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  • 1
    ISSN: 1573-0867
    Keywords: alley cropping ; fertilizer N ; Leucaena leucocephala ; leucaena prunings ; maize residues ; 15N recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field microplot experiments were conducted in the semi-arid tropics of northern Australia to evaluate the response of maize (Zea mays L.) growth to addition of N fertilizer and plant residues and to examine the fate of fertilizer15N in a leucaena (Leucaena leucocephala) alley cropping system, in which supplemental irrigation was used. Leucaena prunings, maize residues and N fertilizer were applied to alley-cropped maize grown in microplots which were installed in the alleys formed by leucaena hedgerows spaced 4.5 metres apart. The15N-labelled fertilizer was used to examine the fate of fertilizer N applied in the presence of mulched leucaena prunings and maize residues. Application of leucaena prunings increased maize yield while addition of N fertilizer in the presence of the prunings produced a further increase in maize production. There was a significant positive interaction between N fertilizer and leucaena prunings in increasing maize production. The addition of maize residues in the presence of N fertilizer and leucaena prunings decreased maize yield and N uptake and increased fertilizer15N loss from 38% to 47%. Maize recovered 24–79% of fertilizer15N in one cropping season, depending on application rate of N fertilizer and field management of plant residues. About 20–34% of fertilizer15N remained in the soil. More than 37% of fertilizer15N was apparently lost from the soil and plant system largely through denitrification when N fertilizer was applied at 40 kg N ha−1 or more in the presence or absence of plant residues. Application of N fertilizer improved maize yield and increased the contribution of mulched leucaena prunings to crop production in the alley cropping system.
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  • 2
    ISSN: 1573-0867
    Keywords: leucaena ; maize ; 15N recovery ; residual15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Legume residues have been credited with supplying mineral nitrogen (N) to the associated cereal crop and improving soil fertility in the long term. Few studies using15N have reported the fate of legume N and fertilizer N in the presence of legume residues in soil-plant systems over periods of two years or longer. A field experiment was conducted in microplots to evaluate: (1) the residual value of the15N added in leucaena residues; (2) the residual value of fertilizer15N applied in the presence of unlabelled leucaena residues in the first year to maize over three subsequent years; and (3) the long-term fate of residual fertilizer and leucaena15N in a leucaena alley cropping system. There was a significant increase in maize production over three subsequent years after addition of leucaena residues. The residual effect of fertilizer N increased maize yield in the second year when N fertilizer was applied at 36 kg N ha−1 in the first year in the presence of leucaena residues. Of the leucaena15N applied in the first year, the second, third and fourth maize crop recovered 2.6%, 1.8% and 1.4%, respectively. The corresponding values for the residual fertilizer15N were 0.7%, 0.4% and 0.3%. About 12–14% of the fertilizer15N added in the first year was found in the 200 cm soil profile over the following three years. This differed from the 38–41% of leucaena15N detected in the soil over the same period. Most of the residual fertilizer and leucaena15N in the soil was immobilized in the top 25 cm with less than 1% leached below 100 cm. More than 36% of the leucaena15N and fertilizer15N added in the first year was apparently lost from the soil-plant system in the first two years. No further loss of the residual leucaena and fertilizer15N was detected after two years.
