Genotype x environment interactions and optimum resource allocation for sugarcane yield trials in Swaziland

To account for genotype x environment (G x E) interactions, sugarcane varieties are tested in multi-environment trials (METs) across multiple crop-years and seasons (early vs. late) under fully irrigated conditions in Swaziland. This study aimed to quantify the main sources of variation relevant to the MET network, identify mega-environments, evaluate adaptability of imported sugarcane varieties, and optimize resource use within the testing network. Nine varieties (eight imported Mauritian and one South African variety) were tested at two sites (Mhlume – M and Simunye – S), harvested early (E) and late (L) in the season across five crop-years in replicated (8) Latin square designs. A linear mixed model analysis of cane yield (tons of cane per ha; TCH), sucrose content (SUC%), sucrose yield (tons of sugar per ha; TSH), and fiber content (FIB%) showed that variety x season interactions were highly significant (P < 0.001) and larger than variety x site interactions for most traits. Genotype + genotype x environment (GGE) biplots revealed clustering of environments into two mega-environments by season rather than by site. Two Mauritian varieties were superior in each of the early and late mega-environments. Broad-sense heritability (H²) for all traits was larger than 0.79, with the highest value observed for FIB% (0.89). Resource optimization analysis, using variance components, suggested that future testing be conducted at a single site, across two seasons, with replicate numbers >5, and harvested across approximately five crop-years. Strong variety x season interactions should be exploited more aggressively in irrigated sugarcane selection programs.     

Soil CO2 emissions in cropland with fodder maize (Zea mays L.) with and without riparian buffer strips of differing vegetation

Agroforestry Systems - Vegetated land areas play a significant role in determining the fate of carbon (C) in the global C cycle. Riparian buffer vegetation is primarily implemented for water...     

Chemical composition,nitrogen degradability and in vitro ruminal biological activity of tannins in vines harvested from four tropical sweet potato (Ipomoea batatas L.) varieties

This study investigated the potential of vines from four sweet potato varieties (Tia Nong 57, Tia Nong 66, Ligwalagwala and Kenya) as alternative feed resources for ruminant livestock. The chemical composition [neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP) and acid detergent insoluble nitrogen (ADIN)], in vitro ruminal nitrogen (N) degradability and in vitro ruminal biological activity of tannins in the vines, harvested at 70 and 110 days after planting (DAP), were determined. Variety and harvesting stage did not (p > 0.05) influence CP and NDF content of the vines. Concentration of CP ranged from 104.9 to 212.2 g/kg DM, while NDF ranged from 439.4 to 529.2 g/kg DM across harvesting stages and varieties. Nitrogen degradability (ND) at 70 and 110 DAP was highest (p < 0.05) in Ligwalagwala (743.1 and 985.0 g/kg DM, respectively). Treatment of vines with tannin‐binding polyethylene glycol (PEG) increased (p < 0.05) in vitro ruminal cumulative gas production parameters (a, b and c). The in vitro ruminal biological activity of tannins, as measured by increment in gas production parameters upon PEG inclusion, had a maximum value of 18.2%, suggesting low to moderate antinutritional tannin activity. Ligwalagwala vines, with highly degradable N, would be the best protein supplement to use during the dry season when ruminant animals consume low N basal diets and maintenance is an acceptable production objective. Tia Nong 66 and Kenya varieties, with less degradable N, may be more suitable for use as supplements for high‐producing animals such as dairy goats.     

Soil carbon dioxide (CO2) fluxes in permanent upslope pasture and downslope riparian buffers with varying vegetation

Background

Riparian buffers are primarily implemented for their water quality functions in agroecosystems. Their location in the agricultural landscape allows them to intercept and process pollutants from immediately adjacent agricultural land. Vegetated riparian buffers recycle soil organic matter, which elevates soil carbon (C), which upon processing, processes and releases carbon dioxide (CO₂). The elevated soil C and seasonally anoxic environments associated with riparian buffers promote denitrification and fermentation, further increasing soil CO₂ production.

Aim

Against this context, a replicated plot-scale experiment was established at North Wyke, UK, to measure the extent of soil CO₂ emissions in permanent pasture served by grass, willow, and woodland riparian buffers, as well as a no-buffer control.

Methods

Soil CO₂ was measured using the static chamber technique in conjunction with soil and environmental variables between June 2018 and February 2019.

