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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Tropical deforestation monitoring using Landsat time series and breakpoint detection
Schultz, Michael - \ 2018
University. Promotor(en): Martin Herold, co-promotor(en): Jan Clevers; Jan Verbesselt. - Wageningen : Wageningen University - ISBN 9789463434669 - 132
Meer doen met sla dankzij DNA
Hintum, Theo van - \ 2018

Artikel in Financieel Dagblad (24-03-2018) over samenwerking CGN en BGI (China) door Flip Schultz. Theo van Hintum wordt geinterviewd.

Forest Change and REDD+ Strategies
Avitabile, V. ; Schultz, M. ; Salvini, G. ; Pratihast, A.K. ; Bos, A.B. ; Herold, Nadine ; Manh, Cuong Pham ; Quang, Hien Vu ; Herold, M. - \ 2017
In: Land Use and Climate Change Interactions in Central Vietnam / Nauditt, A., Ribbe, L., Springer Science (Water Resources Development and Management ) - ISBN 9789811026232 - p. 33 - 68.
In recent years the United Nations initiative on Reducing Emissions from Deforestation and forest Degradation (REDD+) program gained increasing attention in the policy arena, representing a valuable incentive for developing countries to take actions to reduce greenhouse gas emissions and at the same time promote sustainable forest management and improve local livelihoods. To design an effective REDD+ implementation plan at the local level it is crucial to make an in-depth analysis of the international and national requirements, analyse the forest change processes and related drivers at sub-national scale, and assess the local management options and constrains to ultimately select the appropriate policy mix and land management interventions. The present chapter first describes the state and historical changes of forests in Vietnam, identifies the direct and underlying drivers of deforestation and forest degradation at national scale, discusses the role of forests for climate change mitigation and indicates the key activities for reducing carbon emissions in Vietnam. Second, the main biophysical parameters and processes are assessed at sub-national scale for the Vu Gia Thu Bon river basin. The land cover and carbon stocks are mapped and quantified for the year 2010 and the land cover change and related carbon emissions are estimated for the period 2001–2010, allowing to model the land cover change and predict deforestation risks until the year 2020. Among the areas at higher risk of deforestation, the Tra Bui commune located in Quang Nam province is selected to design a sub-national REDD+ implementation plan in the third part of the chapter. The plan is based upon an in-depth analysis of the local context and land cover change dynamics, the local drivers of deforestation and a conducted stakeholder involvement process in the commune. Based upon this analysis, the last section provides recommendations about the local land management strategies that could be introduced in the commune and discusses the policy interventions are likely to enable their implementation.
Open land cover from OpenStreetMap and remote sensing
Schultz, Michael ; Voss, Janek ; Auer, Michael ; Carter, Sarah ; Zipf, Alexander - \ 2017
International Journal of applied Earth Observation and Geoinformation 63 (2017). - ISSN 0303-2434 - p. 206 - 213.
OpenStreetMap (OSM) tags were used to produce a global Open Land Cover (OLC) product with fractional data gaps available at osmlanduse.org. Data gaps in the global OLC map were filled for a case study in Heidelberg, Germany using free remote sensing data, which resulted in a land cover (LC) prototype with complete coverage in this area. Sixty tags in the OSM were used to allocate a Corine Land Cover (CLC) level 2 land use classification to 91.8% of the study area, and the remaining gaps were filled with remote sensing data. For this case study, complete are coverage OLC overall accuracy was estimated 87%, which performed better than the CLC product (81% overall accuracy) of 2012. Spatial thematic overlap for the two products was 84%. OLC was in large parts found to be more detailed than CLC, particularly when LC patterns were heterogeneous, and outperformed CLC in the classification of 12 of the 14 classes. Our OLC product represented data created in different periods; 53% of the area was 2011–2016, and 46% of the area was representative of 2016–2017.
Role of reservoir operation in sustainable water supply to Subak irrigation schemes in Yeh Ho River Basin
Yekti, Mawiti Infantri - \ 2017
University. Promotor(en): E. Schultz, co-promotor(en): I. Nyoman Norken; László Hayde. - Leiden : CRC Press/Balkema - ISBN 9781138065437 - 250
irrigation systems - irrigation - water supply - sustainability - basin irrigation - indonesia - rivers - irrigatiesystemen - irrigatie - watervoorziening - duurzaamheid (sustainability) - kombevloeiing - indonesië - rivieren

A Subak irrigation scheme, primarily in Bali, Indonesia concerns an irrigation system of which the construction, operation and management are based on agreed principles of technology, management of agriculture and religious community. Subak systems have been well known since the 9th Century. As a manifestation of the Cultural Landscape of Bali Province the Subak schemes are since June, 2012 included in the World Heritage List of UNESCO. These systems are managed by a Subak Association based on the Tri Hita Karana philosophy - harmony between human beings and God, harmony between people and nature, and harmony between people and people.

The problem of insufficient water in the dry season developed in the Yeh Ho River Basin. Because of this the main objective of this study was to develop an optimal reservoir operation strategy in relation to the water supply of the Subak irrigation schemes, capable to support agricultural productivity at upstream, midstream and downstream level. Based on a Generic Algorithm the RIBASIM model was applied using the dependable 80% of discharge and shifting the start of land preparation. The results provide evidence that the cropping pattern of the fifth scenario results in an overall optimal agriculture production of the Subak schemes. The recoverable flow considered in the river basin scheme model plays an important role in the optimisation. Nevertheless, if a normal hydro-climate occurs, the other scenarios, especially the first scenario, can be applied as well. This reflects the applicability of the Tri Hita Karana philosophy on harmony among people and harmony among people and nature.

The effect of litter size, parity and farrowing duration on placenta expulsion and retention in sows
Björkman, S. ; Oliviero, C. ; Rajala-Schultz, P.J. ; Soede, N.M. ; Peltoniemi, O.A.T. - \ 2017
Theriogenology 92 (2017). - ISSN 0093-691X - p. 36 - 44.
Oxytocin - Parturition - Placenta expulsion - Retained placenta - Sow

