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921.
R. J. Kaitho I. V. Nsahlai B. A. Williams N. N. Umunna S. Tamminga J. van Bruchem 《Agroforestry Systems》1997,39(2):129-144
The aim of this work was to assess whether degradability, gas production or chemical constituents could predict the preference
of browses. Forty tropical browse species leaves with a crude protein (CP) content ranging from 79 to 307 g kg-1 DM were used for this study. The neutral detergent fibre (NDF) ranged from 220 to 694 g kg-1 DM, while acid detergent fibre (ADF) ranged from 146 to 523 g kg-1 DM. The NDF-bound nitrogen (NDFN) and ADF-bound nitrogen were particularly high in Calliandra calothyrsus, Acacia polyacantha,
Sesbania sesban, Acacia venosa and Acacia hockii. High levels of tannins were observed in Acacia species especially A. dolichocephala,
A. hockii, A. microbotrya and A. salicina. High levels were also observed in Flemingia macrophyla and Leucaena pallida. The
browse species differed (P < 0.05) in DM in sacco degradability coefficients. High potential degradability (PD) and effective
degradability (ED) were observed in Sesbania spp, Moringa stenopetala, Indigofera arrecta, Chamaecytisus palmensis and Atriplex
spp. The browses differed (P < 0.05) in asymptotic gas (Ag) production (ml g-1 OM), but had similar (P > 0.05) times of incubation at which half of the asymptotic gas had been formed. Preference and DM
intake were positively correlated (P < 0.01) to NDFN, but negatively correlated (P < 0.05) to NDF and ADF. The PD and Ag were
negatively (P < 0.001) related to NDF, ADF and lignin. Total phenols (TP) and condensed tannins (CT) were negatively (P <
0.05) related to PD, ED and Ag. A positive correlation was observed between CT and NDF-bound condensed tannins (r = 0.55,
P < 0.001) and, CT and TP (r = 0.40, P < 0.01). Prediction equations were poor for DM intake and preference, moderate for
gas production and good for potential and effective degradabilities. The phenolic components were more related to dry matter
degradation and gas production than to preference and dry matter intake. NDFN and Ag made a positive contribution to both
preference and DM intake. It was concluded that chemical constitutes such as N, NDF, NDFN, ADF and lignin are essential to
predict the nutritive value of browses.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
922.
H. W. Fassbender L. Alpízar J. Heuveldop H. Fölster G. Enríquez 《Agroforestry Systems》1988,6(1):49-62
Models for cycles for organic matter and nutrients element (N, P, K, Ca and Mg) are presented for the agroforestry systems of cacao (Theobroma cacao) withCordia alliodora orErythrina poeppigiana in Turrialba, Costa Rica.For the models, system reserves (soil, humus, vegetation divided into leaves, branches, stems, fine roots, fruits) and transference between compartments (production and decomposition of litter residues) inputs (fertilizer, rainfall) and outputs (harvests) of the system are considered.The implications of the models are discussed in detail.Aspects of net primary production in the systems studied are considered.N fixation is calculated on the basis of balances. Analysis of soil water showed high variations that coincided with rainfall patterns and pruning of theE. poeppigiana.For part I see Vol. 4, No. 3, 1986 For part II see this issueAgroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesellschaft für Technische Zusammenarbeit), Turrialba, Costa Rica 相似文献
923.
M.E.?Isaac A.M.?GordonEmail author N.?Thevathasan S.K.?Oppong J.?Quashie-Sam 《Agroforestry Systems》2005,65(1):23-31
The conversion of forests to agroecosystems or agroforests comes with many changes in biological and chemical processes. Agroforestry,
a tree based agroecosystem, has shown promise with respect to enhanced system nutrient accumulation after land conversion
as compared to sole cropping systems. Previous research on tropical agroforestry systems has revealed increases in soil organic
matter and total organic nitrogen in the short term. However, research is lacking on long-term system level sustainability
of nutrient cycles and storage, specifically in traditional multi-strata agroforestry systems, as data on both the scope and
duration of nutrient instability are inconclusive and often conflicting. This study, conducted in Ghana, West Africa, focused
on carbon and nitrogen dynamics in a twenty-five year chronosequence of cacao (Theobroma cacao Linn.) plantations. Three treatments were selected as on-farm research sites: 2, 15 and 25-year-old plantations. Soil carbon
(C, to a depth of 15 cm) varied between treatments (2 years: 22.6 Mg C ha−1; 15 years: 17.6 Mg C ha−1; 25 years: 18.2 Mg C ha−1) with a significant difference between the 2- and 15- and the 2- and 25-year-old treatments (p < 0.05). Total soil nitrogen in the top 15 cm varied between 1.09 and 1.25 Mg N ha−1 but no significant differences were noted between treatments. Soil nitrification rates and litter fall increased significantly
with treatment age. However, photosynthetically active radiation (PAR) and soil temperature showed a significant decrease
with age. No difference was found between decay rates of litter at each treatment age. By 25 years, system carbon sequestration
rates were 3 Mg C ha−1 y−1, although results suggest that even by 15 years, system-level attributes were progressing towards those of a natural system. 相似文献
924.
