South-eastern Lowveld Of Zimbabwe Research Articles

An outbreak of Gynanisa maja (Lepidoptera: Saturniidae) larvae in the south-eastern lowveld of Zimbabwe.

The larvae of speckled emperor moths (Gynanisa maja) are important plant defoliators in savanna ecosystems of southern Africa and a valuable food resource for indigenous communities. Population explosions of G. maja larvae can negatively impact an area's primary productivity thereby altering herbivory patterns and associated ecosystem processes. Harvests of the larvae enhance socio-economic livelihoods of local people by providing a source of protein and improving household incomes. We report on a population outbreak of G. maja larvae that occurred in south-eastern Zimbabwe between December 2022 and January 2023 and discuss the ecological and social significance of the event. A total biomass weight of 5811 tons of G. maja larvae was estimated over the area of the outbreak and extensive defoliation was recorded in Colophospermum mopane trees. We could not associate the outbreak with any obvious environmental conditions and speculate that it may have been caused by subtle triggers that are not easily identified.

The pattern of anthrax at the wildlife-livestock-human interface in Zimbabwe.

Anthrax is an important but neglected zoonosis in southern Africa and elsewhere which occurs naturally in herbivorous wildlife and livestock. Fatal outbreaks in animals are spaced by potentially extended periods of non-activity during which the bacterium is maintained in soil. The ecology of the pathogen in the multi-host system and the environment is still not fully understood. This study investigated the patterns of anthrax in Zimbabwe in order to better understand the occurrence of disease in susceptible wildlife and livestock and hence its control. The study used available data in governmental reports between 1995 and 2018 and structured interviewer-administered questionnaires of local communities in three porous wildlife-livestock-human interface sites where livestock/wildlife interactions were documented from previous researches. Two non-interface sites were also included for comparison based on known previous anthrax outbreaks. Respondents from non-interface sites had significantly higher odds (χ2 = 23.2, OR = 3.5, 2.1<OR<5.8, p<0.001) of reporting anthrax outbreaks than their counterparts at the interface. Overall 20.0% (74/372) of the respondents reported that some anthrax carcasses were left to dissipate into the environment indicating a risk of environmental contamination. In livestock a total of 214 outbreaks with 2911 losses (mainly cattle) were recorded between 2000 and 2018, while 10 outbreaks with 3171 deaths were noted in wildlife. In humans 99 outbreaks were recorded involving 903 individual cases with 16 fatalities due to enteric infections following the consumption of infected meat between 2010 and 2018. Since its first incidence in wildlife in 2004–2005 in the south-eastern Lowveld of Zimbabwe, anthrax appears to be establishing endemic status along the Zambezi River basin. The disease has expanded spatially affecting 45 (72.6%) of the country’s 62 rural districts in a single decade. Thus, robust multi-disciplinary efforts are encouraged for surveillance and disease containment measures to minimize its impact on livestock, wildlife and humans.

Brucellosis and chlamydiosis seroprevalence in goats at livestock-wildlife interface areas of Zimbabwe.

In Zimbabwe, there have been no chlamydiosis and limited brucellosis studies in goats. This study was conducted to determine the seroprevalence and risk factors of the two diseases in goats at three different livestock–wildlife interface areas: porous, non-porous and non-interface in the south-eastern lowveld of Zimbabwe. Collected sera (n = 563) were tested for Brucella antibodies using the Rose Bengal plate test (RBPT) and the complement fixation test (CFT); and for Chlamydia abortus antibodies using the CFT. All tested goats were negative for Brucella antibodies. Overall, chlamydial seroprevalence was 22%. The porous [c2 = 9.6, odds ratio (OR) = 2.6, p = 0.002] and non-porous (c2 = 37.5, OR = 5.8, p < 0.00001) interfaces were approximately three and six times more likely to be chlamydial seropositive than the non-interface area, respectively. Chlamydial seroprevalence was not associated with sex (c2 = 0.5, OR = 1.2, p = 0.5), abortion history in female goats (c2 = 0.7, OR = 1.3, p = 0.4), keeping goats with cattle (c2 = 0.2, OR = 1.5, p = 0.7) or flock size (c2 = 0.03, OR = 1.4, p = 0.9). Our study provides the first serological evidence of chlamydiosis in goats in Zimbabwe and the results suggest that proximity to wildlife is associated with increased chlamydial seropositivity. Further studies are required to determine the role of chlamydial infection on goat reproductive failure and that of wildlife on C. abortus transmission to domestic ruminants.