The hypothesis was that a prolonged parturition impairs placenta expulsion and can lead to retained placentas in sows. Furthermore, we hypothesized that application of oxytocin around the time of expulsion of the first placental part improves placenta expulsion. We recorded 142 parturitions of 101 Yorkshire x Large White sows. We determined parity, gestation length, number of liveborn and stillborn piglets, farrowing duration (time between first and last piglet) and the outcome variables: number of expelled placental parts, placenta expulsion duration (time between first and last placental part), first placental part expulsion (time between last piglet and first placental part) and last placental part expulsion (time between last piglet and last placental part). The relationship between farrowing duration and each of the outcome variables was investigated using four distinct multivariable models. Use of oxytocin (used in 44 out of 142 parturitions) increased number of expelled placental parts (3.8 ± 0.2 vs. 2.9 ± 0.3; P = 0.035), decreased the placenta expulsion duration (172 ± 44 vs. 328 ± 26 min; P = 0.011) and time of last placental part expulsion (148 ± 48 vs. 300 ± 24 min; P = 0.025). If oxytocin was not used, farrowing duration obeyed a quadratic relationship with the number of expelled placental parts (P = 0.001), placenta expulsion duration (P = 0.002) and time of last placental part expulsion (P = 0.024). If oxytocin was used, number of expelled placental parts was positively associated with number of liveborn piglets (β = 0.2 ± 0.1; P = 0.002) and affected by parity. 5th parity sows expelled more placental parts (4.3 ± 0.4) than 4th (3.2 ± 0.3; P = 0.024) and 3rd parity sows (2.7 ± 0.4; P = 0.008). Furthermore, placenta expulsion duration was positively associated with number of liveborn piglets (β = 18 ± 8 min; P = 0.025). First placental part expulsion was negatively correlated with farrowing duration (β = 0.3 ± 0.1; P = 0.001). Sows that experienced total (no expulsion of placental parts; n = 4) and partial retained placentas (no expulsion of placental parts after birth of the last piglet; n = 4) had longer farrowing durations (1009 ± 275 and 734 ± 136 min) than sows with no retained placentas (369 ± 202 min; P = 0.021 and P = 0.004). The results show that a prolonged parturition impaired and oxytocin improved placenta expulsion in sows. Furthermore, retained placentas occurred in 3–6% of the sows and was correlated with a prolonged parturition.

Critically ill patients demonstrate large interpersonal variation in intestinal microbiota dysregulation : a pilot study
Lankelma, Jacqueline M. ; Vught, Lonneke A. van; Belzer, Clara ; Schultz, Marcus J. ; Poll, Tom van der; Vos, Willem M. de; Wiersinga, W.J. - \ 2017
Intensive Care Medicine 43 (2017)1. - ISSN 0342-4642 - p. 59 - 68.
Antibiotics - Critically ill - Gut microbiota - Intensive care unit - Sepsis

Purpose: The intestinal microbiota has emerged as a virtual organ with essential functions in human physiology. Antibiotic-induced disruption of the microbiota in critically ill patients may have a negative influence on key energy resources and immunity. We set out to characterize the fecal microbiota composition in critically ill patients both with and without sepsis and to explore the use of microbiota-derived markers for clinical outcome measurements in this setting. Methods: In this prospective observational cohort study we analyzed the fecal microbiota of 34 patients admitted to the intensive care unit. Fifteen healthy subjects served as controls. The fecal microbiota was phylogenetically characterized by 16S rRNA gene sequencing, and associations with clinical outcome parameters were evaluated. Results: A marked shift in fecal bacterial composition was seen in all septic and non-septic critically ill patients compared with controls, with extreme interindividual differences. In 13 of the 34 patients, a single bacterial genus made up >50% of the gut microbiota; in 4 patients this was even >75%. A significant decrease in bacterial diversity was observed in half of the patients. No associations were found between microbiota diversity, Firmicutes/Bacteroidetes ratio, or Gram-positive/Gram-negative ratio and outcome measurements such as complications and survival. Conclusions: We observed highly heterogeneous patterns of intestinal microbiota in both septic and non-septic critically ill patients. Nevertheless, some general patterns were observed, including disappearance of bacterial genera with important functions in host metabolism. More detailed knowledge of the short- and long-term health consequences of these major shifts in intestinal bacterial communities is needed.

