Effect of Moistube and subsurface drip irrigation on cowpea (Vigna unguiculata (l.) Walp) production in South Africa

Moistube irrigation (MTI) is a new subsurface irrigation technology where the water emits from a semipermeable membrane at a slow rate  depending on applied pressure and soil water potential. There is lack of information on how various crops respond to MTI. This study determined growth, yield and water use efficiency (WUE) of cowpea (Vigna unguiculata (L.) Walp) under varying water regimes under MTI and subsurface drip irrigation (SDI), using field and glasshouse experiments in summer and winter of 2018, respectively. A splitplot design arranged in randomized complete blocks, replicated 3 times, with SDI as the control experiment was used. The main plot was irrigation type while the sub-plots were the water regimes. The water treatments consisted of full irrigation (100% of crop water requirement (ETc)), and deficit irrigation (DI) of 70% ETc and40% ETc. Water deficit had a significant effect (p < 0.05) on time to flowering; plants under 40% ETc flowered 14 days earlier than plants at 100% ETc. There were significant (p < 0.05) differences in yield components. Grain yields were 1 280 kg∙ha–1, 2 401 kg∙ha–1 and 3 189 kg∙ha–1 for 40% ETc, 70% ETc and 100% ETc, respectively, but no significant (p > 0.05) differences were recorded between SDI and MTI. However, at 40% ETc, SDI had 15% higher yield than MTI. Biomass varied significantly (p < 0.05) with irrigation type and water treatment. Grain WUE varied significantly (p < 0.05) among the water regimes. The highest WUE was achieved under SDI at 70% ETc but was not significantly different from that under MTI at 70% ETc. In conclusion, performance of cowpea was similar under the two irrigation systems under moderate DI but was better for SDI under severe DI with respect to biomass and WUE for the summer trial. Moderate DI improved the grain WUE while all the DI conditions improved the biomass WUE. Keywords: crop growth deficit irrigation indigenous legume irrigation semi-permeable membrane water use efficiency yiel

Calibration and Evaluation of the FAO AquaCrop Model for Canola (Brassica napus) under Varied Moistube Irrigation Regimes

The AquaCrop model was calibrated and validated for canola (Brassica napus) under Moistube irrigation (MTI) and various water regimes [(i) 100%, (ii) 75%, and (iii) 55% of crop water requirement (ETc)] over two seasons, 2019 and 2020. The normalised root mean square (nRMSE), Model Efficiency (EF), R2, and the Willmot’s index of agreement (d) statistics were used to evaluate the model’s efficiency in simulating biomass (B), canopy cover (CC), yield (Y), and harvest index (HI). The calibration results indicated the model simulated with accuracy the CC (under 100% ETcR2 = 0.99, EF = 0.92, nRMSE = 6.4%, d = 0.98) and 75% ETc (R2 = 0.99, EF = 0.92, nRMSE = 10.3%, d = 0.98). The model simulated CC well for validation for 100% ETc (R2 = 0.97, EF = 0.93, nRMSE = 22.5%, d = 0.98) and 75% ETc (R2 = 0.84, EF = 0.45, nRMSE = 59.2%, d = 0.86) irrigation regimes. Final biomass simulations were reasonably good under 100% ETc, 75% ETc, and 55% ETc irrigation regimes (R2 > 0.90, d > 0.65). The study showed the usefulness of AquaCrop for assessing yield response of canola to full and deficit irrigation scenarios under MTI

Development and Assessment of an Updated Tool for the Design of Soil and Water Conservation Structures in the Sugar Industry of South Africa

Sugarcane in South Africa is grown on wide-ranging soils, sometimes in non-ideal climates and on steep topographies where soils are vulnerable to erosion. Sugarcane fields are protected against erosion through, inter alia, the use of engineered waterways, contour banks and spill-over roads. A comparison of design norms in the National Soil Conservation Manual and norms used in the sugar industry clearly shows discrepancies that need to be investigated. Furthermore, the sugar industry design nomograph was developed based on an unsustainable soil loss limit, does not include any regional variations of climate and the impact on soil erosion and runoff and does not include vulnerability during break cropping. The aim of this research was to develop and assess updated design norms for soil and water conservation structures in the sugar industry of South Africa. The Agricultural Catchments Research Unit (ACRU) model estimates event-based erosion and the ACRU was used to conduct simulations for the different practices in the sugar industry and the outcome used to build the updated tool for the design of soil and water conservation structures in the sugar industry of South Africa, using MS Access with a graphical user interface. The updated tool is robust, based on sustainable soil loss limits, includes regional variations of climate and their impact on soil erosion and runoff and also includes vulnerability during break cropping. It is more representative of conditions in the sugar industry of South Africa and therefore recommended for use in place of the current sugar industry design norms

A geospatial web-based integrative analytical tool for the water-energy-food nexus: the iWEF 1.0

