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1.
A split-plot experiment was conducted in southern Chile to study the effects of tree cover and level of fertilizer application
at establishment on the morphology and development of the legumes Lotus uliginosus and Trifolium subterraneum, when sown in
conjunction with Festuca arundinacea as the companion grass. Trees were 13-year-old Pinus radiata, spaced at 4 × 12.5 m intervals
and with a mean canopy diameter of 4.8 m. At 150 days after sowing the total area of Lotus leaves and length of Lotus stems/plant
were not affected by tree cover. Individual plants had fewer stems but they were longer. For Trifolium, despite large increases
in individual petiole length and leaf area, total petiole length and leaf area/plant were reduced by tree cover because of
a reduced number of petioles/plant. At 275 days after sowing, the number and weight of Lotus components/ha was not affected
by tree cover, although companion grass development was reduced. By 640 days the number and weight of Lotus components/ha
was reduced but only to the same degree as the companion grass. Trifolium plant development, and in particular seed yield,
was affected by tree cover at 275 and 640 days and to a greater extent than Lotus or the companion grass. A high level of
fertilizer application at establishment induced a greater development of both legumes at 275 days, but by 640 days the effects
were much reduced. It is concluded that both Lotus uliginosus and Trifolium subterraneum respond to tree cover by increasing
stem length and leaf area, but that in situations with low soil fertility, the development of Lotus is less affected by tree
cover than Trifolium.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Naba R. Devkota Peter D. Kemp John Hodgson Ian Valentine I. Komang D. Jaya 《Agroforestry Systems》2009,76(2):363-374
Silvopastoral systems in New Zealand that incorporate trees planted to control soil erosion on hills largely rely on the productivity
of the pastoral system for financial returns. The effect on pasture productivity of increasing the tree canopy height by pruning
Italian gray alder (Alnus
cordata) was investigated by measuring the response of light, soil moisture, soil temperature, pasture production of major pasture
species, and grazing behaviour of sheep. A split-plot design with four replicates was used. The main plot treatments were
three levels of shade (81, 23, and 12% of available photosynthetic photon flux (PPF)), created by pruning 11 year old alder
grown at the same density. The sub-plot treatments were four pasture mixes: perennial ryegrass (Lolium perenne), Yorkshire fog (Holcus lanatus), and cocksfoot (Dactylis
glomerata), each sown with white clover (Trifolium repens), and cocksfoot sown with lotus (Lotus
pedunculatus). Soil temperature was highest under light shade. Total herbage yield at 50 mm stubble height from October to May under heavy
and medium shade was 60 and 80%, respectively, of the total herbage harvested under light shade. Cocksfoot had the greatest
herbage yield, either with lotus or white clover. The tillering of perennial ryegrass was suppressed by shade more than for
the other grass species making ryegrass unsuitable for use in this silvopastoral system. More sheep grazed in the light shade
than in the heavy shade, but there was no difference in sheep preference for cocksfoot or Yorkshire fog. Lotus was grazed
more frequently than white clover. Pruning of alder to increase canopy height has the potential to improve the productivity
of the understorey pasture and its acceptability to sheep. 相似文献
3.
The willows Salix matsudana x alba and S. kinuyanagi, and the leguminous shrub Dorycnium rectum, are used for soil conservation in New Zealand and have potential value as browse plants. Two experiments were conducted in the lower North Island to ascertain the effect of selected establishment and cutting practices on their browse yield and nutritive value. A hill site experiment determined the effect of rooted and unrooted stem cuttings on establishment and initial production of the Salix species. A flat site experiment determined the effect of cutting height (0.10–0.30 m, 0.80 m, and 1.20 m above ground) and cutting frequency (once or twice per year) on yield of the Salix species and D. rectum. The establishment and dry matter (DM) yields of the Salix species were unaffected by the type of stem cutting. S. matsudana x alba (1.2 kg DM/tree) plants yielded more edible DM than S. kinuyanagi (0.9 kg DM/tree) and D. rectum (0.4 kg DM/tree). Cutting height had no effect on edible DM yield but affected total DM yield of the Salix species. Nitrogen concentration in edible DM, of all species, was 18–22 g/kg DM. In vitro organic matter digestibility of S. matsudana x alba (648–691 g/kg DM) and D. rectum (664–666 g/kg DM) was greater than S. kinuyanagi (611–615 g/kg DM). The condensed tannin concentration in edible DM of S. kinuyanagi was four-fold higher than in S. matsudana x alba (255 vs. 59 g/kg DM). It was concluded that S. matsudana x alba had the greatest potential as a browse species and D. rectum the least.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
4.
