soil from farms or nearby areas. This erosion can extend to farms, which also contributes to the formation of gullies.

It’s important to note that runoff water can be useful for improving vegetation cover if managed well. For example, creating contours or terraces or other structures that will hold or harvest can facilitate tree growth and reducing the need for frequent irrigation. Those are some of the factors that made us introduce the project here.

What staple crops do small-scale farmers grow in Karatu district?

The common staples are maize, beans, pigeon pea, cowpea, and pumpkins, and they are all intercropped. But we have introduced bananas. In one piece of land, you can see four or five crops growing. The main reason for the intercropping is because in Karatu, most small-scale farmers have two acres or less of land and only a few have over five acres. Diversifying farming is key to helping farmers improve their food security and fertility.

If farmers can grow multiple crops and keep livestock, they will create an ecosystem where crop residues are used as fodder and livestock manure is used as a source of crop nutrients.

Are there other reasons that farmers use intercropping?

Yes, they grow more than one crops in their small pieces of land to minimize the impact of crop failure from poor rains. But intercropping and poor rains result in very low yields for the resilient crops that survive. So we tell them to apply manure to ensure the soil is fertile so that the crops that survive the poor rains yield well. And we have also taught them water harvesting so that their farming can continue when rains are poor.

What measures have you and your organization MVIWA Arusha introduced to address soil erosion in Karatu district?

In 2017, we started by planting trees in gullies in order to restore degraded land. We select species such as Grevillia robusta, Croton megalocapus, Acrocarpus species, Cordia africana, Senna siamea, Acacia species, Euphorbia tirucalli, and sisal because they are fast-growing, drought-resistant and can hold the soil and slow water runoff. But we discovered that euphorbia hampered the growth of other plants. So we introduced sisal, which, besides holding the soil in place, benefits farmers who harvest and sell it commercially. The waste from sisal can also be returned to the farm as mulch to improve soil organic matter and help conserve moisture.

We also recommended that farmers plant indigenous trees like Acacias, especially Acacia nilotica that act as a windbreak and prevent soil erosion. Acacia nilotica also has pods that farmers can feed their goats and it’s generally a good tree for the environment. For example, it fixes nitrogen in the soil, and protects cropland from fire and wind, as well as producing roots which help hold the soil.

We encourage farmers to also plant exotic trees like Grevillea and Acrocarpus fraxinifolius that are fast-growing, multipurpose trees that can be harvested for timber or firewood. Acrocarpus fraxinifolius is best grown in field boundaries where it acts as a windbreak. Grevillea robusta is one of the best agroforestry trees. It can be planted on field boundaries for demarcation or as a windbreak. Supplemented with elephant grass which anchors the soil, it also strengthens ridges or contours and improves the soil when its leaves fall and add to the soil organic matter.

How did you work with farmers to address the degraded soils on their lands?

To address the degraded soils, we have introduced banana farming. When the bananas mature and are harvested, their stalks are left on the farm as mulch, which increases soil organic matter and minimizes soil erosion.

Banana farming is integrated with cover crops like lablab and mucuna species, also called velvet bean. These legumes are good at adding nitrogen to the soil and combating soil erosion. Also, we emphasize agroforestry and agroecology practices because these approaches build soil resilience to different forms of erosions.

All these practices have boosted crop yields. We’ve also introduced and strengthened poultry keeping as a source of income and nutrition stability to the community. This helps farmers produce eggs and chickens for sale and get much-needed manure for their degraded farms.

To help us understand how soil erosion and degradation has affected small-scale farmers, we now talk to Ansila Paskali, a farmer for 18 years in Karatu district and a wife and mother of four. Besides the common staples, she also grows sunflower, from which she makes oil for household use. Ansila, please first tell us the advice you received to address the soil erosion and degradation that is common here.

My farm is an acre and half in size and on a slope. Two years back, heavy rain and strong water runoff from the hills caused gullies to be formed. That destroyed a quarter of the land. So the MVIWA Arusha team advised us to make bunds and plant indigenous grasses on them to hold the bunds in place. We were also advised to plant trees in the farm such as leucaena species and trees like sesbania, which provide fodder for livestock.

And I’ve seen results! Last year, my farm wasn’t destroyed by runoff from the rains—and not just me but my fellow farmers who adopted similar practices. Other farmers are coming to ask us for advice on carrying out similar practices to prevent soil erosion on their farms. I anticipate that the quarter-acre that was destroyed will be rehabilitated and I will be able to farm on it again next year.

Where do you plant the trees?

I planted the sesbania and the leucaena fodder plants on in alleys and dispersed through the farm, on the perimeters and on the gullies created by water runoff. The gullies are as wide as five walking strides. So when it rains, the plants slow down the water runoff and trap leaves, small branches, and the soil particles that are being washed away. As a result, I’ve seen those gullies disappear gradually as they are filled with soil.

Being legumes, these plants also make our farms fertile by fixing nitrogen in the soil. They also don’t interfere with the pigeon peas and other crops I grow. And when those legume trees shed their leaves, we leave them on the ground and they add humus and enrich the soil with different materials and make it fertile.

