Matopos Research Station Research Articles

Species dependent correlation analysis and regression models of body weight on linear body measures in indigenous sheep and goats of Zimbabwe

<p>Measurements of live weight in goats and sheep are an important source of information for a range of scientific fields and applications in animal husbandry activities. The study was conducted to investigate the relationship between body weight and body measurements and to predict live body weight from body measurements in indigenous Matabele goats and indigenous Sabi sheep at Matopos Research Station in Zimbabwe. For this purpose, data on body weight (BWT) and linear body measurements (LBM) such as heart girth (HG), body length (BL), wither height (WTH), and rump height (RH) were collected from randomly selected females of each species at the age of 4 years. The corresponding means, standard deviations (SD), and coefficients of variation (CV) were determined for body weight and linear body measurements. Bivariate correlations between bodyweight and linear body measure characteristics were also determined. Simple and multiple regression were used to develop a model to predict BWT using linear body measures. Indigenous Matabele goat females’ CV ranged from 15.77% to 22.68%, while indigenous Sabi sheep females’ CV ranged from 19.16% to 19.37%. The CV was calculated by dividing the mean by the standard deviation. At 4 years of age, the mean BWT of the indigenous Sabi sheep and female Matabele goat were 35.96 ± 0.83 kg and 27.90 ± 0.66 kg, respectively. In indigenous Matabele goat females, the average linear body measures were HW (74.20 ± 0.53 cm), WTH (48.55 ± 0.53 cm), BL (47.53 ± 0.61 cm), and RH (57.50 ± 0.88 cm). The mean values for native Sabi sheep were 63.33 ± 0.70 cm, WTH (52.00 ± 0.80 cm), BL (51.26 ± 0.78 cm), and HW (85.56 ± 1.04 cm). The results showed a strong and positive correlation between BWT and linear body measures in female indigenous Matabele goats. The phenotypic correlation values were HG (<em>r</em> = 0.79), BL (r = 0.70), WTH (<em>r</em> = 0.68), and RH (<em>r</em> = 0.56), in decreasing order. In indigenous Sabi sheep, the phenotypic correlation for BWT and linear body measurement was high and positive for HG (<em>r</em> = 0.73), and positive and moderate to low with WTH (<em>r</em> = 0.41), BL (<em>r =</em> 0.32), and RH (<em>r</em> = 0.36). Again, the results also indicated that HG had a high and positive phenotypic correlation with BL (<em>r</em> = 0.53), while modest correlation was observed with HG and WTH (<em>r</em> = 0.41) and HG and RH (0.32). The optimal regression models for easily measuring body weight using HHG are BWT = −46.711 + 1.006 HG (<em>R</em><sup>2</sup> = 60%) and BWT = −15.209 + 0.586 HG (<em>R</em><sup>2</sup> = 53%) for indigenous Matabele goats and indigenous Sabi sheep, respectively. It is recommended that smallholder farmers use HG measurements to estimate body weight in both indigenous Sabi sheep and indigenous Matabele goat females at the age of 4 years.</p>

Effect of plant population and row orientation on crop yield under sorghum-cowpea intercropping systems in semi-arid Zimbabwe

Smallholder farmers commonly practise intercropping to improve crop yield per unit land area. Proper combination of plant population and row orientation of the component crops needs to be established and this prompted this investigation. A 2x7 factorial experiment was laid in a RCBD with three replications, at Matopos Research Station in Natural Region IV of Zimbabwe. Treatments consisted of sorghum planted at a constant population of 55556plants/ha intercropped with cowpea (C) simultaneously planted at varying populations of 111111plants/ha (C1), 166667plants/ha (C3) and 222222plants/ha (C3) in East-West (EW) and North-South (NS) row orientation. Interaction of cowpea population density and row orientation significantly (p<0.05) influenced crop yield and its attributes. Treatment NS-SC3 produced lowest number of pods/plant and grains/pod of 2.6 and 6.1 respectively. Highest cowpea grain yield (637.2kg/ha) was obtained in EW-C3 and lowest (92.4kg/ha) in EW-SC3. Sorghum yield was highest in NS-S (1296.5kg/ha) and lowest in EW-SC3 (491.9kg/ha). LER showed that intercropping performed better than sole crops except for EW-SC3 and NS-SC3 which had LER of 0.800 and 0.905 respectively. Highest LER of 1.312 was obtained in EW-C2. Farmers should plant sorghum-cowpea intercrops in EW row orientation for increased cowpea grain yield but NS row orientation for sole sorghum.

