| 1. |
- Aboulila, Tarek Selim, et al.
(author)
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Influence of geometric design of alternate partial root-zone subsurface drip irrigation (APRSDI) with brackish water on soil moisture and salinity distribution
- 2012
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In: Agricultural Water Management. - : Elsevier BV. - 1873-2283 .- 0378-3774. ; 103, s. 182-190
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Journal article (peer-reviewed)abstract
- In alternate partial root-zone irrigation (APRI) a significant amount of irrigation water can be saved without considerable yield reduction. In this paper, Hydrus-2D/3D was used to investigate the impact of geometric design of alternate partial root-zone subsurface drip irrigation (APRSDI) with brackish water for growing tomato on soil moisture and salinity distribution. Three inter-plant emitter distances (IPED; 20, 30, and 40 cm), two emitter depths (10 and 20 cm), and three irrigation water salinity levels (0, 1, and 2 dS m-1) were used to implement the proposed simulation scenarios in loamy sand soil during a 40-day simulation period. The simulation results showed that higher soil moisture content was found beneath the plant trunk in case of 20 cm (short IPED) and near the domain border in case of 30 and 40 cm IPED. Short IPED guarantees more water in the maximum root density zone. A deeper wetting front occurred for deep emitter depth, while the wetting front reached the soil surface for shallow emitter depth. Salinity results revealed that as irrigation water salinity increased, the salinity in the top soil increased. In addition, the salinity at the soil surface increased as IPED and emitter depth increased. Higher root water uptake rates were recorded in the case of 20 cm IPED while the emitter depth did not show any considerable effect on root water uptake rates. Moreover, the applied irrigation water was fully consumed by the plant in case of short IPED. Emitter depth and salinity of irrigation water had negligible effect on amount of irrigation water extracted by plant roots and percolated amount below the bottom boundary of the flow domain. Overall, short IPED is recommended in APRSDI with or without brackish irrigation water regardless of the emitter depth.
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| 2. |
- Andersson, Jafet C. M., et al.
(author)
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Potential impacts of water harvesting and ecological sanitation on crop yield, evaporation and river flow regimes in the Thukela River basin, South Africa
- 2011
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In: Agricultural Water Management. - : Elsevier BV. - 0378-3774 .- 1873-2283. ; 98:7, s. 1113-1124
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Barron, Jennie, et al.
(author)
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Run-off water harvesting for dry spell mitigation in maize (Zea mays L.) : results from on-farm research in semi-arid Kenya
- 2005
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In: Agricultural Water Management. - : Elsevier BV. - 0378-3774 .- 1873-2283. ; 74:1, s. 1-21
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Campana, Pietro Elia, 1984-, et al.
(author)
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Towards an operational irrigation management system for Sweden with a water–food–energy nexus perspective
- 2022
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In: Agricultural Water Management. - : Elsevier B.V.. - 0378-3774 .- 1873-2283. ; 271
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Journal article (peer-reviewed)abstract
- The 2018 drought in Sweden prompted questions about climate-adaptation and -mitigation measures – especially in the agricultural sector, which suffered the most. This study applies a water–food–energy nexus modelling framework to evaluate drought impacts on irrigation and agriculture in Sweden using 2018 and 2019 as case studies. A previous water–food–energy nexus model was updated to facilitate an investigation of the benefits of data-driven irrigation scheduling as compared to existing irrigation guidelines. Moreover, the benefits of assimilating earth observation data in the crop model have been explored. The assimilation of leaf area index data from the Copernicus Global Land Service improves the crop yield estimation as compared to default crop model parameters. The results show that the irrigation water productivities of the proposed model are measurably improved compared to conventional and static irrigation guidelines for both 2018 and 2019. This is mostly due to the advantage of the proposed model in providing evapotranspiration in cultural condition (ETc)-driven guidelines by using spatially explicit data generated by mesoscale models from the Swedish Meteorological and Hydrological Institute. During the drought year 2018, the developed model showed no irrigation water savings as compared to irrigation scenarios based on conventional irrigation guidelines. Nevertheless, the crop yield increase from the proposed irrigation management system varied between 10% and 60% as compared to conventional irrigation scenarios. During a normal year, the proposed irrigation management system leads to significant water savings as compared to conventional irrigation guidelines. The modelling results show that temperature stress during the 2018 drought also played a key role in reducing crop yields, with yield reductions of up to 30%. From a water–food–energy nexus, this motivates the implementation of new technologies to reduce water and temperature stress to mitigate likely negative effects of climate change and extremes. By using an open-source package for Google Earth®, a demonstrator of cost-effective visualization platform is developed for helping farmers, and water- and energy-management agencies to better understand the connections between water and energy use, and food production. This can be significant, especially during the occurrence of extreme events, but also to adapt to the negative effects on agricultural production of climate changes.