Results

Cumulative soil CO₂ fluxes were in the descending order: woodland riparian buffer; 11,927.8 ± 1987.9 kg CO₂ ha^–1 > no-buffer control; 11,101.3 ± 3700.4 kg CO₂ ha^–1 > grass riparian buffer; 10,826.4 ± 2551.8 kg CO₂ ha^–1 > upslope pasture; 10,554.6 ± 879.5 kg CO₂ ha^–1 > willow riparian buffer; 9294.9 ± 1549.2 5 kg CO₂ ha^–1. There was, however, no evidence of significant differences among all treatments of the current study.

Conclusions

Despite the lack of significant differences, the results from our short-term study show that the woodland riparian buffer had relatively larger soil CO₂ emissions than the remainder of the other riparian buffers and the upslope pasture it serves. Our short-term findings may be useful in developing soil CO₂ mitigation strategies through careful selection of riparian buffer vegetation and may be useful in calibrating mechanistic models for simulating such emissions from similar agro systems.     

Condensed Tannins in Traditional Wet‐Cooked and Modern Extrusion‐Cooked Sorghum Porridges

The profile and quantities of condensed tannins (CT) in foods are affected by processing due to their highly reactive nature, which may affect their antioxidant activity and the nutritional value of the foods. The objective was to compare the quantity and profile of condensed tannins in traditional wet‐cooked and modern ready‐to‐eat extrusion‐cooked sorghum porridges. CT were analyzed using normal‐phase HPLC with fluorescence detection and their content was compared to CT and total phenols determined with standard colorimetric assays. Both the traditionally prepared and instant porridges had significantly reduced CT polymers (DP > 8), with retentions of 38 and 9%, respectively, of the CT present in the whole grain. Oligomer (DP 2–8) and monomer (DP 1) contents in traditional porridges were not significantly different from those of grain. In extruded porridges, the oligomers were reduced and the monomer content was increased. The extractable CT oligomers and monomers in the extrusion‐cooked sorghum porridges may be more biologically available because extrusion appears to increase their availability.     

Infiltration-excess runoff properties of dryland floodplain soil types under simulated rainfall conditions

The study estimated infiltration-excess runoff properties of three floodplain soil-types under aquifer water management at Anglo American Kolomela Iron Ore mine in Postmasburg, Northern Cape Province of South Africa. Rainstorm regimes of amounts 60 (high), 30 (medium), and 15 (low) mm with respective intensities of 1.61, 0.52, and 0.27?mm min^?1 were simulated on 1 m² plot with 1% slope. Infiltration-excess runoff properties were affected by a rainstorm, but not soil-type. When combined with rainstorm, soil-type affected accumulative run-off rates. High rainstorm had different (p?≤?0.05) accumulative runoff rates (0.1–0.61?mm min^?1) and increased with clay content. Different response times of 4, 10, and 17?min for respective high, medium, and low rainstorms were quickest on higher clay plus silt content and bulk-density under high and lower rainstorms, respectively. Lower rainstorms had similar effects on accumulative runoff rates (0.01–0.05?mm min^?1), total runoff yield (0.59–18?mm), and runoff coefficients (4.29–18%). Under the high rainstorm, total runoff yields (11.4–25.8?mm) and runoff coefficients (19–42.9%) were different and increased with clay plus fine-silt content. Although simulated rainstorms had constant intensities, results showed high rainstorms to be of primal influence on infiltration-excess runoff. Clay plus silt content and bulk-density influenced infiltration-runoff properties for respective high and lower rainstorms. Apart from rainstorm characteristics, surface clay plus silt content and bulk-density are important for harnessing surface runoff in floodplains for aquifer recharge.     

Rainfall simulation to identify the storm-scale mechanisms of gully bank retreat

Gully erosion is one of the main causes of soil loss in drylands. Understanding the dominant mechanisms of erosion is important to achieve effective erosion control, thus in this study our main objective was to quantify the mechanisms involved in gully bank retreat as a result of three processes, falling of entire soil aggregates, transport of soil material by splash and by water running along gully banks (runoff), during rainfall events. The study was conducted in the sloping lands of the KwaZulu-Natal province, a region that is highly affected by gully erosion. Artificial rain was applied at 60 mm h⁻¹ for 45 min at the vertical wall of a gully bank typical to the area. The splash material was collected by using a network of 0.045 m² buckets. The sediments in the running water were assessed by sampling the runoff collected from a microplot inserted within the base of the bank, and collecting the fallen aggregates after the rainfall simulation was complete. Results indicated that the overall erosion for the simulation was 721 g m⁻² h⁻¹. Runoff erosion proved to be the dominant mechanism and amounted to 450 g m⁻² h⁻¹, followed by splash and fall down of aggregates (about 170 g m⁻² h⁻¹). Gully bank retreat occurred at a rate of 0.55 mm h⁻¹ and assuming that the soil bulk density is 1.3 g cm⁻³, this corresponds to a retreat of 8.8 mm y⁻¹. Extrapolations to the watershed level, where about 500 m² of gully bank are observed per hectare, would lead to an erosion rate of 4.8 t ha⁻¹ y⁻¹. These limited results based on a simulated storm show that the three main mechanisms (runoff, splash and fall down of aggregates) are responsible for the retreat of gully banks and that to mitigate gully erosion, appropriate measures are required to control all three mechanisms. Further research studies are needed to confirm and to scale up, both in time and space, as these data are obtained at one location and from a single artificial storm.     