Structure and spatial interactions of savanna trees along a local stress gradient in a semi-arid environment

Competition and facilitation vary inversely along environmental stress gradients. Here we ask how environmental stress along a slope gradient influences plant-plant interaction in a semi-arid savanna. We attempted to link spatial patterns and ecological interactions, so we analysed the spatial distribution of three Vachellia (Acacia) tree species and assessed the consequences of their interaction on plant structural variables (height, basal area, biomass and canopy cover) at Matopos Research Station, Zimbabwe. Spatial patterns among and between the tree species were assessed using both univariate and bivariate analysis. To understand the extent of tree species isolation, we applied the species mingling index. Canopy cover varied significantly between species at both ends of the stress gradient, while basal area did not differ among the three species at any slope position. The woodland showed differential recruitment levels for the three species across the catena, which may indicate future changes in composition. The mingling index showed that there was species isolation in the bottom and middle catena. Pair-wise interactions of plants reflected two common spatial patterns, clustering, interpreted as suggesting facilitation, and random, interpreted as neutral. In some cases these patterns changed with spatial scale, indicating that the stress gradient hypothesis (SGH) may be influenced by the spatial scale at which species are interacting. Our univariate analyses corroborate the evidence that plants in semi-arid environments have a clustered distribution and that catenas can produce differential recruitment levels of the different species.

Spatial pattern analysis of encroaching tree species (Vachellia karrooandVachellia nilotica) after fire suppression in a semi-arid savanna

Abstract:Bush encroachment has serious consequences on ecosystem functioning through alteration of species composition and ecosystem productivity. However, little is known regarding the spatial patterning of invading shrubs in semi-arid savannas. Cartesian coordinates of two invading woody species (Vachellia karrooandV. nilotica), were recorded in a 20 × 20-m plot on a grassland at Matopos research station, south-west Zimbabwe. We recorded a total of 308 plants including both saplings and shrubs from the two study plant species. Second-order spatial statistics was applied in order to understand the spatial pattern of encroaching plants. We predicted that the encroaching plants would be spatially aggregated because of facilitation that occurs in harsh environmental conditions. Consistent with our predictions, the two species were aggregated, with no evidence of inter- and intra specific species competition. This study demonstrates that encroaching trees in semi-arid savanna generally do not show self organization during early growth stages.

Weed growth and crop yield responses to tillage and mulching under different crop rotation sequences in semi‐arid conditions

AbstractConservation agriculture (CA) is thought to reduce weed pressure from the third year of adoption, when recommended practices are followed. Weed growth and crop yield were assessed during the third and fourth year of maize–cowpea–sorghum rotation, second and third year of maize–cowpea rotation and first and second year of maize monocropping on a clay loam soil at Matopos Research Station (annual rainfall, 573 mm) following recommended CA management practices. Each experiment had a split‐plot randomized complete block design with mouldboard plough (CONV), minimum tillage (MT) with ripper tine and planting basins as main‐plot factor and maize residue mulch rate (0, 2 and 4 t/ha) as a subplot factor, with threefold replication. All subplots were surface mulched and weeded by hoe at the same time. We hypothesized that under MT weed growth would be considerable with maize monocropping but from year 3 of CA, weed growth would decrease and crop yield increase relative to values from unmulched CONV. Minimum tillage increased weed growth in 2nd year of maize monocropping. Under the maize–cowpea rotation, the considerable weed growth in planting basins was likely due to the large intrarow spacing and poor light competiveness of the cowpea variety. Mulch contributed to weed growth being suppressed by up to 36% under CA in the maize–cowpea–sorghum rotation relative to unmulched CONV. When planted on the same date, crop yield did not differ between CA and unmulched CONV. Maize–cowpea–sorghum rotation grain yield (3143 kg/ha) was double that under monocropping, probably due to improvements in soil physical and chemical conditions.