Carbon emissions from land cover change in Central Vietnam
Avitabile, Valerio ; Schultz, Michael ; Herold, Nadine ; Bruin, Sytze De; Pratihast, Arun Kumar ; Manh, Cuong Pham ; Quang, Hien Vu ; Herold, Martin - \ 2016
Carbon Management 7 (2016)5-6. - ISSN 1758-3004 - p. 333 - 346.
The carbon emissions and removals due to land cover changes between 2001 and 2010 in the Vu Gia Thu Bon River Basin, Central Vietnam, were estimated using Landsat satellite images and 3083 forest inventory plots. The net emissions from above- and belowground vegetation biomass were equal to 1.76 ± 0.12 Tg CO2, about 1.1% of the existing stocks. The vast majority of carbon emissions were due to forest loss, with the conversion of forest to cropland accounting for 67% of net emissions. Forest regrowth had a substantial impact on net carbon changes, removing 22% of emissions from deforestation. Most deforestation occurred in regrowth forest (60%) and plantations (29%), characterized by low carbon stock density. Thus identifying the type of forest where deforestation occurred and using local field data were critical with net emissions being 4 times larger when considering only one forest class with average carbon stock, and 5–7 times higher when using literature default values or global emission maps. Carbon emissions from soil (up to 30 cm) were estimated for the main land change class. Due to the low emission factors from biomass, soils proved a key emission category, accounting for 30% of total land emissions that occurred during the monitoring period.
Performance of vegetation indices from Landsat time series in deforestation monitoring
Schultz, Michael ; Clevers, Jan G.P.W. ; Carter, Sarah ; Verbesselt, Jan ; Avitabile, Valerio ; Quang, Hien Vu ; Herold, Martin - \ 2016
International Journal of applied Earth Observation and Geoinformation 52 (2016). - ISSN 0303-2434 - p. 318 - 327.
The performance of Landsat time series (LTS) of eight vegetation indices (VIs) was assessed for monitoring deforestation across the tropics. Three sites were selected based on differing remote sensing observation frequencies, deforestation drivers and environmental factors. The LTS of each VI was analysed using the Breaks For Additive Season and Trend (BFAST) Monitor method to identify deforestation. A robust reference database was used to evaluate the performance regarding spatial accuracy, sensitivity to observation frequency and combined use of multiple VIs. The canopy cover sensitive Normalized Difference Fraction Index (NDFI) was the most accurate. Among those tested, wetness related VIs (Normalized Difference Moisture Index (NDMI) and the Tasselled Cap wetness (TCw)) were spatially more accurate than greenness related VIs (Normalized Difference Vegetation Index (NDVI) and Tasselled Cap greenness (TCg)). When VIs were fused on feature level, spatial accuracy was improved and overestimation of change reduced. NDVI and NDFI produced the most robust results when observation frequency varies
Error Sources in Deforestation Detection Using BFAST Monitor on Landsat Time Series Across Three Tropical Sites
Schultz, Michael ; Verbesselt, Jan ; Avitabile, Valerio ; Souza, Carlos ; Herold, Martin - \ 2016
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9 (2016)8. - ISSN 1939-1404 - p. 3667 - 3679.
Accurate tropic deforestation monitoring using time series requires methods which can capture gradual to abrupt changes and can account for site-specific properties of the environment and the available data. The generic time series algorithm BFAST Monitor was tested using Landsat time series at three tropical sites. We evaluated the importance of how specific effects of site and radiometric correction affected the accuracy of deforestation monitoring when using BFAST Monitor. Twelve sets of time series of normalized difference vegetation index (NDVI) Landsat data (2000–2013) were analyzed. Time series properties varied according to site (Brazil, Ethiopia, and Vietnam) and which correction scheme was applied: Atmospheric Correction and Haze Reduction 2 and 3 (ATCOR 2 and 3), Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS), or Dark Object Subtraction (DOS). Mapping accuracy was compared using 1200 reference points per site and consistent designs for sampling, analysis (overall accuracy, user’s accuracy, and producer’s accuracy), and response (ground truth and very-high-resolution data). With the exception of DOS, mapping accuracies across correction methods were found to be similar but varied greatly with site. Mapping errors were modeled using a set of error parameters that yielded information on data and site-specific environmental properties. Important parameters for characterizing mapping errors were found to be variance of the NDVI and soil signal as well as availability of time series data, and forest edge effects. Based upon the results, local fine-tuning of the algorithm is essential for some areas but for others default settings create satisfactory accuracies.
Utilizing the global land cover 2000 reference dataset for a comparative accuracy assessment of 1 km global land cover maps
Schultz, M. ; Tsendbazar, N.E. ; Herold, M. ; Jung, A. ; Mayaux, P. ; Goehman, H. - \ 2015
In: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. - ISPRS - p. 503 - 510.
Many investigators use global land cover (GLC) maps for different purposes, such as an input for global climate models. The current
GLC maps used for such purposes are based on different remote sensing data, methodologies and legends. Consequently,
comparison of GLC maps is difficult and information about their relative utility is limited. The objective of this study is to analyse
and compare the thematic accuracies of GLC maps (i.e., IGBP-DISCover, UMD, MODIS, GLC2000 and SYNMAP) at 1 km
resolutions by (a) re-analysing the GLC2000 reference dataset, (b) applying a generalized GLC legend and (c) comparing their
thematic accuracies at different homogeneity levels. The accuracy assessment was based on the GLC2000 reference dataset with
1253 samples that were visually interpreted. The legends of the GLC maps and the reference datasets were harmonized into 11
general land cover classes. There results show that the map accuracy estimates vary up to 10-16% depending on the homogeneity of
the reference point (HRP) for all the GLC maps. An increase of the HRP resulted in higher overall accuracies but reduced accuracy
confidence for the GLC maps due to less number of accountable samples. The overall accuracy of the SYNMAP was the highest at
any HRP level followed by the GLC2000. The overall accuracies of the maps also varied by up to 10% depending on the definition
of agreement between the reference and map categories in heterogeneous landscape. A careful consideration of heterogeneous
landscape is therefore recommended for future accuracy assessments of land cover maps.
* Corresponding author
1. INTRODUCTION
The consistent and continuous observation of land cover is one
of the most important foundations for understanding the Earth’s
environment and ecosystems (Verburg et al., 2011). Currently,
several global land cover datasets (GLC) have been developed
and these datasets are evolving towards higher spatial resolution
(Gong et al., 2013; Mora et al., 2014) . Most GLC maps were
developed by individual groups as one-time efforts and the
subsequent mapping standards reflect the varied interests,
requirements and methodologies of the originating programs
(Herold et al., 2006). These differences of GLC maps and the
effects of their quality on the model outcome are not always
considered when selecting a map as an input for specific
modeling applications (Verburg et al., 2011). Uncertainties of
GLC maps can result in considerable differences in modeling
outcomes (Hibbard et al., 2010; Nakaegawa, 2011; Verburg et
al., 2011).
The accuracies of GLC maps are assessed using independent
validation datasets and regional maps or cross validated against
training datasets. The results of accuracy assessments of
previous maps indicate that overall area-weighted accuracy is
around 70% for the existing GLC maps (Defourny et al., 2012).
However, the use of different approaches in the GLC map
production (e.g., classification scheme, data sources and
algorithms) as well as in validation data collection (e.g.,
sampling scheme, data source and method of reference
classification) raise inconsistency issues and make map
comparisons difficult. Several comparative analyses of land
cover maps were conducted at regional levels
Water productivity of sunflower under different irrigation regimes on Gezira clay soil, Sudan
Elsheikh, E.R.A. - \ 2015
University. Promotor(en): E. Schultz, co-promotor(en): H.S. Adam; A.M. Haile. - Leiden : CRC Press/Balkema - ISBN 9781138029149 - 162
helianthus annuus - zonnebloemen - irrigatie - irrigatiesystemen - watergebruik - waterbeschikbaarheid - sudan - sunflowers - irrigation - irrigation systems - water use - water availability
Impact of improved operation and maintenance on cohesive sediment transport in Gezira Scheme, Sudan
Osman, I.S.E. - \ 2015
University. Promotor(en): E. Schultz, co-promotor(en): A.K. Osman; F.X. Suryadi. - Leiden : CRC Press/Balkema - ISBN 9781138028807 - 183
sediment - geologische sedimentatie - waterbeheer - irrigatiekanalen - irrigatie - irrigatiewater-toedieningsschema - sudan - geological sedimentation - water management - irrigation channels - irrigation - irrigation scheduling
Summary

Efficient operation and maintenance of irrigation schemes are needed for improving the hydraulic performance of the canals, enhancing the crop yields and insuring sustainable production. There is a great need to enhance the researches and for a variety of tools such as water control and regulation equipment, decision support systems, as well as field surveys and valuation techniques. Water management becomes difficult when dealing with sediment transport in irrigation canals. Most of the studies simulate the sediment transport of relatively coarse grain sizes. The sediment problem in irrigation canals becomes more complicated when dealing with cohesive sediment transport. Therefore, more research is needed to enhance the understanding of the behaviour of cohesive sediment transport under a variety of operation conditions.

This study has been carried out in the Gezira Scheme in Sudan. The scheme, which is one of the largest irrigation schemes in the world under a single management, is located in the arid and semi-arid region. The scheme is chosen as a case study since it can act as a model for similar irrigation schemes. The scheme has a total area of 880,000 ha and uses 35% of Sudan’s current allocation of Nile waters. This represents 6 – 7 billion m3 per year. The scheme is irrigated from the Blue Nile River, which is characterized by its high load of fine sediment. The scheme is facing severe sediment accumulation in its irrigation canals, which represents a challenge to those responsible for the operation and maintenance of the canals. Each year large investments are required to maintain and to upgrade the canal system to keep it in an acceptable condition.

A large quantity of cohesive sediment enters the scheme every year. According to previous studies, about 60% of the sediment deposits in the irrigation canals. The sediment accumulation in the canals reduces the canal conveyance capacity, causes irrigation difficulties, creates inequity and inadequate water supply and increases the rate of aquatic weed growth. The sedimentation problems are not only seriously affecting the performance of the irrigation canals, but are also jeopardizing their sustainability, as well as affecting crop production. Two canals in the scheme have been selected to be studied in detail: Zananda Major Canal, which takes water from Gezira Main Canal at 57 km from the offtake at Sennar Dam, and Toman Minor Canal at 12.5 km from the offtake of Zananda Major Canal.

