African Journal of Range and Forage Science

Diet preference of black rhinoceros Diceros bicornis at Welgevonden Game Reserve, South Africa, across seasons

Joti Daya — 2024-08-05

Diet preference of the black rhinoceros Diceros bicornis was determined in Welgevonden Game Reserve (WGR), located in the Waterberg region of Limpopo Province, South Africa. Fieldwork was conducted in the dry, early wet and late wet seasons. Diet preference was determined using microhistological faecal analysis and browse availability surveys. A chi-square goodness-of-fit test assessed similarity between the observed diet composition based on dung samples and the expected diet composition. To account for potential non- independence between browse availability and diet composition, a weighted approach was employed where browse availability was just one of several contributing factors to the expected composition. Plant species selectivity was quantified by Ivlev’s electivity index. Results obtained from this indicated that these black rhinos preferentially browsed certain plant species across different seasons. Plant species observations in the dung samples from the dry season totalled 3 984, with the evergreen Natal gum Euclea natalensis dominating the diet; for the early wet season, plant observations in the dung totalled 1 479, with buffalo thorn Ziziphus mucronata dominating in the diet; for the late wet season, plant observations in the dung totalled 4 424, with the small deciduous tree Ochna pulchra dominating in the diet. By obtaining information on food selection and the availability of browse species across seasons, this study provides a clearer understanding of black rhinos’ forage preference in WGR.

The recent fire regimes of Luengue-Luiana and Mavinga national parks, Angola

Willem A. Nieman — 2024-08-05

The adjoining Luengue-Luiana and Mavinga national parks in southeastern Angola are two of the largest though least actively managed protected areas in Africa. The parks are home to a diversity of wildlife and are managed as a single unit. The area is characterised as a fire-dependent savanna, where fires may be naturally ignited (such as by lightning), but where the fires each year are frequently set by people. As a result of the lack of resource investment, uncontrolled fires dominate the region, potentially negatively affecting biodiversity. The past fire regimes (2001–2021) of the two parks were investigated with use of the MODIS and VIIRS remote-sensing instrument. Extremely short fire return intervals dominated the landscape, with almost half (47.8%) of the area experiencing a subsequent fire within a year of the previous fire, and an additional 30% of the area burning within two years after a preceding fire. Only 2.4% of the landscape was shown to remain fire-free for a period of ten years or more. Overall, the fire intensities were highest from August to October, with the largest areas burnt between August and September. Fire frequency, seasonality and intensity were influenced by the land-cover type, and a comparison of the different satellite products was made. This information is the first of its kind for the region and is intended to provide a basis from which fire management activities can be coordinated.

Seasonal distribution of livestock in Samburu county, northern Kenya: a response to variable pasture and water in semi-arid rangelands

G.L. Lelenguyah — 2024-08-05

Spatial and temporal climate variability dictate herd mobility of transhumant communities, and therefore understanding this interrelationship is key to sustainable management of rangelands, especially in the face of the changing climate. This study was undertaken in Samburu county in Kenya, an area characterised by varying climatic conditions, land uses and agro-ecological zones, to determine the interrelationship between rainfall and temperature variability and the mobility of herds. To achieve the research objectives, 20 years of data for temperature, rainfall, normalised difference vegetation index (NDVI) and georeferenced data (GIS) together with field data obtained through household interviews and community participatory mapping were utilised. Only Samburu Central is endowed with good rainfall and the pastoralists graze their animals around their homes all year round. Rarely does livestock in Samburu East graze around homesteads due to low rainfall and degraded pastures. The spatial distribution patterns of the herds followed pasture availability as shown by vegetation NDVI patterns. Areas with higher NDVI of over 0.3 attracted herd concentration but with high in situ mobility to maximise on grazing of the most nutritious pastures. This study proposes grazing management embedded in observed herd mobility and grazing resource use patterns as a strategy towards adapting the pastoral communities to the changing climate.

Grass dynamics along a woody-plant density reduction gradient in a South African savanna

Piet Monegi — 2024-08-05

Woody plant encroachment threatens ecosystem services and functioning, thereby reducing herbaceous plant population persistence and community stability. We assessed the impact of woody removal intensity (WRI) on the grass ground cover, grass composition, diversity and richness, and rangeland condition in a South African savanna over a period of four growing seasons (2018–2022). Selective tree removal was applied to reduce woody density (4 065 ± 109 plants ha⁻¹) of the control (0% WRI) to 10, 20, 50, 75 and 100% WRIs, with four replicates per WRI. Rangeland condition, measured as the abundance of decreaser grass species, at 50, 75 and 100% was significantly higher than the control (0% WRI), with 50% WRI recording the greatest contribution. However, grass species diversity and evenness were similar across the treatments. In addition, herbaceous cover increased across the woody removal gradient, with the control plots recording the lowest cover. Overall, results showed that moderate removal of trees (i.e. 50%) in rangelands encroached by woody plants has the potential to maximise rangeland condition and can be used as a strategy for the restoration of herbaceous vegetation.