Farm-level simulators such as the Agroforestry Estate Model use as inputs either yield tables or outputs from forest modeling
tools. Forest models rely upon assumptions on site index, stem diameter (DBH) distribution, wood production and tree mortality,
which may or may not apply to agroforestry practices. Differences may arise because of the effects on tree growth of unusual
spacings and configurations, fertilizer, pruning and grazing regimes, and tree-understory relationships as well. We examined
data from published or existing field trials to determine mid- and long-term trends in tree growth and understory yields in
silvopastoral practices with southern pines (Pinus spp.) in the United States. Tree DBH and height were greater in practices with improved pastures than in those with spontaneous
grasses. Understory affected DBH more than height and, therefore, DBH-height relationships differed among practices. Sigmoidal
models predicted that tree height will peak at different age depending on tree spacing and understory type. These changes
may affect the accuracy of site indices and wood yield predictions. Livestock gains decrease linearly with increasing stand
basal area and stand age, although forage yields sometimes decay exponentially. In one of the experiments, livestock gains
decreased to almost zero at age 19 but with stand basal areas at that age markedly differing (14 and 25 m2 ha–1) for two different spacings. Additional data would allow to generate empirical algorithms to obtain farm-level simulations
of broad application, improve economic analysis and generate hypotheses to guide future experimental work.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
G. B. Douglas A. S. Walcroft S. E. Hurst J. F. Potter A. G. Foote L. E. Fung W. R. N. Edwards C. van den Dijssel 《Agroforestry Systems》2006,66(2):165-178
Silvopastoral systems involving poplars are widespread in rural landscapes in a number of regions of New Zealand. The effect
of widely spaced trees of Populus nigra × P. maximowiczii, aged 8–11 years, on the growth and botanical composition of understorey pasture mixes was determined over 3 years at a southern
North Island hill country site. Pasture mixes comprised existing pasture, and two introduced test swards comprising new grass
(Agrostis capillaris, Dactylis glomerata, Lolium perenne) and legume (Lotus uliginosus, Trifolium repens) cultivars. Pasture accumulation beneath trees (6.6 t DM ha−1 year−1) was 23% less than open (unshaded, no trees) pasture (8.6 t DM ha−1 year−1) and differences in accumulation occurred between tree aspects (North and South sides of trees) when trees were foliated.
In early spring, North plots produced 11–14% more herbage than South plots whereas in late summer, South plots produced up
to 44% more herbage than North plots. Yield of both test swards (6.4 and 8.0 t DM ha−1 year−1) was not significantly different from that of the existing sward (7.4 t DM ha−1 year−1) but productivity varied between swards in spring and summer. One test sward included Lotus uliginosus cv. Grasslands Maku, and the sward produced 30% more DM than the other swards in mid-summer. Dactylis glomerata cv. Grasslands Wana comprised 37% of the DM of swards in which it was sown and was the most successful cultivar, followed
by Grasslands Maku. Both cultivars are recommended for silvopastoral systems where pasture is lightly grazed. 相似文献
6.