Seasonal Spatial Distribution of the Mango Fruit Fly (Ceratitis cosyra) in Mango Trees Pruned to Give Three Different Pruning Canopies in High Density Mango Production in the South Eastern Lowveld of Zimbabwe

The mango fruit fly (Ceratitis cosyra Walker) is the major pest of economic importance and which restricts mango exports from infested production areas in the SADC region. The effect of three pruning techniques, box/rectangle, spherical/round and the central leader, on assessing spatial distribution of fruit fly populations in high density mango production were investigated at Chiredzi Research station (21°01’S, 31°33’E) from 2010 to 2013. Results showed a significant rise in the number of adult fly catches among pruning techniques as from July to December (p&lt; 0.05). Traps baited with Malathion 25% WP with molasses as an attractant were used to trap the flies. Results from all treatments indicated a significant rise in mean adult fruit fly catches from the months of July to December. It can be concluded that spatial distribution of the mango fruit fly is influenced by the fruiting and ripening patterns of mango.

Phenotypic and genetic characterisation revealed the existence of several biotypes within the Neorautanenia brachypus (Harms) C.A. wild accessions in South East Lowveld, Zimbabwe

BackgroundLocal communities in the South Eastern Lowveld of Zimbabwe have adopted the feeding of livestock with Neorautanenia brachypus (Harms) C.A. tuber to mitigate against climate change. Differences within Neorautanenia brachypus (Harms) tuber flesh colour and preferences by cattle have been observed, suggesting possible diversity within the N. brachypus plant community. This study aimed at distinguishing the N. brachypus wild plant species through phenotypic and genetic characterization using morphological descriptors and random amplified polymorphic (RAPD) markers respectively. Leaf samples were selected using judgmental sampling techniques from wards 11–15 in Sengwe (Chiredzi district) for leaf morphology and molecular characterization. RAPD-PCR analysis was done using 18-screened random decamer primers to confirm the diversity in the plant population. The similarity of the biotypes was evaluated using binary coding on the basis of the presence or absence of a morphological indicator as well as distinct DNA amplicon fragments. Primer 7.0.13 was used to estimate morphological and genetic similarities using the unweighted pair group method with arithmetic average (UPGMA). The cluster number was estimated using the Elbow method part of the R package.ResultsInitially, 14 biotype groups were identified from 96 accessions visually characterized basing of leaf characteristics. All the leaf biotypes displayed arcuate venation with differences observed for leaf shape, tip shape and leaf margins. The 14 biotypes clustered into six groups based on the binary data of the morphological characteristics. RAPD primers generated three hundred and sixty eight distinct amplicons with 77.5% being polymorphic from the 14 biotypes. The number of bands produced per primer ranged from four (OPF-02) to 44 (UBC-746). The PIC value ranged from 0.1327 to 0.1873 for the RAPD primers. Use of molecular markers collapsed the biotypes into five clusters. Both the leaf descriptors and RAPD markers showed the existence of genetic diversity within the wild accessions of N. brachypus.ConclusionsA combination of morphological and RAPD markers effectively refined the resolution of the genetic diversity within the N. brachypus wild accessions to nine biotypes. These findings have indicated to the existence of more than one biotype of N. brachypus with potentially different properties. The favorable biotypes can further be promoted through incorporation in pastures as alternative feed or complementary feed to livestock. As such the output of this study will serve as a guide for N. brachypus germplasm management and improvement.

Effect of Soil Type and Foliar Factors on the Distribution of Imbrasia belina in the Southeastern Lowveld of Zimbabwe.