The hypothesis of the study postulates that the operation and maintenance of an irrigation scheme has a major influence on the hydrodynamic behaviour of canals and hence on sediment movement and deposition. The aim of this study was to improve the operation and maintenance procedures for better sediment and water management. This can be achieved through better understanding of the sediment processes in the irrigation canals of the Gezira Scheme and to understand clearly the link between irrigation system operation and resulting system performance in terms of transport of cohesive sediment.

Data collection and field measurements have been conducted during the flood season between June and October in 2011 and 2012. Sediment sampling and water level measurements have been conducted on a daily basis at selected locations. The manually recorded water levels include about 1080 readings per year. In addition about 1290 sediment samples were analysed for different locations during the study period. Cross-sectional surveys have been performed at the beginning and end of the flood season to address the spatial and temporal variation of the sediment deposition in the canals under study and to detect changes in the bed profile. The head regulator and outlet control structures were calibrated by using the measured stage-discharge relationships. More elaboration is given to the properties of cohesive sediment and identification of the dominant factors that cause deposition in irrigation canals. Sediment properties were tested such as grain size distribution, mechanical and physico-chemical properties of the sediment. The irrigation schedules, cropped area and sowing dates for different crops were reported. Other data such as canal design data, historical data of the sediment and flow for certain canals were reviewed.

The analysis of the data indicates a variation of the water level along the canals under study. It should be noted that the operation control in Gezira Scheme is by using upstream control structures. The field data show that the flow release in the system is not regularly adjusted in a systematic way to meet the demand and maintain the required water level. Continuous change in gate setting results in instability of the water level. This situation became worse with more sediment deposition. The water level has been raised far above the design level and there is lapse in working levels especially at the major and minor canals. The rise is found to be about 1.6 and 1.2 m above the design level at the head of the major and minor canals under study. Furthermore, reduction in the water depth has been detected along the canals as result of bed rise and enlarging of canal sections due to improper desilting. The results demonstrate that the supply of water was extremely large during the flood season of 2011 compared to the actual crop water requirement, especially during the period of high sediment concentration. The delivery performance ratio indicated an oversupply at the major canal in 2011 during most of the time. The study also provides some valuable insight into the nature of sediment in Gezira Scheme.

There is a limitation in the existing models that deal with fine sediment transport in irrigation canals. Most of the sediment transport models are developed for estuaries and rivers. Therefore there was a great need to develop a simple but effective numerical model that incorporates control structures to simulate the fine sediment transport in irrigation canals. Although there are similarities between rivers and irrigation canals, irrigation canals are different. The presence of a large number of flow control structures and the high influence of the side banks on the velocity distribution create some differences in both types of channels. Hence, it was important to develop a model dealing with fine sediment in irrigation canals, including different types of hydraulic structures.

In line with this the one dimensional numerical model Fine SEDiment Transport (FSEDT) dealing with fine sediment transport in irrigation canals has been developed. The model has been used as a tool to study the mechanism of water and sediment flow under different operation and maintenance scenarios. The water surface profile has been predicted by using the predictor corrector method to solve the gradually varied flow equation. The prediction of sediment concentration is based on the solution of the one dimensional advection-diffusion equation. The bed material exchange was determined based on the Partheniades (1962) and Krone (1965) equations. The change in bed level was computed based on the sediment mass balance equation that was solved numerically by using the finite difference method. The model has been applied in the Gezira Scheme. On the basis of the field data the model has been calibrated and validated. The predicted bed profiles depict good agreement with the measured ones. The model is capable to predict the bed profile for any period of simulation. The model can predict the sediment concentration hydrograph at different points within a canal reach, in addition to the total volume of the sediment deposition in the reach. The output of the model can be presented in tabular or graphical form.

The sediment transport in the irrigation canals has been simulated by adopting different scenarios. The interrelationship between water flow and sediment transport in the irrigation canals under changing flow conditions has been investigated. Two scenarios of operation were tested at the major canal under study. The model evaluated the indent system that has been applied in Gezira Scheme for many years in regard to sediment deposition. Another proposed scenario based on crop water requirement was also tested. In addition, operation under future changed conditions in case of reduction in the sediment concentration was tested. The different operation scenarios have been compared with the existing condition based on data collected during the flood season in 2011 in terms of sedimentation. Based on this, the following remarks are made:

the effect of varying crest settings of the movable weirs has been investigated and less sediment deposition was found to occur when the crest level was set at its lowest position. The sediment transport in the canals is influenced by the operation of the hydraulic structures, especially upstream of movable weirs. The effect is extended to about 3 km upstream of the weir;

for many years the indent system of water allocation was applied in the Gezira Scheme based on duty and cropped area. However, this system of operation has been absent during the last years. The slope of Zananda Major Canal became 13 cm/km and 18 cm/km for the first and second reaches respectivelycampaigns

the reduction of the water delivery during the period of high concentration between 10 July and 10 August, based on the crop water requirement results in reduction in the sediment deposition by 51 and 55% for the first and second reaches respectively when compared to the situation in 2011;

the reduction of the Blue Nile River sediment concentration by 50% as result of the construction of the Ethiopia Renaissance Dam and/or improvement in the land use has been simulated. The results of the simulation of the suspended sediment transport at the major canal indicate that the deposition will be 74 and 81% lower for the first and second reaches respectively when compared with the situation in 2011.

At the minor canals, the night storage weirs were designed as cross structures. The idea behind the night storage system was to store water during the night by closing all field outlet pipes and the gates of the cross structures along the minor canal at 6:00 pm and releasing them at 6:00 am. Although this system has been vanished to keep pace with crop intensification and to cope with the deterioration of the water supply due to the poor maintenance of the canals, this scenario has also been simulated. The hydrodynamic flow in the canals during the filling time has been simulated by using the DUFLOW model since the model can be applied for unsteady flow. A spreadsheet has been designed to predict the deposition every hour based on the output of the DUFLOW model. The night storage system has been compared with the continuous system regarding the sediment transport in addition to other scenarios. It was found that:

the continuous system reduces the amount of deposited sediment by 55% compared to the night storage system;

about 29% of the sediment was reduced in 2011 when the system was operated based on crop water requirement;

the deposition lightly increased with reduced capacity of the field outlet pipes. The

The main findings and the contributions that are made by this study:

the study comes up with a model dealing with cohesive sediment in irrigation canals for effective sediment and water management, which can be applied widely for similar irrigation schemes dealing with fine sediment;

it is possible to improve the sediment and water management by improving the operation and maintenance. The high irrigation efficiency is tending to mitigate the inflow sediment load and as a consequence less deposition is expected;

the study comes up with strategies of water management that can reduce the deposition in irrigation canals by operating the system continuously based on crop water requirement at the period of high sediment concentration with the field outlet pipes operating at their full capacity.

