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Papers by Mabrouk El-Sharkawy

Research paper thumbnail of Observations on the parasitic behaviour of Thesium Vahl. (Santalaceae). (a) hosts and mode of attachment of haustorial structure

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Research paper thumbnail of Effects of artificial topsoil removal on sorghum, peanut, and cassava yield

ABSTRACT: Topsoil loss by soil erosion frequently results in crop productivity decline. This stud... more ABSTRACT: Topsoil loss by soil erosion frequently results in crop productivity decline. This study evaluated the impact of 5, 10, 13, and 40 cm topsoil removal on the productivity of sorghum (Sorghum bicolor L.), peanut (Arachis hypogaea L.), and cassava (Manihot esculenta Crantz). The trial was conducted on the Centro Internacional de Agricultura Tropical (CIAT) experimental station at Santander de Quilichao, Colombia. The soil was a well drained, kaolinitic-amorphous, isohyperthermic Oxic Dystropept. Organic matter was a key factor for productivity and the yields of these three crops were dramatically reduced by topsoil loss. Fertilizer could not restore lost productivity. The most important constraint to plant growth was aluminum saturation which increased sharply with topsoil loss.

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Research paper thumbnail of Host-parasite relationship in Cistanche spp. Hoffmgg. et Link

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Research paper thumbnail of Response of cassava (Manihot esculenta Crantz) to water stress and fertilization

Photosynthetica

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Research paper thumbnail of Photosynthesis and yield performance of cassava in seasonally dry and semiarid environments

Photosynthetica

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Research paper thumbnail of Pioneering research on C4 leaf anatomical, physiological, and agronomic characteristics of tropical monocot and dicot plant species: Implications for crop water relations and productivity in comparison to C3 cropping systems

Photosynthetica, 2009

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Research paper thumbnail of El-Sharkawy, M.A.: How can calibrated research-based models be improved for use as a tool in identifying genes controlling crop tolerance to environmental stresses in the era of genomics—from an experimentalist's perspective. — Photosynthetica 43 (2): 161-176, 2005

Photosynthetica, 2005

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Research paper thumbnail of Photosynthetic and Respiratory Exchanges of Carbon Dioxide by Leaves of the Grain Amaranth

The Journal of Applied Ecology, 1968

ABSTRACT

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Research paper thumbnail of Grass barriers in cassava hillside cultivation: Rooting patterns and root growth dynamics

Field Crops Research, 1995

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Research paper thumbnail of Response of Cassava to Prolonged Water Stress Imposed at Different Stages of Growth

Experimental Agriculture, 2002

A two-year field trial was conducted to study the effects of prolonged water stress on cassava (M... more A two-year field trial was conducted to study the effects of prolonged water stress on cassava (Manihot esculenta) productivity, and on nutrient uptake and use efficiency. Four contrasting cultivars were supplied with adequate fertilization and watering, except when water was excluded by covering the soil with plastic sheets for different periods, depending on treatment: from two to six months, four to eight months, or from six to twelve months after planting (early, mid-season and terminal stress respectively). Sequential harvests were made at 2, 4, 6, 8 and 12 months after planting to determine leaf area index and shoot and root biomass. At final harvest, nitrogen, phosphorus, potassium, calcium and magnesium concentrations in shoots and storage roots were determined.During both early and mid-season stress, leaf area index and shoot and root biomass were significantly smaller than those in the controls across all cultivars. After recovery from stress, leaf area index was greatly e...

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Research paper thumbnail of Genetic Variation Within Cassava Germplasm in Response to Potassium

Experimental Agriculture, 2000

As cassava is grown mostly by small resource-limited farmers throughout the tropics on low-fertil... more As cassava is grown mostly by small resource-limited farmers throughout the tropics on low-fertility soils with little fertilization and, due to the large potassium (K) export in harvested roots, genotypes that tolerate low-K soils and respond to K fertilization are warranted. The objective of this study was to evaluate cassava germplasm and identify such genotypes.Fourteen cultivars of cassava (Manihot esculenta) selected from the core germplasm at CIAT were grown under rainfed conditions for ten months over five consecutive seasons in Inceptisols either with no K application or with 50, 100 or 200 kg K ha−1 applied annually together with adequate nitrogen and phosphorus. All cultivars responded to K application both in terms of root and shoot biomass with the highest yields obtained by CM 507-37 and M Ven 25 in the absence of K application and at high K levels. These cultivars had the highest adaptation indices to low K and the highest K use efficiency for total biomass production...