Root Length Density in Maize/Cowpea Intercropping under a Basin Tillage System in a Semi-Arid Area of Zimbabwe

A study to assess the effect of intercropping maize (Zea mays L.) and cowpea (Vigna unguiculata L.) within the same basin or outside the basin on root length density (RLD) was conducted at the International Crop Research Institute for Semi-Arid Tropics (ICRISAT) Matopos Research Station from December 2009 to April 2010. The experiment was laid out in a Randomised Complete Block Design (RCBD) with four treatments replicated four times namely; sole maize, sole cowpea, maize-cowpea intercrop with cowpea and maize planted within the same basin and maize-cowpea intercrop with cowpea planted 20 cm outside the maize basin. There was significant difference (P

Weed seed bank response to tillage and residue management in semi-arid Zimbabwe

The influence of conservation agriculture (CA) on weed ecology has been a concern to many researchers across the world and is the focus of this study in southern Africa. An experiment to look at the impacts of various tillage systems with different levels of crop residue on maize (Zea mays L.) was established in 2004/2005 season. The experiment was carried out at the International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), Matopos Research Station, Zimbabwe. Three main tillage systems were compared, ripping tillage (RT), planting basins (PB) and conventional tillage (CT), with three different crop residue levels: 0, 4 and 8 tons ha−1. In 2007 soil samples were collected in the inter-row and in-row positions prior to tillage at 0–50 mm, 50–100 mm and 100–200 mm depths. The objective was to determine the effect of the treatment factors on weed seed bank species after three cropping cycles using the germination method. Nine major weed species were identified, with all the weeds unaffected by either tillage or mulching level. Eleusine indica, Corchorus tridens and Setaria species were the dominant weed species across all treatments. Setaria spp. was the dominant weed in the inter-row position of ripped plots. Although there was no significant individual treatment effect, there were significant (p < 0.05) interactions, with CT having reduced seed banks of Setaria spp. and E. indica compared to RT and PB. Percentage increases point to E. indica and Setaria spp. increasing under PB and RT compared to CT. C. tridens was significantly higher in PB compared to RT and CT in the 0–50 mm depth in the in-row position. This study probably coincided with the transition period in the weed bank succession process and needs to be repeated at a later date in the rotation. The majority of the weed species were not affected by any of the treatment combinations, a response attributed to plasticity of weeds to the tillage and residue level selection pressure.

Response of weed flora to conservation agriculture systems and weeding intensity in semi-arid Zimbabwe

A field study was conducted in the fifth (cowpea crop) and sixth (sorghum crop) seasons of a long-term conservation agriculture trial at Matopos Research Station to determine the effect of tillage, maize mulch rates and intensity of hoe weeding on weed density and community diversity. The experiment was a split-plot randomized complete block design with three replications. Tillage was the main plot factor; conventional tillage versus the minimum tillage (MT) systems of ripper tine and planting basins. Maize mulch rate (0, 4 and 8 t ha-1) was the sub-plot factor to which was super-imposed the intensity of hoe weeding treatment (low and high) as from the fifth season. Tillage system had no significant (P<0.05) effect on weed density and diversity. Whereas the maize mulch rate of 4 t ha-1 increased weed density in both crops, the mulch rate of 8 t ha-1decreased the density of Portulaca oleracea and Corchorus tridens in sorghum. Weed density was lower and community diversity higher in the high than the low weeding intensity treatment in sorghum. Although, frequent hoe weeding can be used to control weeds in MT systems, labour shortages may ultimately limit the area under MT in smallholder agriculture. Key words: Tillage, maize mulch, weed density, community diversity, cowpea (Vigna unguiculata (L.) Walp.), sorghum (Sorghum bicolor (L.) Moench).

Crop yield and weed growth under conservation agriculture in semi-arid Zimbabwe

Constraints to effective weed management may be the main reason for the small area under minimum tillage (MT) in smallholder farming in southern Africa. The effect of maize residue mulching and intensity of hand hoe weeding on the growth of weeds, cowpea (Vigna unguiculata cv. IT 86D-719) and sorghum (Sorghum bicolor cv. Macia) was investigated in the fifth and sixth years of a conservation agriculture (CA) field experiment at Matopos Research Station (28°30.92′E, 20°23.32′S). The experiment was a split-plot randomized complete block design with three replications. Tillage was the main plot factor (conventional tillage – mouldboard plough compared against MT systems – ripper tine and planting basins) and maize residue mulch rate (0, 4 and 8tha−1) the sub-plot factor. Hoe weeding was done either four times (high weeding intensity) or twice (low weeding intensity) during the cropping season. Planting and weeding were done at the same time in all treatments. There was markedly greater early season weed growth in MT systems relative to mouldboard plough (MBP) in both crop species. In sorghum, MT (planting basins: 40.3kgha−1; ripper tine: 34.8kgha−1) systems had higher cumulative weed biomass measured after planting than MBP (29.9kgha−1) system. Maize mulching was generally associated with increased mid- to late-season weed growth in the two crops probably due to improved soil moisture conservation during periods of low precipitation. Weed suppression by the maize mulch was observed only in sorghum and limited to early in the cropping season with no effect observed for the remainder of the sorghum rotation phase. The high weeding intensity treatment had lower weed growth in both crops and better sorghum yield than low weeding intensity. The MT systems had poor crop establishment which translated into low yields. Cowpea grain yield obtained from MT systems was less than 300kgha−1 compared to 413kgha−1 in MBP. The poor sorghum establishment in MT systems translated into low grain yield as sorghum grain yield was lowest in planting basins (2602kgha−1) and highest in MBP with 4159kgha−1. Results suggest that CA systems require early and frequent hoe weeding even after four years to reduce weed infestations and improve crop growth. This higher demand on a smallholder household's limited labor supply throughout the cropping season will be a key determinant of the spread and adoption of CA in southern Africa.

