V. H. Kabambe

Imazapyr (herbicide) seed dressing increases yield, suppresses Striga asiatica and has seed depletion role in maize ( Zea mays L.) in Malawi

The parasitic weed species, Striga asiatica (L.) Kuntze, also known as witchweed, is one of the major constraints in maize production in Malawi. Most of the control measures do not protect a current crop from damage. In 1998/99 season, a trial was initiated at Chitedze Research Station under artificial infection, to evaluate the effects of seed dressing with imazapyr (an acetolactate synthase {ALS} inhibiting herbicide) using three seed treatment methods (coating, priming or drenching) and three herbicide rates (15, 30 and 45 g active ingredient ha-1) on S. asiatica suppression, maize growth and yield. The maize hybrid IntA/IntB//Pioneer325irMZ98F2, bearing target site resistance to imazapyr (IR maize), was used as test crop. In the subsequent season, normal or non-IR maize was planted on the same plots of 1998/99, to assess the residual or spill-over effects on Striga emergence, maize growth and yield. In the first season, results showed that imazapyr seed dressing suppressed (P emergence to 6.7 plants m-2 compared to 14.7 plants m-2 in untreated control. At 106 DAP, the number of Striga that flowered in untreated plots was 6.2 plants m-2, compared to significant (P > 0.05) yield differences. In the subsequent season, imazapyr treatments gave no residual or spill-over effects on maize growth and yield (P > 0.05. There were significant (P Striga emergence similar to the first season. The results therefore suggest that the use of ALS inhibiting herbicides not only suppresses Striga emergence, but also has a seed depletion role in integrated management of Striga without any spill-over or, herbicide injury in subsequent unprotected maize. This technology would be simple for farmers to adopt.

Scaling out best fit legume technologies for soil fertility enhancement among smallholder farmers in Malawi

4WVI-Malawi, Mulonyeni ADP, Mchinji, Malawi. 5 CARE-Malawi, Lilongwe, Malawi. 6 SOFECSA Coordination Office, CIMMYT, Harare, Zimbabwe. Accepted 23 January, 2012 Maize (Zea mays L.) is a major staple food in Malawi. However, low soil fertility resulting from low and inappropriate use of fertilizer practices, continuous monocropping and inappropriate crop residues management coupled with limited resources and droughts keep yields low. This had led to a quest for sustainable solutions such as maize-legume intercropping or rotation including more efficient use of crop residues in smallholder farming systems. Innovation platforms (IP) built around learning centres (LC) located on smallholder farmers’ fields in target locations were used as an approach to disseminate integrated soil fertility management (ISFM) technologies and build capacity of farmers, extension staff and other stakeholders. Rotating maize with either groundnut or groundnut intercropped with pigeonpea increased maize grain yield (3678 and 3071 kg ha -1 respectively) compared to sole maize

Using innovation platforms to scale out soil acidity-ameliorating technologies in Dedza district in central Malawi

Soil acidity is a serious constraint in crop production in some parts of Malawi, particularly in high rainfall and high altitude areas. A learning platform was established in Bembeke Extension Planning Area (EPA) (14° 21′ E and 34° 21′ S, 1650 masl, normal annual rainfall of 1300 to 1500 mm) in Dedza District to scale out lime applications as amendments to low pH soils. In 2006/2007 and 2007/2008 seasons, 36 and 150 two-plot trials, respectively were established to serve as learning centers for the comparison of application of 2 t/ha of dolomitic lime to no application in maize ( Zea mays L.) crop fertilized at 69:21:0+4S. In 2007/2008 season, a similar study compared application of compost manures. Application of lime increased (P < 0.05) maize yields from 3.58 to 4.68 t/ha in 2006/2007 and 3.35 to 4.2 t/ha in 2007/2008. In 2007/2008, the residual effects of lime increased (P < 0.05) yields of maize and beans ( Phaseolus vulgaris ). An innovation platform comprising of farmers, government and NGO extension and researchers organized exchange tours and end of season review meetings. The number of farmers hosting the learning centers grew from 36 to 150 due to the IP interactions. At the end of the project support in 2008, the participating farmers were willing to invest in the technology and raised funds for purchase of lime, assisted by government extension. The IP was unable to effectively engage any agri-input dealer to follow up on the demand on lime expressed by farmers. Application of compost manure increased maize yields from 4.25 to 5.84 t/ha, compared to 2.31 t/ha as practiced by farmers. Key words : Dolomitic lime, innovation platforms, composting, soil acidity, Malawi.

Release of cowpea line IT99K-494-6 for yield and resistance to the parasitic weed, Alectra vogelii Benth. in Malawi

Field trials were conducted between 2008/09 and 2009/10 seasons to evaluate four new cowpea lines, selected in preliminary studies, for yield, adaptation and resistance to the parasitic weed Alectra vogelii in Malawi. The design was randomised complete block design with 4 replicates at research stations and 5 at on-farm sites. For on-farm, villages were the sites and each farmer hosted one replicate. The trial sites were Lisasadzi, Mngwangwa, Bunda College, Chitedze Research Station, Rivirivi and Mpokwa in 2008/09 season and in 2009/10 the sites at Chitedze and Mpokwa were replaced by Mkwinda and Chitala Research Station. Four promising cowpea lines, IT98K-503-1, IT97K-825-15, IT99K-7-21-2-2-1 and IT99K-494-6, all originally from IITA and selected for resistance to parasitic weed Alectra vogelii in screen house studies, were compared with released varieties Sudan 1, IT82E-16 and a farmers local entry. The following parameters were evaluated: cowpea grain yield, plants/m2, seeds/pod, seed weight (g/100 seeds), days to mid-flower, days to maturity, disease scores (scale 1 [clean] – 9 [most severe]) and A. vogelii emergence (plants/m2). The line IT99K-494-6 was found to have comparable or better agronomic traits as compared to control varieties and was eventually released in Malawi in January 2011. The line which is medium maturing has brown grain texture with yield potential of 1-2.0 t/ha. Such a resistant variety is important in A. vogelii hot spots to reduce build up in soil seed bank and a viable option for farmers to rotate with cowpeas in order to manage other pests such as Striga asiatica, an important parasitic weed, or improve soil fertility through the nitrogen fixation of cowpeas. Key words: Legumes, witchweeds, parasitic weeds, cowpea, Alectra vogelii, Vigna unguiculata.