The snacking habits of white preschool ·children

Three-day estimated dietary records were kept for 194 white 3- and 4-year-old children to deterMine and evaluate the extent, nature and quality of their snacking. All but 1 child ate between meals, with morning and afternoon snacking being favoured in terms of frequency and quantity. Soft drinks were .consumed most frequently, followed by fresh fruits and fruit juices, sweets and chocolates, milk and sugar. Between-meal eating contributed more than one-third of the average day's energy and approximately one-quarter of most vitamins and minerals to the children's diets. Foods eaten between meals were, however, significantly less nutrient-dense than mealtime foods. Non-basic foods supplied more energy to the diet than _ any of the five basic food groups, but minimal quantities of micronutrients. Sugar consumption, mostly in the form of sugary foods and drinks, was high, but was not consumed exclusively between meals. Such children should be encouraged to make more use of basic commodities, particularly when snacking

A comparison of experimental designs for cultivar evaluations

CITATION: Saul, H., Booyse, M. & Swanepoel, P. A. 2020. A comparison of experimental designs for cultivar evaluations. South African Journal of Plant and Soil, 37(2):144-151, doi:10.1080/02571862.2019.1703049.The original publication is available at https://www.tandfonline.comSpatial heterogeneity and the lack of clear or significant treatment responses in agricultural field experiments complicates recommending the most suitable cultivar(s) to producers for a specific area. Increased attention should be given to the experimental design of cultivar trials, as failure to capture spatial heterogeneity may increase the unexplained variance and thus might influence the accuracy of results. A randomised complete block design (RCBD) is the most popular design in variety trials in South Africa. However, latinised row-column designs (LRCD) is widely recommended in literature for field experimentation, because of the efficiency to control heterogeneity in two dimensions. The aim of this study was to compare the efficiency of RBCD with LRCD and recommend the more appropriate design for use by practitioners in cultivar trials. Wheat (Triticum aestivum) was used as a test crop. An analysis of variance was performed on the data produced from both designs conducted on wheat in the Swartland region of South Africa over a two-year period. An LRCD provided better accuracy and model or design estimations than RCBD. The results demonstrated the value of eliminating variance in two directions rather than one direction. We therefore recommend the use of LRCD in preference to RCBD in variety trials.https://www.tandfonline.com/doi/abs/10.1080/02571862.2019.1703049Post-prin

Environmental Impact of Rotationally Grazed Pastures at Different Management Intensities in South Africa

Nitrogen fertilization, irrigation and concentrate feeding are important factors in rotational pasture management for dairy farms in South Africa. The extent to which these factors affect environmental efficiency is subject to current and intense debate among scientists. A three-year field study was conducted to investigate the yield response of different N-fertilizer treatments (0 (N0), 220 (N20), 440 (N40), 660 (N60) and 880 (N80) kg N ha-1 year-1) on grazed pastures and to calculate the carbon footprint (CF) of milk produced. Excessive N-fertilization (N60 and N80) did not increase herbage dry matter and energy yields from pastures. However, N80 indicated the highest N-yield but at the same time also the highest N surpluses at field level. A maximum fertilizer rate of 220 kg ha-1 year-1 (in addition to excreted N from grazing animals) appears sufficient to ensure adequate herbage yields (~20 t DM ha-1 year-1) with a slightly positive field-N-balance. This amount will prevent the depletion of soil C and N, with low N losses to the environment, where adequate milk yields of ~17 t ECM ha-1 with a low CF (~1.3 kg CO2 kg ECM-1) are reached. Methane from enteric fermentation (~49% ± 3.3) and N2O (~16% ± 3.2) emissions from irrigated pastures were the main contributors to the CF. A further CF reduction can be achieved by improved N-fertilization planning, low emission irrigation techniques and strategies to limit N2O emissions from pasture soils in South Africa

Excessive nitrogen fertilization is a limitation to herbage yield and nitrogen use efficiency of dairy pastures in South Africa

CITATION: Phohlo, M. P., Swanepoel, P. A. & Hinck, S. 2022. Excessive nitrogen fertilization is a limitation to herbage yield and nitrogen use efficiency of dairy pastures in South Africa. Sustainability, 14(7), 4322, doi:10.3390/su14074322.The original publication is available at https://www.mdpi.comPublication of this article was funded by the Stellenbosch University Open Access FundThe response of crop yields to fertilizers is a long-standing topic of agricultural production. Currently, in dairy-pasture systems, nitrogen (N) fertilizer is used as a management tool that is said to be directly proportional to pasture yield. We evaluated a large dataset consisting of data from 153 fields over five years to examine the effects of N fertilization on pasture yield and nitrogen use efficiency in the Eastern Cape province of South Africa. Fertilizer application rates were grouped into three treatments viz., 350 kg N ha−1 , and herbage yield response over the years was analyzed with mixed models. There were no differences found between treatments for total annual herbage yield over the years. High N fertilizer rates did not translate to a higher herbage yield of pastures. The N rate had a weak but significant negative correlation with the total annual yield and only accounted for 6% of the yield variation. The N use efficiency of pastures improved with reduced N application rates. Pasture yield varies through different seasons. Spring and summer account for the highest yield, coinciding with warm and moist conditions favorable for N mineralization in the soil. Farmers need to consider the time of the year and plan their monthly or seasonal fertilizer application accordingly to account for peak N mineralization rates.https://www.mdpi.com/2071-1050/14/7/4322Publisher's versio

Utilisation of cover crops: implications for conservation agriculture systems in a mediterranean climate region of South Africa

