Aligning conservation agriculture among various disciplines in South Africa

CITATION: Swanepoel, P. A. 2021. Aligning conservation agriculture among various disciplines in South Africa. South African Journal of Plant and Soil, 38(3):185-195, doi: 10.1080/02571862.2021.1954249.The original publication is available at https://www.tandfonline.comn South Africa, the term Conservation Agriculture (CA) is often used to describe any soil conservation action rather than a combination of the three management principles that CA encompasses, namely minimum soil disturbance, using a diversity of crops in rotation or association, and protecting the soil with an organic soil cover. A workshop was held with delegates from tertiary institutions, research institutions, government and private companies, in January 2019, to share and exchange CA research experiences and lessons, and to identify research gaps in the field of CA in South Africa. By collating the information from the workshop, this article aims to align CA approaches among various disciplines in South Africa and to identify the inevitable challenges with CA and (mis-)perceptions of CA in South Africa. It was clear that CA is applicable to most farming systems, but is context specific. No specific CA practice can be recommended as a panacea to solve issues experienced in all systems. Adaptation and application of CA within different South African farming systems needs to be dealt with sensibly and realistically, in ways that are based on practical rather than purely theoretical considerations. It is important that CA is not advocated without taking sustainable intensification into account. Dealing with CA sensibly requires a multidisciplinary approach.Publisher's versio

Microbial Community Response to Various Degrees of Pasture Soil Disturbance

Commercial dairy farming from planted pasture is commonly practised in the southern Cape region of South Africa. These pastures are established by various methods ranging in degree of disturbance from no-tillage to conventional tillage. Different establishment methods may alter the below-ground ecosystem, and depending on the degree of disturbance, lead to changes in microbial biodiversity and soil health. Disturbance of pasture soil may play an important role in regulating soil microbial community structure. The aim of this study was to investigate changes in soil microbial community-level physiological profiles of kikuyu (Pennisetum clandestinum) pastures reinforced with annual ryegrass (Lolium multiflorum) by various degrees of soil disturbance

Revisiting Nitrogen Fertilisation Rates of Kikuyu and Kikuyu-Ryegrass Pastures

Irrigated pastures are used for dairy production in South Africa. Minimum-tillage and nitrogen (N) fertilisation are important management practices for kikuyu (Pennisetum clandestinum) and ryegrass (Lolium spp.) pastures. Nitrogen fertiliser application rates as high as 500 kg N ha-1 year-1 have been reported. Conventional tillage as well as cutting and removal of herbage material (opposed to removal through grazing) are the basis on which these fertiliser guidelines were developed. The current management practices have substantially changed the soil organic carbon and N stoichiometry. The aim of this study was to determine an optimum rate of N application of kikuyu and kikuyu-ryegrass pastures. Five fixed N fertiliser rates (0, 20, 40, 60 and 80 kg N ha-1 grazing cycle-1) were evaluated. Soil characteristics and pasture performance were monitored over a two year period. Nitrate concentrations and total mineral soil N were substantial, compared to the control, when more than 40 kg N ha-1 grazing cycle-1 were applied, leading to potential losses to the environment. Differences in biomass production were mostly due to seasonal variation, while N treatment effects within a season were generally small. As N treatments increased on both the study sites, the self-sown clover component decreased. Agronomic nitrogen use efficiency was similar across treatments and seasons on both sites, with the exception of winter in the first year on the kikuyu-ryegrass site. The results indicate that the soil could be saturated with N, at least to a point where herbage production response is minimal. A positive response in terms of crude protein was observed in some of the higher N treatments, but up to a point where it was no longer favourable for milk production. It is therefore concluded that the current N guidelines needs to be revisited as they pose a risk to the environment and farm economics

Establishing Baseline Values for Soil Quality Indicators in the Southern Cape of South Africa

Commercial dairy farming on pasture is commonly practiced in the southern Cape region of South Africa. In terms of its sustainability, quantification of the impact of dairy-pasture management on soil quality is essential. To comprehend the behaviour of soils in terms of quality, indicators should be assessed to screen the general direction of soil quality within a management system. Development of a soil quality assessment framework necessitates establishment of baseline values for soil quality indicators. The aim of this study was to establish baseline values for soil quality indicators for dairy-pasture soils in the southern Cape. Physical, chemical and biological indicators on a no-till kikuyu (Pennisetum clandestinum)-ryegrass (Lolium spp.) pasture were compared to those of a virgin soil. Stratification ratios, which demonstrated the rate at which the indicator decreased with depth, were assessed for soil organic matter (SOM) related indicators. Biological indicators showed a well-established and well-functioning microbial population in the improved pasture soil. Stratification ratios demonstrated that the soil quality of the improved pasture system was improved relative to the virgin soil. Chemical indicators showed that the impact of nutrient management was favourable to pasture productivity. The association between the chemical and biological indicator were better established in the managed pasture. Physical indicators demonstrated that management practices adversely impacted the ability of the soil to provide physical support and structural functionality. This data were used in developing a first approximation of baseline values. Further research is warranted to validate them on representative commercial dairy farms in the southern Cape

