33 research outputs found
Water footprint of growing vegetables in selected smallholder irrigation schemes in South Africa
No full textKnowledge of water use, through water foot printing (WF) in smallholder agriculture crop production is the key to the global fight against poverty, achievement of food security and sustainability within the world’s rural community. Water footprint of a crop can be defined as the volume of fresh water used to produce a certain crop in all the steps in the production line. This study, therefore aimed at contributing towards improvements in rural livelihoods by raising awareness of the increased productive use of green, blue and grey water in smallholder agriculture in South Africa. This was done through determination of water footprints of five vegetable crops, i.e. potatoes (Solanum tuberosum), tomatoes (Solanum lycopersicum), dry beans (Phaseolus vulgaris), cabbage (Brassica oleracea spp) and spinach (Spinacia oleracea) in the 2000-2013 period. Quantification of water footprints has been done worldwide but, in South Africa (SA) focus has mostly been on the industrial and domestic sector. Water footprint assessment framework, was used to estimate the full impact of vegetable production on water resources at Zanyokwe, Thabina and Tugela Ferry irrigation schemes as case studies. The CROPWAT@ model was used to calculate crop evapotranspiration, differentiating green and blue water. Local climatic data were obtained from SA weather services, while the crop and soil parameters were obtained from the FAO data base. Nitrogen was considered the main pollutant hence its use in the grey water footprint calculation. Generally, Thabina irrigation scheme had the highest water footprint, followed by Tugela Ferry irrigation scheme whilst Zanyokwe irrigation scheme had the lowest. Green beans had the highest water footprint at all the three irrigation schemes with Thabina irrigation scheme having the highest (3535.1 m3/ton). For Tugela Ferry irrigation scheme, the calculated WF was 2753 m3/ton whilst the lowest was observed at ZIS i.e. 2407.6 m3/ton. Cabbage had the lowest water footprint. The highest water footprint for growing cabbage was 254.5 m3/ton in TFIS, 223.1 m3/ton in TIS and the lowest was 217.8 m3/ton in ZIS. The differences observed in the WF of a crop at each scheme maybe attributed to the differences management, weather and environmental characteristics, in the three locations. Moreover, the needs for ET are related to soil type and plant growth, and primarily depend on crop development and climatic factors which are closely related to climatic demands. The grey water footprint was calculated using the recommended fertilizer application rates for all the three sites. Green beans had the highest WFgrey i.e. 373 m3/ton and the lowest was cabbage with 37 m3/ton. Potato, spinach and tomatoes had 156 m3/ton, 214 m3/ton and 132 m3/ton, respectively. Grey water footprint in this study was higher as compared to other studies, possibly because of the high rates of nitrogen fertilizers used in the calculations and the low yields farmers get. Compared with estimates from other studies, the water footprints of vegetable production within smallholder irrigation schemes was relatively high. There is therefore, a need to focus on crop management and tillage practices that will help in increasing yield while minimizing water usage
Water footprint of growing vegetables in selected smallholder irrigation schemes in South Africa
No full textCrop water footprint (WF) is the volume of fresh water used to produce a certain crop in all the steps in the production line. The CROPWAT model was used to calculate crop evapotranspiration, differentiating green and blue water in Zanyokwe (ZIS), Thabina (TIS) and Tugela Ferry (TFIS) Irrigation Schemes. Green beans had the highest water footprint in all three irrigation schemes with 3 535.7 m3/t in TIS, 2 753 m3/t in TFIS and 2 407.6 m3/t in ZIS. Cabbage had the lowest water footprint. The highest water footprint for growing cabbage was 254.5 m3/t in TFIS, followed by 223.1 m3/t in TIS, and the lowest was 217.8 m3/t in ZIS. Green WF represented the highest percentage of water use at ZIS (50.5%), followed by blue water at 26.5% while grey water constituted 22.9%. At TFIS blue, green and grey water use was 23.1%, 56.7% and 20.2%, respectively. The differences observed in the WF of different crops and different schemes were attributed to the differences in weather and environmental characteristics. Green beans had the highest grey water footprint, i.e., 373 m3/t and the lowest was cabbage with 37 m3/t. Potato, spinach and tomatoes had footprints of 156 m3/t, 214 m3/t and 132 m3/t, respectively. For future research it is necessary to consider the possibility and trade-offs of shifting production of each crop to the places where it is most efficient, and to focus on blue water scarcity in each of the case study locationsKeywords: smallholder irrigation schemes, water footprint, evapotranspiration, water us
Carbon Input and Maize Productivity as Influenced by Tillage, Crop Rotation, Residue Management and Biochar in a Semiarid Region in South Africa