The absence of proper maintenance activities and water management has a prominent role in increasing the deposition along the irrigation canals in Gezira Scheme. Improving the operation and maintenance is not the only way to mitigate the sedimentation in the irrigation canals. A great consideration needs to be given to improve the design since conditions based on the original design have been changed with time such as the operation system (night storage system, indent system), cropping intensity and geometry of the canals. In other words, rehabilitation of the system will not be one of the solutions to mitigate the accumulation of the deposition along the canals but the system itself needs remodelling. The developed model can be used to assess the new design and to evaluate the proposed management plans in terms of transport of cohesive sediment.

The power of regression to the mean: A social norm study revisited
Verkooijen, K.T. ; Stok, F.M. ; Mollen, S. - \ 2015
European Journal of Social Psychology 45 (2015)4. - ISSN 0046-2772 - p. 417 - 425.
field-experiment - alcohol-use - implementation intentions - descriptive norms - injunctive norms - college-students - peer norms - behavior - drinking - interventions
This research follows up on a study by Schultz et al. (2007), in which the effect of a social norm intervention on energy consumption was examined. The present studies included control groups to examine whether social norm effects would persist beyond regression to the mean. Both studies had a 2 (baseline consumption: below mean versus above mean)¿×¿2 (message condition: no-message control versus norm message) design. Based on baseline fruit (Study 1) or unhealthy snack (Study 2) consumption, students were classified as above mean or below mean for consumption. One week later, half of the students in the above-mean and below-mean groups received normative feedback; control groups did not. Neither study showed an effect of norm messages on behavior relative to control, providing evidence for regression to the mean as an alternative explanation. Findings highlight the importance of control groups to distinguish social norm intervention effects from mere regression to the mean.
Sustainable use of land and water under rainfed and deficit irrigation conditions in Ogun-Osun River Basin, Nigeria
Adeboye, O.B. - \ 2015
University. Promotor(en): E. Schultz, co-promotor(en): K.O. Adekalu; K. Prasad. - Leiden : CRC Press/Balkema - ISBN 9789462572782 - 237
landgebruik - watergebruik - duurzaamheid (sustainability) - irrigatie - regenafhankelijke landbouw - watertekort - modellen - bodemwaterbalans - gewasopbrengst - nigeria - land use - water use - sustainability - irrigation - rainfed agriculture - water deficit - models - soil water balance - crop yield
Summary

Human population is increasing faster than ever in the history. There is an urgent need to scale up food production in order to meet up with food demands, especially in Sub-Saharan Africa. In Ogun-Osun River Basin, Nigeria, more than 95% of the crop production is done under rainfed conditions. Fluctuation in rainfall as a result of climate change is a major challenge in the recent times in the basin. Land productivity can be greatly improved by using affordable water conservation practices by peasant farmers who produce crops in the basin. Similarly, water saving measures would have to be adopted by using drip irrigation and application of water at critical stages of growth of crops. Fertility of the soil needs to be maintained by cultivating crops that naturally replenish soil nutrients. Such measures will go a long way in ensuring sustainable use of land and water in Ogun-Osun River Basin.

An indeterminate cultivar of Soybeans TGX 1448 2E was cultivated at the Teaching and Research Farms of Obafemi Awolowo University, Ile-Ife, Nigeria during the rainy seasons from May to September, 2011 and June to October, 2012. Similarly, the crop was drip irrigated for two dry seasons from February to May in 2013 and from November, 2013 to February, 2014. The purpose of conducting the experiments in the rainy and dry seasons was to compare the yields and their components and to evaluate the performances of the crop in terms of water use and productivity. The experimental field during the dry season was located at about 1 km from the field used during the rainy season due to the nearness to the source of water. During the experiments in the four seasons, key biometric data of the crop were taken from emergence to physiological maturity. The crop cycle during the rainfed experiment lasted for 117 and 119 days in 2011 and 2012 respectively, while in the dry season it lasted for 112 days in the first season and 105 days in the second season. The lengths of the crop cycles in the four seasons differed a little bit. This is attributed to environmental factors such as weather conditions, nutrient availability in the soil and period of cultivation. During the rainy seasons, six water conservation treatments were used namely Tied ridge, Mulch, Soil bund, Tied ridge plus Soil bund, Tied ridge plus Mulch, Mulch plus Soil bund and Direct sowing without water conservation measure (conventional practice), which was the control treatment. The treatments were placed in a randomised complete block design with four replicates in an area of 31 by 52 m (1,612 m2) and standard agronomic measures were taken. Soil water balance approach was used in determining evapotranspiration during the rainfed and irrigation seasons. Seasonal evapotranspiration was partitioned into the productive transpiration from the plants and non-productive evaporation from the soil.

Seasonal average canopy extinction coefficients were 0.46 and 0.51 respectively in the rainy seasons of 2011 and 2012, while in the dry seasons of 2013 and 2013/2014 they were 0.43 and 0.49. The plant height ranged from 51.3 cm for Soil bund to 67.8 cm for the conventional practice in 2011 while in 2012, it ranged from 60.3 cm for Tied ridge plus Soil bund to 80.3 cm for Mulch plus Soil bund. The minimum fraction of Intercepted Photosynthetically Active Radiation was 0.13 during establishment for Tied ridge plus Soil bund while the peak fraction was 0.97 during seed filling for Soil bund during the rainy seasons. Similarly, the minimum and peak leaf area indices were 0.13 m2 m-2 for Tied ridge plus Soil bund during establishment in 2011 and 6.61 m2 m-2 for Soil bund during seed filling in 2012. There were strong and significant correlations between the fraction of Intercepted Photosynthetically Active Radiation and the leaf area indices (LAI) (0.70 ≤ r2 ≤ 0.99) in 2011 and (0.93 ≤ r2 ≥ 0.99) in 2012 by using an exponential model. Seasonal rainfall in 2011 and 2012 was 539 and 761 mm respectively. Seasonal water storages in the soil in 2011 ranged from 407 mm for the conventional practice to 476 mm for Tied ridge plus Mulch, while in 2012 it ranged from 543 mm for Tied ridge to 578 mm for Tied ridge plus Soil bund.