The aims of this study were to find out whether soil parameters (i.e., soil texture, soil pH, and available nitrogen (N) and phosphorus (P)) and level of tannins in the bark of tree as measured by total amount of N & P in the droppings significantly influenced Imbrasia belina distribution in the Southeastern Lowveld of Zimbabwe. The samples were collected in February-March 2013. Standard methods were employed on 80 samples across the four tenure regimes studied. Soil pH, percentage clay, silt, and sand were randomly measured across the four tenure regimes. The study results revealed that soil pH (p=0.475), % silt (p=0.172), % sand (p=0.907), available nitrogen (p=0.192), available phosphorus (p=0.247), and the mean tannin level (p=0.999) influenced the distribution of Imbrasia belina in the study area. Multiple comparison analysis showed that there were significant differences in percentage clay (p=0.044) between Gonakudzingwa Small-Scale Farms (GSSCF) and Chikombedzi Communal Area (CCA). However, Mwenezi Resettlement Area (MRA) and Gonarezhou National Park (GNP) results were insignificant for percentage silt (p=0.172) and percentage sand (p=0.907), respectively. The soil and foliar factors discussed are critical in determining Imbrasia belina distribution, forest health, and vitality.

Understanding factors structuring zooplankton and macroinvertebrate assemblages in ephemeral pans

• Understanding invertebrate communities might help us make conserve and better manage ephemeral habitats. • Copepods were the most dominant and abundant taxa in all pans. • Thirty-three macroinvertebrate taxa belonging to 12 orders were recorded from the pans. • Flood plain pans had a more diverse macroinvertebrate fauna different from that of endorheic pans. • Vegetation is important for invertebrate taxa distribution in the pans. Ephemeral aquatic ecosystems have a global distribution being most abundant in semi-arid and arid regions. Due to anthropogenic impacts threatening these environments, there is a need to understand various factors and processes structuring animal communities in these habitats. Macroinvertebrate and zooplankton assemblages were studied in different ephemeral (i.e. flood plain, large endorheic and small endorheic) pans in the south-eastern Lowveld of Zimbabwe in the wet season. Ten Cladoceran species, Calanoids and Cyclopoids taxa and thirty-three macroinvertebrate taxa were identified over the entire hydroperiod. Predator macroinvertebrates were the dominant taxa especially in endorheic pans. The pan categories differed significantly in both zooplankton and macroinvertebrates composition and richness, with zooplankton and macroinvertebrate taxa richness being high in flood plain pans. Conductivity, fish presence, hydroperiod, maximum depth, turbidity and vegetation cover played a major role in shaping both zooplankton and macroinvertebrate communities. The macroinvertebrate community assemblage reveals that small endorheic and flood plain pans represent extremes ends of the environmental gradient in the region while large endorheic pans represent an intermediate end.

Impact of irrigation based sugarcane cultivation on the Chiredzi and Runde Rivers quality, Zimbabwe

Agriculture is vital in sustaining human livelihoods. However, agriculture as it is currently practiced, is contributing to the degradation of freshwater ecosystems globally. We investigated impacts of irrigation return flows from sugarcane farming on water quality and health status of the Chiredzi and Runde Rivers, a biodiversity hotspot region in south-eastern Lowveld of Zimbabwe. The water quality at inlets from the crop field into the wetland system; wetland outlets into the river systems; and river sites upstream and downstream of wetland outlets were monitored during the dry and wet seasons. The wetland system formed naturally from excessive drainage from the cane fields but its purifying capacity was unknown to date. An assessment of the water physical-chemical variables (at all sites) and macroinvertebrate communities (at river sites only) was carried out. Results showed that the wetland was deficient in its purifying capacity as it was already saturated by salts and nutrients from high irrigation return flow loads. A significant seasonal variation was observed for conductivity, reactive phosphorus (RP), pH and total phosphorus (TP) concentrations among the inlets to the wetland whereas among the river sites significant seasonal differences were observed for ammonium, dissolved oxygen, nitrate, RP, pH, TP and turbidity concentrations during the dry season. From the macroinvertebrate community data the impact of the irrigation return flows on the river system was apparent, as the good water quality sites were characterised by a high diversity of pollution sensitive macroinvertebrate taxa, while the irrigation impacted sites were characterised and dominated by pollution tolerant taxa. High ion concentration (conductivity and salinity) and pH were found to be important in structuring macroinvertebrate communities as determined using multivariate analysis in the river system. In conclusion, the river water quality was significantly impacted by irrigation return flows and this greatly reduced the ecological health as highlighted by low macroinvertebrate diversity and increases in physical-chemical variables.