Introduction The water-energy-food (WEF) nexus has evolved into an important transformative approach for facilitating the timely identification of trade-offs and synergies between interlinked sectors for informed intervention and decision-making. However, there is a growing need for a WEF nexus tool to support decision-making on integrated resources management toward sustainable development. Methods This study developed a geospatial web-based integrative analytical tool for the WEF nexus (the iWEF) to support integrated assessment of WEF resources to support resilience building and adaptation initiatives and strategies. The tool uses the Analytic Hierarchy Process (AHP) to establish numerical correlations among WEF nexus indicators and pillars, mainly availability, productivity, accessibility, and sufficiency. The tool was calibrated and validated with existing tools and data at varying spatio-temporal scales. Results The results indicate the applicability of the tool at any spatial scale, highlighting the moderate sustainability in the management of WEF resources at various scales. The developed iWEF tool has improved the existing integrative WEF nexus analytical tool in terms of processing time and providing geospatial capabilities. Discussion The iWEF tool is a digital platform that automatically guides policy and decision-making in managing risk from trade-offs and enhancing synergies holistically. It is developed to support policy and decision-making on timely interventions in priority areas that could be showing signs of stress

Assessing Progress towards Sustainable Development Goals through Nexus Planning

Sustainable Development Goals (SDGs) acknowledge the inter-linkages between human wellbeing, economic prosperity, and a healthy environment and, hence, are associated with a wide range of topical issues that include the securities of water, energy and food resources, poverty eradication, economic development, climate change, health, among others. As SDGs are assessed through targets to be achieved by 2030 and monitored through measurable indicators, this study applied the nexus planning model to monitor and evaluate progress towards SDGs using South Africa as a case study. The study highlighted pathways to ensure socio-ecological sustainability and environmental health by establishing the connectivity between SDGs and nexus approaches. The linkages between SDGs and nexus planning facilitated the sustainable management of resources in an integrated manner. They addressed the cross-sectoral synergies, value-addition, and trade-offs within interlinked sectors. The connectedness of current challenges facing humankind (climate change, rapid urbanisation, migration, and the emergence of novel infectious diseases) require transformative approaches that address these cross-cutting challenges holistically. Managing the intricate relationships between distinct but interconnected sectors through nexus planning has provided decision support tools to formulate coherent strategies that drive resilience and sustainability. The established linkages between nexus planning and SDGs have strengthened cross-sectoral collaboration and unpacked measures for cooperative governance and management through evidence-based interventions. As food production, water provision, and energy accessibility are the major socio-economic and environmental issues currently attracting global attention; the methodology promotes attaining sustainability by 2030

L2: Reworked Project proposal-Small-scale Water Infrastructure

The Limpopo Basin is prone to frequent droughts and short season rainfall making agricultural production a very risky enterprise. The need assist to farmers and rural communities to optimize the utilization of low rainwater and existing SWI to boost agricultural productivity, standard of living and reduce poverty. A multi-level participatory approach shall be used to assess the causes of the SWIs failure in all the four basin countries. Rehabilitation guidelines which shall consider governance, institutional issues, technical, environmental compliance issues and multiple use systems (MUS) shall be produced by a team of multi-disciplinary experts. Additionally, the study shall explore alternative design approaches of new SWIs that will support multiple use systems (small-scale cash crop irrigation schemes, domestic use, livestock watering, aquaculture, rural industries, etc), improve livelihood of the rural community, improved food security and nutritional requirements for children and women. Field trials and demonstrations of rain water harvesting (RWH) techniques shall be done with the utmost cooperation of the farming community as a way of empowering them, fostering ownership and ultimate adoption of the recommended technologie

Aquaponics in South Africa: Results of a national survey

Aquaponic system is a productive, innovative and sustainable fish and vegetable production system that could contribute to the needed innovation in agriculture in the face of drought, soil pollution and climate change. Aquaponics are still an emerging practice worldwide, but particularly in South Africa. This study was conducted in 2016 using an online survey questionnaire to collect information about the types of systems used, the management and distribution of aquaponics in South Africa. A total of 44 responses were captured within three months. The most commonly raised fish was tilapia (82%). The most commonly raised plants were leafy vegetables (75%). Since aquaponics is still not practiced by many and aquaponics systems are mostly small, aquaponics in South Africa can be considered an emerging practice. Most of the current aquaponics practitioners have limited aquaponics production knowledge. We therefore conclude that attention should be paid to raising the awareness about the potential of aquaponics, and raising the technological knowledge of aquaponics operators to increase the number of aquaponics operations and to increase the total amount of food produced in and with aquaponics. Keywords: Aquaponics, Leafy vegetables, Tilapia, Small system

Towards integrated water resource management: a conceptual framework

A workshop paper on integrated water resource management in Zimbabwe.This chapter suggests that integrated water resource management debate needs to be taken beyond its prima facie grounds if the concept is to yield fruit. According to the Collins Concise Dictionary Plus, integrate means to make or be made into a whole. If this is applied to the subject at hand, the question becomes what constitutes integrated water resource management? Stated differently, what exactly is being integrated in integrated water resource management? The task of the chapter is not just to argue for integrated water resource management but to sketch a conceptual framework. A conceptual framework can be regarded as a template incorporating (a set of) ideas about how a subject can be visualized and operationalized. A useful conceptual framework, we suggest, needs to come to grips with both theoretical and practical issues.Special thanks are due to the Netherlands Organization for International Cooperation in Higher Education (NUFFIC), The Hague, for providing financial support towards the hosting of the workshop upon which this book is based. NUFFIC also met part of the publication costs. The two coordinating committees of the Zimbabwe Programme on Women, Extension, Sociology and Irrigation (ZIMWESI), a NUFFIC-funded inter-university exchange programme in research and training between the University of Zimbabwe and Wageningen Agricultural University deserve special mention for the moral support they gave us