Radiation Use efficiency was determined by plotting dry above ground biomass measured at intervals of seven days against the Daily Photosynthetically Active Radiation from Solar radiation and the Instantaneous Photosynthetically Active Radiation measured near solar noon for all the treatments. For the Photosynthetically Active Radiation obtained from solar radiation, Radiation Use Efficiency of the crop ranged from 1.18 g MJ-1 for Tied ridge to 1.98 g MJ-1 of Intercepted Photosynthetically Active Radiation for Tied ridge plus Soil bund in 2011, while in 2012 it ranged from 1.45 g MJ-1 for Tied ridge to 1.92 g MJ-1 for Mulch. There was no significant difference in the average seasonal Radiation Use Efficiency in the two seasons. By using instantaneous measurement of the Photosynthetically Active Radiation, Radiation Use Efficiency ranged from 0.80 g MJ-1 of Intercepted Photosynthetically Active Radiation for Tied ridge to 1.65 g MJ-1 for Tied ridge plus Soil bund in 2011, while in 2012 it ranged from 0.94 g MJ-1 for Tied ridge to 1.24 g MJ-1 for Soil bund. The two approaches gave relatively similar values of Radiation Use Efficiency. Positive -correlation coefficients (0.50 ≤ r2 ≤ 0.89) were found among the treatments between the dry above ground biomass simulated by using a light model and those measured in the field in the two seasons.

The seasonal crop water use ranged from 311 mm for Mulch plus Soil bund to 406 mm for Tied ridge plus Soil bund in 2011, while in 2012 it ranged from 533 mm for Mulch plots to 589 mm for Soil bund. Seasonal transpiration ranged from 190 mm for Tied ridge plus Mulch to 204 mm for Soil bund in 2011 while in 2012 it ranged from 164 mm for Tied ridge plus Mulch to 195 mm for Mulch plot. Seasonal evaporation was higher in 2012 ranging from 338 mm for Mulch plots to 408 mm for Soil bund while in 2011 it ranged from 311 mm for Mulch plus Soil bund to 406 mm for Tied ridge plus Soil bund. Water storage in the soil and seasonal crop water use are significantly related. Similarly, the seasonal crop water use, Intercepted Photosynthetically Active Radiation and Radiation Use efficiency were highly related for the crop over the two seasons.

Marketable seed yield ranged from 1.68±0.50 t ha-1 for Tied ridge to 2.95±0.30 t ha-1 for Tied ridge plus Soil bund in 2011, while in 2012 the yield ranged from 1.64±0.50 t ha-1 for the conventional practice to 3.25±0.52 t ha-1 for Mulch plus Soil bund. In 2011, seed yield for Tied ridge plus Soil bund was 15.6, 15.9, 25.4, 28.5, 43.1 and 47.1% higher than seed yield for Mulch plus Soil bund, Soil bund, Mulch, Tied ridge plus Mulch, Tied ridge and conventional practice respectively. In 2012, seed yield for Mulch plus Soil bund was 7.4, 21.8, 32.0, 32.3, 43.7 and 49.5% higher than the seed yields for Soil bund, Tied ridge, Mulch, Tied ridge plus Mulch, Tied ridge plus Soil bunds and Direct sowing respectively. Average seasonal seed yield of the crop was significantly related to the Total Intercepted Photosynthetically Active Radiation but not to the Radiation Use Efficiency. Harvest indices ranged from 47.4±4.5% for Tied ridge to 57.6±1.1% for Tied ridge plus Soil bund in 2011 and 53.1±3.0% for Soil bund to 58.1±2.3% for Tied ridge 2012. The highest harvest indices were obtained in Tied ridge plus Soil bund and Tied ridge in 2011 and 2012 respectively. Harvest index was not significantly related to both Intercepted Photosynthetically Active Radiation and Radiation Use Efficiency of the crop.

Average seasonal transpiration efficiencies - the ratio of the dry above ground biomass at harvest to the seasonal transpiration - for all the treatments were 7.0 kg ha-1 mm-1 in 2011 and 14.9 kg ha-1 mm-1 in 2012. Transpiration efficiency of the crop was strongly related to Intercepted Photosynthetically Active Radiation but not to Radiation Use Efficiency under field conditions in the rainy seasons. The peak water productivity for seed was 7.99 kg-1 ha-1 mm-1 in 2011 and 5.76 kg-1 ha-1 mm-1 for Mulch plus Soil bund in 2012. Water productivity for seed was strongly and significantly related to Intercepted Photosynthetically Active Radiation. However, it was not significantly related to Radiation Use Efficiency. These findings will provide information to the crop yield modellers during the simulation of yields of Soybeans under water conservation practices.

The construction of ridges and Soil bund especially for Tied ridge, Mulch plus Soil bund and Tied ridge plus Soil bund increased the average seasonal cost of production by 28.9% compared with Mulch and conventional practice and by 10.1% compared with Soil bund. In addition, economic water productivity was 3.90 US$ ha-1 mm-1 for Mulch plus Soil bund while for Soil bund and conventional practice, it was 3.30 and 2.27 US$ ha-1 mm-1 respectively.

Due to increase in demand for food, there is the need to produce more crop per drop of water under rainfed conditions and to manage water for agriculture at basin scale. The key priority in the study area was to increase the seed yields, water and economic productivity and the financial benefits at the end of a cropping season. The results show that the use of Mulch plus Soil bund had the average maximum transpiration efficiency, seed yield, water and economic productivity, and revenue of 1,630 US$ per ha. By comparing the average seasonal transpiration efficiency, crop water use, yield, water productivity and costs of production for the six conservation practices with those of the conventional practice in the two rainy seasons, Mulch plus Soil bund had the maximum average seed yield, water and economic productivity. Mulch plus Soil bund is hereby recommended for the cultivation of the crop in the study area. Other conservation practices, such as Soil bund, also performed satisfactorily in terms of seed yield and water productivity, although with a slight reduction in revenue. The use of these water conservation practices will not only increase the yields of the crop, but reduce depletion of water in the soil, which could initiate or increase land degradation in the study area to the barest minimum. Hence, sustainability of land and water in Ogun-Osun River Basin can be ensured. These findings demonstrate that land and water productivity of Soybean under rainfed conditions can be significantly improved with water conservation practices under the current fluctuations of rainfall and competition for land resources between agriculture and urban land use in Ogun-Osun River Basin.

Field trials were also conducted for two irrigation seasons from February to May, 2013 and November, 2013 to February, 2014. The crop was planted in a Randomized Complete Block Design with three replicates and in-line drip irrigation was applied to supply water to the crops. Five treatments were selected and these are: (i) full irrigation, skipping of irrigation every other week during (ii) flowering; (iii) pod initiation; (iv) seed filling and (v) commencement of maturity. Biometric data, which are number of leaves, plant height, leaf area indices and dry above ground biomass, were taken and recorded every week from sowing until maturity in the two irrigation seasons. Soil moisture contents were taken at the root zone of the plants prior to irrigation in order to determine the net irrigation water requirements at each stage of growth. Harvest indices were determined for each treatment. Number of pods per plant, number of seeds per pod and yields under each treatment were determined after physiological maturity in each season. Regression equations were generated for: (i) yield; (ii) number of pods per plant; (iii) number of seeds per pod; (iv) number of leaves; (v) seasonal transpiration and leaf area indices. Similarly, regression equations were generated for: (i) plant heights; (ii) seasonal transpiration; (iii) number of pods per plant; (iv) number of seeds per pod; (v) dry above ground biomass. Linear regressions were also fitted to the yield, dry above ground biomass and seasonal crop water use. The crop response factor was determined. Water productivity and Irrigation water productivity were computed and compared for each treatment. Linear models were fitted to the water productivity, irrigation water productivity and harvest index.

