Christian Thierfelder strides into a plot of maize, reaches down, and scratches through the mulch with his fingers to grab a clump of soil.
Holding it up, the senior agronomist with CIMMYT’s Harare field station lets it crumble through his fingers — it is moist but not muddy, and the decaying plant material gives it a spongy texture.
Then he walks across to another field being produced under conventional methods, where a hoe has been used to create rows of ridges. The soil from this field is rocky and hard. It sifts through his fingers like the sandy silt that it is.
“In the conventional system, they leave everything bare, which helps them to control the weeds,” he said. “In the CA system, we encourage them to leave the residues from the previous crop on the soil.”
Over time that decaying residue becomes the compost that creates the sponge-like texture.
“When you look, the soil (under CA) is very loose and when you get a heavy rainfall, the water can infiltrate because there is a lot of biological activity — earthworms, beetles and ants and so on that create these biopools, like a sponge,” Thierfelder said.
“The rainfall hits the soil surface and infiltrates, whereas on the conventional system, it just runs off or stands there. It cannot infiltrate because it is mostly compacted between the ridges.”
That’s what makes CA “climate smart,” during a dry spell, Thierfelder said.
“The conventional system can only make use of the water that is in the ridge and not farther down in the soil,” he said. “In the CA system, there is access to deeper layers and there is a lot of water that has infiltrated before.
“The maize can actually access the water much better because of an improved root system. And also, because of the residues on top, there is less evaporation of water — it just has more water available for plant growth.”
The decaying mulch builds the soil’s organic matter and fertility, as well as its water-holding capacity.
But the system also provides distinct advantages to smallholder farmers, which is why the push is on by CIMMYT and other food security, environmental and faith-based organizations to support its widespread adoption.
“What farmers often do in this area because of their fear of not being food secure is they plant a large area to maize,” Thierfelder said.
“And that’s actually counterproductive because maize is a crop that you cannot sell with a lot of profit. It’s just good for food. So the idea of introducing a rotation can only come in when farmers are food secure.”
CA techniques reduce the risk of crop failure, which means they can sow a smaller area to the staple maize.
“Then there is room for new crops, cash crops, rotational crops, nutritional crops that help them a lot to improve their diet to reduce malnutrition to reduce the problem of stunting,” he said. “That’s a very good way to overcome all of these at once.”
Thierfelder said herbicides are used, particularly in the early stages.
“Most of the weeding is done by women, and if you introduce a technology like herbicides you can dramatically reduce the burden on women,” he said. “What we have seen on these plots is the weeds become less and less every year because you don’t turn the soil anymore and you don’t bring new weed seeds on the surface.
“We have seen in trials and also on farms that in about four or five seasons there are very few weeds coming up and they can pull them up,” he said.
Governments on side
Governments are joining the campaign. The government of Malawi recently completed a task force report identifying CA techniques that are well adapted to Malawi growing conditions, said Gilbert Kapunda, project manager for the Sustainable Land Management Promotion Project, an initiative of the country’s agriculture and food security department.
Kapunda said CA is seen as an important component of the country’s climate adaptation plan because of its ability to improve the soil and conserve moisture. Governments in the neighbouring countries of Zimbabwe and Zambia are also now promoting it.
“In areas where they have used CA, the technology actually conserves moisture in the soil, so when you have a dry spell you still have maize growing,” Kapunda said.
The Malawian government is now mounting an extension effort to drive more CA adoption in the rural areas.
But getting farmers to change is hard. After all, it was only a few years ago that the government was promoting the ridge-row system most farmers still use.
“The biggest challenge we are facing is actually the mindset,” he said.
Co-operator editor Laura Rance is visiting three African countries in February and March on secondment to the Canadian Foodgrains Bank.