Your search found 52 records
1 Robain, H.; Le Troquer, Yann; Sounyaphong, P.; Chiakoua, B. X.; Bourdon, Emmanuel; Ribolzi, Olivier. 2008. Assessment of soil organisation and monitoring of soil water content using electrical resistivity tomography in the uplands of Lao PDR. Lao Journal of Agriculture and Forestry, Special issue no.17:167-182.
Soil water content ; Electrical conductivity ; Monitoring ; Groundwater recharge ; Sloping land ; Infiltration ; Catchment areas / Laos / Houay Pano Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H041775)
http://www.nafri.org.la/documents/newsletter/Journal/journal_17/section9.pdf
https://vlibrary.iwmi.org/pdf/H041775.pdf
https://vlibrary.iwmi.org/pdf/H041775.pdf
(0.78 MB)
2 Qureshi, Asad Sarwar; Eshmuratov, D.; Bezborodov, G. 2011. Determining optimal groundwater table depth for maximizing cotton production in the Sardarya Province of Uzbekistan. Irrigation and Drainage, 60(2):241–252. [doi: https://doi.org/10.1002/ird.568]
Cotton ; Simulation models ; Calibration ; Groundwater table ; Soil water content ; Water balance ; Irrigation practices ; Salinity ; Evapotranspiration / Uzbekistan / Syr Darya River Basin
(Location: IWMI HQ Call no: PER Record No: H042963)
(0.32 MB)
Poor on-farm irrigation practices and rising groundwater table depths are the major reasons for low cotton yields in the Sardarya province of Uzbekistan. To ensure sustainability of cotton production in the area, precise calculations of irrigation requirements are needed to optimize crop yields and to keep groundwater table depth below the root zone to avoid soil salinization. To determine optimal groundwater table depth and irrigation amounts for the Sardarya province of Uzbekistan, the Soil–Water–Atmosphere–Plant (SWAP) model was used. SWAP was calibrated and validated using measured data from an experimental cotton field during the agricultural year of 2006 and 2007. The calibrated SWAP model was then used to simulate optimal groundwater table depth and irrigation amounts. The simulation results show that for the existing conditions in the study area, a groundwater table depth of approximately 200 cm together with an irrigation application of 2500m3 ha1 will be the most appropriate combination for optimal cotton yields ( 3.0 t ha1). However, to achieve maximum potential yields of cotton (5–6 t ha1), leaching of excessive salts from the root zone through freshwater application would be imperative. This would require rehabilitation of the existing drainage network in the area.
3 Shaw, E. M.; Beven, K. J.; Chappell, N. A.; Lamb, R. 2011. Hydrology in practice. 4th ed. London, UK: Spon Press. 543p.
Hydrology ; Measurement ; Analysis ; Hydrological cycle ; Hydrometeorology ; Evaporation ; Evapotranspiration ; Precipitation ; Aquifers ; Climate change ; Networks ; Rain ; Hydraulic conductivity ; Moisture content ; Rivers ; Flow ; Water quality ; Models ; Soil water content ; Flooding ; Risk management ; Drought ; Runoff ; Groundwater ; Water resource management ; Policy ; Legal aspects ; Remote sensing / UK
(Location: IWMI HQ Call no: 551.48 G000 SHA Record No: H043491)
(0.42 MB)
4 Luthin, J. N. (Ed.) 1957. Drainage of agricultural lands. Madison, WI, USA: American Society of Agronomy. 620p.
Agricultural land ; Drainage ; Surface drainage ; Soil water ; Soil moisture ; Soil water content ; Soil organic matter ; Soil permeability ; Water table ; Irrigation water ; Hygroscopicity ; Hydraulic conductivity ; Wells ; Pumping ; Engineering ; Crops
(Location: IWMI HQ Call no: 631.62 G000 LUT Record No: H043948)
(0.09 MB)