No full textConservation agriculture (CA) as a system is still evolving on many of the smallholder farms in sub-Saharan Africa (SSA) and questions on the impact of individual components and pathways toward adoption still require answers. A short-term study was conducted to investigate the effect of tillage, crop rotation, and crop residue management, including maize residue biochar on above ground biomass, cumulative carbon (C) input, soil organic carbon (SOC), and maize grain yield. A split–split plot design was used to evaluate two tillage operations (conventional tillage (CT) and no-till (NT)), three crop rotations (maize–fallow–maize (MFM), maize–oat–maize (MOM), and maize–vetch–maize (MVM)), and three-crop residue management (retention (R+), removal (R−), and biochar (B)). The cumulative above ground biomass produced in the MOM rotation was significantly higher by 78.9% and 88.7% relative to MVM and MFM rotations, respectively. The cumulative C input under residue management treatments ranged from 10.65 to 12.16 Mg ha−1. The highest SOC was observed under R+ (1.10%) followed by B (1.0%) and the lowest was in R− (0.96%). Crop residue management significantly affected grain yields in 2015/2016 (p < 0.05) and 2016/2017 (p < 0.01) summer seasons. Biochar did not result in an obvious improvement in both C input and crop yield. Smallholder farmers can potentially switch from CT to NT without any significant yield penalty, as well as adopt MOM and R+ practices for increased biomass and C input
Carbon Dioxide Fluxes and Carbon Stocks under Conservation Agricultural Practices in South Africa
No full textUnderstanding the impacts of agricultural practices on carbon stocks and CO2 emission is imperative in order to recommend low emission strategies. The objective of this study was to investigate the effects of tillage, crop rotation, and residue management on soil CO2 fluxes, carbon stock, soil temperature, and moisture in the semi-arid conditions in the Eastern Cape of South Africa. The field trial was laid out as a split-split-plot design replicated three times. The main plots were tillage viz conventional tillage (CT) and no-till (NT). The sub-plots were allocated to crop rotations viz maize–fallow–maize (MFM), maize–oat–maize (MOM), and maize–vetch–maize (MVM). Crop residue management was in the sub-sub plots, viz retention (R+), removal (R−), and biochar (B). There were no significant interactions (p > 0.05) with respect to the cumulative CO2 fluxes, soil moisture, and soil temperature. Crop residue retention significantly increased the soil moisture content relative to residue removal, but was not different to biochar application. Soil tilling increased the CO2 fluxes by approximately 26.3% relative to the NT. The carbon dioxide fluxes were significantly lower in R− (2.04 µmoL m−2 s−1) relative to the R+ (2.32 µmoL m−2 s−1) and B treatments (2.36 µmoL m−2 s−1). The carbon dioxide fluxes were higher in the summer (October–February) months compared to the winter period (May–July), irrespective of treatment factors. No tillage had a significantly higher carbon stock at the 0-5 cm depth relative to CT. Amending the soils with biochar resulted in significantly lower total carbon stock relative to both R+ and R−. The results of the study show that NT can potentially reduce CO2 fluxes. In the short term, amending soils with biochar did not reduce the CO2 fluxes compared to R+, however the soil moisture increases were comparable
The Role of Social Inclusion in Restoring Communal Rangelands in Southern Africa: A Systematic Review of Approaches, Challenges, and Outcomes
No full textRangeland restoration in southern Africa faces complex challenges that require the involvement of diverse social groups to ensure both ecological and social sustainability. This systematic review focuses on the role of social inclusion in rangeland restoration across multiple countries in the region, specifically examining the engagement of marginalized groups such as women, youth, and indigenous communities. We conducted a comprehensive search using the PRISMA approach, utilizing Scopus and other literature sources. Initially, we found 853 articles published between 2000 and 2024, which were subsequently screened down to 20 studies that met stringent inclusion criteria. This review identifies key strategies and outcomes associated with social inclusion in restoration efforts. Our findings reveal that participatory planning, gender-inclusive strategies, indigenous engagement, and capacity building are crucial for gaining community support, promoting social equity, and enhancing ecological resilience. However, challenges such as power dynamics, cultural norms, and resource constraints often impede the full realization of these inclusive practices. Despite these barriers, integrating local and indigenous knowledge and empowering marginalized groups significantly strengthens governance structures and leads to more sustainable restoration outcomes. Our review highlights the necessity of adopting holistic and inclusive approaches in rangeland restoration where social inclusion is not just a component but a central pillar of successful ecological management. It emphasizes the importance of social inclusion in the restoration of communal rangelands in southern Africa and provides insights into the approaches used, challenges faced, and outcomes achieved in incorporating social inclusion in rangeland restoration efforts. Our findings underscore the significance of collaborative efforts and social inclusion among local communities, policymakers, and stakeholders to achieve the sustainable restoration of communal rangelands in southern Africa
Black (Acacia mearnsii) and silver wattle (Acacia dealbata) invasive tree species impact on soil physicochemical properties in South Africa: A systematic literature review