Tracer methods to assess nutrient uptake distribution in multistrata agroforestry systems 总被引:3,自引:0,他引:3
Separate assessment of nutrient uptake by individual plants in mixed cropping with trees is impossible without tracer techniques.
The different 15N-to-14N isotope ratio of atmospheric and soil N can be used to study the contribution of biologically fixed N to the nutrition of
associated trees. In most cases, the assessment of nutrient uptake distribution is an appropriate way of evaluating how to
improve the transfer of biologically fixed N. Radioisotopes (e.g., 32P), stable isotopes (e.g., 15N) and rare elements (e.g., Sr) can be used to determine relative root activity distribution by applying the tracer to different
soil depths or distances from trees. A broadcast application of the tracer instead of point application makes it possibe to
calculate uptake values per unit area. The direct determination of nutrient pathways with such robust experiments offers considerable
advantages for improving nutrient use efficiency and complementarity in multistrata agroforestry systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
925.
Green manure applications in alley cropping systems often include twigs despite their potential to absorb (immobilize) nitrogen (N). To assess the impact of twigs on net N mineralization or immobilization from hedge row cuttings, we separated cuttings fromCalliandra calothyrsus andGliricidia sepium into leaf-only, twig-only, and mixed (leaf + twig) fractions and incubated them with moist soil in the laboratory. Soil extractable inorganic N did no differ among treatments after two weeks, but after four and eight weeks was greatest in leaf-only, and least in twig-only treatments. After two weeks, extractable N from the leaf-only treatment rose steadily, while that from the twig-only and mixed treatments was variable due to periods of net mineralization and net immobilization. The pattern of variation in mixed treatments paralleled that of twig-only, indicating that net immobilization in the mixture was largely caused by the presence of twigs. Extractable N from the mixture was somewhat lower than that predicted from the sum of leaf-only and twig-only treatments. We conclude that twigs in green manure reduce short-term N availability to associated crops in agroforestry systems. 相似文献
926.
Quantitative field measurements of biological nitrogen fixation (BNF) and biomass production by four different understorey pastures in a Pinus radiata-pasture agroforestry system were determined over a period of one year. The trees were two years old at the beginning of this study and the understorey pastures were being cut and removed for silage. The BNF was determined using the 15N dilution technique. Pastures of ryegrass+clover, cocksfoot+clover, phalaris+clover and lucerne were used. Substantial amounts of BNF were found (71 to 230 kg N ha–1 year–1) with lucerne showing the highest N fixation. However, lucerne derived only 71 to 72% of its N from the atmosphere (%Ndfa) during the spring/summer period compared to 83–97% with clovers, thus the net N demand from the soil was substantially higher with lucerne. This caused increased N stress to the trees. Clover in ryegrass+clover pasture fixed more N than the other grass+clover pastures. Although pasture position in relation to trees did not affect annual pasture total DMY and %Ndfa, pastures north of tree row grew better than those in other positions. Trees significantly affected the BNF of legumes and the botanical composition of pastures with highest BNF and legume production occurring in pastures midway between two rows of trees. These results suggest that it would be advantageous to evaluate different legumes and grasses for tolerance of shade and moisture stress in future studies. As the trees studied were only 1.5 to 3 m in height, their effects on BNF, seasonal pasture biomass production and botanical composition are expected to increase with tree dominance in the ecosystem with time. Amounts of N fixed were related to the productivity (i.e. dry matter and N yield) and seasonal persistence of the legumes. The productivity was high in spring and summer and low in autumn and winter. 相似文献
927.