5 Hillel, D. 1982. Introduction to soil physics. London, UK: Academic Press. 364p.
Soil physics ; Soil structure ; Soil water content ; Soil temperature ; Soil compaction ; Flow discharge ; Tillage ; Infiltration ; Surface runoff ; Groundwater ; Drainage ; Evaporation ; Soil moisture ; Water balance ; Energy balance
(Location: IWMI HQ Call no: 631.4 G000 HIL Record No: H043951)
(0.48 MB)
6 Black, C. A.; Evans, D. D.; Ensminger, L. E.; White, J. L.; Clark, F. E. (Eds.) 1965. Method of soil analysis: part 1 - Physical and mineralogical properties including statistics of measurement and sampling. Madison, WI, USA: American Society of Agronomy. 770p. (Agronomy 9)
Soil analysis ; Measurement ; Sampling ; Chemicophysical properties ; Calibration ; Water content ; Soil water content ; Soil hydraulic properties ; Hydraulic conductivity ; Water intake ; Water table ; Evapotranspiration ; Porosity ; Soil air ; Heat capacity ; Heat transfer ; Radiation ; Particle density ; Bulk density ; Consistency ; Shear strength ; Rupture ; Penetrometers ; Bearing characteristics ; Microscopy ; Photometry ; Infrared spectrophotometry ; X rays ; Chemical composition
(Location: IWMI HQ Call no: 631.4 G000 BLA Record No: H043954)
(0.49 MB)
7 Erkossa, Teklu. 2011. Tillage effects on physical qualities of a vertisol in the central highlands of Ethiopia. African Journal of Environmental Science and Technology, 5(12):1008-1016. [doi: https://doi.org/10.5897/AJEST10.089]
Soil management ; Field preparation ; Tillage ; Ridge tillage ; Furrows ; Soil analysis ; Soil moisture ; Soil water content ; Hydraulic conductivity ; Highlands ; Rain / Ethiopia
(Location: IWMI HQ Call no: e-copy only Record No: H044664)
http://www.academicjournals.org/ajest/PDF/pdf%202011/Dec/Erkossa.pdf
https://vlibrary.iwmi.org/pdf/H044664.pdf
https://vlibrary.iwmi.org/pdf/H044664.pdf
(0.14 MB) (289.9KB)
In the highlands of Ethiopia, tillage methods and frequency affect drainage, soil erosion, moisture conservation, weeding and harvesting of crops. This is through their effects on soil physical, chemical and biological qualities. In this study, four tillage methods for land preparation, “broad bed and furrows”,” green manure”, “reduced tillage “and the traditional tillage “ridge and furrows” were evaluated for their effects on soil physical quality indicators. The study was superimposed on the field experiment conducted on a vertisol area at Caffee doonsa for five years (1998 to 2002) in the central highland of Ethiopia. Penetration resistance (PR), aggregate stability, water-holding capacity, crust strength and thickness, texture, porosity, saturated hydraulic conductivity, bulk density and water holding capacity were the soil physical quality indicators considered. The result indicated that only PR was significantly (p<0.05) affected, where as the other parameter have shown a slight changes that are consistent with the effects on the bio-chemical parameters as previously reported. Broad bed furrows, and reduced tillage resulted in the highest and the lowest PR, respectively under both the moist and dry soil conditions. Green manure increased aggregate stability and reduced surface crust strength, which was linked to its increased organic matter content and consequent improved microbial activities.
8 Kizito, Fred; Dragila, M. I.; Sene, M.; Brooks, J. R.; Meinzer, F. C.; Diedhiou, I.; Diouf, M.; Lufafa, A.; Dick, R. P.; Selker, J.; Cuenca, R. 2012. Hydraulic redistribution by two semi-arid shrub species: implications for Sahelian agro-ecosystems. Journal of Arid Environments, 83:69-77. [doi: https://doi.org/10.1016/j.jaridenv.2012.03.010]
Agroecosystems ; Soil water content ; Soil moisture ; Food crops ; Microclimate / West Africa / Senegal / Peanut Basin
(Location: IWMI HQ Call no: e-copy only Record No: H044987)
(0.72 MB)
Hydraulic redistribution is the process of passive water movement from deeper moist soil to shallower dry soil layers using plant roots as conduits. Results from this study indicate that this phenomenon exists among two shrub species (Guiera senegalensis and Piliostigma reticulatum) that co-exist with annual food crops in Sahelian agro-ecosystems. Real-time measurements were conducted for soil water content, soil water potential and microclimate variables notably; air temperature, relative humidity, wind speed, precipitation and solar irradiance. Additionally, sap flow measurements were conducted in shrub roots using the thermal dissipation technique on intact and coppiced shrubs. Monthly predawn leaf water potential was measured using a portable pressure chamber. Soil water potential (Js) at the 20 cm depth declined significantly during the dry season with diel changes in Js of 0.6 to 1.1 MPa. These variations were attributed to passive water release from shrub roots resulting in overnight rewetting of drier upper soil layers. Sap flow measurements on tap and lateral shrub roots indicated daily reversals in the direction of flow. During the peak of the dry season, both positive (toward shrub) and negative (toward soil) flows were observed in lateral shrub roots with sap flow in the lateral roots frequently negative at night and rapidly becoming positive soon after sunrise. The negative sap flow at night in superficial lateral roots and the periodic positive flow in the descending tap roots were indicative of hydraulic redistribution. Hydraulic redistribution may be an important mechanism for drought stress avoidance while maintaining plant physiological functions in both shrubs and neighboring annuals in water-limited environments.
