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CTA. 2004. Beans. Rural Radio Resource Pack 04/01. Wageningen, The Netherlands: CTA.
Permanent link to this item: http://hdl.handle.net/10568/57345
Festo Ngulu, an expert in plant disease, discusses land preparation and weed management, both chemical and manual, in the context of bean production.
Beans Cue: Like other crops, beans can be seriously affected by weed infestation. Farmers living around Arusha in Tanzania, for example, have major problems with a weed known as Mexican Poppy, and the presence of this, and other weeds, is one factor that is limiting bean yields to just 400 kgs per hectare. Festo Ngulu, a plant health specialist at the Selian Agricultural Research Institute spoke recently to Lazarus Laiser about the ways in which smallholder farmers are being encouraged to tackle the problem of weeds in their bean crops. IN: ?Broadly speaking we have two ? OUT: ?low crop and that?s a loss.? DUR?N 3?55? BACK ANNOUNCEMENT: Mr. Festo Ngulu of the Selian Agricultural Research Institute in Arusha, Tanzania. Transcript Ngulu Broadly speaking we have two types of weeds, these are broad leafed and the grasses. The intensity or the combination of these two types varies from one place to another but severe weed infestation can cause as much as 80% crop loss. So I think it is important to take note of the fact that they are one of the major constraints to bean production. Now there are several methods which farmers can use to control the weed infestations in their farms. One of the key methods is to prepare land correctly. That is to make sure that the land is well prepared and all the weeds are ploughed under before the rains come. The second method is to make sure that the farmer uses weed free seeds. In some cases you find that there are some weed species which are disseminated along with our seeds. So I think it is important for the farmer to make sure that he has a reputable source of his seed. The second aspect I think is the actual management of weeds in the farm. Farmers are advised to make sure that their farm is weed free at least prior to flowering. They can use a hand hoe if he is a small-scale farmer or they can use herbicides. Some of these are pre-planting herbicides, some are pre-emergence herbicides and the last type is post-emergence herbicides. The herbicides are particularly effective on large-scale farms in the sense that the farmer can conduct the operation within a short time and can ensure effective control of the weeds. Laiser How effective are these methods? Ngulu They are quite effective. But one thing to note here is we have our different herbicides and none of these are effective against all weed species. So I think it is important for the farmer to select a combination which can tackle the weed spectrum in his field effectively. Laiser When do you think is the right time to use these methods of weed control? Ngulu It depends on the type of herbicide he is using. For instance I mentioned the pre-plant herbicides, these have to be applied before the farmer actually plants. But they have to be incorporated in the soil. Now for the pre-emergence, soon after planting the farmer has to spray the herbicides before the seedlings emerge. And for the last category, that?s the post-emergence the farmer has to come in immediately after the crop has come up just when the weeds are starting to shoot from the ground. Laiser What strategies of weed control are mostly appropriate for smallholder farmers in growing this crop? Ngulu I think hand weeding is okay after flowering because at that time the canopy of the bean plants will have come together and effectively covering the soil surface. So you?ll have occasional weed plants coming up and this is where I think hand weeding is practical. But during the early stages before flowering I think hand weeding is not effective. We encourage them to use a hand hoe if they cannot afford to buy the herbicides. It is a bit tedious and for those who have large acreages I think it is not advisable for them to adopt this method. But for the small-scale farmer and especially where some of them inter-crop maize and beans I think this is the only way, it is the only method which they can effectively use to control the weeds. Laiser What are the key factors that farmers should remember about these methods you have mentioned? Ngulu I think the key factor is timeliness of the different operations. That if you are going to prepare your land, prepare it early enough so that the weeds decompose before the rains come or at least weeds like couch grass. If you do the ploughing during the dry season you are bound to kill a large proportion of those stems. The other thing is, the important thing is for farmers to come in and do the weeding operation before the weeds actually have an upper hand on the bean plants because as you mentioned they compete with the bean plants for nutrients, water and light. So the moment the weeds get an upper hand it means that the farmer will get a very low crop and that?s a loss. End of track.