Embracing indigenous knowledge systems in the management of dryland ecosystems in the Great Limpopo Transfrontier Conservation Area: the case of Chibememe and Tshovani communities, Chiredzi, Zimbabwe

The important role indigenous knowledge systems (IKS) is described in redefining the biodiversity conservation agenda of the Chibememe and Tshovani communities in the Sangwe Communal Lands, Chiredzi, in the management of dryland ecosystems of the southeastern low veld of Zimbabwe. These communities constitute part of the Great Limpopo Transfrontier Conservation Area (GLTFCA). We explored ways in which the use of IKS by Chibememe and Tshovani communities have contributed to the conservation and sustainable utilisation of forest, water and wildlife resources in light of existing contemporary scientific value systems, policy and institutional frameworks. Participant observation, interviews with traditional leaders and elders, focus group discussions and literature review techniques were employed within a case study framework. Our results revealed that IKS approaches are used in the management of dryland forest, water and wildlife resources in the Chibememe and Tshovani communities and have contributed positively to the conservation and sustainable utilisation of dryland resources. We conclude that IKS play a critical role in the management of dryland forest, water and wildlife resources at the local community level and have potential to contribute to the conservation of transfrontier conservation area resources such as in the GLTFCA, provided they are recognised, respected, preserved, protected, as well as integrated into mainstream dryland ecosystem conservation. We recommend that, for communities and their biodiversity to survive, conventional science and IKS should complement and should not seek to undermine each other.

A study of the ichthyofauna of a small tropical reservoir, south-eastern lowveld, Zimbabwe

Fish diversity in Malilangwe Reservoir in the south-eastern lowveld of Zimbabwe was investigated in 2011 to determine the community structure. The aim of this study was to determine the current status of an artificial fish community in a small reservoir that does not normally overflow and to assess how the fish have adapted to this environment. Eight species belonging to five families were collected from the reservoir. The cichlids Oreochromis mossambicus, O. macrochir, O. placidus and Tilapia rendalli made up 46% by number of the sample, the cyprinid Labeo altivelis made up 40% of the sample, and T. rendalli, the least numerous species, made up 0.2% of the sample. The population of T. rendalli seemed to be depleted, whereas largemouth bass Micropterus salmoides, which were formerly numerous, appeared to be absent. Oreochromis placidus bred throughout the study period, whereas Clarias gariepinus, Hydrocynus vittatus, L. altivelis, O. macrochir and O. mossambicus showed an apparent lack of recruitment between July and August 2011. The growth performances of C. gariepinus, O. mossambicus, O. macrochir and O. placidus were assessed by means of the growth performance index (φ′) with values ranging from 3.10 to 3.41. The rates of total mortality (Z) were estimated for four species; the highest rate was 5.64 for O. placidus and the lowest was 1.17 for C. gariepinus.