9 Kutilek, M.; Nielsen, D. R. 1994. Soil hydrology. Cremlingen, Germany: Catena Verlag. 370p.
Soils ; Hydrology ; Soil classification ; Soil genesis ; Soil moisture ; Soil water ; Soil water content ; Soil water potential ; Soil water retention ; Soil porosity ; Gravimetric analysis ; Infiltration ; Evapotranspiration
(Location: IWMI HQ Call no: 631.45 G000 KUT Record No: H045089)
(0.46 MB)
10 Hoffman, G. J.; Evans, R. G.; Jensen, M. E.; Martin, D. L.; Elliott, R. L. (Eds.) 2007. Design and operation of farm irrigation systems. 2nd ed. St. Joseph, MI, USA: American Society of Agricultural and Biological Engineers (ASABE). 863p.
Irrigation development ; Irrigation systems ; Design ; Furrow irrigation ; Surface irrigation ; Sprinkler irrigation ; Microirrigation ; Drip irrigation ; Subsurface irrigation ; Irrigation water ; Wastewater irrigation ; Water management ; Water table ; Irrigated farming ; Food production ; Fiber ; Water supply ; Drought ; Environmental effects ; Water storage ; Water requirements ; Water distribution ; Pumping ; Water quality ; Surface water ; Runoff ; Soil water content ; Hydraulic conductivity ; Salinity control ; Drainage systems ; Land forming ; Surveys ; Models ; Chemigation / USA
(Location: IWMI HQ Call no: 631.7.3 G300 HOF Record No: H045968)
(0.65 MB)
11 James, L G. 1993. Principles of farm irrigation system design. New York, NY, USA: John Wiley. 543p.
Irrigation requirements ; Irrigation scheduling ; Farms ; Irrigation systems ; Sprinkler irrigation ; Trickle irrigation ; Surface irrigation ; Irrigation water ; Evapotranspiration ; Water quality ; Water law ; Pumps ; Spacing ; Discharges ; Mathematical models ; Soil water content ; Infiltration
(Location: IWMI HQ Call no: 631.587 G000 JAM Record No: H045974)
(0.56 MB)
12 Mai, V. T.; Hoanh, Chu Thai; Van Keulen, H.; Hessel, R. 2013. Spatial modelling for nitrogen leaching from intensive farming in Red River Delta of Vietnam. Asian Journal of Water, Environment and Pollution, 10(3):51-61.
Intensive farming ; Nitrogen ; Leaching ; Rivers ; Deltas ; Irrigation ; Land use ; Soil water content ; Vegetables ; Crop production ; Fertilizers ; Weather ; Models ; Calibration / Vietnam / Tam Duong District / Red River Delta
(Location: IWMI HQ Call no: e-copy only Record No: H046039)
(1.12 MB)
In this study, a spatial dynamic model was developed, to simulate nitrogen dynamics in Van Hoi commune, Tam Duong district, Vietnam, for different soil and land use types, under different irrigation and fertilizer regimes. The model has been calibrated using measured nitrogen concentrations in soil solution in March and August 2004 and validated for data from March and August 2005. Lateral flow was low in this level area. Percolation was the main process leading to high nitrogen leaching losses to ground water. Calculated annual leaching losses varied from 88 to 122 kg N ha–1 in flowers, 64 to 82 in vegetables of the cabbage group, 51 to 76 in chili, 56 to 75 in vegetables of the squash group, and 36 to 55 in rice.
