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  • 1
    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
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  • 2
    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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  • 3
    ISSN: 1572-9680
    Keywords: Acacia saligna ; intercropping ; pruning ; resource capture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We tested the hypothesis that shallow-rooted crops and deep-rooted trees will share the available water in a complementary manner, when grown together, in a field trail in the Turkana district of northern Kenya during 1994 to 1996. Such studies have been few in dryland agroforestry. The effects of two different Acacia saligna (Labill.) H. Wendl. tree planting densities (2500 and 833 trees per ha), tree pruning (no pruning vs. pruning) and annual intercrops (no intercrop vs. intercrop) on total biomass production and their interactions were tested. In 1996 Sorghum bicolor (L.) Moench was used during the first vegetation period and Vigna unguiculata (L.) Walp. during the second. We used naturally generated runoff water for irrigation to supplement low rainfall amounts typical for the area. High biomass production (〉 13 t ha−1 over a two year period) was observed irrespective of intercropping of pruned trees or sole tree stands. Although the pruning treatment reduced total tree biomass yields by a quarter, the introduction of annual intercrops after the pruning of trees outweighed this loss. The yields of the intercrops in the pruned tree treatments were similar to their yields when grown as monocrops. The calculation of land equivalent ratios showed overyielding for intercropped, pruned systems. The high values for LER (1.36 at low and 1.47 at high density of trees) indicate that there is complementarity in resource use between the different species.
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  • 4
    ISSN: 1572-9680
    Keywords: Acacia saligna ; complementarity ; cowpea ; intercroppig ; resource capture ; sorphum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Water is the most limiting factor for plant production in arid to semiarid regions. In order to overcome this limitation surface runoff water can be used to supplement seasonal rainfall. During 1996 we conducted a runoff irrigated agroforestry field trial in the Turkana district of Northern Kenya. The effects of two different Acacia saligna (Labill.) H. Wendl. tree planting densities (2500 and 833 trees per ha), tree pruning (no pruning vs. pruning) and annual intercrops (no intercrop vs. intercrop: Sorghum bicolor (L.) Moench during the first season and Vigna unguiculata (L.) Walp. during the second season) on water use were investigated. The annual crops were also grown as monocrops. Water consumption ranged from 585 to 840 mm during the first season (only treatments including trees). During the second season, which was shorter and the plants relied solely on stored water in the soil profile, water consumption was less than half of that during the first season. Highest water consumptions were found for non-pruned trees at high density and the lowest were found for the annual crops grown as monocrops. Tree pruning decreased water uptake compared to non-pruned trees but soil moisture depletion pattern showed complementarity in water uptake between pruned trees and annual intercrops. The highest values of water use efficiency for an individual treatment were achieved when the pruned trees at high density were intercropped with sorghum (1.59 kg m−3) and cowpea (1.21 kg m−3). Intercropping and high tree density increased water use efficiency in our runoff agroforestry trial. We ascribe the observed improvement in water use efficiency to the reduction of unproductive water loss from the bare soil.
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  • 5
    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.
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  • 6
    Publication Date: 2017-06-30
    Description: Understanding pathways of genetic information transfer from one generation to another is particularly important when open-pollinated seeds are collected for reforestation or for enrichment of native forests. Noth...
    Print ISSN: 0048-0134
    Electronic ISSN: 1179-5395
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by SpringerOpen
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  • 7
    Publication Date: 2003-04-01
    Print ISSN: 1525-755X
    Electronic ISSN: 1525-7541
    Topics: Geography , Geosciences , Physics
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  • 8
    Publication Date: 2018
    Description: 〈div data-abstract-type="normal"〉〈p〉A major challenge in addressing the loss of benefits and services provided by the natural environment is that it can be difficult to find ways for those who benefit from them to pay for their preservation. We examine one such context in Malawi, where erosion from soils disturbed by agriculture affects not only farmers’ incomes, but also damages aquatic habitat and inhibits the storage and hydropower potential of dams downstream. We demonstrate that payments from hydropower producers to farmers to maintain land cover and prevent erosion can have benefits for all parties involved.〈/p〉〈/div〉
    Electronic ISSN: 2059-4798
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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