Investigating the effects of different grazing ratios and stocking rate of cattle and goats under mixed-species grazing on different plant species

The study focused on investigating the effects of different grazing ratios and stocking rate of cattle and goats under mixed species grazing on different species of plant. The experimental site was Matopos Research Station farm in Zimbabwe. This study was confined to the commonest grass species and forbs at the experimental site. Treatments spanned a period of eight years; from 1999 to 2007. Generally, heavy goats stocking rate resulted in low productivity of browse biomass while heavy cattle stocking rate resulted in low herbaceous biomass productivity. The present results do not support existence of a linear relationship between herbaceous biomass productivity and annual rainfall. Rather, a quadratic relationship existed, suggesting that there might be other factors in addition to rainfall that accounted for biomass productivity. Grazing ratios and stocking rate of cattle and goats, year and their interactions affected the productivity of plant species in the rangeland. Finally, farmers are encouraged to practice mixed-species grazing at an optimal grazing ratio of 4 cattle and 36 goats per 20 ha of rangeland.

Heavily stocked 5-paddock rotational grazing effect on cross-bred Afrikaner steer performance and herbaceous vegetation dynamics in a semi-arid veld of Zimbabwe

A ten-year high stocking rate trial, mimicking communal areas was initiated at Matopos Research Station, Zimbabwe. Afrikaner steer crosses grazed continuously or rotationally at a high stocking rate (0.4 LU.ha-1) in two 45 ha areas, with one fenced into five 9 ha camps each for the rotational grazing sites, with 30 animals per site. It was hypothesized that, heavily stocked rotation will not improve herbage biomass, decreaser species abundance, basal cover or animal performance. Biomass, basal cover and decreaser species abundance were not (P > 0.05) significantly different between the grazing systems, save for Themeda triandra, Setaria incrassata and Panicum novemnerve, but were significant (P < 0.05) in terms of annual variation. Mean maximum steer weight gain was higher (P < 0.05) under continuous grazing. It was concluded that, the creation of rigid rotational grazing schemes in communal areas without proper stocking rates will not improve animal performance, herbage production, basal cover, but might have an effect on species abundance. In higher rainfall years, heavy stocking has no adverse effects on performance. Hence, any plans of grazing interventions on livestock management in communal areas, should consider stocking rate and rainfall, with a rapid stock reduction strategy in projected low rainfall years. Key words: Basal cover, communal areas, grazing system, herbage biomass, stocking rate, weight gain.

Systematic environmental influences and variances due to direct and maternal effects and trends for yearling weight in cattle

Pedigree yearling records from 1021 local Tuli calves born at Matopos Research Station were analyzed for non genetic factors, genetic parameers and trends on the yearling weight. It was found that sre year of brth, sex of calf age of dam had sgnfcant effect (p Keywords: Non genetic, Direct, Maternal trends, Yearling weight, Growth traits, Tuli cattle

Long-term selection experiment with Afrikaner cattle 4. Cow fertility and calf survival

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at the Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over six generations of selection (40 years) were analyzed. The average incidence of calving success (the presence or absence of a calf) was 68%. Heritability and repeatability (in parenthesis) estimates for calving success and calving date were 0.08 ± 0.02 (0.10 ± 0.02) and 0.09 ± 0.02 (0.17 ± 0.02), respectively. Favourable genetic trends were shown (-0.8 ± 0.09 days/generation for calving date). Correlation estimates of sires’ EBV between measures of fertility and growth were all unfavourable. A significant interaction was manifested for calving success and was due to the markedly poorer performance (10 percentage units) of the S line cows in the NS environment. The interaction serves to reinforce the commonly held principle that cattle, and in particular breeding cows, be reared in a similar environment in which selection takes place advocating antagonistic selection (upwards selection in a poor environment). Calf losses within the first 24 h of birth and pre-weaning were 3.8% and 8%, with heritability estimates of 0.15 ± 0.07 and 0.07 ± 0.03, respectively. It is recommended that fertility and calf survival be included in routine breed evaluations. There is a need to implement data collection strategies to ensure that all calving activities are comprehensively recorded.

