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

The relationship of Trifolium repens and T. ambiguum with host-specific Rhizobium bacteria for potential incorporation into sustainable, low N input pastures

Research on efficient management systems to optimise Trifolium repens-Rhizobium symbiosis, is lacking in South Africa. The amount of nitrogen (N) fixed by symbiotic rhizobia in root nodules of T. repens is ultimately determined by health of the soil environment. Soil organic matter (SOM) is the main attribute that will sustain soil health as it affects the chemical, physical and biological aspects of soil. The aim of this study was to determine the potential of T. repens and T. ambiguum to sustain low N input pastures. The hypotheses of this study is that SOM can play an important role in ensuring good soil health, which supports the optimum growth and production of Trifolium spp. in low N input pastures. Four Trifolium repens cultivars were evaluated in field conditions to determine the effect of Rhizobium bacteria on the potential of the cultivars to nodulate. The cultivars Grasslands Huia, Haifa, Ladino and Regal were selected for assessment. The thousand-seed-mass (TSM) of each cultivar was measured to determine the quality and viability of the seed; and to determine the interaction between seed mass and nodulation. Mean TSM values of T. repens cultivars differed significantly, with Huia having the highest TSM followed by Haifa, Ladino and Regal. Biomass production was also measured as an indicator of efficiency of nitrogen fixation. The cultivar Huia, with the heaviest seed, showed the highest biomass production. After eight weeks of growth, the nodulation index was determined from the size, number and colour of the bacterially associated root nodules. All plants, regardless of cultivar, formed nodules within eight weeks. It was concluded that TSM had no notable effect on nodulation. Planting date with associated temperature effects and the intrinsic cultivar effect also had no influence on nodulation. It was therefore concluded that nodulation potential of the four cultivars tested was similar in the specific environmental conditions. The total number of symbiotic rhizobial cells per gram of soil as affected by soil C content and the host plant was also determined. Inoculated and un-inoculated seeds were planted on five soil treatments, each with a different level of soil C. The plant infection technique (most-probable-number/MPN technique) was used to quantify the rhizobial numbers in soil as affected by soil C content and the host plant. The mean MPN-value ranged from 8907 to 78 Rhizobium cells per gram of soil for T. repens treatments, and 0 to 436 for T. ambiguum treatment. Soil C had no effect on the number of Rhizobium bacteria present in the soil. Inoculation however, had a significant effect on the MPN value of T. ambiguum, but not for T. repens. Most symbiotic Rhizobium was detected between a soil C content of 2.03% to 3.80% in both inoculated and non-inoculated soils. The spread plate count was used to determine the total number of symbiotic and saprophytic rhizobia. This method was used to quantify both symbiotic and free-living rhizobia. The effect of different levels of soil C on the amount of atmospheric N fixed was assessed by the N difference technique. Arctotheca calendula (cape weed) served as the reference plant in this study, to determine what percentage of N is derived from the atmosphere (%Ndfa). Biomass production was determined and served as the parameter to establish the efficiency of the Rhizobium bacteria in the soil. Inoculating seed with host specific rhizobia had no effect on the amount of N fixed. The mean %Ndfa differed significantly between soil organic C treatments with the species T. repens but did not differ significantly between soil organic C treatments with T. ambiguum. It was concluded from this study that symbiotic rhizobia introduced by inoculant was much more efficient in higher C content soils than free-living rhizobia, which highlights the importance of inoculation in improving the sustainable production of T. repens pastures. Although the amount of N fixed increased as the level of soil organic matter decreased, the efficiency of N fixation decreased proportionally. This explains the bigger change in soil N content on soil with a high C content. This study has thus highlighted the importance of soil organic carbon in the host specific Rhizobium inoculation sucsess, of T. repens low N input pasture systems.Dissertation (MSc(Agric))--University of Pretoria, 2010.Plant Production and Soil Scienceunrestricte

An evaluation of the water and sanitation programme as implemented through the Mvula Trust by the Limpopo Department of Education