13 Dasgupta, P.; Das, B. S.; Sen, S. K. 2015. Soil water potential and recoverable water stress in drought tolerant and susceptible rice varieties. Agricultural Water Management, 152:110-118. [doi: https://doi.org/10.1016/j.agwat.2014.12.013]
Water stress ; Soil water potential ; Drought tolerance ; Lowland ; Rice ; Plant growth ; Plant developmental stages ; Soil water content ; Crop yield ; Physiological response ; Models / India / Kharagpur
(Location: IWMI HQ Call no: e-copy only Record No: H047497)
(0.73 MB)
We conducted a two-year field experiment to determine if water stress could be exploited to recover yield in one drought resistant (Vandana) and three susceptible (IR36, IR72 and Swarna) rice varieties. Stress was induced in active tillering, flowering and grain filling stages by suspending irrigation until the soil became sufficiently dry and plants began to show stress symptoms when irrigation was resumed, such that plants could recover from stress. We observed that terminal soil water potential (SWP) as low as -110 kPa in the active tillering stage was less detrimental to relative water content, proline content, and electrolyte leakage. A 27% rise in the level of stress led to ~8%, 44% and 21% increase in yield in IR36, Vandana and Swarna. The possible causes are 23%, 39% and 10% increase in the corresponding root biomass ofthe varieties, resulting in higher water uptake in the vegetative stage treatment plots. This was further supported by high correlations between yield and terminal SWP in this treatment. Critical limits of SWP may be identified to exploit the potential of rice varieties to sustain or improve yield under water stress. Results also suggest an opportunity to design a water saving strategy in lowland rice production.
14 Finley, S. 2016. Sustainable water management in smallholder farming: theory and practice. Wallingford, UK: CABI. 198p.
Water management ; Sustainability ; Smallholders ; Rainfed farming ; Conservation agriculture ; Water resources ; Water availability ; Water productivity ; Water use efficiency ; Rainwater ; Water harvesting ; Water quality ; Soil water content ; Water holding capacity ; Plant water relations ; Crop management ; Water requirements ; Evapotranspiration ; Climate change ; Irrigation water ; Water distribution ; Water storage ; Irrigation methods ; Irrigation scheduling ; Irrigation efficiency ; Strategies ; Land degradation
(Location: IWMI HQ Call no: 631.7 G000 FIN Record No: H047765)
(0.44 MB)
15 Rao, S. S.; Tanwar, S. P. S.; Regar, P. L. 2016. Effect of deficit irrigation, phosphorous inoculation and cycocel spray on root growth, seed cotton yield and water productivity of drip irrigated cotton in arid environment. Agricultural Water Management, 169:14-25. [doi: https://doi.org/10.1016/j.agwat.2016.02.008]
Water productivity ; Water deficit ; Irrigation water ; Drip irrigation ; Furrow irrigation ; Water use ; Soil water content ; Plant growth ; Root systems ; Phosphorus ; Seed inoculation ; Chlormequat ; Crop yield ; Cottonseed ; Rain ; Evaporation ; Arid zones / India / Rajasthan / Pali
(Location: IWMI HQ Call no: e-copy only Record No: H047796)
(1.09 MB)
Irrigation water is scarce and expensive resource constraining crop production in arid and semi-arid region of India. Most producers’ aims to maximize yield per unit of water applied but it requires a better understanding of crop response to various levels of water stress. A field experiment was conducted during 2009–2011 to investigate the effect of deficit irrigation through drip irrigation; phosphorus solubilizing bacterial (PSB) inoculation and chloromequat chloride (cycocel) spray on seed cotton yield and water productivity (WP) of cotton. Experimental treatments comprised of three drip irrigation levels designated as 1.0 ETc (full irrigation as control), 0.8 ETc and 0.6 ETc (regular deficit irrigation) which receive 80% and 60% of the 1.0 ETc irrigation, were kept in main plots. The factorial combination of PSB inoculation and cycocel spray were included as good management practices (GMP) in sub-plots. A furrow irrigation treatment was also kept as absolute control. The result reveals that drip irrigation in cotton at 1.0 ETc significantly increased mean seed cotton yield by 33.5% and saved 30% irrigation water as compared to furrow irrigation which recorded 1859 kg ha-1 seed cotton yield with 582 mm irrigation water. Deficit irrigation at 0.8 ETc caused 17% water savings with only 6.4% reduction in yield as compared to 1.0 ETc. PSB inoculation and/or cycocel spray significantly increased number of bolls plant-1, boll weight and seed cotton weight plant-1 over control. The interaction effect of deficit irrigation and GMP was significant on seed cotton yield and water productivity. Therefore, deficit irrigation at 0.8Etc along with PSB inoculation and cycocel spray should be considered as useful tool for water saving and higher yield in arid and semi-arid regions where irrigation water supplies are limited.