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| 5. |
- Caretta, Martina Angela, 1986-
(author)
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Managing variability and scarcity. An analysis of Engaruka : A Maasai smallholder irrigation farming community
- 2015
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In: Agricultural Water Management. - : Elsevier BV. - 0378-3774 .- 1873-2283. ; 159, s. 318-330
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Journal article (peer-reviewed)abstract
- 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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| 6. |
- Carotti, Laura, et al.
(author)
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Improving water use efficiency in vertical farming: Effects of growing systems, far-red radiation and planting density on lettuce cultivation
- 2023
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In: Agricultural Water Management. - Stockholm : IVL Svenska Miljöinstitutet AB. - 0378-3774 .- 1873-2283. ; 285, s. 108365-108365
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Journal article (peer-reviewed)abstract
- Vertical farms (VFs) are innovative urban production facilities consisting of multi-level indoor systems equipped with artificial lighting in which all the environmental conditions are controlled independently from the external climate. VFs are generally provided with a closed loop fertigation system to optimize the use of water and nutrients. The objective of this study, performed within an experimental VF at the University of Bologna, was to quantify the water use efficiency (WUE, ratio between plant fresh weight and the volume of water used) for a lettuce (Lactuca sativa L.) growth cycle obtained in two different growing systems: an ebb-and-flow substrate culture and a high pressure aeroponic system.Considering the total water consumed (water used for irrigation and climate management), WUE of ebb-and-flow and aeroponics was 28.1 and 52.9 g L−1 H2O, respectively. During the growing cycle, the contribution generated by the recovery of internal air moisture from the heating, ventilation and air conditioning (HVAC) system, was quantified. Indeed, by recovering water from the dehumidifier, water use decreases dramatically (by 67 %), while WUE increased by 206 %. Further improvement of WUE in the ebb-and-flow system was obtained through ameliorated crop management strategies, in particular, by increasing planting densities (e.g., 153, 270 and 733 plants m−2) and by optimizing the light spectrum used for plant growth (e.g., adjusting the amount of far-red radiation in the spectrum). Strategies for efficient use of water in high-tech urban indoor growing systems are therefore proposed.
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| 7. |
- Elfman, Lena, et al.
