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CTA. 2004. Sweet potato. Rural Radio Resource Pack 04/01. Wageningen, The Netherlands: CTA.
Permanent link to this item: http://hdl.handle.net/10568/57353
Research scientist Thumbiko Mkandawire discusses hoeing, hand weeding, intercropping and herbicides as methods of weed control in this crop.
Sweet potato Cue: Sweet potatoes have a lot of enemies. Pests and diseases can be extremely destructive, causing huge losses if not controlled. Weeds are not usually regarded as such as serious problem, although if allowed to grow unchecked, can reduce final harvests by more than half. One advantage sweet potatoes have over other root crops, such as yams and cassava, is that their stems and leaves spread quickly, shading the soil and preventing weed growth. The most important time for weeding, therefore, is early in the life of the crop, when the soil around the plants is bare. To find out more about when, and how to weed, Patrick Mphaka visited a crop research centre close to the city of Blantyre in Malawi, where new types, or cultivars of sweet potato are being developed. IN: ?Sweet potato is increasingly becoming ? OUT: ?are acceptable to the end-users.? DUR?N 5?05? BACK ANNOUNCEMENT: Mr. Thumbiko Mkandawire of Bvumbwe Agricultural Research Station in Malawi. Transcript Mphaka Sweet potato is increasingly becoming an important crop in Malawi and the region. This is so because of its drought resistant characteristic in the face of the current unreliable rains which continuously affect the production of other crops such as maize. To revamp the growing of the crop, Bvumbwe Agricultural Research Station Root Crop Commodity Team has been doing some research on various Sweet Potato varieties. One of the important aspects of any crop is weed control. To find out how weeds can effectively be controlled in Sweet potatoes, I had a chat with Mr Thumbiko Mkandawire, an Agricultural Research Scientist of the Root Crop Commodity Team. I caught up with him in a plot of sweet potatoes. Thumbiko In here we have got different varieties of sweet potato. Some are the released varieties, some are still under experimentation. Some are very promising compared to the local varieties. Mphaka Could we focus on weed control, how do you control the weeds in here? Thumbiko In here, normally once we have started irrigating the crops or using the rain fed, weeds start to emerge. Most of the times, weeds tend to grow faster than the clones. So in the first place we use the hoe, then later on we use the hand weeding because if we tend to use the hoe, we may end up cutting the vines hence in the end, we may predispose the vines to the disease-causing organisms. Hence we end up losing the varieties. Mphaka What you have just said, is it something which the farmers do practise or its something which they have not been practising but it?s something which you tell them to be practising because of the advantages you have just outlined? Thumbiko Farmers are very knowledgeable. If you go to their fields you will find that two to three weeks after planting, if they have observed that the weeds are growing faster than the desired crop, you will find that farmers will take a hoe and weed, and remove the weeds. Once the plant has developed fully, and it has started putting up some of the roots into the soil, the farmers normally they do not use a hoe. They use the hands because they are running away from predisposing the crop from the disease-causing organisms as well as the soil insects. Mphaka Now, what would you say is commonly practised: as you have done growing just sweet potatoes on a piece of land, or inter-cropping? Thumbiko In other areas, the farmers do intercrop with other crops, but in other areas, the farmers they just grow one particular field with sweet potatoes as you know that in Malawi we have got a problem of land especially in the Southern Region. Therefore the farmers normally do portion a piece of land to a specific crop. Mphaka If you look at the two scenarios, which area becomes more problematic when it comes to weeds? Thumbiko: This one depends on how knowledgeable the farmer is. But in most cases in terms of labour use and minimisation of labour costs to the farmers, they tend to intercrop the sweet potato with other crops. But at times it might bring about competition for nutrients and other aspects, hence in the end, you may find that there might be a reduction in the yield in both crops. But if the crop can be grown in pure state, you find that yield returns tend to be higher than in the intercrop. Mphaka We have noticed that some of the farmers start growing their sweet potatoes towards the end of the rainy season, while others, at the same time as they are growing the maize. Now, if you look at the two methods, which one is correct, and which one would control the weeds much better? Thumbiko The first one is a better approach in weed control management than the delayed one, because you will be able to control the weeds before they flower; you end up reducing their mechanism for multiplication in terms for seed production. And at the same time you may end up getting a lot of yield returns than if you delay in planting because even though the sweet potatoes are drought tolerant crops, but also they do require a lot of moisture for their growth and development so they should be able to put up a lot of bigger roots. But if they delay in planting, that means they will be losing some vegetative growth hence in the end they may end up having lower returns. Mphaka There is a lot of development nowadays and you can use chemicals to control weeds. How far have we gone in that area in Malawi? Thumbiko As far as I know, we haven?t yet come up with that research because our research focuses on the smallholder farmers, and we know that smallholder farmers, most of them they are resource poor, and if you develop that technology, the rate of adoption will not be as high as expected. Therefore, our main focus of attention in terms of research development is towards developing technologies that will be easily adopted, and appropriate to the targeted group, in this case the smallholder farmers. That is why the main focus of our research in terms of root crop development in Malawi, is to develop cultivars that are disease resistant to major diseases and pests, and also, developing the cultivars that tend to produce or give more yields, and at the same time, varieties that are acceptable to the end-users. End of track.