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Research paper thumbnail of Losses of Organic Matter and Nutrients by Water Erosion in Cassava-Based Cropping Systems

Experimental Agriculture, 1997

Erosion trials under natural rainfall were conducted at two locations in the Andean hillsides of ... more Erosion trials under natural rainfall were conducted at two locations in the Andean hillsides of south-west Colombia on moderate slopes. Sediment-bound losses of seven cassava (Manihot esculenta) cropping systems per cropping period ranged from 26 to 1726 kg ha−1 for organic matter, 0.9 to 65.5 kg ha−1 for total nitrogen, 0.03 to 2.1 kg ha−1 for exchangeable magnesium, 0.04 to 2.8 kg ha−1 forexchangeable potassium and 0.004 to 0.8 kg ha−1 for Bray-II phosphorus. Runoff water contributed substantially to total available potassium, magnesium and phosphorus losses. Concentrations of soluble phosphorus in runoff water from heavily eroded continuously clean-tilled fallow plots were slightly higher than from cropped and fertilized plots. Enrichment ratios for sediments from these highly aggregated Inceptisols were low. Sand-sized particles were selectively removed by water erosion. The higher proportion of nutrient losses with run-off water in our study stressed the importance of runoff c...

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Research paper thumbnail of Photosynthesis and yield performance of cassava in seasonally dry and semiarid environments

Photosynthetica, 1997

PHOTOSYNTHETTCA 33 (2): 249-257, 1997 Photosynthesis and yield performance of cassava in seasonal... more PHOTOSYNTHETTCA 33 (2): 249-257, 1997 Photosynthesis and yield performance of cassava in seasonally dry and semiarid environments SM DE TAFUR, MA EL-SHARKAWY* and F. CALLE Physiology and Breeding Sections, Cassava Program, Centro Internacional de ...

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Research paper thumbnail of Pioneering research on C 4 leaf anatomical, physiological, and agronomic characteristics of tropical monocot and dicot plant species: Implications for crop water …

Photosynthetica, 2009

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Research paper thumbnail of Prospects of photosynthetic research for increasing agricultural productivity, with emphasis on the tropical C 4 Amaranthus and the cassava C 3 -C 4 crops

Productivity of most improved major food crops showed stagnation in the past decades. As human po... more Productivity of most improved major food crops showed stagnation in the past decades. As human population is projected to reach 910 billion by the end of the 21 st century, agricultural productivity must be increased to ensure their demands. Photosynthetic capacity is the basic process underlying primary biological productivity in green plants and enhancing it might lead to increasing potential of the crop yields. Several approaches may improve the photosynthetic capacity, including integrated systems management, in order to close wide gaps between actual farmer's and the optimum obtainable yield. Conventional and molecular genetic improvement to increase leaf net photosynthesis (P N) are viable approaches, which have been recently shown in few crops. Bioengineering the more efficient C 4 into C 3 system is another ambitious approach that is currently being applied to the C 3 rice crop. Two under-researched, yet old important crops native to the tropic Americas (i.e., the C 4 a...

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Research paper thumbnail of Global warming: causes and impacts on agroecosystems productivity and food security with emphasis on cassava comparative advantage in the tropics/subtropics

Photosynthetica, 2014

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Research paper thumbnail of Genotypic variations in activities of phosphoenolpyruvate carboxylase and correlations with leaf photosynthetic characteristics and crop productivity of cassava grown …

Photosynthetica, 2008

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Research paper thumbnail of How can calibrated research-based models be improved for use as a tool in identifying genes controlling crop tolerance to environmental stresses in the era of genomics—from an experimentalist’s perspective

PHOTOSYNTHETICA 43 (2): 161-176, 2005

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Research paper thumbnail of Cassava biology and physiology

