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  • 1. Andersson, Jafet C. M.
    et al.
    Zehnder, Alexander J. B.
    Rockström, Johan
    Stockholms universitet, Stockholm Resilience Centre.
    Yang, Hong
    Potential impacts of water harvesting and ecological sanitation on crop yield, evaporation and river flow regimes in the Thukela River basin, South Africa2011Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 98, nr 7, s. 1113-1124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study we explore the potential impacts of two strategies, namely in situ water harvesting (in situ WH) and fertilisation with stored human urine (Ecosan), to increase the water and nutrient availability in rain-fed smallholder agriculture in South Africa's Thukela River basin (29,000 km(2)). We use the soil and water assessment tool (SWAT) to simulate potential impacts on smallholder maize yields, river flow regimes, plant transpiration, and soil and canopy evaporation during 1997-2006. Based on the results, the impacts on maize yields are likely to be small with in situ WH (median change: 0%) but significant with Ecosan (median increase: 30%). The primary causes for these effects are high nitrogen stress on crop growth, and low or untimed soil moisture enhancement with in situ WH. However, the impacts vary significantly in time and space, occasionally resulting in yield increases of up to 40% with in situ WH. Soil fertility improvements primarily increase yield magnitudes, whereas soil moisture enhancements reduce spatial yield variability. Ecosan significantly improves the productivity of the evaporative fluxes by increasing transpiration (median: 2.8%, 4.7 mm season(-1)) and reducing soil and canopy evaporation (median: -1.7%, -4.5 mm season(-1)). In situ WH does not generally affect the river flow regimes. Occasionally, significant regime changes occur due to enhanced lateral and shallow aquifer return flows. This leads to higher risks of flooding in some areas, but also to enhanced low flows, which help sustain aquatic ecosystems in the basin.

  • 2.
    Barron, Jennie
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för systemekologi.
    Okwach, G
    Run-off water harvesting for dry spell mitigation in maize (Zea mays L.): results from on-farm research in semi-arid Kenya2005Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 74, nr 1, s. 1-21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Maize (Zea mays L.) yields obtained by small-holder farmers in semi-arid zones in sub-Sahara Africa (SSA) are often less than half of potential yields. Water deficit during critical crop growth stages together with low nutrient input interacts to reduce yields. Collection of surface run-off, which could be used as supplemental irrigation may prove beneficial in improving current small-holder farming system in SSA. This paper presents the results of an on-farm study of the effects of supplemental irrigation (SI) on maize yield in semi-arid Kenya. Surface run-off from a catchment of 2.7 ha was harvested in a hand-dug earth dam of 300 m2. The water was supplied by gravity to mitigate dry spells in fertilized (SI30, SI80 kg N ha−1) and non-fertilized (SI0 kg N ha−1) maize. Treatments of SI were compared to non-irrigated treatments (NI80, NI30, NI0 kg N ha−1). Rainfall varied, during the five seasons of study, from 196 to 564 mm. The volume of water harvested in the dam ranged between 1% and 4% of seasonal rainfall. The outtake for supplemental irrigation varied between 20 and 240 mm per season. Seepage losses accounted for 11 to 74% of harvested dam water. Lowest maize yields were in NI0, representing farmers’ current practise. SI with fertilizer increased yields compared to non-irrigated and fertilised treatments (NI30, NI80) for low rainfall seasons (<300 mm). High rainfall seasons (>300 mm) resulted in no yield increase for SI compared to NI. Mean seasonal grain yield for SI and fertilizer (30 or 80 kg N ha−1) of 1796 kg ha−1 was significantly higher (P < 0.001) than NI0 kg N ha−1 of 1319 kg ha−1, and higher than SI0 kg N ha−1 and NI30 kg N ha−1 (P < 0.01). Lowest average rain and irrigation water use efficiency (RUE, kg grain mm−1 ha−1) was for NI0 with RUE = 2.1, and highest for SI30 with RUE = 4.1. Water harvesting of surface run-off added as SI resulted in improved maize yields as a result of dry spell mitigation, but only in combination with N fertilizer. To upgrade on-farm water management in semi-arid SSA, the results suggest that supplemental irrigation combined with fertilizer may reduce the currently existing yield gap in small-holder farming systems.