First results on bathymetry, stratification and physicochemical limnology of a small tropical African reservoir (Malilangwe, Zimbabwe)

The study provides a 9-month record of Malilangwe Reservoir water chemistry periodicity, for the period between February and October 2011. Malilangwe Reservoir is a small (211 ha), shallow (mean depth 4.54 m) reservoir situated in the south-eastern lowveld of Zimbabwe. The reservoir has not spilled in nearly 11 years, which makes it a unique system as most reservoirs of comparable size spill annually. This is the first bathymetric and limnological study of the reservoir where the morphology and physicochemical quality of the water body were examined. The reservoir was not strongly stratified during the hot-wet and hot-dry season with oxygen depletion of < 2 mg·l -1 DO being observed in the bottom layers (<6 m depth). Nutrient concentrations varied throughout the seasons. The reservoir exhibited marked seasonal fluctuations in water level, which decreased by over 149 cm between February and October. The N:P ratio rose to as high as 10.9 and generally reflected high levels of phosphorus in the reservoir. There were significant differences (p<0.05) in Secchi depth transparency between the study sites. Differences observed in water quality were due to water level fluctuations, with poor water quality conditions being experienced during the hot-dry season and the cool-dry season when water levels were low. The reservoir was classified as being mesotrophic. Therefore, there is a risk of eutrophication, especially since the reservoir is currently merely a sink for nutrients. Keywords: Bathymetry, limnology, water level fluctuation, stratification, Malilangwe

Wildlife as Insurance against Rainfall Fluctuations in a Semi-Arid Savanna Setting of Southeastern Zimbabwe

This paper presents modeling approaches for wildlife conservation in a semi-arid savanna setting where there are frequent occurrences of drought. The model was used to test the extent to which wildlife income offers opportunities to reduce fluctuations in income as a result of variations in annual rainfall. For the application of the model the wildlife and agro-pastoral systems of southeastern Zimbabwe were simulated. Results show that wildlife income has the potential to compensate for some of the losses in expected income from livestock during droughts. However, wildlife income becomes second best to irrigated agriculture in stabilizing income in areas that show highly fluctuating rainfall. Possible reasons for this include high costs of exploiting the wildlife resource, and the small fraction of wildlife revenues received by households and communities. In order to search for sustainable solutions in areas such as the southeastern low veld of Zimbabwe, it is also important to be aware that the current human population and livestock densities are far above current sustainable levels. Our results therefore suggest that current and future efforts to conserve biodiversity are doomed to fail if there are no efforts made to decongest areas surrounding parks of high densities of human and herbivore populations, and to let local households earn more revenues from wildlife.

Modeling sedimentation rates of Malilangwe reservoir in the south-eastern lowveld of Zimbabwe

Modelling the sedimentation rates using the Wallingford (2004) equations with the aid of NDVI (remote sensing) to assess land degradation was carried out for Malilangwe reservoir catchment in the south eastern lowveld of Zimbabwe. Siltation life of the reservoir was determined from rate of incoming sediment, trap efficiency and reservoir capacity using the Wallingford method. The average rainfall of the study area was about 560 mm while runoff from the catchment ranged from 0.3 mm (minimum) to 199 mm (maximum) with an overall average runoff of 50.03 mm. Results showed that the overall mean annual sediment concentration was approximately 2,400 ppm. The reservoir capacity to inflow ratio was estimated at 0.8 with a sedimentation rate of 120.1 tkm -2 year -1 . Calculated probability of the dam filling is 26.8 %. Results also showed that the siltation life of the reservoir was (100 years according to the Wallingford method. The Normalised Difference Vegetation Index (NDVI) showed progressive decline (p 0.05) of the vegetation health from 2000 to 2009. While acknowledging the limitations of techniques used, this study demonstrates in part the effectiveness of sedimentation modelling and remote sensing as a tool for the production of baseline data for assessment and monitoring levels of land degradation in the Malilangwe reservoir catchment.

Water conflicts on the Manjirenji-Mkwasine irrigation water supply canal, Masvingo province, Zimbabwe

The case of the 45 km long Manjirenji-Mkwasine irrigation water supply canal in the south-eastern lowveld of Zimbabwe in Masvingo Province presents risks of conflicts among the different irrigator categories which this study investigated along with the questions on conceptual model, stakeholder participation and institutional arrangements through which the operation of the canal was mediated. Eighty percent of the respondents indicated that they have either witnessed or been involved in water related conflicts ranging from illegal water diversions to non-payment for water use. While several institutional arrangements were involved in conflict resolution, more than 87% of the stakeholders indicated that these were ineffective. A conceptual model on shared irrigation water is proffered drawing from insights on meaningful stakeholder participation, institutional support, treatment of water as an economic good and also as a natural resource. This model can minimize conflicts among stakeholders for the sustainability of the shared Manjirenji-Mkwasine irrigation canal. Key words: Manjirenji-Mkwasine irrigation water supply canal, water conflicts, conflict management, stakeholder participation, institutional arrangements, sustainable irrigation water service, Zimbabwe.