Training from MVIWA Arusha also helped us learn the importance of mulching for soil fertility and moisture conservation. After harvests, we used to bulk the residues from dry maize and the pea crop and feed it to our livestock. But now after harvest, we spread the drying crop residues all over the land as mulch to cover the soil and replenish it with organic matter to make it fertile. But if it is necessary to use the crop residues as fodder, we make sure that we return the livestock manure back to the farm.

I also spoke to Florian Gitu, a husband and father of three and another Karatu farmer who learned the land restoration practices and has applied them to address soil erosion and degradation on the five acres of his extended family’s land. Florian also trains other farmers in Karatu on practices to help avoid soil erosion and degradation and the recommended way to plant different crops.

Gitu, what advice do you give to farmers here in Karatu who are struggling with soil erosion and land degradation based on what you’ve learned from MVIWA Arusha?

In this area, many gullies that might be formed through water runoff and soil erosion can be prevented. We tell colleague farmers in this area whose lands are ploughed with tractors that they should plough across the contour of the hills, perpendicular to the flow of water runoff, to disperse it.

Soil erosion can also be minimized by planting trees or cover vegetation on gullies. The vegetation helps trap soil that is carried by the water runoff, and eventually the gullies fill up and the land becomes level. Though my farm is on a slope and in the past I’ve experienced lots of flooding, I now plough it in a way that reduces the speed of water runoff and spreads the water over the farm so that no gullies form and there is minimal damage.

We also urge farmers to maintain permanent soil cover on their land by spreading residues from harvested crop residue to form a mulch instead of feeding them to livestock. That shields the soil from the harsh sun. And when it’s ploughing time, the mulch is worked into the soil and becomes manure that makes the soil fertile. Cover crops also help slow water runoff and minimize land destruction.

In Karatu, we plant Mucuna pruriens and lablab as well as Grevillea robusta and Acacia nilotica to help trap the soil, fill the gullies, and reduce runoff. Mucuna is upupu in Swahili and lablab is fiwi or ngwara, while Grevillea is mgrivea and Acacia nilotica is mgunga. The two legume cover crops also suppress the stubborn purple nutsedge weed and couch grass, commonly known as sangari in Swahili. Also, more training is needed for farmers who are skeptical that leguminous trees like sesbania can improve soil fertility on their farms.

Florian, suppose a farmer has livestock and relies onharvested crop residues to feed them. Can they still usethe crop residues as mulch?

In that case, they should set aside some land for growing only livestock fodder. Let’s assume, for example, that a farmer has four acres of land. Then they can set aside an acre to grow livestock fodder. But if this suggestion doesn’t work a famer can use the crop residues as fodder and the manure produced by the livestock plus the crop residues left over after feeding the livestock should be taken back to the farm.

After the gullies are filled with soil and the land is level, are there practices you and other Karatu farmers have adopted that help farmers get more yields even on small pieces of land?

As we speak, I’m on the farm with my workers and we are planting maize. We use a rope for planting. I’ve become an expert at that and it helps farmers get more yield per acre.

Please explain that process for us and how it helps farmers.

We use a rope when planting and apply manure, but more importantly we strictly follow the planting instructions on the seed packet. If you have one acre of land for planting maize and the instructions say you plant two maize seeds in a single hole spaced 45 centimetres apart, you don’t waste land like you would if you blindly plant.

And if you later top dress with urea or NPK fertilizer when the maize has six leaves or is at knee level, that helps suppress striga weed and increases the possibility of getting high yields. By following these instructions, you can get yields of 28 to 30 bags of maize per acre. In our five acres 15 years ago, we harvested 50 bags of maize. Today on those five acres, after the training, we get 100 or more bags of maize by planting the right way. For beans we get eight to 10 bags per acre, depending on the variety. For yellow soya, we used to get three bags, but today we harvest five bags per acre. So all those MVIWA-Arusha trainings have helped us address the gulley problems and improve soil fertility. And we’ve seen great and positive changes.

Quite inspiring. Through these land restoration efforts, are there other aspects of your lives that have been transformed here?

Some farmers lived in mud houses, but today with their livelihoods improving, they are building brick houses. Because of what has happened to us, I feel such transformation can happen to farmers still struggling with soil erosion and degradation in Karatu. This transformation happened within seven years after I started adopting these land restoration practices I learned from MVIWA Arusha. Farmers are coming to me for advice and I visit them on their farms to train them on what I’ve learned and implemented on land restoration.

HOST: Dear listener, before we conclude, let’s review what we learned in this program.

If uncontrolled, water runoff can form gullies that make farming challenging.

But gullies can be filled by planting leguminous trees or cover crops or other vegetation that slow the momentum of the runoff and trap the soil.

Soil infertility can be addressed by planting leguminous trees or cover crops.

Residues from harvested crops should be left on farm as mulch to cover the soil and make it fertile and also reduce erosion.

Ensure that soil on hills has a permanent soil cover.