  • 3.
    Caretta, Martina Angela
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Kulturgeografiska institutionen.
    Managing variability and scarcity. An analysis of Engaruka: A Maasai smallholder irrigation farming community2015Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 159, s. 318-330Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article examines the common-pool regime of Engaruka, a smallholder irrigation farming community in northern Tanzania. Irrigation is a complex issue due to water asymmetry. Water use is regulated in Engaruka through boundary, allocation, input and penalty rules by a users’ association that controls and negotiates water allocation to avoid conflicts among headenders and tailenders. As different crops – maize and beans, bananas and vegetables – are cultivated, different watering schemes are applied depending on the water requirements of every single crop. Farmers benefit from different irrigation schedules and from different soil characteristics through having their plots both downstream and upstream. In fact, depending on water supply, cultivation is resourcefully extended and retracted. Engaruka is an ethnically homogeneous and interdependent community where headenders and tailenders are often the same people and are hence inhibited to carry out unilateral action. Drawing on common-pool resource literature, this study argues that in a context of population pressure alongside limited and fluctuating water availability, non-equilibrium behavior, consisting in negotiating water rights and modifying irrigation area continuously through demand management, is crucial for the satisfaction of basic and productive needs and for the avoidance of water conflicts.

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  • 4.
    Enfors, Elin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Systemekologiska institutionen. Stockholms universitet, Stockholm Resilience Centre.
    Barron, Jennie
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Makurira, Hodson
    University of Zimbabwe.
    Rockström, Johan
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Tumbo, Siza
    Sokoine University of Agriuclture.
    Yield and soil system changes from conservation tillage in dryland farming: A case study from North Eastern Tanzania2011Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 98, nr 11, s. 1687-1695Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Yield levels in smallholder farming systems in semi-arid sub-Saharan Africa are generally low. Water shortage in the root zone during critical crop development stages is a fundamental constraining factor. While there is ample evidence to show that conservation tillage can promote soil health, it has recently been suggested that the main benefit in semi-arid farming systems may in fact be an in situ water harvesting effect. In this paper we present the result from an on-farm conservation tillage experiment (combining ripping with mulch and manure application) that was carried out in northeastern Tanzania from 2005 to 2008, testing this hypothesis. Special attention was given to the effects on the water retention properties of the soil. The tested conservation treatment only had a clear yield increasing effect during one of the six experimental seasons (maize grain yields increased by 41%, and biomass by 65%), and this was a season that received exceptional amounts of rainfall (549 mm). While the other seasons provided mixed results, there seemed to be an increasing yield gap between the conservation tillage treatment and the control towards the end of the experiment. Regarding soil system changes, small but significant effects on chemical and microbiological properties, but not on physical properties, were observed. This raises questions about the suggested water harvesting effect and its potential to contribute to stabilized yield levels under semi-arid conditions. We conclude that, at least in a shorter time perspective, the tested type of conservation tillage seems to boost productivity during already good seasons, rather than stabilize harvests during poor rainfall seasons. Highlighting the challenges involved in upgrading these farming systems, we discuss the potential contribution of conservation tillage towards improved water availability in the crop root zone in a longer-term perspective.

  • 5.
    Gordon, Line J.
    et al.
    Stockholms universitet, Stockholm Resilience Centre.
    Finlayson, C. Max
    Falkenmark, Malin
    Stockholms universitet, Stockholm Resilience Centre.
    Managing water in agriculture for food production and other ecosystem services2010Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 97, nr 4, s. 512-519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Agricultural systems as well as other ecosystems generate ecosystem services, i.e., societal benefits from ecological processes. These services include, for example, nutrient reduction that leads to water quality improvements in some wetlands and climatic regulation through recycling of precipitation in rain forests. While agriculture has increased ‘provisioning’ ecosystem services, such as food, fiber and timber production, it has, through time, substantially impacted other ecosystem services. Here we review the trade-offs among ecosystem services that have been generated by agriculture-induced changes to water quality and quantity in downstream aquatic systems, wetlands and terrestrial systems. We highlight emerging issues that need urgent attention in research and policy making. We identify three main strategies by which agricultural water management can deal with these large trade-offs: (a) improving water management practices on agricultural lands, (b) better linkage with management of downstream aquatic ecosystems, and (c) paying more attention to how water can be managed to create multifunctional agro-ecosystems. This can only be done if ecological landscape processes are better understood, and the values of ecosystem services other than food production are also recognized.