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Research paper thumbnail of Stress-Tolerant Cassava: The Role of Integrative Ecophysiology-Breeding Research in Crop Improvement

Open Journal of Soil Science, 2012

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Research paper thumbnail of Observations on the parasitic behaviour of Thesium Vahl. (Santalaceae). (a) hosts and mode of attachment of haustorial structure

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Effects of artificial topsoil removal on sorghum, peanut, and cassava yield

ABSTRACT: Topsoil loss by soil erosion frequently results in crop productivity decline. This stud... more ABSTRACT: Topsoil loss by soil erosion frequently results in crop productivity decline. This study evaluated the impact of 5, 10, 13, and 40 cm topsoil removal on the productivity of sorghum (Sorghum bicolor L.), peanut (Arachis hypogaea L.), and cassava (Manihot esculenta Crantz). The trial was conducted on the Centro Internacional de Agricultura Tropical (CIAT) experimental station at Santander de Quilichao, Colombia. The soil was a well drained, kaolinitic-amorphous, isohyperthermic Oxic Dystropept. Organic matter was a key factor for productivity and the yields of these three crops were dramatically reduced by topsoil loss. Fertilizer could not restore lost productivity. The most important constraint to plant growth was aluminum saturation which increased sharply with topsoil loss.

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Research paper thumbnail of Host-parasite relationship in Cistanche spp. Hoffmgg. et Link

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Research paper thumbnail of Response of cassava (Manihot esculenta Crantz) to water stress and fertilization

Photosynthetica

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Research paper thumbnail of Photosynthesis and yield performance of cassava in seasonally dry and semiarid environments

Photosynthetica

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Research paper thumbnail of Pioneering research on C4 leaf anatomical, physiological, and agronomic characteristics of tropical monocot and dicot plant species: Implications for crop water relations and productivity in comparison to C3 cropping systems

Photosynthetica, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of El-Sharkawy, M.A.: How can calibrated research-based models be improved for use as a tool in identifying genes controlling crop tolerance to environmental stresses in the era of genomics—from an experimentalist's perspective. — Photosynthetica 43 (2): 161-176, 2005

Photosynthetica, 2005

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Photosynthetic and Respiratory Exchanges of Carbon Dioxide by Leaves of the Grain Amaranth

The Journal of Applied Ecology, 1968

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Grass barriers in cassava hillside cultivation: Rooting patterns and root growth dynamics

Field Crops Research, 1995

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Response of Cassava to Prolonged Water Stress Imposed at Different Stages of Growth

Experimental Agriculture, 2002

A two-year field trial was conducted to study the effects of prolonged water stress on cassava (M... more A two-year field trial was conducted to study the effects of prolonged water stress on cassava (Manihot esculenta) productivity, and on nutrient uptake and use efficiency. Four contrasting cultivars were supplied with adequate fertilization and watering, except when water was excluded by covering the soil with plastic sheets for different periods, depending on treatment: from two to six months, four to eight months, or from six to twelve months after planting (early, mid-season and terminal stress respectively). Sequential harvests were made at 2, 4, 6, 8 and 12 months after planting to determine leaf area index and shoot and root biomass. At final harvest, nitrogen, phosphorus, potassium, calcium and magnesium concentrations in shoots and storage roots were determined.During both early and mid-season stress, leaf area index and shoot and root biomass were significantly smaller than those in the controls across all cultivars. After recovery from stress, leaf area index was greatly e...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Genetic Variation Within Cassava Germplasm in Response to Potassium

Experimental Agriculture, 2000

As cassava is grown mostly by small resource-limited farmers throughout the tropics on low-fertil... more As cassava is grown mostly by small resource-limited farmers throughout the tropics on low-fertility soils with little fertilization and, due to the large potassium (K) export in harvested roots, genotypes that tolerate low-K soils and respond to K fertilization are warranted. The objective of this study was to evaluate cassava germplasm and identify such genotypes.Fourteen cultivars of cassava (Manihot esculenta) selected from the core germplasm at CIAT were grown under rainfed conditions for ten months over five consecutive seasons in Inceptisols either with no K application or with 50, 100 or 200 kg K ha−1 applied annually together with adequate nitrogen and phosphorus. All cultivars responded to K application both in terms of root and shoot biomass with the highest yields obtained by CM 507-37 and M Ven 25 in the absence of K application and at high K levels. These cultivars had the highest adaptation indices to low K and the highest K use efficiency for total biomass production...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Losses of Organic Matter and Nutrients by Water Erosion in Cassava-Based Cropping Systems