16 Sreelash, K.; Buis, S.; Sekhar, M.; Ruiz, L.; Tomer, S. K.; Guerif, M. 2017. Estimation of available water capacity components of two-layered soils using crop model inversion: effect of crop type and water regime. Journal of Hydrology, 546:166-178. [doi: https://doi.org/10.1016/j.jhydrol.2016.12.049]
Water holding capacity ; Water availability ; Estimation ; Soil water content ; Soil hydraulic properties ; Layered soils ; Soil moisture ; Field capacity ; Wilting point ; Water stress ; Crop management ; Models ; Sensitivity analysis ; Leaf Area Index ; Maize ; Sorghum ; Sunflowers ; Turmeric ; Remote sensing ; Catchment areas / South India / Berambadi Catchment
(Location: IWMI HQ Call no: e-copy only Record No: H048041)
(1.43 MB)
Characterization of the soil water reservoir is critical for understanding the interactions between crops and their environment and the impacts of land use and environmental changes on the hydrology of agricultural catchments especially in tropical context. Recent studies have shown that inversion of crop models is a powerful tool for retrieving information on root zone properties. Increasing availability of remotely sensed soil and vegetation observations makes it well suited for large scale applications. The potential of this methodology has however never been properly evaluated on extensive experimental datasets and previous studies suggested that the quality of estimation of soil hydraulic properties may vary depending on agro-environmental situations. The objective of this study was to evaluate this approach on an extensive field experiment. The dataset covered four crops (sunflower, sorghum, turmeric, maize) grown on different soils and several years in South India. The components of AWC (available water capacity) namely soil water content at field capacity and wilting point, and soil depth of two-layered soils were estimated by inversion of the crop model STICS with the GLUE (generalized likelihood uncertainty estimation) approach using observations of surface soil moisture (SSM; typically from 0 to 10 cm deep) and leaf area index (LAI), which are attainable from radar remote sensing in tropical regions with frequent cloudy conditions. The results showed that the quality of parameter estimation largely depends on the hydric regime and its interaction with crop type. A mean relative absolute error of 5% for field capacity of surface layer, 10% for field capacity of root zone, 15% for wilting point of surface layer and root zone, and 20% for soil depth can be obtained in favorable conditions. A few observations of SSM (during wet and dry soil moisture periods) and LAI (within water stress periods) were sufficient to significantly improve the estimation of AWC components. These results show the potential of crop model inversion for estimating the AWC components of two-layered soils and may guide the sampling of representative years and fields to use this technique for mapping soil properties that are relevant for distributed hydrological modelling.