  • 6. Makurira, H.
    et al.
    Savenije, H.H.G.
    Uhlenbrook, S.
    Rockström, Johan
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Senzanje, A.
    The effect of system innovations on water productivity in subsistence rainfed agricultural systems in semi-arid Tanzania2011Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 98, nr 1, s. 1696-1703Artikel i tidskrift (Refereegranskat)
  • 7. Pourghasemian, Nasibeh
    et al.
    Moradi, Rooholla
    Naghizadeh, Mehdi
    Landberg, Tommy
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Mitigating drought stress in sesame by foliar application of salicylic acid, beeswax waste and licorice extract2020Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 231, artikel-id 105997Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study evaluated the effects of salicylic acid (SA), beeswax waste extract (BWE) and licorice extract (LE) as novel biostimulants, on drought-induced oxidative stress on sesame. The treatments consisted of three drought stress conditions (full irrigation, 90 % field capacity (FC); moderate stress, 60 % FC; and severe stress, 30 % FC) together with four exogenous foliar applications (control, water; LE, 5000 ppm; BWE, 2000 ppm; and SA, 1.5 mM). Plants subjected to drought stress displayed significant reduction in plant height, leaf area index, biological and seed yield, chlorophyll a and b content, quantum efficiency of photosystem II (Fv/Fm), net photosynthetic rate (P-n), stomatal conductance (g(s)), transpiration (T-r) and water use efficiency (WUE). Drought stress stimulated Malondialdehyde (MDA), proline, protein and carotenoid contents, and catalase (CAT), ascorbate peroxidase (APX), Guaiacol peroxidase (GPX) and glutathione reductase (GR) activity, while the exogenous foliar application of substances mitigated the oxidative damages. The alleviated effect of BWE on drought stress was more effective than those of LE and SA. In conclusion, it could be recommended that the application of the natural substances may lead to overcoming the negative effects of drought stress by regulating osmoprotectants content and antioxidant defense system, increasing mineral nutrients in plant organs and adjusting photosynthesis systems; consequently, contributing to improving the sesame productivity.

  • 8.
    Rockström, Johan
    et al.
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Karlberg, Louise
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Wani, S.P.
    Barron, Jennie
    Stockholms universitet, Stockholm Resilience Centre, Stockholm Environment Institute.
    Hatibu, N.
    Managing water in rainfed agriculture: the need for a paradigm shift2010Ingår i: Agricultural Water Management, ISSN 0378-3774, E-ISSN 1873-2283, Vol. 97, nr 4, s. 543-550Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rainfed agriculture plays and will continue to play a dominant role in providing food and livelihoods for an increasing world population. We describe the world's semi-arid and dry sub-humid savannah and steppe regions as global hotspots, in terms of water related constraints to food production, high prevalence of malnourishment and poverty, and rapidly increasing food demands. We argue that major water investments in agriculture are required. In these regions yield gaps are large, not due to lack of water per se, but rather due to inefficient management of water, soils, and crops. An assessment of management options indicates that knowledge exists regarding technologies, management systems, and planning methods. A key strategy is to minimise risk for dry spell induced crop failures, which requires an emphasis on water harvesting systems for supplemental irrigation. Large-scale adoption of water harvesting systems will require a paradigm shift in Integrated Water Resource Management (IWRM), in which rainfall is regarded as the entry point for the governance of freshwater, thus incorporating green water resources (sustaining rainfed agriculture and terrestrial ecosystems) and blue water resources (local runoff). The divide between rainfed and irrigated agriculture needs to be reconsidered in favor of a governance, investment, and management paradigm, which considers all water options in agricultural systems. A new focus is needed on the meso-catchment scale, as opposed to the current focus of IWRM on the basin level and the primary focus of agricultural improvements on the farmer's field. We argue that the catchment scale offers the best opportunities for water investments to build resilience in small-scale agricultural systems and to address trade-offs between water for food and other ecosystem functions and services.

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