Experimental Agriculture, 1997

Erosion trials under natural rainfall were conducted at two locations in the Andean hillsides of ... more Erosion trials under natural rainfall were conducted at two locations in the Andean hillsides of south-west Colombia on moderate slopes. Sediment-bound losses of seven cassava (Manihot esculenta) cropping systems per cropping period ranged from 26 to 1726 kg ha−1 for organic matter, 0.9 to 65.5 kg ha−1 for total nitrogen, 0.03 to 2.1 kg ha−1 for exchangeable magnesium, 0.04 to 2.8 kg ha−1 forexchangeable potassium and 0.004 to 0.8 kg ha−1 for Bray-II phosphorus. Runoff water contributed substantially to total available potassium, magnesium and phosphorus losses. Concentrations of soluble phosphorus in runoff water from heavily eroded continuously clean-tilled fallow plots were slightly higher than from cropped and fertilized plots. Enrichment ratios for sediments from these highly aggregated Inceptisols were low. Sand-sized particles were selectively removed by water erosion. The higher proportion of nutrient losses with run-off water in our study stressed the importance of runoff c...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Photosynthesis and yield performance of cassava in seasonally dry and semiarid environments

Photosynthetica, 1997

PHOTOSYNTHETTCA 33 (2): 249-257, 1997 Photosynthesis and yield performance of cassava in seasonal... more PHOTOSYNTHETTCA 33 (2): 249-257, 1997 Photosynthesis and yield performance of cassava in seasonally dry and semiarid environments SM DE TAFUR, MA EL-SHARKAWY* and F. CALLE Physiology and Breeding Sections, Cassava Program, Centro Internacional de ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Pioneering research on C 4 leaf anatomical, physiological, and agronomic characteristics of tropical monocot and dicot plant species: Implications for crop water …

Photosynthetica, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Prospects of photosynthetic research for increasing agricultural productivity, with emphasis on the tropical C 4 Amaranthus and the cassava C 3 -C 4 crops

Productivity of most improved major food crops showed stagnation in the past decades. As human po... more Productivity of most improved major food crops showed stagnation in the past decades. As human population is projected to reach 910 billion by the end of the 21 st century, agricultural productivity must be increased to ensure their demands. Photosynthetic capacity is the basic process underlying primary biological productivity in green plants and enhancing it might lead to increasing potential of the crop yields. Several approaches may improve the photosynthetic capacity, including integrated systems management, in order to close wide gaps between actual farmer's and the optimum obtainable yield. Conventional and molecular genetic improvement to increase leaf net photosynthesis (P N) are viable approaches, which have been recently shown in few crops. Bioengineering the more efficient C 4 into C 3 system is another ambitious approach that is currently being applied to the C 3 rice crop. Two under-researched, yet old important crops native to the tropic Americas (i.e., the C 4 a...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Global warming: causes and impacts on agroecosystems productivity and food security with emphasis on cassava comparative advantage in the tropics/subtropics

Photosynthetica, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Genotypic variations in activities of phosphoenolpyruvate carboxylase and correlations with leaf photosynthetic characteristics and crop productivity of cassava grown …

Photosynthetica, 2008

Bookmarks Related papers MentionsView impact

Research paper thumbnail of How can calibrated research-based models be improved for use as a tool in identifying genes controlling crop tolerance to environmental stresses in the era of genomics—from an experimentalist’s perspective

PHOTOSYNTHETICA 43 (2): 161-176, 2005

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Cassava biology and physiology

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Stress-Tolerant Cassava: The Role of Integrative Ecophysiology-Breeding Research in Crop Improvement

Open Journal of Soil Science, 2012

Bookmarks Related papers MentionsView impact