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Nutrient cycling in an agroforestry system with runoff irrigation in Northern Kenya (1998)

Lehmann, J. ; Weigl, D. ; Droppelmann, K. ; [et al.]

Springer

Agroforestry systems 43 (1998), S. 49-70

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ISSN: 1572-9680

Keywords: Acacia saligna ; nutrient balance ; nutrient leaching ; resin core ; soil solution ; Sorghum bicolor

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract A nutrient balance was determined for sole and alley cropped Sorghum bicolor and Acacia saligna in a runoff irrigation system in Northern Kenya. Nutrient input including precipitation and runoff, and output through harvest and leaching were measured for N, P, K, Ca and Mg using adsorption resins, tensiometry and suction cups. Various management scenarios are discussed with respect to nutrient return. Nutrient input with rainfall was generally low in comparison to nutrient uptake or leaching losses. The irrigation water, however, constituted an important nutrient input, especially for Ca and Mg. Nutrient export with the harvest was large for N and K, but can effectively be reduced by a nutrient return with mulch. Nutrient leaching losses from the topsoil (0–30 cm) were lower in the sorghum monoculture than in the tree-based systems. In the subsoil (120 cm), however, leaching was effectively reduced by the trees. In the agroforestry system, leaching losses of N under the sorghum were 53% lower than in the sorghum monoculture. This could be attributed to a higher root abundance and a higher ratio of nutrient uptake-to-leaching in the agroforestry system than in the monocultures indicating a higher nutrient efficiency. The lower leaching losses in the agroforestry system compared to the crop monoculture could not compensate for the additional nutrient export in tree biomass. A nutrient return by mulching crop residues and acacia leaves was essential for a positive nutrient balance in the agroforestry system. Combining annual and perennial crops provided a higher internal nutrient cycling than the monocultures.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1026447119829

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Nutrient interactions of alley cropped Sorghum bicolor and Acacia saligna in a runoff irrigation system in Northern Kenya (1999)

Lehmann, Johannes ; Weigl, Doris ; Peter, Inka ; [et al.]

Springer

Plant and soil 210 (1999), S. 249-262

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ISSN: 1573-5036

Keywords: Acacia saligna ; nutrient competition ; 15N ; resin core ; soil solution ; Sorghum bicolor ; Sr

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract In a runoff irrigation system in Northern Kenya, we studied the nutrient interactions of sole cropped and alley cropped Sorghum bicolor (L.) Moench and Acacia saligna (Labill.) H.L. Wendl. The trees were pruned once before the cropping season and the biomass was used as fodder for animals. The nutrient contents in leaf tissue, soil and soil solution were monitored and the uptake of applied tracers (15N, Sr) was followed. The grain yield of alley cropped sorghum was similar to or slightly higher than in monoculture and did not decrease near the tree-crop interface. Foliar N and Ca contents of the crop were higher in the agroforestry combination than in monoculture, corresponding to higher soil N and Ca contents. Soil solution and soil mineral N dynamics indicate an increase of N under the tree row and unused soil N at the topsoil in the alley of the sole cropped trees as well as below 60 cm depth in the crop monoculture. The N use efficiency of the tree+crop combination was higher than the sole cropped trees or crops. Competition was observed for Zn and Mn of both tree and crop whereas for Ca only the tree contents decreased. P, K, Mg and Fe dynamics were not affected by alley cropping at our site. The lower uptake of applied Sr by trees in alley cropping compared to those of the monoculture stand suggested a lower competitiveness of the acacia than sorghum, which did not show lower Sr contents when intercropped. The study showed the usefulness of combining soil and plant analyses together with tracer techniques identifying nutrient competition, nutrient transfer processes and the complementary use of soil nutrients, as the main features of the tree-crop combination.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004698403770

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Hexose transporter expression and function in mammalian spermatozoa: Cellular localization and transport of hexoses and vitamin C (1998)

Angulo, Constanza ; Rauch, María Cecilia ; Droppelmann, Andrea ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 71 (1998), S. 189-203

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ISSN: 0730-2312

Keywords: glucose transporters ; sperm ; dehydroascorbic acid ; fructose ; 2-deoxy-D-glucose ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: We analyzed the expression of hexose transporters in human testis and in human, rat, and bull spermatozoa and studied the uptake of hexoses and vitamin C in bull spermatozoa. Immunocytochemical and reverse transcription-polymerase chain reaction analyses demonstrated that adult human testis expressed the hexose transporters GLUT1, GLUT2, GLUT3, GLUT4, and GLUT5. Immunoblotting experiments demonstrated the presence of proteins of about 50-70 kD reactive with anti-GLUT1, GLUT2, GLUT3, and GLUT5 in membranes prepared from human spermatozoa, but no proteins reactive with GLUT4 antibodies were detected. Immunolocalization experiments confirmed the presence of GLUT1, GLUT2, GLUT3, GLUT5, and low levels of GLUT4 in human, rat, and bull spermatozoa. Each transporter isoform showed a typical subcellular localization in the head and the sperm tail. In the tail, GLUT3 and GLUT5 were present at the level of the middle piece in the three species examined, GLUT1 was present in the principal piece, and the localization of GLUT2 differed according of the species examined. Bull spermatozoa transported deoxyglucose, fructose, and the oxidized form of vitamin C, dehydroascorbic acid. Transport of deoxyglucose and dehydroascorbic acid was inhibited by cytochalasin B, indicating the direct participation of facilitative hexose transporters in the transport of both substrates by bull spermatozoa. Transport of fructose was not affected by cytochalasin B, which is consistent for an important role for GLUT5 in the transport of fructose in these cells. The data show that human, rat, and bull spermatozoa express several hexose transporter isoforms that allow for the efficient uptake of glucose, fructose, and dehydroascorbic acid by these cells. J. Cell. Biochem. 71:189-203, 1998. © 1998 Wiley-Liss, Inc.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

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Human Erythrocytes Express GLUT5 and Transport Fructose (1997)

Concha, Ilona I. ; Velásquez, Fernando V. ; Martı́nez, Juan M. ; [et al.]

American Society of Hematology

In: Blood. 1997; 89(11): 4190-4195. Published 1997 Jun 01. doi: 10.1182/blood.v89.11.4190.

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Publication Date: 1997-06-01

Description: Although erythrocytes readily metabolize fructose, it has not been known how this sugar gains entry to the red blood cell. We present evidence indicating that human erythrocytes express the fructose transporter GLUT5, which is the major means for transporting fructose into the cell. Immunoblotting and immunolocalization experiments identified the presence of GLUT1 and GLUT5 as the main facilitative hexose transporters expressed in human erythrocytes, with GLUT2 present in lower amounts. Functional studies allowed the identification of two transporters with different kinetic properties involved in the transport of fructose in human erythrocytes. The predominant transporter (GLUT5) showed an apparent Km for fructose of approximately 10 mmol/L. Transport of low concentrations of fructose was not affected by 2-deoxy–D-glucose, a glucose analog that is transported by GLUT1 and GLUT2. Similarly, cytochalasin B, a potent inhibitor of the functional activity of GLUT1 and GLUT2, did not affect the transport of fructose in human erythrocytes. The functional properties of the fructose transporter present in human erythrocytes are consistent with a central role for GLUT5 as the physiological transporter of fructose in these cells.

Print ISSN: 0006-4971

Electronic ISSN: 1528-0020

Topics: Biology , Medicine