Lokouna Djassoga walks across the ridges in his field, hoe in hand. On this misty December morning, he is harvesting yams. The farmer stops at each mound of earth, breaks it open, and unearths three or four, sometimes five tubers. He sorts them into those he will eat and those he will save for the next planting. Behind him, friends and children also have their hands in the earth, collecting large tubers for eating.
Mr. Djassoga farms in Blakpa, a village just outside Atakpamé, a city 160 kilometres north of Lomé, the capital of Togo. Like him, many farmers harvest their yams in December.
He is proud to see that the tops of his yams, which he planted months ago, have grown into long, fat tubers. He says, “The harvest is not bad. I counted on having six to eight basins of yams this year.” Basins are a traditional unit of measurement in this area.
Mr. Djassoga has more than one parcel of land. He harvested yams on his largest field this year, but last year, he grew beans on this field.
He explains: “The objective is to benefit the yams with rich, green manure. The manure comes from the degradation of the bean crop residues that I bury at the base of the mounds when I make them.”
He adds: “It is not profitable to plant yams on the same land two years in a row. I never do it, otherwise the harvest falls automatically. The number of basins [harvested] in the last year will be notably inferior to the first.”
This experience is what led the 34-year-old farmer to rotate his crops. Mr. Djassoga and his friends understand the importance of crop rotation, one of the three main principles in conservation agriculture. Conservation agriculture promotes minimum tillage, permanent soil cover—for example, with crop residues—and crop rotation or intercropping. This approach to farming allows farmers to cultivate land in a way that enables it to remain productive for a long time.
Crop rotation involves rotating which crops are planted in a single field in successive seasons. When farmers rotate crops, one crop often contributes nutrients that are used by the crop that follows it.
Mr. Djassoga will plant yams again in February or March, but in a different field.
Farmers grow yams at different times of the year, depending on the region. In humid zones, farmers build mounds in October and then plant their yams and cover the mounds with plants or stones. When the first rains arrive in February, they remove the plants and place stakes. The first harvest is in August. At this time, farmers insert a stick into the mound, find the head of the tuber and remove it, then re-cover the roots to produce more yams. The farmer returns in December to disassemble the mounds and unearth the tubers.
This same land is then prepared for maize. Mr. Djassoga explains: “I grow maize for two months, starting in April and harvesting in June. Even without fertilizer, I harvest enough. If it rains again in July, it is possible to plant beans. If not, I wait until the next rainy season.”
Tsipoaka Kossi Mensah is the chief agronomist with the NGO, Association Mieux-Etre Pour Tous, an organization that works to improve the livelihoods of Togolese people.
He says that with crop rotation, the choice of crops is very important—from the start of the rotation, to the middle, and the final crops.
He explains: “There is a logic in the succession of the crops: the tubers—like yams, cassava, sweet potato—are the head of the rotation. They increase the porosity of the soil, which allows good water circulation. Then the cereals, like maize and sorghum. Because of the porosity, they can plunge their roots deep into the soil and grow correctly. They are the intermediary crops. Finally, the farmer can plant legumes (like beans and groundnuts) which reinforce and fix nitrogen in the soil.”
He says that farmers might be successful planting the same crop in the same field season after season if they have rich soil, but that, over time, the soil will become depleted and the farmer will need to use composted manure or animal waste. However, by simply rotating which crops are planted in the field and ensuring legumes are part of this rotation, farmers can maintain good soil fertility.
Mr. Mensah cautions that crop rotation does have its limits, and suggests that farmers also adopt intercropping. This technique, also called “twinning,” consists of planting two crops in the same field at the same time—for example, okra and groundnuts. These intercropped plants produce more between them than they would if planted separately.
This work was created with the support of Canadian Foodgrains Bank as part of the project, “Conservation Agriculture for building resilience, a climate smart agriculture approach.” This work is funded by the Government of Canada, through Global Affairs Canada, www.international.gc.ca.