Tillage practices affect weeds differently in monoculture vs. crop rotation

Reduced tillage practices are widely considered to be more sustainable than conventional tillage practices, but many producers remain reluctant to reduce tillage due to difficulties controlling weeds. Crop rotation is often put forward as the best means to manage weeds in reduced tillage systems, but uncertainties remain around how different tillage practices and crop rotations interact. Here, we assess the effects of four different tillage practices on weed seedbank density and composition in wheat (Triticum aestivum) monoculture (WWWW), and two different rotations, wheat-medic-wheat-medic (annual medic, Medicago spp.; WMWM), and wheat-canola-wheat-lupin (Brassica napus, Lupinus spp.; WCWL). We use data across a whole four-year rotation period from a long-term experiment replicated at two sites in South Africa's winter rainfall region. The four tillage practices assessed follow a gradient of soil disturbance: conventional tillage (CT, soil inversion through ploughing), minimum tillage (MT, shallow soil loosening), no tillage (NT, direct drilling with tine openers) and zero tillage (ZT, direct drilling with disc openers)

The Effect of Planting Date on the Dry Matter Production of Italian and Westerwolds Ryegrass in the Southern Cape of South Africa

Perennial pasture species such as lucerne (Medicago sativa), kikuyu (Pennisetum clandestinum), perennial ryegrass (Lolium perenne) and perennial clovers (Trifolium spp.) make an important contribution to the fodder flow programmes for dairy production in the southern Cape. One of the main challenges when these species make up the primary pasture base within a pasture system is the mutually low growth rates during winter (Van Heerden et al., 1989; Swanepoel et al., 2014). In order to bridge pasture shortages during the critical winter months, producers establish annual Italian (Lolium multiflorum var. italicum) and Westerwolds ryegrass (L. multiflorum var. westerwoldicum) either as pure swards, mixtures or over-sown it into perennial pastures. The production potential and seasonal growth of annual ryegrass varieties are affected by climate and may not follow the same pattern of production as in other regions. The aim of this study was to determine the production potential of Italian and Westerwolds ryegrass planted at different planting dates in the southern Cape of South Africa

Spatial relationships and movement patterns of the air cargo industry in airport regions

BACKGROUND : During the past few years, with the increase in air traffic and the expansion of airports, very few industries had such a large spatial development and movement impact as that of airport-related clusters or airport regions. Although much research was done on the various impacts of the airport industry, very little research was done on the air cargo industry in airport regions. OBJECTIVES : This article specifically explored the unique spatial relationships, impacts, trends and movement patterns of the air cargo industry within a typical airport region. METHOD : The article focused on the OR Tambo International Airport in Gauteng, South Africa, as a case study and was informed by an extensive quantitative spatial and land use analysis and modelling of the study area. RESULTS : The article presented findings and insights on the movement patterns and relationships between (1) the airport facility and (2) the spatial configuration of air cargo industries in the particular airport region. These findings also provided some framework for a possible spatial model and guideline that could assist in steering and managing development and movement patterns in airport regions. CONCLUSION : The article provided new insights and understanding on the spatial dynamics of airport regions and the air cargo industry, ultimately addressing some gaps in this knowledge field. The article in the end highlighted the need for a different and novel approach to the planning and management of the air cargo industry in airport regions and a basis for further research.http://www.jtscm.co.zaam2018Town and Regional Plannin

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

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

\u3cem\u3eRhizobium\u3c/em\u3e-White Clover Symbiosis and Nitrogen Fixation along a Soil Organic Carbon Gradient

Sustainable cultivated pasture production in the southern Cape region of South Africa requires management practices that will support soil quality (Swanepoel and Botha 2012). Soil organic carbon (Corg) sequestration is regarded as one of the most important ways to promote soil quality. Dairy farmers in the southern Cape attempt to increase Corg by following minimum-tillage practices. These irrigated dairy-pastures require high levels of nitrogen (N) to maintain highly productive pastures. Nitrogen fertilisers have be-come very expensive and severely strain profitability of these dairy-pastures. Forage legumes are frequently incorporated into the grass pastures to overcome economic and environmental problems associated with high levels of inorganic fertiliser application. Their capacity to fixate atmospheric N contributes greatly to nutritional value, palatability and subsequently profitability of pastures (Botha 2003). Since C and N are biophilic compounds, Corg may have a direct effect on the N-fixating legume plant or the Rhizobium population that infects its roots (Swanepoel et al. 2011). The aim of this study was to determine the effects of Corg on white clover (Trifolium repens) biomass production and N-fixation by host-specific Rhizobium