R. Lal 《Agroforestry Systems》1989,8(1):7-29
Field experiments were conducted on a tropical Alfisol at Ibadan, Nigeria, to evaluate the effects on soil moisture and crop yields of three agroforestry systems. Effects of agroforestry treatments involving two perennial shrubs (Leucaena leucocephala and Gliricidia sepium), each at 2-m and 4-m row spacings, were compared with no-till and plow-till systems of seedbed preparation. Measurements were made for soil properties, runoff and erosion, nutrient losses in runoff, and crop growth and yield for a uniform maize (Zea mays) and cowpea (Vigna unguiculata) rotation. All of the six plots, each measuring 70 × 10m, were established on a natural slope of about 7%. Alterations in soil properties and effects on crop growth were evaluated for six consecutive years from 1982 through 1987.Seed germination and seedling establishment of Leucaena hedgerows were satisfactory while establishment of Gliricidia from stem cuttings was unsatisfactory. Maize germination and crop stand were normal while that of cowpea were suppressed by both Leucaena and Gliricidia. Maize growth and yield were suppressed only in the vicinity of hedgerows. Maize grain yield in agroforestry systems averaged about 10 percent lower than that of the control. In contrast with maize, agroforestry systems drastically suppressed cowpea grain yield. The average cowpea yield in agroforestry systems was 30 to 50% of the control. Regardless of the mangement system, grain yields declined over time at the rate of 340 and 96 kg ha–1yr–1 for maize and cowpea, respectively.Hedgerows of Leucaena and Gliricidia acted as windbreaks. Consequently, soil moisture content in the top 0–5 cm layer in agroforestry systems was generally higher than that in the control during both wet and dry seasons. 相似文献
7.
Firebreaks are useful to reduce the extent of forest fires, however, when they are cleared down the slope, soil erosion is
increased and the native tall sward in summer can increase fire risk. The sown mixture Trifolium brachycalycinum (Katznl. & Morley) and Cynodon dactylon L. Pers. has already proved to be useful for both fire prevention (the short sward remains green in summer, creating easy
access) and biomass production (clover can give high yields with high palatability and protein levels). This pasture needs
to be grazed to be kept short and reduce fuel biomass in summer. Unfortunately, there is not much livestock reared in Central
Italy and animals are normally fed indoors. In this article, a trial in a coastal farm of Central Italy is reported to investigate
the efficiency of horses in maintaining the sown species botanical composition, soil cover, sward height, biomass (before
and after grazing) and fuel biomass in summer in a firebreak over 4 years. The mixture was intensively grazed over short periods
during spring and summer. Animals grazed both the sown species and native plants, they trampled on the remaining herbage,
breaking the stems, and leaving short and compact dry mulch. Very little combustible vegetation was left in the hot season
and horse grazing is recommended for farms that have firebreaks. 相似文献
8.
A small scale agroforestry study which was begun in 1952 was revisited in 1985 to evaluate the long-term influence of site preparation and grazing on tree growth and survival in a Douglas-fir (Pseudotsuga menziesii)-white oak (Quercus garryana)-sheep silvopastoral system. In 1952–1953, two-year-old Douglas-fir seedlings were planted at the rate of 2500 trees/ha under three levels of site preparation: (1) no treatment, (2) oak thinned by 50%, and (3) oak clearcut. From 1954 to 1960, yearling ewes grazed one-half of each of the three thinning treatments for 3–4 weeks each spring. The conifers have been undisturbed since grazing was discontinued in 1960. Survival of planted conifers averaged 64% in 1985 and did not vary among either site preparation or grazing treatments. From 1964 to 1985, trees on the thinned and clearcut plantations grew an average of 1060 and 990 cm in height, respectively, compared to 900 cm on the unthinned plantation. Diameter at breast height (dbh) averaged 3.8 and 5.6 cm greater on thinned or clearcut plantations, respectively, than on the unthinned control by 1985 (p < 0.05). Conifers on grazed plantations had increased height and dbh growth during the first 12 years of plantation life, averaging 63 cm taller (p < 0.10) and 0.7 cm greater in dbh (p < 0.05) than the ungrazed plots by 1964. By 1985 the difference in height (122 cm) and dbh (1.0 cm) between grazed and ungrazed plantations was not statistically significant. These data suggest that although site preparation can positively influence conifer growth, total clearfelling is no better than thinning oaks. Furthermore, proper grazing can increase height and dbh growth of the conifers during and immediately after the grazing years. 相似文献
9.