17 Mustafa, S. M. T.; Vanuytrecht, E.; Huysmans, M. 2017. Combined deficit irrigation and soil fertility management on different soil textures to improve wheat yield in drought-prone Bangladesh. Agricultural Water Management, 191:124-137. [doi: https://doi.org/10.1016/j.agwat.2017.06.011]
Irrigation management ; Water deficit ; Soil fertility ; Soil management ; Soil texture ; Water productivity ; Models ; Crop yield ; Wheat ; Irrigation scheduling ; Soil water content ; Soil types ; Meteorological observations ; Drought ; Precipitation ; Strategies / Bangladesh / Dhaka / Mymensigh / Rajshahi / Rangpur
(Location: IWMI HQ Call no: e-copy only Record No: H048223)
(2.35 MB)
Proper utilization of water resources is very important in agro-based and drought-prone Bangladesh. Sustainable use of water resources in agriculture requires irrigation schedules based on local environmental conditions, soil type and water availability. In this study, the water productivity model AquaCrop was used to simulate different water and fertilizer management strategies in a drought prone area of Bangladesh to obtain management recommendations. First, the Standardised Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) were determined to quantify the aggregated deficit between precipitation and the evaporative demand of the atmosphere, which confirm that meteorological drought is occurring frequently in the study area. Also, the AquaCrop model was successfully calibrated and validated for wheat in the area, which was confirmed by the several statistical indicators, and could be used to design water and fertilizer management strategies. Simulations identified stem elongation (jointing) to booting and flowering stage as the most water sensitive stages for wheat. Deficit irrigation during the most water sensitive stages could increase the interannual yield stability and the grain yield compared to rainfed conditions for different soil fertility levels on loamy and sandy soils by 21–136% and 11–71%, respectively, while it could increase water productivity compared to full irrigation strategies. Deficit irrigation resulted in grain yields almost equal to yields under full irrigation and could at the same time save 121–197 mm of water per growing season. Specifically, we suggest two irrigation applications: one at the stem elongation (jointing) to booting stage and another at the flowering stage for loamy soils; and one at the end of seedling development to the beginning of crown root initiation stage and another at the flowering stage for sandy soils. Given the water scarcity in the region, instead of optimal fertility levels, moderate fertility levels are recommended that result in 60% of the potential biomass production for loamy soils and in 50% for sandy soils in combination with the suggested deficit irrigation strategies.
18 Nyagumbo, I.; Nyamadzawo, G.; Madembo, C. 2019. Effects of three in-field water harvesting technologies on soil water content and maize yields in a semi-arid region of Zimbabwe. Agricultural Water Management, 216:206-213. [doi: https://doi.org/10.1016/j.agwat.2019.02.023]
Water harvesting ; Technology ; Soil water content ; Crop yield ; Maize ; Semiarid zones ; Dry farming ; Water conservation ; Drought ; Rain ; Soil moisture ; Slope / Zimbabwe / Shurugwi / Mukandabvute / Takara / Kuchicha
(Location: IWMI HQ Call no: e-copy only Record No: H049202)
(0.54 MB)
Climate change and recurring mid-season dry spells have resulted in perennial droughts and poor yields in most smallholder farming areas located in marginal arid to semi-arid lands (ASAL) of Zimbabwe where they are dependent on rainwater for agricultural crop production. One approach that can be used to adapt to changing climatic pattern is in-field water harvesting. This study evaluated the soil profile water content and maize yields of 3 infield water harvesting technologies namely infiltration pits (IF), fanya juus (FJ) and contour ridges with cross ties (CRCT) in comparison to standard contour ridges (SC). The three systems are currently the focus of extension recommendations for water conservation in semi-arid regions of the country. Soil water content was measured on a regular basis using gravimetric methods at locations upslope and down slope of each structure. The average volumetric water content was signifcantly different between treatments, and it varied with increasing distance from the water harvesting structures. The average profile soil moisture content, over the three seasons were 8.3, 8.2, 8.1 and 7.8% for CRCT, FJ, IF and SC repectively. CRCT, FJ and IF retained more water for a greater distance from the harvesting structures compared to the SC. Maize yields were significantly higher in the water harvesting technologies compared to SC. Maize yields were 1196, 1164, 1250 and 749 kg ha-1 for CRCT, FJ, IF and SC respectively. There as a good correlation between water content and maize yields (R2 = 0.80). It was concluded that improved water harvesting structures when compared to SC have the potential to increase maize yields in areas with water shortages, hence they can be a useful strategy for climate change adaptation.