Rainfall contribution to the crop water use was 262 and 50 mm for 2013 and 2013/2014 irrigation seasons respectively. Maximum Leaf Area Index in the 2013 irrigation season was 7.10 m2 m-2 for full irrigation during seed filling, while in the 2013/2014 irrigation season, it was 3.44 m2 m-2 for full irrigation during flowering. The dry above ground biomass after maturity ranged from 359 g m-2 where irrigation was skipped every other week at the commencement of maturity to 578 g m-2 for full irrigation. The seed yields ranged from 1.81 t ha-1 when irrigation was skipped every other week during seed filling to 3.11 t ha-1 for full irrigation. Average seasonal seed yield for full irrigation was 18.8, 21.8, 24.4 and 47.9% higher than yields for treatments where irrigation was skipped every other week during flowering, pod initiation, commencement of maturity and seed filling respectively. Seasonal transpiration ranged from 217 mm when irrigation was skipped every other week during seed filling to 409 mm for full irrigation in the 2013 irrigation season, while in the 2013/2014 irrigation season it ranged from 28 mm for the treatment where irrigation was skipped every other week during seed filling to 223 mm for full irrigation. Seasonal crop water use ranged from 463 mm when irrigation was skipped every other week during flowering to 523 mm for full irrigation in the 2013 irrigation season, while in the 2013/2014 irrigation season it ranged from 364 mm when irrigation was skipped every other week during seed filling to 507 mm for full irrigation. Harvest indices ranged from 56.0% when irrigation was skipped during seed filling to 65.9% when irrigation was skipped during flowering in the 2013 irrigation season, while in the 2013/2014 irrigation season, it ranged from 43.2% when irrigation was skipped during seed filling to 63.9% for full irrigation. Water productivity for seed production ranged from 3.89 kg ha mm-1 when irrigation was skipped during seed filling to 5.95 kg ha-1 mm-1 for full irrigation in the 2013 irrigation season while in the 2013/2014 irrigation season, it ranged from 1.93 kg ha mm-1 when irrigation was skipped during seed filling to 3.00 kg ha-1 mm-1 for full irrigation. Irrigation water productivity ranged from 8.90 kg ha mm-1 when irrigation was skipped during seed filling to 14.0 kg ha-1 mm-1 when irrigation was skipped during flowering in 2013, while in the 2013/2014 irrigation season, it ranged from 2.24 kg ha-1 mm-1 when irrigation was skipped during seed filling to 3.32 kg ha-1 mm-1 for full irrigation. Leaf area indices and yield, number of leaves, number of pods per plant, number of seeds per pod and seasonal transpiration were significantly correlated. Similarly, dry above ground biomass and seasonal transpiration, number of pods per plant, number of seeds per pod were significantly correlated. The crop response factor (Ky), a measure of the relative decrease in seed yield due to relative decrease in evapotranspiration, was 2.24. It indicates that the deficit irrigation imposed on the crop was high and that relative decrease in yields due to deficit irrigation was higher than relative decrease in evapotranspiration.

Results show that skipping of irrigation at any growth stage of the crop led to reduction in the leaf area indices, dry above ground biomass and seasonal crop water use. Deficit irrigation had significant effects on both the dry matter and yields. The effect of deficit irrigation was more pronounced on seed yields than on dry matter. Severity of the effects of deficit irrigation depended on the stage of growth and its duration. Deficit irrigation reduced significantly dry matter at flowering and pod initiation. However, deficit irrigation did not affect the plant height. Number of seeds per plant at flowering and commencement of maturity were reduced significantly by deficit irrigation. The number of seeds per pod was significantly reduced when irrigation was skipped at pod initiation only. Seed yields were significantly reduced when irrigation was skipped during seed filling. In the 2013 irrigation season water productivity when irrigation was skipped during flowering was 2.3, 16.1, 23.5, and 36.1% higher than water productivity for full irrigation, when irrigation was skipped during pod initiation, commencement of maturity and seed filling respectively. In the same season, irrigation water productivity when irrigation was skipped during flowering was 15, 20, 29.3 and 36.4% higher than for full irrigation, when irrigation was skipped during pod initiation, commencement of maturity and seed filling respectively. In the 2013/2014 irrigation season, however, water productivity for full irrigation was 8.7, 16.3, 24.7 and 35.7% higher than when irrigation was skipped during pod initiation, commencement of maturity, flowering and seed filling respectively. Similarly, irrigation water productivity was 7.2, 15.4, 24.1 and 32.5% higher than when irrigation was skipped during pod initiation, commencement of maturity, flowering and seed filling respectively. In addition, irrigation water productivity for full irrigation was 24.1 and 32.5% higher than when irrigation was skipped during flowering and seed filling respectively. Stage of growth, its duration, water requirements and seasonal environmental conditions influenced the seasonal water use, water productivity and irrigation water productivity of Soybean. Maximum water productivity and irrigation water productivity were obtained when irrigation was skipped every other week during flowering only in the first season, whereas in the second season full irrigation gave the peak water and irrigation water productivity. This suggests that irrigation water productivity of Soybean can be improved upon by skipping irrigation during flowering and pod initiation.

In this study, the costs of production for all the irrigation scenarios were high. This is due to the high cost of water, which constituted between 54 to 59% of the production cost if water is purchased and cost of drip irrigation equipment, which constituted between 75.6 to 76.7% of the total cost of production if water would be given without financial implication. Under the prevailing price and economic conditions after harvest, the use of in-line drip irrigation does not offer economic benefit to peasant farmers, who are the predominant growers of the crop in the study area. Economic benefit may be achieved after long periods of usage with proper maintenance of the irrigation facilities and elimination of the fixed cost from the total cost of production.

The water driven crop model AquaCrop was calibrated and validated to predict canopy cover, dry above ground biomass, seed yield, evapotranspiration, soil moisture content and water productivity of the crop. The simulated and measured data compare adequately except for water productivity that was over predicted in the validation data set. The AquaCrop model predicted canopy cover with error statistics of 0.93 ≤ E ≤ 0.98 for both full and deficit irrigation and the degree of agreement d = 0.99 with 4.3 ≤ RMSE ≤ 5.9 (root mean square error) for full irrigation while for deficit irrigation, 0.96 ≤ d ≤ 0.99 with 5.3 ≤ RMSE ≤ 5.8. Dry above ground biomass was predicted with error statistics of 0.08 ≤ RMSE ≤ 0.14 t ha-1 with 0.98 ≤ d ≤ 0.99 for full irrigation, while for deficit irrigation it was 0.06 ≤ RMSE ≤ 1.09 t ha-1 with 0.85 ≤ d ≤ 0.99. One in every five predictions of the above ground biomass was outside 20% deviation from the measured values.