A small scale agroforestry study which was begun in 1952 was revisited in 1985 to evaluate the long-term influence of site
preparation and grazing on tree growth and survival in a Douglas-fir (Pseudotsuga menziesii)-white oak (Quercus garryana)-sheep silvopastoral system. In 1952–1953, two-year-old Douglas-fir seedlings were planted at the rate of 2500 trees/ha under
three levels of site preparation: (1) no treatment, (2) oak thinned by 50%, and (3) oak clearcut. From 1954 to 1960, yearling
ewes grazed one-half of each of the three thinning treatments for 3–4 weeks each spring. The conifers have been undisturbed
since grazing was discontinued in 1960. Survival of planted conifers averaged 64% in 1985 and did not vary among either site
preparation or grazing treatments. From 1964 to 1985, trees on the thinned and clearcut plantations grew an average of 1060
and 990 cm in height, respectively, compared to 900 cm on the unthinned plantation. Diameter at breast height (dbh) averaged
3.8 and 5.6 cm greater on thinned or clearcut plantations, respectively, than on the unthinned control by 1985 (p < 0.05).
Conifers on grazed plantations had increased height and dbh growth during the first 12 years of plantation life, averaging
63 cm taller (p < 0.10) and 0.7 cm greater in dbh (p < 0.05) than the ungrazed plots by 1964. By 1985 the difference in height
(122 cm) and dbh (1.0 cm) between grazed and ungrazed plantations was not statistically significant. These data suggest that
although site preparation can positively influence conifer growth, total clearfelling is no better than thinning oaks. Furthermore,
proper grazing can increase height and dbh growth of the conifers during and immediately after the grazing years. 相似文献
10.
The Center for Agroforestry at the University of Missouri has tested numerous native legumes for potential use in agroforestry
and selected Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan ex Robinson and Fern.) and panicled tick clover (Desmodium paniculatum (L.) DC.) for further testing. Our objective was to document the effect of arbuscular mycorrhizae (AM) (Glomus spp.) and Rhizobium on growth and nutrient concentration of these legumes. Seeds were planted in a greenhouse and inoculated with one of two
species of AM and/or one of two strains of Rhizobium. Plants were harvested after 80 d and data taken on leaf and stem dry weight, root fresh weight, stem height, nodulation,
AM colonization, and N, P, K, Ca, and Mg concentration. Inoculation with Rhizobium did not affect plant growth in Illinois bundleflower, but colonization by Glomus intraradices increased all plant growth variables except stem height. Nutrient concentration was unaffected by the presence of either
endophyte. In contrast, inoculation of panicled tick clover with Rhizobium str. 41Z10 increased leaf dry weight (32%) compared to the control and root fresh weight (41%) compared to str. 32Z3, and
colonization by G. intraradices increased leaf dry weight (35%) and stem height (26%). Both species of AM increased P and K concentration (41% and 55%, respectively)
in panicled tick clover. Our results suggest that the growth of these legumes can be improved by the use of proper AM species
and/or Rhizobium strains. However, additional research to identify the best Rhizobium and AM inoculates for these plant species is important in developing strategies for their use in agroforestry.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
11.
Since 1985, Ecuador's Ministry of Agriculture has undertaken a demonstration project to promote improved agroforestry practices in already cleared lands of Ecuador's Amazon lowlands to promote regeneration of deforested areas. An important expected outcome of this project is to ameliorate growing population pressures on remaining national forests and natural reserves. These practices include managing natural regeneration of marketable timber trees intercropped to Coffea canephora var. robusta and grass-legume associations, using adequate techniques of coffee pruning, and planting Desmodium ovalifolium CIAT 350 as a ground cover crop or a forage legume in paddocks of the genus Brachiaria. This research was conducted to assess the potential economic impact of such a strategy and to feed back information on research and policy issues.Improved agroforestry practices in this region are not only technically practicable but also economically feasible. Proposed technologies enhance long-term productivity of both land and labor while saving on external inputs and hired labor, making on-going systems more adoptable and sustainable. Future land-use policies should consider on-farm primary forest preservation and controlled natural regeneration of high-value timber in secondary forests as socially efficient land-use patterns. Future research must address germplasm of grass and forage legumes both shade tolerant, and less field management-demanding than current ones.To have a lasting effect this technology should probably be incorporated into a Regional Forest Management Plan, for sustainable production at the secondary forests created with agroforestry technology.in cooperation with Fundación para el Desarrollo Agropecuario del Ecuador, FUNDAGRO, Casilla No. 219, Suc. 16 CEQ, Quito, Ecuador 相似文献
12.