Evaluation of in situ and ex situ forage germplasm collections reveals the first occurrence and seed-transmission of alfalfa mosaic virus and southern bean mosaic virus in Urochloa species

Woubit Dawit — 2024-08-05

Grasses of the genus Urochloa (Urochloa species syn. Brachiaria species) are among the most important tropical forage grasses of African origin. The International Livestock Research Institute (ILRI) Forage Genebank maintains 671 Urochloa grass accessions, belonging to 28 species, of which 261 (39%) accessions are Urochloa brizantha (A.Rich.) R.D.Webster. The susceptibility of Urochloa grasses to disease and insect pests is a key challenge to the sustainable production of these grasses in Africa. In this study, using a dot blot assay and RT-PCR, we report for the first time the association of Alfalfa Mosaic Virus (AMV) and Southern Bean Mosaic Virus (SBMV) with 92% of the tested accessions conserved in situ and ex situ in the ILRI forage genebank. In addition, virus transmission from seed to plant and from legume to grass was confirmed through the bioassay test. The detection of these two viruses in Urochloa species presents a new challenge to germplasm conservation, distribution, and their sustainable production in the region, and demands immediate attention towards developing an effective method of cleaning viruses from the conserved germplasm. Furthermore, there is an urgent need to assess the economic importance of diseases in the grasses, and for the selection of germplasm that shows resistance to diseases.

Fermentation characteristics of maize–forage legume mixtures ensiled in small-scale silos

P.E. Mosebi — 2024-08-05

This study was conducted to evaluate the ensiling characteristics of maize–forage legume mixtures in small-scale silos. Sole and intercrops forage materials were harvested 80 days after planting and ensiled in small-scale silos, that is: plastic bags, plastic drums, and small pits, for 60 days. After ensiling, samples were collected to examine the chemical composition, microbial community and fermentation quality. Mixed silages stored in the drum silos had significantly (p ≤ 0.05) higher DM content (35.69%) than that from pit and bag silos. The drum silos had significantly (p ≤ 0.05) higher crude protein concentration (20.57% DM) in sole legume silages than other silo types. Neutral detergent fibre concentration (39.76% DM) of sole forage silages was greatest in bag silos than in other silos. High in vitro dry matter digestibility and water-soluble carbohydrate values (58.15 and 12.19% DM respectively) for mixed silages were recorded in drum silos. Bag silos showed lower numbers of lactic acid bacteria and higher populations of enterobacteria (4.86 and 4.26 log10 CFU g⁻¹ respectively) in sole forage silages than other silos. Mixed silages ensiled in drum silos produced significantly lower (p ≤ 0.05) pH (3.03) and ammonia nitrogen content (3.73% TN) compared to pit and bag silos. The study concluded that ensiling maize–forage legume mixtures in drum silos can have a positive effect on the nutritive value of ruminants’ feeds. Therefore, the recommended forage type for ensiling is mixed silages.

Effect of botanical composition calibration on the accuracy of undisturbed sward height and comparative yield method techniques for herbage mass estimation in tropical heterogeneous pastures

Diana Marcela Valencia-Echavarria — 2024-08-05

This study aimed to evaluate the influence of botanical composition calibration on the accuracy of undisturbed sward height and comparative yield method (CYM) techniques for herbage mass estimation in tropical heterogeneous pastures. Two studies were conducted using two grazing systems based on heterogeneous pastures. Herbage mass was estimated using CYM and undisturbed sward height techniques within quadrats (SHQ) or at a set of standard points in the paddocks (SHP). SHQ had a higher adjusted R2 when calibrated with the Urochloa brizantha cv. Marandú (U. brizantha) proportion compared to the simple SHQ model (0.75 vs 0.68), while RSE was lower (0.18 vs 0.21). The R2 increased (0.63 to 0.68), while both residual means and RSE decreased (−2.30 to –0.05 and 0.22 to 0.20, respectively) when SHP was calibrated with U. brizantha. It also resulted in a reduction of mean squared prediction error (MSPE) to CYM, SHQ, and SHP, respectively. The CYM allows for higher accuracy of herbage mass estimation in tropical heterogeneous pastures than undisturbed sward height, irrespective of botanical calibration. However, the botanical composition calibration had positive effects on the models from undisturbed sward height, and the calibration with U. brizantha increased the accuracy of herbage mass prediction.

Lucerne establishment in dryland conditions: effects of crop residues and wheat as a nurse crop

Stephan le Roux — 2024-08-05

Establishing lucerne (Medicago sativa) in dryland conditions poses challenges due to unpredictable rainy seasons and seedling vulnerability. A potential solution is adopting a nurse crop during the first year in the same field. This study aimed to assess the impact of wheat as a nurse crop and crop residue on lucerne establishment in South Africa’s Mediterranean climate region. The experiment employed a split-plot design with two treatment factors across six blocks. Half of the area received wheat straw, while the rest had low residue content with almost bare soil. The nurse crop combinations included wheat alone, lucerne alone, and a wheat-lucerne mixture. Results revealed competition between wheat and lucerne when planted together. When plant populations, total biomass, wheat grain yield and grain quality were considered, wheat performed better in pure stands, as did lucerne when grown without wheat. Germination of lucerne was significantly impacted by high crop residue levels. Wheat achieved superior grain yield without crop residue, despite producing less biomass. Results indicated that it is advisable to avoid using a nurse cropping system for lucerne in this Mediterranean climate region.

Book Review: ‘Global Application of Prescribed Fire’

Craig Morris — 2024-08-05

No Abstract