Field quantification of the water footprint of an apple orchard, and extrapolation to watershed scale within a winter rainfall Mediterranean climate zone

Gush, Mark B; Dzikiti, Sebinasi; Laan, M. van der; Steyn, Michael; Manamathela, Sibongile Amelia; Pienaar, Harrison

doi:10.1016/j.agrformet.2019.02.042

Cited by 22 publications

(12 citation statements)

References 29 publications

(37 reference statements)

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“…The study assessed the rural livelihoods, health and wellbeing of the population in South Africa using a WEF nexus analytical livelihoods model from a complex systems perspective [91] Gush M…”

Section: Referencesmentioning

confidence: 99%

A Review of the Water–Energy–Food Nexus Research in Africa

Botai

Ncongwane

et al. 2021

Sustainability

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Notwithstanding the dispersed nature of the water, energy and food (WEF) nexus scholarship in the African continent, its strategic importance to the African agenda has gained widespread attention in research and planning circles. In this regard, the bibliometric science mapping and content analysis of the WEF nexus scientific publication trends, the conceptual, intellectual and social structures, as well as the inherent paradigmatic shifts in the WEF nexus body of knowledge in the African continent have been undertaken, using the nexus body of literature accessed from the Web of Science and Scopus core collection databases. The review results confirmed that, whilst the WEF nexus scholarship has expanded since 2013, there is also evidence of growth in the conceptual, intellectual and social structures of the WEF nexus in the African continent. These shifts have resulted in the emergence of hot topics (subfields) including modelling and optimization, climate variability and change, environmental ecosystem services sustainability, and sustainable development and livelihoods. The review further determined that these structures have evolved along two main perspectives of WEF nexus research development, i.e., the interdisciplinary and transdisciplinary domains. In support of the interpretation of the visual analytics of the intellectual structure and changing patterns of the WEF nexus research, the shifts in positivist, interpretivist and pragmatic paradigmatic perspectives (these are underpinned by the ontology, epistemology, and methodology and methods) are considered when explaining WEF nexus research shifts: (a) From the unconnected silo paradigms that focus on water, energy and food (security concerns) to interconnected (and sometimes interdependent or nested) linkages or systems incorporating environmental, social-economic and political drivers (also viewed as subfields) in a bid to holistically support the Sustainable Development Goals (SDGs) across the African continent; and (b) in the evaluation of the WEF nexus scholarship based on novel analytical approaches. We contend that whilst the theories of science change underpin this apparent expansion, the macro-economic theory will find use in explaining how the WEF nexus research agenda is negotiated and the Integrative Environmental Governance (IEG) is the duly suited governance theory to bridge the inherent disconnect between WEF nexus output and governance processes uncovered in the literature. Overall, operational challenges and opportunities of the WEF nexus abound, transitioning the WEF nexus research to practice in Africa, motivating the need to take advantage of the scholar–practitioner research underpinnings, as contemplated in the transdisciplinary research approach, which is characterised by the dual quest for new knowledge and considerations of use. Yet, there is need for more coordinated and collaborative research to achieve impact and transition from WEF nexus thinking to WEF nexus practice.

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Section: Referencesmentioning

confidence: 99%

A Review of the Water–Energy–Food Nexus Research in Africa

Botai

Ncongwane

et al. 2021

Sustainability

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“…2013). Yet the available water resources are already fully allocated in more than 80% of the catchments across the country (Gush et al, 2019). For this reason, it is essential that major water users e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, all the fruit are grown under irrigation yet water resources in the country are under great strain. The Western Cape region, for example, is projected to experience severe water shortages in future due to rising competition between irrigated agriculture, increasing industrial activities, and the rapidly growing population of the Cape Town Metropolitan (Dzikiti et al, 2018a;Gush et al, 2019). Climate change is also projected to exacerbate the water problems by increasing the frequency and severity of droughts and extreme weather events in the region (Midgley and Lotze, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Sustainable management of irrigation requires accurate quantitative information on evapotranspiration (ET) which is the second largest water balance component in orchards (Villalobos et al, 2013). Many studies have quantified ET in apple orchards (Gush et al, 2019;Gush and Taylor, 2014;Li et al, 2007;Mobe et al, 2020;Ntshidi et al, 2018;Volschenk, 2017;Zanotelli et al, 2019). Besides the work by Li et al (2007) and Wang and Wang (2017), few studies have investigated, in detail, the partitioning of evapotranspiration into its constituent components in apple orchards of varying age groups.…”