Investigation of a parasitic outbreak of Lernaea cyprinacea Linnaeus (Crustacea: Copepoda) in fish from Zimbabwe

ABSTRACT Infestation of fish by the crustacean ectoparasite Lernaea cyprinacea Linnaeus, 1758 was investigated to establish the extent of infestation, potential effects of the parasite and its ecological adaptations. Fish samples were collected from impoundments in the Malilangwe Wildlife Reserve in the southeastern lowveld of Zimbabwe and these included the cichlids Oreochromis mossambicus, Oreochromis placidus and Tilapia rendalli, the cyprinids Labeo altivelis and Barbus paludinosus, the clariid Clarias gariepinus, the centrarchid Micropterus salmoides and the characid Hydrocynus vittatus. All the cichlids and one cyprinid (L. altivelis) were infested with L. cyprinacea. The two Oreochromis species exhibited prevalence as high as= 100% and mean intensity up to 149 parasites per fish. Lernaea cyprinacea exhibited an aggregated distribution in host populations and were attached mostly to the ventral and caudal regions of hosts, while the head was the least preferred attachment site. With a few exceptions...

Investigation of a parasitic outbreak of Lernaea cyprinacea Linnaeus (Crustacea: Copepoda) in fish from Zimbabwe

Infestation of fish by the crustacean ectoparasite Lernaea cyprinacea Linnaeus, 1758 was investigated to establish the extent of infestation, potential effects of the parasite and its ecological adaptations. Fish samples were collected from impoundments in the Malilangwe Wildlife Reserve in the southeastern lowveld of Zimbabwe and these included the cichlids Oreochromis mossambicus, Oreochromis placidus and Tilapia rendalli, the cyprinids Labeo altivelis and Barbus paludinosus, the clariid Clarias gariepinus,> the centrarchid Micropterus salmoides and the characidHydrocynus vittatus. All the cichlids and one cyprinid (L. altivelis) were infested with L. cyprinacea. The two Oreochromis species exhibited prevalence as high as= 100% and mean intensity up to 149 parasites per fish. Lernaea cyprinacea exhibited an aggregated distribution in host populations and were attached mostly to the ventral and caudal regions of hosts, while the head was the least preferred attachment site. With a few exceptions, there was no significant correlation between parasite prevalence and intensity with host size, sex, condition factor, gonadosomatic index or fecundity.

Taxonomy and Faunistics of the Helminth Parasites of Clarias gariepinus (Burchell, 1822), and Oreochromis mossambicus (Peters, 1852) from Temporary Pans and Pools in the Save-Runde River Floodplain, Zimbabwe

Two freshwater fish species, Clarias gariepinus and Oreochromis mossambicus, were collected from pans, dry-season pools, and tributaries of the Save and Runde rivers in the southeastern lowveld of Zimbabwe from December 2004 until June 2006. Helminth parasites infecting these fish were isolated from the gills, skin, muscles, body cavity, gall bladder, stomach, and intestines and were examined microscopically. Adult helminths were collected from the darter, Anhinga melanogaster, a piscivorous bird, to compare and possibly link them to the larvae recovered from fish. Stomach contents of the birds were analyzed, and their prey fish species were identified. Larval helminths collected include digenean metacercariae (clinostomes and strigeids), larval cestodes (gryporhynchids), and juvenile nematodes (Contracaecum). Adult worms include the monogeneans Macrogyrodactylus clarii, Macrogyrodactylus karibae, and Macrogyrodactylus congolensis; the digenean Clinostomum complanatum; the nematodes Paracamallanus cyathopharynx, Contracaecum rudolphi, Contracaecum multipapillatum, and Contracaecum rodhaini; and the cestodes Polyonchobothrium clarias and Echinorhynchotaenia tritesticulata. Many of these observations are the first record of that particular parasite species in Zimbabwe or southern Africa. Morphological measurements were made and compared with the original species description, and some unique morphological features are here described.