Long-term selection experiment with Afrikaner cattle 1. Environmental factors affecting calf growth traits

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976 lines were sub-divided into four lines with 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data collected over a 40-year period (1958 to 1997) were analyzed. There were no line differences, however, productivity in the S environment was superior compared with the NS environment. While there were no environment differences in birth weight, calves born early in the S environment were estimated to be 90 kg (33%) heavier at 18 months than calves born late in the NS environment. The performance of calf growth from birth to 18 months in this study has emphasized the importance of matching animal physiological status with seasonal changes in the sub-tropics. The effect of previous lactation status (PLS) increased from 1.2 ± 0.13 kg at birth to 7 ± 0.6 kg at 205 days of age, a difference that persisted to 18 months (5 ± 0.9 kg). Given the significant and consistent detrimental effects of PLS on calf growth, it is recommended that this effect be considered in routine evaluations.

Long-term selection experiment with Afrikaner cattle 2. Genetic parameters and genotype x environment interaction for calf growth traits

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) was analyzed. The direct heritability estimates were moderate for birth weight (0.4), but low (0.1 to 0.2) for the other traits, similarly maternal heritabilities were low (0.1 to 0.2). Permanent environmental effects due to dam were moderate (0.3) for weights at 205 days, weaning and at 12 months, and was still an important effect at 18 months. Relatively large negative (-0.4) direct-maternal genetic correlations were indicated for weaning and yearling weights. There were indications that all post-weaning weight traits evaluated were closely related giving rise to their joint inclusion in joint multivariate analysis. There were no indications of line x environment interactions, however, interaction of sire x year was important for all the traits highlighting the tremendous year to year variations experienced in the sub-tropics. There is a need to evaluate selection for genotypic stability, particularly for the more extensive farming environments.

Long-term selection experiment with Afrikaner cattle 3. Selection applied and response in calf growth traits

A selection and line x environment interaction study with grade Afrikaner cattle was established in 1956 at Matopos Research Station, Zimbabwe. Two selection lines of 100 cows each were reared in different management environments. The non-supplemented (NS) line relied on the range throughout the year and was mated to calve with the onset of the rains (December to February). The supplemented (S) line was offered protein-rich supplements during the dry season and mated to calve prior to the onset of the rains (October to December). In 1976, after approximately two generations of selection, lines were sub-divided into 75 cows each, where one sub-line remained within each environment as a control; the remaining sub-lines were interchanged between environments. Bulls were selected on weaning weight within control lines, while replacement heifers were selected on weight at mating within sub-line. Data recorded over approximately six generations of selection (40 years) were analyzed. The average age of sires and dams at the time of birth of their progeny was 5.9 and 7.5 years respectively in the pre-crossover phase and was reduced to 4.4 and 6.5 years respectively in the post-crossover phase. The rate of inbreeding across lines and environments was 1.2%/generation. The cumulative selection differential trends for both the S and NS lines for adjusted weaning weight plotted against generation number were very low, relatively linear and greater for the S line (0.10 s.d./year) compared with the NS line (0.08 s.d./year). Direct and correlated responses were uniformly low, approximating 1% of the trait mean per generation, and indicating that considerable attention was given to secondary characters. These results concur with general findings of effective direct and correlated responses of weight traits to individual selection.

Productivity and residual benefits of grain legumes to sorghum under semi-arid conditions in south-western Zimbabwe: Unravelling the effects of water and nitrogen using a simulation model