Section: Introductionmentioning

confidence: 99%

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Contribution of understorey vegetation to evapotranspiration partitioning in apple orchards under Mediterranean climatic conditions in South Africa

Ntshidi

Dzikiti

Mazvimavi

et al. 2021

Agricultural Water Management

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Orchard evapotranspiration (ET) is a complex flux which has been the subject of many studies. It often includes transpiration from the trees, cover crops and weeds, evaporation from the soil, mulches and other orchard artefacts. In this study we investigated the contribution of the orchard floor evaporative fluxes to whole orchard ET focusing on the transpiration dynamics of understorey vegetation which is currently not well known. Data on the partitioning of ET into its constituent components were collected in apple (Malus Domestica Bork) orchards with varying fractional canopy cover. The study orchards were in the prime apple growing regions in South Africa. The orchards were planted to the Golden Delicious/Reinders and the red cultivars (i.e. Cripps' Pink/ Royal Gala/ Fuji). Tree transpiration was quantified using the heat ratio method and the thermal dissipation sap flow techniques. Understorey transpiration was measured at selected intervals using micro stem heat balance sap flow gauges calibrated against infrared gas analyser readings. Orchard ET was measured using an open path eddy covariance system while the microclimate, radiation interception, and soil evaporation were also monitored. Orchard floor evaporative fluxes accounted for as much as 80% of the measured ET in young orchards with dense understorey vegetation that covered most of the orchard floor. In these orchards the understorey transpiration was of the same order of magnitude as the bare moist soil evaporation suggesting that water use by the understorey vegetation was substantial. However, in mature orchards with a high canopy cover (>55% fractional cover), orchard floor water losses were less than 30% of the measured ET. Understorey transpiration rates were much lower, contributing less than 10% of the whole orchard ET. Significant volumes of water can be saved, especially in young orchards, by keeping the orchard floor vegetation short, reducing the area occupied by understorey vegetation, and by reducing the wetted ground surface area.

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“…There therefore, is a need to identify and adopt effective irrigation management strategies that increase the water productivity, i.e. producing more fruit per unit volume of water used (Gush et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Modelling water utilization patterns in apple orchards with varying canopy sizes and different growth stages in semi-arid environments

Mobe

Dzikiti

Dube

et al. 2021

Scientia Horticulturae

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Accurate estimates of orchard evapotranspiration (ET) and its components are important for precise irrigation scheduling, irrigation system designs, and optimal on-farm water allocation particularly in water-limited environments. Direct measurements of ET remain costly, laborious and sometimes difficult to apply over heterogeneous surfaces such as crop fields. Therefore, accurate crop water-use models are required for on-farm precise water resources management. In this study, we adopted and improved the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model developed by Fisher et al 2008 to estimate crop water use across different apple plants. Specifically, the model was developed to quantify the partitioning of apple orchard water use into beneficial (tree transpiration) and non-beneficial water use (orchard floor evaporation) as influenced by tree canopy cover. Data were collected in twelve orchards spread across key apple producing regions in the Western Cape Province of South Africa over three growing seasons (2014/15, 2015/16, 2016/17). Model ET estimates were tested against ET data measured; using the eddy covariance method and transpiration measured based on sap flow monitoring techniques. The results showed that the original Fisher PT-JPL model performed poorly in ET estimation across all the orchards under study. The model yielded lower R 2 , ranging from 0.02 to 0.64 and Nash-Sutcliffe Efficiency (NSE) from -10.93 to 0.20. Thus, we subsequently improved the model by incorporating soil moisture and vapour pressure deficit stress factors and by introducing a variable Priestley and Taylor coefficient (α). The modified PT-JPL model demonstrated an improvement in ET estimates. The root mean square of error (RMSE) of the estimated daily ET varied from ±0.60 mm/d to ±1.99 mm/d whereas the mean absolute error (MAE) varied from ±0.49 mm/d to ±1.91 mm/d, while the R 2 varied from 0.54 to 0.75 in orchards with varying canopy cover. The findings of this work underscore the utility of the modified PT-JPL model for estimating ET and its components in apple orchards from planting until the trees reach full-bearing age.

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Field quantification of the water footprint of an apple orchard, and extrapolation to watershed scale within a winter rainfall Mediterranean climate zone

Cited by 22 publications

References 29 publications

A Review of the Water–Energy–Food Nexus Research in Africa

A Review of the Water–Energy–Food Nexus Research in Africa

Contribution of understorey vegetation to evapotranspiration partitioning in apple orchards under Mediterranean climatic conditions in South Africa

Modelling water utilization patterns in apple orchards with varying canopy sizes and different growth stages in semi-arid environments

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