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  • 3
    ISSN: 1573-5036
    Keywords: alley cropping ; C/N ratio ; decomposition ; fertilizer N ; leucaena N ; leucaena residues ; lignin ; maize ; N mineralization ; 15N recovery ; N uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The success of alley cropping depends to a large extent on the efficiency of transfer of nitrogen (N) from the legume hedgerow plants to the non-legume crop. Here the idea is examined that leucaena prunings (residues) can supply enough N to maize plants to significantly reduce the degree of N deficiency. Two experiments on decomposition of leucaena leaf, stem, and petiole and mineralization of N from leucaena residues were conducted in field microplots which received application of either15N-labelled leucaena materials or ammonium sulphate fertilizer. The microplots were installed in alleys formed by leucaena hedgerows spaced 4.5 metres apart and cropped with maize. The decomposition of leucaena leaves, stems and petioles was estimated by several methods. The decomposition ranged from 50–58% with leaves, 25–67% with stems and 38–51% with petioles 20 days after addition. More than 55% of the N was released in 52 days during decomposition of leucaena residues. By 20 days after application of15N-labelled leucaena 3.3–9.4% of the added15N was found in the maize plants, 32.7–49.0% was in the leucaena residues, 36.0–48.0% in the soil and 0.3–21.9% lost (deficit). By 52 days 4.8% of the15N applied in leucaena prunings was taken up by maize, 45.1% was detected in the residues, 24.9% in the soil and 25.2% lost. However, when N fertilizer was applied, 50.2% of the fertilizer N was recovered by maize, 35.5% was retained in the soil and 14.3% apparently lost. There was a marked increase in maize plant dry matter and N uptake in the microplots with addition of leucaena prunings compared with those in the microplots without leucaena added. Most of the15N remaining in the soil profile, derived from leucaena residues, was detected in the top 25 cm soil with less than 2% found below 25 cm. ei]H Lambers
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  • 4
    ISSN: 1573-5036
    Keywords: decomposition ; fertilizer N ; leucaena residues ; maize residues ; N loss ; N uptake ; 15N recovery ; residue incorporation ; residue N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In an alley cropping system, prunings from the hedgerow legume are expected to supply nitrogen (N) to the associated cereal. However, this may not be sufficient to achieve maximum crop yield. Three field experiments with alley-cropped maize were conducted in a semi-arid environment in northern Australia to determine: (1) the effect of N fertilizer on maize growth in the presence of fresh leucaena prunings; (2) the effect of incorporation of leucaena and maize residues on maize yield and the fate of plant residue15N in the alley cropping system; and (3) the15N recovery by maize from15N-labelled leucaena, maize residues and ammonium sulphate fertilizer. Leucaena residues increased maize crop yield and N uptake although they did not entirely satisfy the N requirement of the alley crop. Additional N fertilizer further increased the maize yield and N uptake in the presence of leucaena residues. Placement of leucaena residues had little effect on the availability of N to maize plants over a 2 month period. The incorporation of leucaena residues in the soil did not increase the recovery of leucaena15N by maize compared with placement of the residues on the soil surface. After 2 months, similar proportions of the residue15N were recovered by maize from mulched leucaena (6.3%), incorporated leucaena (6.1%) and incorporated maize (7.6%). By the end of one cropping season (3 months after application) about 9% of the added15N was taken up by maize from either15N-labelled leucaena as mulch or15N-labelled maize residues applied together with unlabelled fresh leucaena prunings as mulch. The recovery of the added15N was much higher (42.7%) from the15N-labelled ammonium sulphate fertilizer at 40 kg N ha-1 in the presence of unlabelled leucaena prunings. Most of the added15N recovered in the 200 cm soil profile was distributed in the top 25 cm soil with little leached below that. About 27–41% of the leucaena15N was apparently lost, largely through denitrification from the soil and plant system, in one cropping season. This compared with 35% of the fertilizer15N lost when the N fertilizer was applied in the presence of prunings. ei]H Lambers
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 26 (1998), S. 199-215 
    ISSN: 0271-2091
    Keywords: air-conditioning unit ; k-∊ model ; Reynolds stress model ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Details are given of a study to obtain experimental data in an idealized environment for the purpose of evaluating the corresponding computational predictions and which supplement parallel measurements made in actual packaged air-conditioning units. The system consisted of a purpose-built low-speed wind tunnel with a working section constructed to reproduce particular features of the real units. In the experiment, both the mean velocity profiles and turbulence properties of the flow are obtained from triple-hot-wire anemometry measurements. A numerical model, based on finite volume methodology, was used to obtain the solution of the Reynolds-averaged Navier-Stokes equations for incompressible isothermal flow. The Reynolds stress terms in the equations are calculated using the standard k-∊ model and second-moment closure (Reynolds stress) models. The accuracy of the two models was evaluated against the experimental measurements made 10 mm downstream of a baffle. The results show that the standard k-∊ model gave the better agreement except in regions of strong recirculation. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 37 (1994), S. 1437-1443 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An alternative quadrilateral element for Reissner - Mindlin plates, which extends the mixed formulation described in Part 1 using linked interpolations, is presented. Differently from element Q4BL presented in Part I, this element (Q4BLa) employs four internal rotation nodes and a linear approximation for transverse shear forces. It is shown that the element passes various patch tests, it does not possess any zero-energy mode and its performance is good for both thick and thin plates.
    Additional Material: 3 Ill.
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