Designing a transfrontier conservation landscape for the Maputaland centre of endemism using biodiversity, economic and threat data

A number of global priority region schemes have been developed, but local assessments are needed to identify priority areas for conservation within these regions. Here, we describe results from a conservation assessment for Maputaland, part of a biodiversity hotspot in southern Africa that is also the focus of the Lubombo Transfrontier Conservation Area (TFCA) initiative between South Africa, Mozambique and Swaziland. The TFCA seeks to establish new state-, private- and communally-managed conservation areas to boost economic development through nature-based tourism and game ranching. The assessment will guide the TFCA process and used a systematic conservation planning approach to design a landscape to conserve 44 landcover types, 53 species and 14 ecological processes. The assessment also included data on modelled risk of agricultural transformation, of which low-risk areas were selected where possible. The current PA systems in the three countries cover 3830 km², which represents 21.2% of the region, and meet the representation targets for 46% of the conservation features. The proposed conservation landscape adds 4291 km² of new core areas and 480 km² of linkages and, if appropriate, could provide potential revenues of US$18.8 million from game ranching, based on modelled large ungulate density, life history and game auction data. We also discuss the benefits of including data on widely distributed, better known conservation features together with less-well studied, range-restricted species and the advantages of using agricultural transformation risk data in conservation assessments.     

Setting Agricultural Research Priorities： The Case for the Agricultural Sector in Swaziland

The study determined the research priorities in Swaziland agricultural sector. Data collection used existing documents on agricultural research prioritizing, Nominal Group Technique and modified Delphi technique, with analysis of data using content categorization and, group and individual ranking of submissions. Findings showed the agricultural priorities from national policies are tied-up with mitigating the effects of HIV and AIDS on food security, reduction of poverty and, sustainable development. The findings also revealed forty-three field crops areas needing research. Seven horticulture areas and eleven livestock sector areas were of high priority. A considerable number of research areas in field crops, horticulture and livestock indicated that the current research system has not adequately addressed research needs, despite efforts made by the private sector, University of Swaziland and Ministry of Agriculture and Cooperatives, for Swaziland to achieve self-sufficiency in food production. Recommendation was that the identified research priorities should be used as basis for directing the limited resources in conducting agricultural research. The participation of all stakeholders would facilitate efficient use of resources and facilitate collaboration amongst research institutions. The University of Swaziland should develop research priorities aligned with national policies and objectives, to facilitate funding for research by both government and donor agencies.     

Building capacity for improved veterinary epidemiosurveillance in southern Africa

A workshop to produce recommendations on training requirements for improved epidemiosurveillance of livestock diseases in southern Africa was organised at the Department of Veterinary Tropical Diseases in the Veterinary Faculty of the University of Pretoria. It was attended by 23 persons representing 10 different southern African countries. The majority of the participants were actively involved in veterinary epidemiosurveillance and many of them were members of the SADC Epidemiology and Informatics Subcommittee. Discussions focused on (i) epidemiosurveillance networks and their 2 main components, i.e. (ii) diagnosis and (iii) information flow. The debates were guided by 3 questions; (i) what are the requirements for an effective network, (ii) what cannot be achieved with existing capacity and (iii) how can the current capacity be improved. Workshop participants developed lists of realistic capacity building needs, which were divided into structural needs and training requirements. Structural needs mainly concerned communication means and quality assurance. With regard to training, the need for appropriate continuing education of all actors at the various disease management levels (non-professional, para-professional, professional) was expressed. Special emphasis was put on capacity building at the lowest level, i.e. the livestock owner and the para-professionals at the community level. At the international level, it was felt that special emphasis should be put on building capacity to improve the understanding of international agreements on trade in animals and animal products and to improve the capacity of negotiating such agreements.