The APSIM model was used to assess the impact of legumes on sorghum grown in rotation in a nutrient-limited system under dry conditions in south-western Zimbabwe. An experiment was conducted at Lucydale, Matopos Research Station, between 2002 and 2005. The model was used to simulate soil and plant responses in the experiment. Sequences of cowpea ( Vigna unguiculata), pigeonpea ( Cajanus cajan), groundnut ( Arachis hypogaea) and sorghum ( Sorghum bicolor) were used in the rotations. Legumes accumulated up to 130 kg of N ha −1 which was potentially available for uptake by sorghum in the following season. The APSIM model predicted total biomass, grain and N yields of the legume phase within the experimental error and performed well in predicting sorghum yield and N supplied in the rotation after cowpea and groundnut. The model generally under-predicted sorghum total biomass and grain yield after pigeonpea. Observed patterns of crop water use, evaporative losses during the dry season and re-charge of soil profile at the start of the rainy season were generally well predicted by the model. An assessment of output on sorghum N and water stresses in the rotation indicated that the legume–cereal rotation is more driven by soil nitrogen availability than water availability even under semi-arid conditions. Further legume–cereal rotation analysis using the model will assist in the understanding of other processes in the rotations in dry environments.

Effect of minimum tillage and mulching on maize ( Zea mays L.) yield and water content of clayey and sandy soils

Rainfed smallholder agriculture in semi-arid areas of southern Africa is subject to numerous constraints. These include low rainfall with high spatial and temporal variability, and significant loss of soil water through evaporation. An experiment was established at Matopos Research Station, Zimbabwe, to determine the effect of mulching and minimum tillage on maize ( Zea mays L.) yield and soil water content. The experiment was run for two years at two sites: clay (Matopos Research Station fields) and sand (Lucydale fields) soils, in a 7 × 3 factorial combination of mulch rates (0, 0.5, 1, 2, 4, 8 and 10 t ha −1) and tillage methods (planting basins, ripper tine and conventional plough). Each treatment was replicated three times at each site in a split plot design. Maize residue was applied as mulch before tillage operations. Two maize varieties, a hybrid (SC 403) and an open pollinated variety (ZM 421), were planted. Maize yield and soil water content (0–30 and 30–60 cm depth) were measured under each treatment. On both soil types, neither mulching nor tillage method had a significant effect on maize grain yield. Tillage methods significantly influenced stover production with planting basins giving the highest stover yield (1.1 t ha −1) on sandy soil and conventional ploughing giving 3.6 t ha −1 on clay soil during the first season. The three tillage methods had no significant effect on seasonal soil water content, although planting basins collected more rainwater during the first half of the cropping period. Mulching improved soil water content in both soil types with maximum benefits observed at 4 t ha −1 of mulch. We conclude that, in the short term, minimum tillage on its own, or in combination with mulching, performs as well as the farmers’ traditional practices of overall ploughing.

A phenotypic study of growth traits in indigenous. Nguni cattle of Zimbabwe

Data from 2438 indigenous Nguni calves born at Matopos Research Station representing a total of 526 dams and 56 sires were used to evaluate the phenotypic variability and correlations of growth traits. Traits analyzed were weights at birth (BWT) (, weaning (WWT), yearling (YWT) and eighteen. A multivariate statistical model was used to analyze the data using SAS (1985 ). Sex and year of birth were highly significant (p<0.01) on all growth traits. Males were significantly heavier than females for all growth traits. The correlation of BWT with WWT, YWT and 18MO were positive, medium and significant. WWT was highly correlated with post weaning growth traits (YWT and 18MO). The estimates of phenotypic correlations were positive showing no antagonism among the growth traits. Key words: Growth Traits, Correlation, Indigenous Nguni cattle, Zimbabwe.

Resistance of Sabi and Dorper ewes to gastro-intestinal nematode infections in an African semi-arid environment

Sabi and Dorper ewes were evaluated for resistance to gastro-intestinal nematode parasites (predominantly Haemonchus contortus) at the Matopos Research Station in Zimbabwe. Live weights (LWT), blood packed red cell volume (PCV) and faecal egg counts (FEC) were recorded at mating, 1 month before lambing and 1–3-month post-lambing for five separate lambings between 1996 and 2000. Dorper ewes were heavier ( P<0.01) than Sabi ewes at all sampling times. Sabi ewes were more resistant to internal parasites than Dorper ewes as shown by their significantly lower FEC and significantly higher PCV at all sampling times except at 2-month post-lambing for FEC and at weaning (3-month post-lambing) for PCV. At all sampling times except at weaning individual ewes were treated with an anthelmintic when their FEC was greater than 1500 eggs/g (epg) and/or their PCV was less than 20%. The proportion of Dorper ewes that was treated with anthelmintic was significantly higher than that of Sabi ewes at all sampling dates. This effect was particularly marked 1- and 2-month post-lambing. There was a post-parturient rise in FEC in the 2-month period after lambing for both breeds.