19 Tfwala, C. M.; van Rensburg, L. D.; Bello, Z. A.; Zietsman, P. C. 2019. Transpiration dynamics and water sources for selected indigenous trees under varying soil water content. Agricultural and Forest Meteorology, 275:296-304. [doi: https://doi.org/10.1016/j.agrformet.2019.05.030]
Trees ; Transpiration ; Groundwater ; Water availability ; Soil water content ; Water use ; Water depletion ; Evapotranspiration ; Rain ; Chemicophysical properties ; Arid zones / South Africa / Kolomela Mine
(Location: IWMI HQ Call no: e-copy only Record No: H049326)
(2.17 MB)
The major route through which water from the earth’s surface re-enters the hydrologic cycle in forested ecosystems is via tree transpiration (T). It is therefore important to have detailed understanding of the quantity and source of water transpired by different tree species. The aims of this study were to i) assess the trends of T for selected tree species (camel thorn, sweet thorn, shepherd’s tree and buffalo thorn) across a range of soil water content conditions and ii) partition the total T of the selected tree species growing in arid environments dominated by open cast mining activities into soil water and groundwater. Tree T was measured using the compensation heat pulse velocity (CHPV) method, while soil water content was monitored using DFM capacitance probes. The soil water content within the upper 50 cm soil profile ranged from 11 mm during the dry season to 20 mm during the wet season. The deeper soil layer (50–120 cm) was generally wetter compared to the top layer with water content was up to >30 mm during the wet season. The measured tree T ranged from 0.2 mm day-1 on buffalo thorn during the dry season to 1.9 mm day-1 on sheperd’s tree in summer. It was also revealed that T of large (diameter at breast height =46 cm) camel thorn trees is not responsive to seasonal variations of soil water availability and remained constant at approximately 1.2 mm day-1. Diurnal patterns of T did not effect changes on the soil water depletions within the top 120 cm soil profile, which indicated that the trees sourced water beyond this zone. Signs of daytime redistribution were observed within the canopy areas of the investigated trees during very limited soil water conditions of the dry season. It was concluded that the water use of trees is inclined to the seasonal variations, which however is not the case in old trees. Close to 100% of the water transpired by trees in the study area is sourced below 1.2 m (vadose zone and water table). We recommended investigation of daytime redistribution among the indigenous tree species of the study area. We also recommended extension of tree water use studies to other species for comprehensive catchment tree water use calculations to inform water budgets.
20 Akpoti, K.; Kabo-bah, A. T.; Dossou-Yovo, E. R.; Groen, T. A.; Zwart, Sander J. 2020. Mapping suitability for rice production in inland valley landscapes in Benin and Togo using environmental niche modeling. Science of the Total Environment, 709:136165. [doi: https://doi.org/10.1016/j.scitotenv.2019.136165]
Land suitability ; Rice ; Agricultural production ; Environmental modelling ; Linear models ; Forecasting ; Uncertainty ; Water productivity ; Soil water content ; Rainfed farming ; Climatic data ; Soil chemicophysical properties ; Socioeconomic environment ; Valleys / Benin / Togo
(Location: IWMI HQ Call no: e-copy only Record No: H049495)
(5.47 MB)
Inland valleys (IVs) in Africa are important landscapes for rice cultivation and are targeted by national governments to attain self-sufficiency. Yet, there is limited information on the spatial distribution of IVs suitability at the national scale. In the present study, we developed an ensemble model approach to characterize the IVs suitability for rainfed lowland rice using 4 machine learning algorithms based on environmental niche modeling (ENM) with presence-only data and background sample, namely Boosted Regression Tree (BRT), Generalized Linear Model (GLM), Maximum Entropy (MAXNT) and Random Forest (RF). We used a set of predictors that were grouped under climatic variables, agricultural water productivity and soil water content, soil chemical properties, soil physical properties, vegetation cover, and socio-economic variables. The Area Under the Curves (AUC) evaluation metrics for both training and testing were respectively 0.999 and 0.873 for BRT, 0.866 and 0.816 for GLM, 0.948 and 0.861 for MAXENT and 0.911 and 0.878 for RF. Results showed that proximity of inland valleys to roads and urban centers, elevation, soil water holding capacity, bulk density, vegetation index, gross biomass water productivity, precipitation of the wettest quarter, isothermality, annual precipitation, and total phosphorus among others were major predictors of IVs suitability for rainfed lowland rice. Suitable IVs areas were estimated at 155,000–225,000 Ha in Togo and 351,000–406,000 Ha in Benin. We estimated that 53.8% of the suitable IVs area is needed in Togo to attain self-sufficiency in rice while 60.1% of the suitable IVs area is needed in Benin to attain self-sufficiency in rice. These results demonstrated the effectiveness of an ensemble environmental niche modeling approach that combines the strengths of several models.
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