In this paper we analyzed the dry matter yields (DM) produced in an agroforestry trial consisting of pine trees grown over (1) Control (bare ground), (2) ryegrass/clovers (Lolium perene/Trifolium spp.), (3) ryegrass only, and (4) lucerne (Medicago sativa) during the third growing season between 1992 and 1993. In addition these pastures were grown alone in separate plots in the open. The results show that:
相似文献
| 1. | Pasture yields during the one-year period in the agroforestry plots were little affected by the presence of trees although there were seasonal trends: yields were generally unaffected or increased in summer, but reduced in spring as a result of tree shade. Total pasture yield during the one-year period was in the following order: lucerne > ryegrass/clovers > ryegrass. This trend was the exact opposite of that shown by the above-ground tree weight which was reduced in the pasture ground covers by between 16 and 52%. The reduction in tree weights was associated with reduced soil moisture availability arising from competition with the pasture species. Thus the relationship between the yields of trees and pasture species in the agroforestry plots was reciprocal. |
| 2. | The combined DM for both the trees and pastures in the agroforestry plots during the one-year period was in the following order: lucerne (20 t ha–1) > ryegrass/clovers (16 t) > ryegrass (11 t) > control (6 t) which was consistent with the total water used and photosynthetically active radiation (PAR) intercepted. The trees accounted for 55, 44, 34 and 24% of water used respectively in control, ryegrass, ryegras/cclovers and lucerne ground covers. The balance was largely accounted for by pasture transpiration, except in the control where soil evaporation was significant. The fraction of intercepted PAR accounted for by the trees followed a similar trend to that of the water used. |
| 3. | The crop coefficient for water use efficiency (k) (Pa) was 2.3 for radiata pine, 3.6 for ryegrass/clovers, 2.8 for ryegrass and 4.8 for lucerne. The DM produced per unit of water used (kg mm–1 ha–1) during the one-year period was 24.5 for radiata pine, 41.1 for lucerne, 30.0 for ryegrass/clovers and 23.1 for ryegrass. Radiation use efficiency (g DM MJ–1 m–2) was 1.33 for pine, 1.83 for ryegrass/clovers, 1.49 for ryegrass and 2.34 for lucerne. |
| 4. | The land equivalent ratio (LER), i.e. the sum of ratios of DM produced by the plant species in the agroforestry plots to those produced in the sole plots, was 1.95 for ryegrass, 1.71 for ryegrass/clovers and 1.45 for lucerne ground covers. |
| 5. | These results indicate the susceptibility of pasture species to shading and interception of rainfall by the tree crowns (aboveground interactions), and the trees to competition for soil moisture (underground interaction). |
13.
A. C. Varella D. J. Moot K. M. Pollock P. L. Peri R. J. Lucas 《Agroforestry Systems》2011,81(2):157-173
Shade cloth is commonly used in agroforestry research. It produces a continuous, uniform reduced light environment. Shade
cloth and a slatted structure were compared in relation to the inability to represent the light regime and plant responses
of an agroforestry system. The split-split-plot randomised block experiment had main plots as covering status (with or without
radiata pine trees), subplots as artificial shade (none, shade cloth or wooden slats) and sub-subplots as growth rotation,
over sown alfalfa, in three replicates. The quantity of light transmittance was 49% under trees, 41% under cloth and 44% under
slats. Temporal changes and spectral composition under trees were more accurately reproduced under the slats than shade cloth.
The red to far red ratio was 0.64 under tree shade and 0.74 during the shaded period under slats. This compared with 1.31
in open pasture, 1.28 under shade cloth in open and 1.26 under slats during sunny periods. To compensate for low light quantity
and quality, alfalfa had elongated stems and internodes. In open pasture and under cloth in the open, it produced short stems.
The mean dry matter yield under trees was 68% of the 30.3 t ha−1 in open pasture, 56% under cloth and 57% under slats. The slats induced similar morphological responses in alfalfa to those
in the agroforestry system. The magnitude of changes had little effect on growth and yield responses. The artificial slatted
structure approximated the intermittent light environment and consequent plant responses observed in an agroforestry system. 相似文献
14.