Alley cropping of sorghum with Leucaena during the post-rainy season on Vertisols in semi-arid India
A field experiment was conducted for two years (1989– 1991) on a Vertisol in Bijapur, India in a split-plot design, replicated
four times, to evaluate the potential of alley cropping post-rainy season sorghum between Leucaena hedgerows. Leucaena produced
on average 2.74 t per ha of prunings and 1.57 t per ha of wood annually. Alley cropping decreased sorghum yields by 28 to
45% when all Leucaena prunings were removed from the system and by 21 to 24%, when on average 1.92 t per ha prunings were
applied to the soil annually. The reduction of sorghum yield increased as higher rates of N were applied to sorghum. Although
alley cropping increased organic carbon by 21% and available N by 19% at the time of crop sowing, it did not result in increased
crop yields because of competition for water between hedgerows and crops. Calculation of land equivalent ratios based on total
Leucaena biomass indicated that alley cropping was more productive than sole cropping of sorghum only in one year, and that,
too, when no N was applied to sorghum. Therefore, alley cropping of Vertisols with post-rainy season sorghum is not likely
to have any advantage in the short term.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
928.
Field trials were carried out on an Oxic Paleustalf in the humid zone of southwestern Nigeria withLeucaena leucocephala (Lam.) de Wit,Gliricidia sepium (Jacq.) Steud. andSesbania grandiflora (L.) Pers. alley cropped with maize and cowpea. The three leguminous woody species were grown in hedgerows spaced at 2 m. Trials were carried out one year after establishment of the hedgerows using a split-plot design with four replications. TheLeucaena trial had twenty pruning combinations consisting of five pruning heights (25, 50, 75, 100 and 150 cm) and four pruning frequencies (monthly, bi-, tri- and six-monthly). TheGliricidia andSesbania hedgerows were subjected to nine pruning intensities consisting of three pruning heights (25, 50 and 100 cm) and three pruning intensities (monthly, tri- and six-monthly).For the three woody species, biomass, dry wood and nitrogen yield from the hedgerow prunings increased with decreasing pruning frequency and increasing pruning height. Biomass, dry wood and nitrogen yields were in the following orderLeucaena >Gliricidia >Sesbania.The various pruning intensities had no effect on survival ofLeucaena plants. Pruning frequency had a larger effect than pruning height on survival ofGliricidia andSesbania plants. With monthly pruning, about 25 percent of theGliricidia and all of theSesbania plants died within six months of repeated pruning. Even with lower pruning frequencySesbania plants showed lower survival rates thanGliricidia orLeucaena.The various pruning intensities of all the hedgerow species had more pronounced effects on the grain yield of the alley cropped cowpea than on maize grain yield. Higher maize and cowpea yields were obtained with increasing pruning frequency and decreasing pruning height.IITA Journal paper number 335 相似文献
929.
L. Alpízar Professor H. W. Fassbender Coordinator J. Heuveldop Professor H. Fölster G. Enríquez 《Agroforestry Systems》1986,4(3):175-189
The agroforestry systems of cacao (Theobroma cacao) under laurel (Cordia alliodora) and cacao under poro (Erythrina poeppigiana) were studied at CATIE, Turrialba, Costa Rica. An inventory was taken of the organic matter and nutrients (N, P, K, Ca, and Mg) separating the species into their compartments (leaves, branches, trunks and roots). Studies of the litter and of the mineral soil (0–45 cm) yielded these results:
Patterns of nutrient accumulation are discussed in relation to the characteristics of these agroforestry systems. 相似文献
930.
J. Heuveldop H. W. Fassbender L. Alpízar G. Enríquez H. Fölster 《Agroforestry Systems》1988,6(1-3):37-48
During 7 years (1979–1985) cacao harvests (beans and husks) have been recorded for the agroforestry systems ofTheobroma cacao underCordia alliodora andErythrina poeppigiana shade trees. The mean oven dry cacao yields were 626 and 712 kg.ha−1.a−1 cocoa beans underC. alliodora andE. poeppigiana respectively. Harvests have gradually increased over the years and the plantation has now reached maturity.
Annual extraction of N, P, K, Ca and Mg in fruits, which is relatively small, was calculated on the basis of chemical analyses.
The following average values were found (kg.ha−1.a−1):
At the age of 8 years, theC. alliodora trees have reached 26.7 cm diameter (DBH) and 14.0 m in height. Mean annual growth (from age 5 to 7) is 14.6 m3.ha−1.a−1.
Natural plant residue production has been measured for 4 years (Nov. 1981–Oct. 1985). UnderE. poeppigiana it has reached a value of 8.91 t.ha−1.a−1 and underC. alliodora 7.07 t.ha−1.a−1. The shade trees have contributed 57 and 47% respectively. Transference and decomposition rates are high and important in
the nutrient cycles.
The nutrient content of the litter was analysed and corresponding average yearly transfers were (kg.ha−1.a−1):
For part I see Vol. 4, No. 3, 1986.
Agroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesselschaft für Technische Zusammenarbeit),
Turrialba, Costa Rica 相似文献