Early iron manufacturing industries in semi-arid, south-eastern Zimbabwe

Recent research about the history of human settlement and impact on the environment has focused on part of the semi-arid, south-eastern lowveld of Zimbabwe. Two iron-smelting sites were excavated in 2004. Both sites indicated use of local magnetite resources for production beyond immediate subsistence needs. The Kwali Camp smelting site was used by some of the first farmers in the region, associated with the Gokomere tradition on the southeastern Zimbabwean plateau. The Mhangula smelting site was used in a later period and probably supplied iron to elite communities associated with the Zimbabwe State.

Effect of cultivar, seedling age and leaf clipping on establishment, growth and yield of pearl millet (Pennisetum glaucum) and sorghum (Sorghum bicolor) transplants

This study explored the viability of intensifying pearl millet and sorghum production through use of nurseries and transplanting to address the problem of poor stand establishment. The experiments were carried out over two seasons, the 1999/2000 and 2000/2001 seasons in the south eastern lowveld of Zimbabwe where the mean rainfall is less than 500 mm per annum. Treatments included two pearl millet cultivars (PMV2 and PMV3) and two sorghum cultivars (Mutode and Macia). These crops were transplanted with and without leaf clipping at three seedling ages (30, 40 and 50 days for pearl millet; 29, 39 and 49 days for sorghum). Transplants were raised in nursery seedbeds. In the 1999/2000 season, there were significant effects of cultivar (P<0.05) and leaf clipping (P<0.01) on pearl millet grain yield. Clipped seedlings yielded 932 kg ha−1 compared to 797 kg ha−1 for non-clipped seedlings while PMV3 yielded 902 kg ha−1 compared to 820 kg ha−1 for non-clipped seedlings. Mutode yielded significantly (P<0.05) higher than Macia in both seasons, however, leaf clipping tended to increase yields for both cultivars. An increase in seedling age from 29 days also tended to reduce yields. It was concluded that leaf clipping of 30-day old seedlings at transplanting may enhance sorghum and pearl millet yields in the semi-arid tropics.

EFFECT OF ON-FARM SEED PRIMING ON EMERGENCE, GROWTH AND YIELD OF COTTON AND MAIZE IN A SEMI-ARID AREA OF ZIMBABWE

The effects of on-farm seed priming (i.e. seed soaking) on the emergence, growth and yield of cotton and maize were studied in the field in the south-eastern lowveld of Zimbabwe. Experiments were conducted on both crops in the 1999/2000 and 2000/2001 seasons and, in the 2001 winter season, on maize only. The interaction of priming with tillage (ox-drawn ploughing or hand-hoeing) and simulated sowing rainfall regimes (irrigations of 15 mm, 30 mm or 45 mm at planting) was studied. Priming usually increased the rate of emergence in maize, but always decreased final percent emergence in cotton. In the 2000/2001 season, there was an interaction between priming and simulated sowing rainfall regimes such that the 15 mm treatment gave a smaller adverse effect of priming in cotton than the 30 and 45 mm treatments. In maize, however, the 15 mm treatment gave an adverse rather than a positive effect of priming on emergence. There was little effect of tillage on emergence or growth. Priming did not affect the relative growth rate of cotton or maize, although plants grown from primed maize seed were consistently larger at any given date throughout the 2001 winter season. Plants from primed seed also flowered and matured earlier in the winter 2001 season. There were no significant effects of priming on yield, except in the 1999/2000 season, where priming decreased yield in cotton. It was concluded that the effect of priming can depend on crop species.