African Journal of Range and Forage Science

The diversity of epigeal insects after the application of the brush packing restoration method following bush-encroachment control in South Africa

A. Marquart — 2023-10-05

Evidently, bush encroachment caused by factors, such as overgrazing, results in a change in savanna ecosystems. This shift in vegetation structure can affect many factors, including insect fauna. Epigeal arthropods occupy smaller habitat patches and therefore respond to the effects of bush encroachment at finer scales. Different restoration efforts to combat bush encroachment have been implemented. A low-intensity management method is brush packing, which involves the use of removed woody branches to cover the soil surface. This study investigates whether the application of brush packing is effective in the restoration of insect communities. Total insect richness and the tendency towards diversity were higher on bush-controlled plots, irrespective of brush packing. This trend was found for all tested insect orders, except for Hymenoptera. However, non-metric multidimensional scaling ordination clustered distinctive insect communities in areas where brush packing was applied. The results indicate that the application of brush packing results in higher habitat heterogeneity and, consequently, more diversified insect communities on a small scale. We argue that brush packing application does not only benefit vegetation structure, but can also improve insect community composition, thereby increasing overall ecosystem health and stability, making this restoration method suitable for highly degraded areas.

The control of the encroaching shrub Seriphium plumosum (L.) Thunb. (Asteraceae) and the response of the grassy layer in a South African semi-arid rangeland

A. Marquart — 2023-10-05

Large-scale bush encroachment within rangelands is of increasing concern for land users. The aggressive encroachment of the woody shrub Seriphium plumosum (L.) Thunb. (Asteraceae), previously known as Stoebe plumosa, has resulted in a reduction in productivity, causing large socio-economic challenges, such as loss of productive land. In this study, we evaluated the efficacy of four herbicides in combination with mechanical removal of S. plumosum. We measured shrub mortality, regrowth and examined the grass species richness and cover after the execution of the control methods. Furthermore, we compared the productivity of the paddock where S. plumosum had been controlled with a neighbouring unencroached paddock. Five months after herbicide application, the total mortality of all shrubs was recorded. Grass species richness and cover were higher when shrubs had been mechanically removed before herbicide application. Additionally, the use of the non-speciesspecific herbicide (tebuthiuron) resulted in lower species richness and cover, compared to application of a speciesspecific herbicide (metsulfuron-methyl). The productivity of the treated area increased in the year after application. Our results show that when controlling S. plumosum the manual removal of shrubs before applying herbicides can improve the regeneration of the grass layer. This combination of mechanical and chemical control is effective in combating S. plumosum encroachment and increases forage yields in semi-arid rangelands.

Rainfed-based production of Megathyrsus maximus in sub-Saharan Africa: the case of the semi-arid environment of Sudan

Hussein I. Mohamed — 2023-10-05

The performance of rainfed-based Megathyrsus maximus (syn. Urochloa maxima and Panicum maximum) was investigated in the semi- arid pastures of Sudan. Split-plot complete design experiments with three replications were applied for two consecutive seasons (2020–2021). The treatments were two in situ rainwater harvesting systems [i.e. ridges plus terraces (RD) and terraces (TR)], three seeding rates (i.e. 1.5, 2.5 and 3.5 kg ha⁻¹) and two urea fertilisation rates [0 kg ha⁻¹ (Z) and 95 kg ha⁻¹ (F)]. These treatments were compared to a control (a flat, unfertilised and zero-tillage plot). Hydrological, biological and chemical indicators were used in the assessment. The results showed that the adopted RWH improved semi-arid pastures, with the RD treatment providing the best results for sustaining biomass production, water use efficiency, nutritional quality and soil quality. The highest plant density (112 000 plants ha⁻¹) was associated with the RD3.5 treatment. The FSR1.5-RD treatment resulted in the greatest plant length (63.5 cm) and number of leaves per plant (34.59), whilst the FSR3.5-RD resulted in both the highest fresh biomass (25.9 t ha⁻¹) and dry biomass (6.3 t ha⁻¹). The chemical compositions of M. maximus (i.e. crude protein, organic matter and nitrogen contents) were also substantially improved by fertilisation. The water use efficiency of M. maximus was plant-, management- and climate-dependent.

Nutritional quality of Calobota sericea fodders harvested at different phenological stages – opportunities for inclusion in fodder flow programs for extensive livestock farmers

Ethan A. Britz — 2023-10-05

Calobota sericea (Thunb.) Boatwr. & B.-E.van Wyk (Fabaceae) is a native legume from the semi-arid rangelands of South Africa. The species has been prioritised as a forage for water-limited agro-ecological areas. No information regarding the nutritional quality of C. sericea forage harvested at different phenological stages is currently available, limiting our knowledge as to the best time to harvest the forage. The aim of this study was to determine the nutritional quality of C. sericea forage harvested at five phenological stages. Results from the study show that crude protein, fibre, energy and digestibility of the forage decreased with plant maturity, but not all mineral nutrients showed the same trend. In general, C. sericea forage harvested at non-reproductive, early flower bud and full flower stages could provide sufficient energy and protein to maintain livestock condition. At these stages, the neutral detergent fibre and digestibility of the harvested materials are also good, indicating that intake and processing of these forage would not be a problem for the livestock. At these phenological stages most of the mineral nutrients were also sufficiently high to meet the minimum requirements of small stock. Thus, C. sericea forage harvested at the appropriate phenological stages could provide a useful source of forage for resource poor farmers.