The study evaluates the water and sanitation programme as implemented through The Mvula Trust by the Limpopo Department of Education (LDoE) in terms of the agency agreement between the two parties, thereby providing: • A precedent of public services and infrastructure delivery through co-production • A precedent of sustainability innovation in the midst of resource scarcity through the large-scale decentralisation of basic services with off-grid water and sanitation systems. The study looks into the context in which the formal arrangement between The Mvula Trust and the LDoE came into place and which continues to be implemented as an alternative means of public service delivery by the state. It further looks into the extent of the deliverables of the programme, which consists of more than 1 843 projects, and on which more than a billion rand has been spent. The scope of works for most of the projects implemented by The Mvula Trust consist mainly of the provisioning and upgrading of water and sanitation services at public schools in the province, including the construction of the dry waste sanitation facilities and the drilling of boreholes. This decentralised form of basic service delivery, unconnected to municipal water supply or sewer systems, was borne mostly out of necessity, but is an improvement on the unsustainable and unaffordable centralised water supply and sewer systems that have been found to be both unsustainable and unaffordable in the long run. The scale and consistency of the roll-out of decentralised water and sanitation systems by the LDoE is commendable and has made it the norm, rather than the exception at schools in the province. The expenditure on a portion of the programme, that is mostly completed, is evaluated to determine the success or failures of the programme as measured against the cost parameter, and finds that The Mvula Trust managed to complete the overall programme within budget. However, when the data for each addendum is compared, it becomes evident that only three of the eight addendums were completed within budget, four was less than 20% over the budget and one was more than 20% over the budget. When the expenditure data per project is evaluated, it reveals that only 62% of the projects can be deemed to be successful in terms of the cost parameter of projects that finished within the allocated project cost. However, the trendline suggests that The Mvula Trust is increasingly improving in keeping their expenditure within the allocated budget. The study reveals that The Mvula Trust is remunerated 10% of the project cost as an implementing agent management fee, with an additional 2% for disbursements. This management fee percentage is fairly high when compared to other implementing agents, especially when the fees for Professional Service Providers are added, which combined with the management fee result in more than 30% of the construction cost. An evaluation of this capital expenditure at these facilities reveals that there is a substantial difference between the average expenditure per learner depending on the size of the school as measured by the school enrolment in 2017. For primary schools the capital expenditure amounts to R6,818 per learner at micro primary schools, with enrolments of less than 135 learners; as opposed to R1,230 per learner at mega primary schools, with enrolments of more than 931 learners. Similarly, for secondary schools the capital expenditure amounts to R6,242 per learner at micro secondary schools, with enrolments of less than 200 learners; as opposed to R1,387 per learner at mega secondary schools, with enrolments of more than 1 000 learners. With the substantial infrastructure needs that exist at schools in Limpopo, coupled with limited funding to address these challenges, it would be prudent for expenditure to be channelled to where it would have the greatest impact. The data would suggest that the greatest impact would be achieved if priority is given to the implementation of infrastructure projects at larger sized schools

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

Livestock in diverse cropping systems improve weed management and sustain yields whilst reducing inputs

<p>Dataset used for the article: </p> <p>MacLaren, C.; Storkey, J.; Strauss, J.; Swanepoel, P.; and Dehnen-Schmutz, K. (2018). Livestock in diverse cropping systems improve weed management and sustain yields whilst reducing inputs. <em>Journal of Applied Ecology.</em></p> <p> </p

Cover crop biomass production is more important than diversity for weed suppression

Biotic resistance theory suggests that diverse cover crop mixes may be more effective at weed suppression than a cover crop monoculture. However, evidence for this has so far been inconsistent. To investigate, we designed a trial to explicitly test the role of cover crop diversity in weed suppression by comparing eight cover crop mixes that varied in species diversity, functional diversity, and composition. Mixes contained either one, four, or eight species, in equal proportions. Three mixes contained only cereal species, three contained only legumes, and two contained a mix of cereals, legumes, and brassicas. Research was conducted on two farms in South Africa’s winter rainfall region, replicated over 2 yr. Indicators of resource uptake by each mix in terms of light, soil N, and water were measured at three time points throughout the season, approximately 50, 85, and 110 d after emergence (DAE). Aboveground biomass (dry weight) of cover crops and weeds within each mix was measured twice, at approximately 70 and 120 DAE. Regression analyses indicated that cover crop biomass was key to resource uptake and weed suppression, and that early-season N and later-season light availability had the strongest influence on weed biomass. Neither species diversity nor functional diversity affected resource uptake or weed suppression by cover crops. These results indicate that it is important to consider the competitiveness of individual species when designing cover crop mixes. Diverse mixes remain valuable to perform multiple functions but may contribute to weed problems if composed of poorly competitive species

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