No full textInvasive alien plant species are a problem to global biodiversity, ecosystem dynamics, and human livelihood. The risks and potential effects of invasive alien species on local vegetation are growing, particularly the potential loss of ecological services. Thus, this study aimed to synthesise the impacts of acacia 'species' on soil physicochemical properties in South Africa. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework for conducting a systematic review was followed. A total of 16 studies that met the study selection criteria were used. Data were extracted and evaluated by checking if any soil physicochemical parameters increased (+) or decreased (−) the impacts on invaded and cleared soils. The results showed increased quantities of soil organic carbon, total nitrogen, and gravimetric water content in invaded soil than in cleared soil. Acacia species generally positively improved the soil's physical and chemical properties during their invasion, and some minor changes may occur after their clearance, such as a decrease in cations. The results of this study only explain how acacias affect soil physical and chemical properties in three provinces; therefore, there need to be more studies from other provinces which could have further given insights into a particular region
Effects of Maize Residue Biochar Amendments on Soil Properties and Soil Loss on Acidic Hutton Soil
No full textSoil acidification is a serious challenge and a major cause of declining soil and crop productivity in the Eastern parts of South Africa (SA). An incubation experiment investigated effects of different maize residue biochar rates on selected soil properties and soil loss in acidic Hutton soils. Biochar amendment rates were 0%, 2.5%, 5%, 7.5%, and 10% (soil weight) laid as a completely randomized design. Soil sampling was done on a 20-day interval for 140 days to give a 5 × 7 factorial experiment. Rainfall simulation was conducted at 60, 100 and 140 days after incubation to quantify soil loss. Relative to the control biochar amendments significantly improved soil physicochemical properties. After 140 days, biochar increased soil pH by between 0.34 to 1.51 points, soil organic carbon (SOC) by 2.2% to 2.34%, and microbial activity (MBC) by 496 to 1615 mg kg−1 compared to control. Soil aggregation (MWD) changes varied from 0.58 mm to 0.70 mm for the duration of the trial. Soil loss significantly decreased by 27% to 70% under biochar amendment compared to control. This indicates that maize residue biochar application has the potential to improve the soil properties and reduce soil loss in the degraded acidic Hutton soil
Climate change effects on water footprint of crop production: A meta-analysis
No full textThe impact of climate change on both natural and human systems is becoming increasingly severe. One of the areas that is most affected is agriculture, which is responsible for utilising around 70 % of the planet's freshwater and is also under significant pressure to feed the ever-growing global population. This meta-analysis examined the complex relationships between water footprint and climate change, focusing on the effects of rainfall and temperature changes in different geographical areas. The study used a combination of the following search words: climate change, climate variability, global warming, drought, water footprint, blue water footprint, green water footprint, grey water footprint, crop production, crop yield, crop water footprint, crop water use, water usage, precipitation, rainfall, and temperature. The selection of articles followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram procedure, ultimately including 33 articles that met the study criteria out of the 938 articles initially retrieved. The study's findings indicated that the most influential factors of the water footprint varied globally due to natural and human interference conditions. The findings also indicated that all crops were susceptible to changes in temperatures and rainfall distribution, resulting in a decrease in WFblue, WFgrey, and WFtotal, while WFgreen increased with increasing rainfall and temperatures. Temperature had a notable effect on the WFblue of crops grown in areas that receive limited rainfall. Future research should conduct a meta-analysis on the uncertainty associated with climate change projections and its implications for estimating the water footprint of crop production
PROBING COMPETITIVE NONCOVALENT INTERACTIONS: RESONANCE ENHANCED TWO-PHOTON IONIZATION (R2PI) SPECTROSCOPY OF HALOAROMATIC CLUSTERS
No full textAuthor Institution: Department of Chemistry, Marquette University, Milwaukee, WI 53233Non-covalent interactions in bromobenzene have been studied here using resonance two-photon ionization (R2PI) spectroscopy combined with a linear TOF-mass spectrometer. Bromobenzene clusters were created in a supersonic expansion with helium as a carrier gas. The molecules were excited and ionized from the ground state in a two stage process. The general trend observed in the R2PI spectra of all the clusters is the broadness and a red-shift relative to the monomer absorption. Optimized dimer and trimer structures were calculated at the M06-2x/aug-cc-pVDZ level, which show that -stacked and C-H/ interactions are most important in these clusters. TD-DFT calculations of the different cluster conformers have been carried out to assess the geometry changes active upon electronic excitation. The theoretical studies are helpful in explaining trends observed in the R2PI spectra