(author)
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Detection of pesticides used in rice cultivation in streams on the island of Leyte in the Philippines
- 2011
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In: Agricultural Water Management. - : Elsevier BV. - 0378-3774 .- 1873-2283. ; 101:1, s. 81-87
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Journal article (peer-reviewed)abstract
- Targeted sampling of water was performed in streams, the river mouth, and the municipal drinking-water tap in the vicinity of San Francisco, South Leyte, Philippines. Samples were processed on site and transported back to Sweden for analysis by gas chromatography mass spectrometry to identify and quantify the pesticides commonly used in the area. Collaborations were initiated with employees at the local Department of Agriculture and Municipal Disaster Coordinating Council to learn more about the rice cultivation in this area and times for spraying. Detectable levels of pesticides λ-cyhalothrin, cypermethrin and deltamethrin (0.0005–1.4 μg/L) were found in representative water samples. In 47% of samples the detected levels exceeded the recommended limit values for pesticides in surface water according to Swedish guidelines (Swedish Chemicals Agency, 2008). The analysis of samples taken at the river mouth revealed measurable levels of λ-cyhalothrin and cypermethrin, which means that residues of pesticides applied to rice paddy fields were shown to end up at the river mouth. The success of the sampling and analysis methods was confirmed by the data which was in accordance with the expected effect of dilution from day to day. Variable levels of insecticides in the river and all the way down to the sea may have adverse health effects on people using the water and on the aquatic environment, including sensitive coral reefs. This situation is applicable not only to the Philippines, but also to the whole of Southeast Asia, with approximately 70% of their human population living in coastal areas. As Southeast Asia encompasses approximately 34% of the world's coral reefs and between a quarter and a third of the world's mangroves, as well as the global biodiversity triangle formed by the Malay Peninsula, the Philippines, and New Guinea, the need to reduce the impacts of marine pollution in this region is of great importance.
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| 8. |
- Enfors, Elin, 1978-, et al.
(author)
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Yield and soil system changes from conservation tillage in dryland farming : A case study from North Eastern Tanzania
- 2011
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In: Agricultural Water Management. - : Elsevier BV. - 0378-3774 .- 1873-2283. ; 98:11, s. 1687-1695
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Gordon, Line J., et al.
(author)
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Managing water in agriculture for food production and other ecosystem services
- 2010
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In: Agricultural Water Management. - : Elsevier BV. - 0378-3774 .- 1873-2283. ; 97:4, s. 512-519
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Journal article (peer-reviewed)abstract
- 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.
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| 10. |
- Karlberg, Louise, et al.
(author)
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Low-cost drip irrigation of tomatoes using saline water: a suitable technology for southern Africa?
- 2007
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In: Agricultural Water Management. - : Elsevier BV. - 0378-3774 .- 1873-2283. ; 89:1-2, s. 59-70
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Journal article (peer-reviewed)abstract
- Using saline water for. irrigation increases water productivity by freeing up fresh water that can be allocated to domestic or other uses. Drip irrigation is widely regarded as the most promising irrigation system in combination with saline water. Simple drip irrigation kits that are affordable for smallholder farmers have successfully been implemented for irrigation of vegetable gardens in several countries in sub-Saharan Africa. The possibility of using low-cost drip irrigation with saline water to successfully irrigate a common garden crop, tomatoes, was tested in this study. Two low-cost drip irrigation systems with different emitter discharge rates (0.2 and 2.5 1 h(-2)) were used to irrigate tomatoes (Lycopersicon esculentum Mill. cv. "Daniella") with water of three different salinity levels (0, 3 and 6 dS m(-1)). In addition, plastic mulch to minimise soil evaporation was also compared to a "bare soil" or uncovered treatment. Two consecutive tomato crops (spring and autumn) were produced during two growing seasons, starting from September 2003 and ending in April 2004, at the Hatfield Experimental Farm in Pretoria, South Africa. An average yield of 75 Mg ha(-1) was recorded for all treatments and seasons, which can be compared with the average marketable yield for South Africa of approximately 31.4 Mg ha(-1). Even at the highest irrigation water salinity (6 dS m(-1)), a yield above the average marketable yield was achieved, indicating that low-cost drip irrigation works well in combination with saline water. Furthermore, the study showed that the choice of drip irrigation system with regard to discharge rate is of minor importance when irrigating with saline water. However, combining low-cost drip irrigation with plastic mulch increased the yield by on average 10 Mg ha(-1) for all treatments. For the bare soil treatments, rainfall had an important role in the leaching of salts from the soils. Finally, the study showed that specific leaf area was higher at high irrigation water salinities, which is contrary to results from other studies. To be able to generalise the promising findings from this study, there is a need to mechanistically model the impact of different climates, soils and irrigation management practices, as well as the long-term sustainability of these systems.
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