Herbicide trials on Campuloclinium macrocephalum (Asteraceae) during adverse conditions reveal incompatibility with biocontrol and a narrow window of opportunity for chemical control

J.M. Goodall — 2023-10-05

Herbicide trials on pompom weed Campuloclinium macrocephalum (Less.) DC. (Asteraceae) were carried out in grasslands with xeric and hydric soils, at sites in Gauteng, South Africa, from 2005 to 2008. The rust fungus Puccinia eupatorii Dietel, an established self- perpetuating biocontrol agent on C. macrocephalum, caused significant damage to shoots in late summer and autumn. Herbicide efficacy was significantly better on foliage that did not already present symptoms and that was sprayed in early summer compared with on infected plants treated in autumn, at both the xeric (F = 36.71, p < 0.001) and hydric (F = 3.59, p = 0.031) sites. This pathogen has reduced the time available for effective chemical weed control from six months to three months. However, none of the herbicide treatments achieved commercially acceptable mortality rates of ≥80%, and after three annual applications none succeeded in extirpating C. macrocephalum from the plots. Regression analyses of count data showed that metsulfuron-methyl at 45 g ha^–1 (USD 20.05 ha^-1), picloram at 252 g ha^–1 (USD 25.47 ha^–1) and 2,4-D/dicamba/MCPA at 540/360/474 g ha^–1 (USD 45.41 ha^–1) required five annual treatments in summer to eradicate C. macrocephalum, whereas 2,4-D amine at 1 440 g ha^–1 (USD 13.65 ha-1) and MCPA at 1 200 g ha^–1 (USD 14.46 ha–1) required six treatments. Hence, there is a trade-off between the use of slightly more effective herbicides against the lower costs of other selective herbicides.

Do native grasses emerge and establish in areas rehabilitated using vetiver grass?

Lindokuhle X. Dlamini — 2023-10-05

Species-rich grasslands provide important ecosystem services, and in South Africa, approximately 40% of these grasslands are degraded. Vetiver grass (from India) is often used during rehabilitation efforts to restore soil function without a thorough understanding of the potential negative ecological impacts. Hence, a study was initiated to investigate vetiver’s ecological impacts during grassland rehabilitation. Firstly, a field survey was conducted using a contiguous quadrat method to evaluate the extent of grass secondary succession in these rehabilitated sites. Secondly, the effect of vetiver competition and seed sowing method on the recruitment of two native grasses (Eragrostis curvula and Megathyrsus maximus) was examined using pot trials. The field survey results showed no evidence of grass secondary succession, but rather the abundance of bare ground around vetiver, and a marked increase in grass species richness with increasing distance from planted vetiver. Subsequently, in the pot trial, vetiver facilitated emergence in both native grasses, and soil surface sowing of indigenous grass seeds showed greater emergence than other sowing methods. However, vetiver inhibited native grass seedling establishment, even when root competition was excluded. This study suggests that areas rehabilitated using vetiver are unlikely to become productive grasslands with good grazing, because vetiver inhibits colonisation by native grasses.

Seedling establishment and early growth in Calobota sericea subjected to moisture stress

Francuois Müller — 2023-10-05

The South African perennial legume Calobota sericea (Thunb.) Boatwr. & B-E van Wyk has been shown to be drought tolerant as mature plants, but information on drought tolerance of seedlings is lacking. This study evaluated the impact of moisture stress on seedling emergence, survival and growth in C. sericea. In the first trial, pre-germinated seeds were planted at 100, 70, 50 and 40% of soil moisture holding capacity without additional watering. Seedling emergence and mortality was recorded daily for 14 days. In the second trial, seeds were allowed to grow under well-watered conditions for one month, after which moisture stress was imposed for 15 and 30 days. Thereafter, the seedlings were uprooted, for shoot and root measurements. Results from these trials show that C. sericea seedlings will establish even at severely reduced water-availabilities, but without subsequent watering, significant seedling mortality will occur. Calobota sericea seedlings displayed a range of morphological adaptive strategies to moisture stress including the minimisation of water loss and optimisation of water uptake. Further research into the impacts of regular cycles of moisture stress is needed to determine if changes in morphology due to prior moisture stress will result in improved adaptation to subsequent moisture stress.

The influence of grass competition and soil moisture on the growth and phenology of Karoo shrubs in the Eastern Upper Karoo

Lisa Hebbelmann — 2023-10-05

Rainfall in the Nama-Karoo is sporadic and a plant’s ability to access and utilise available soil moisture will determine its ability to persist in the system and to successfully recruit. When summer rainfall in the Eastern Karoo increases, grassiness increases at the expense of shrub canopy cover. This may drive a transition from shrubland toward grassland. The effect of grass–shrub competition on shrub growth and phenology in the Eastern Karoo is not adequately explained by the root–niche separation hypothesis or the succession hypothesis. In an experiment, we measured shrub growth and phenology in the absence (clipping treatment) and presence (control treatment) of grass over the 2017/2018 rainfall season. Grass clipping changed grass species composition over this period, but grass clipping did not benefit shrubs. We found no competitive effect of grasses on shrubs. However, shrub canopy cover showed a strong linear response to soil moisture, as did canopy cover to temperature. Similarly, soil moisture and temperature were important for stem growth and shrub phenology. Patterns of shrub growth and phenology in response to summer and winter rainfall provide important insight for land managers for optimising production while enabling phenological processes that allow recruitment to take place.

The Living Deserts of Southern Africa

Justin du Toit — 2023-10-05

No Abstract

Grasses of East Africa

Peter Goodman — 2023-10-05

No Abstract