The seed yields were predicted with error statistics of RMSE = 0.10 t ha-1 and d = 0.99 and one in five predictions was outside 15% deviation from the measured data. The prediction error statistics for seasonal crop water use for both full and deficit irrigation treatments was 15.4 ≤ RMSE ≤ 58.3 in the two seasons. The AquaCrop model over predicted percolation also in the validation data set. These observations suggest that the percolation components of the model need to be adjusted to ensure better performance. The performance of the AquaCrop model in predicting canopy cover, seed yield and other quantities in this study are commendable and satisfactory.

Specific and distinct features, such as the use of canopy cover rather than leaf area index, make the model suitable for developing countries like Nigeria, where researchers may not have access to state-of-the-art equipment for measuring the leaf area index. Similarly, water productivity that is normalized for atmospheric demand and carbon dioxide concentration and its focus on water makes it suitable for diverse locations. Over the years, it has been observed that no model is universal in its ability to take into consideration all differences in cultivar, environment, weather and management conditions. Other cultivars of Soybeans in Nigeria and other agro-climatic environments need to be tested and fine-tuned in the model, in order to ascertain the accuracy of the model. generally, the model predicted the stated parameters with reasonable degree of accuracy and is hereby recommended for use in Ile-Ife and other parts of Ogun-Osun River Basin and Nigeria.

Although land, water, and economic productivity of the crop were higher where water was conserved under rainfed conditions, treatment of the soil to conserve water and regular maintenance increased the average seasonal cost of production compared with the conventional practice. High cost of production may reduce the benefits obtained by the crop growers, except when there is improvement in the market price. Therefore, sustainable practice of the water conservation measures must be accompanied with lower cost of production. Under irrigation conditions, the land and water productivity are lower compared with rainfed cultivation. The productivity in the dry season reduces with the severity of the water stress. Average crop water productivity and economic water productivity of all the six water conservation measures in the rainy season were higher than with full irrigation in the dry season. The costs of production of the crop in the dry season were significantly above the cost during the rainfed conditions. Higher water productivity under rainfed conditions in this study is in agreement with the finding that in a significant part of the least developed and emerging countries there is larger opportunity for improving water productivity under rainfed conditions compared to irrigated agriculture.

Expansion of arable land may not be feasible in Ile-Ife because of the huge investments involved. Thus, the focus of efforts to expand food production in the area would have to be on raising land productivity on the existing arable lands and improving production efficiencies, outcomes that can only be achieved by using improved cultivars together with improved agronomic practices. Agronomic practices, especially under rainfed conditions, would have to be designed to improve water productivity. Improving water productivity requires vapour shift (transfer) whereby soil physical conditions, soil fertility, crop varieties and agronomy are applied in tandem and managed to shift the evaporation into useful transpiration by plants. During the dry season, the crop would have to be irrigated in order to achieve maximum land and water productivity. Skipping of irrigation during seed filling would have to be avoided in order to prevent significant reduction in yield. Irrigation at the commencement of maturity after the pods have been completely filled with seeds can be skipped. Under water limiting conditions, the amount of water saved by skipping irrigation during flowering, pod initiation, seed filling and maturity can be used for cultivating other crops and thereby increasing the opportunity cost. Incidental rainfall during the dry season would have to be used in order to increase irrigation water productivity of the crop.

Subsurface drainage of valley bottom irrigated rice schemes in tropical savannah : case studies of Tiefora and Moussodougou in Burkina Faso
Keïta, A. - \ 2015
University. Promotor(en): E. Schultz; H. Yacouba. - Leiden : CRC Press/Balkema - ISBN 9789462572638
oryza - ondergrondse drainage - drainage - irrigatie - rijst - savannen - irrigatiesystemen - waterbeheer - burkina faso - subsurface drainage - irrigation - rice - savannas - irrigation systems - water management
Agricultural water productivity optimization for irrigated Teff (Eragrostic Tef) in water scarce semi-arid region of EthiopiaAgricultural water productivity optimization for irrigated Teff (Eragrostic Tef) in water scarce semi-arid region of Ethiopia
Yihun, Y.M. - \ 2015
University. Promotor(en): E. Schultz, co-promotor(en): T. Erkossa Jijo; A. Mehari Haile. - Leiden : CRC Press/Balkema - ISBN 9789462571709 - 82
eragrostis tef - waterbeheer - watergebruik - water - watergebruiksrendement - optimalisatie - ethiopië - water management - water use - water use efficiency - optimization - ethiopia
Hydraulic and operational performance of irrigation schemes in view of water saving and sustainability : sugar estates and community managed schemes In Ethiopia
Dejen, Z.A. - \ 2015
University. Promotor(en): E. Schultz, co-promotor(en): S.B. Awulachew; L. Hayde. - Leiden : CRC Press/Balkema - ISBN 9789462571693 - 165
irrigatie - irrigatiewater-toedieningsschema - hydraulica - duurzaamheid (sustainability) - water - ethiopië - waterbeheer - irrigation - irrigation scheduling - hydraulics - sustainability - ethiopia - water management
Tracking forest cover change using Landsat & Rapid Eye towards S2
Hamunyela, E. ; Verbesselt, J. ; Schultz, M. ; Penndorf, A. ; Frotscher, K. ; Herold, M. ; Reiche, J. ; DeVries, B.R. ; Dutrieux, L.P. ; Calders, K. - \ 2014
Design of non-wide canals for sediment transport. Case study of Sunsari Morang Irrigation scheme, Nepal
Paudel, K.P. ; Schultz, B. ; Depeweg, H. - \ 2014
Irrigation and drainage 63 (2014)5. - ISSN 1531-0353 - p. 584 - 589.
Canal design for sediment transport requires the use of sediment transport predictors. The predictors are derived for a small range of flows and mostly considered for wide canals. The use of these equations in irrigation canals needs some adaptation. In this study we have used a depth-averaged logarithmic velocity distribution in a canal section to compute the sediment transport rate for different predictors under a different range of hydraulic and sediment characteristics. The predictability of the predictors was improved when tested with the selected Brownlie data for rectangular non-wide canals. A rational canal design approach is proposed that uses the sediment transport predictors after applying a correction. The proposed approach has been tested under changing water flows and sediment concentration using the mathematical model SETRIC. The field data of secondary canal S9 of the Sunsari Morang Irrigation Scheme in Nepal have been used. If the canal had been designed with the proposed method there would have been less deposition in the canal network. Copyright © 2014 John Wiley & Sons, Ltd.
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