Purpose Cover crops can provide multiple agroecosystem services to crops produced in conservation agriculture systems. South African grain producers in the Mediterranean climate region are reluctant to integrate cover crops in rainfed systems since cover crops replace cash crops leading to financial losses. Using cover crops as fodder can help cover input costs, while providing a range of advantageous services to the cropping system. The aim of this study was to investigate how cover crop mixtures and the utilisation of cover crops affect soil quality, the quality and quantity of the mulch as well as wheat (Triticum aestivum L.) produced in the subsequent year. Methods A two-year study was conducted in the Western Cape Province of South Africa. In Year 1, diverse legume and cereal-based cover crop mixtures were partially grazed, cut and material removed for haymaking, or left unutilised as a mulch. In Year 2, spring wheat (Triticum aestivum L.) was planted to investigate the effects of cover crop mixtures and utilisation method on subsequent spring wheat yield. Results Cover crops used as hay or for grazing did not affect (P < 0.05) grain yield of wheat that followed in rotation. Legume-based cover crop mixtures increased (P < 0.05) wheat grain protein content regardless of utilisation method. Soil quality and nitrogen content improved (P < 0.05) when cover crops were grazed. Conclusions Cover cropping can be used by South African grain producers as an important agronomic tactic to improve system productivity and support sustainable intensification of rainfed cropping systems

Experimental inoculation of plants and animals with Ebola virus.

Thirty-three varieties of 24 species of plants and 19 species of vertebrates and invertebrates were experimentally inoculated with Ebola Zaire virus. Fruit and insectivorous bats supported replication and circulation of high titers of virus without necessarily becoming ill; deaths occurred only among bats that had not adapted to the diet fed in the laboratory

Triangle-Free Penny Graphs: Degeneracy, Choosability, and Edge Count

We show that triangle-free penny graphs have degeneracy at most two, list coloring number (choosability) at most three, diameter $D=\Omega(\sqrt n)$, and at most $\min\bigl(2n-\Omega(\sqrt n),2n-D-2\bigr)$ edges.Comment: 10 pages, 2 figures. To appear at the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Patterns and drivers of rodent abundance across a South African multi-use landscape

Funding: This research was funded by FCT/MCTES, through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020 (cE3c: UIDB/00329/2020), and by the South African National Research Foundation, South Africa (UID 107099&115040). TAM thanks partial support by CEAUL (funded by FCT-Fundação para a Ciência e a Tecnologia, Portugal, through the project UIDB/00006/2020).South Africa’s decentralized approach to conservation entails that wildlife outside formally protected areas inhabit complex multi-use landscapes, where private wildlife business (ecotourism and/or hunting) co-exist in a human-dominated landscape matrix. Under decentralized conservation, wildlife is perceived to benefit from increased amount of available habitat, however it is crucial to understand how distinct management priorities and associated landscape modifications impact noncharismatic taxa, such as small mammals. We conducted extensive ink-tracking-tunnel surveys to estimate heterogeneity in rodent distribution and investigate the effect of different environmental factors on abundance patterns of two size-based rodent groups (small-and medium-sized species), across three adjacent management contexts in NE KwaZulu-Natal, South Africa: a private ecotourism game reserve, mixed farms and traditional communal areas (consisting of small clusters of houses interspersed with grazing areas and seminatural vegetation). Our hypotheses were formulated regarding the (1) area typology, (2) vegetation structure, (3) ungulate pressure and (4) human disturbance. Using a boosted-regression-tree approach, we found considerable differences between rodent groups’ abundance and distribution, and the underlying environmental factors. The mean relative abundance of medium-sized species did not differ across the three management contexts, but small species mean relative abundance was higher in the game reserves, confirming an influence of the area typology on their abundance. Variation in rodent relative abundance was negatively correlated with human disturbance and ungulate presence. Rodent abundance seems to be influenced by environmental gradients that are directly linked to varying management priorities across land uses, meaning that these communities might not benefit uniformly by the increased amount of habitat promoted by the commercial wildlife industry.Publisher PDFPeer reviewe

Seed-drill opener type and crop residue load affect canola establishment, but only residue load affects yield

Handling crop residue during planting operations is a challenge to conservation agriculture (CA) farmers worldwide. It remains unclear which tools are most effective in which conditions. Canola (Brassica napus L.), an oilseed crop widely used in rotation with cereals, is particularly sensitive to seedbed conditions, and thus may be influenced by residue loads and the choice of seed-drill openers. To identify optimal planting practices, this study compared the performance of disc and tine openers on canola establishment, growth, and yield under differing residue loads in a Mediterranean-type climate region. First, soil disturbance caused by disc and tine openers was evaluated to assess their effect on seedbed conditions; and second, the interacting effects of the openers with different residue loads was investigated. Tine openers and low crop residue loads resulted in the best (P 0.05)

Bounding Helly numbers via Betti numbers

We show that very weak topological assumptions are enough to ensure the existence of a Helly-type theorem. More precisely, we show that for any non-negative integers $b$ and $d$ there exists an integer $h(b,d)$ such that the following holds. If $\mathcal F$ is a finite family of subsets of $\mathbb R^d$ such that $\tilde\beta_i\left(\bigcap\mathcal G\right) \le b$ for any $\mathcal G \subsetneq \mathcal F$ and every $0 \le i \le \lceil d/2 \rceil-1$ then $\mathcal F$ has Helly number at most $h(b,d)$. Here $\tilde\beta_i$ denotes the reduced $\mathbb Z_2$-Betti numbers (with singular homology). These topological conditions are sharp: not controlling any of these $\lceil d/2 \rceil$ first Betti numbers allow for families with unbounded Helly number. Our proofs combine homological non-embeddability results with a Ramsey-based approach to build, given an arbitrary simplicial complex $K$, some well-behaved chain map $C_*(K) \to C_*(\mathbb R^d)$.Comment: 29 pages, 8 figure