Mônica Matoso Campanha Ricardo Henrique Silva Santos Gilberto Bernardo de Freitas Hermínia Emília Prieto Martinez Silvana Lages Ribeiro Garcia Fernando Luiz Finger 《Agroforestry Systems》2004,63(1):75-82
This research compared coffee plants (Coffea arabica L.) grown in an agroforestry and monoculture systems. Data were collected during two years, on vegetative growth, reproductive
development, nutritional status and yield of coffee, besides monitoring air temperature and the tree growth. All trees in
agroforestry system increased in growth, resulting in a reduction in the magnitude of the diurnal temperature variation and
also maximum temperature. Coffee plants in agroforestry system had less branch growth and leaf production, more persistent
and larger leaves, and presented earlier flowering, with a smaller number of productive nodes and flower buds, leading to
smaller berry yield than plants in monoculture system. In both systems, the coffee plants showed adequate leaf nutrient levels,
except for P and K. The yield of 2443 kg ha-1 of coffee from the monoculture was greater than 515 kg ha-1 of coffee from the agroforestry system. 相似文献
15.
《Journal of Sustainable Forestry》2013,32(4):61-80
Abstract Intensive, subsistence agriculture on hillsides of southeast Guatemala has caused extensive soil degradation. This retrospective study evaluated the success of an agroforestry treatment in improving the sustainability of mountainous agricultural systems in terms of soil nutrient status and erosion control. Three years after maize (Zea mays) and pasture fields were alley-cropped with N-fixing Gliricidia sepium trees, soil nutrient levels were examined and compared to nonalley-cropped controls. Agroforestry treatment showed significantly higher soil organic matter (SOM) over paired plots with no alley-cropping (mean 4.3% vs. 3.2% C, p < 0.05). Mean total N was also higher, with 0.12% in the nonagro-forestry control plots compared to 0.16% underthe agroforestry treatment (p <0.05). Some improvement in soil water-holding capacity(WHC) was also observed in the agroforestry systems. Differences in soil levels of available P, ranging from 8.0 to 64.4 μg/g, were not significant and correlated more with site than with agroforestry treatment versus control. Specific soil and site properties such as texture and slope as well as land use and ground cover management largely influenced improvements in soil nutrient status under the agroforestry treatment at each site. Despite increases in soil nutrients, maize plant productivity showed no response to the agroforestry treatment in terms of leaf chlorophyll index or maize plant height. Three years after the initiation of agroforestry, soil erosion rates showed no difference from paired controls; rates were correlated with ground cover and soil characteristics such as texture and surface rockiness rather than with agroforestry treatment. While soil nutrient status had not reached levels optimum for maize growth after three years, the positive trajectory of change in soil nutrients suggests the potential for using agroforestry systems in mountainous regions of Guatemala to increase the sustainability of agricultural production. 相似文献
16.
The presence of trees in fields may help overcome the physiological stress that happens to late sown wheat (Triticum aestivum L.) in subtropical India. Wheat was planted in an agroforestry system with Eucalyptus tereticornis trees on 7 January 1998 in a fan design that provided different combinations of tree row spacing and orientations. Crop profile
microclimatic conditions and the resulting growth responses of the intercropped wheat were studied to explore the potential
of agroforestry systems to influence late sown wheat yields under different tree row spacing and orientations. Agroforestry
treatments exhibited a potential to optimize the microclimatic conditions for seedling emergence, tillering and earhead emergence
at some tree row orientations and distances from the crop. The net radiation distribution at three stages of crop growth indicated
that the radiation availability was lower in all the agroforestry treatments than for the sole crop. The tree row orientation
and distance influence the growth behavior of the crop but the effect of sun angle (which changes with season) can change
their influence over time. The deterioration or amelioration of microclimatic conditions in agroforestry with the passage
of time should be expected because of altered interaction patterns between sunrays and tree canopy resulting from changing
solar elevation and angle of sunrays. Statistically similar harvest indices in all the treatments despite lower total biological
yields in agroforestry treatments revealed that microclimatic conditions under agroforestry were more favorable for wheat
growth attributed to reduction in heat load during the post anthesis period.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
The need for shade tolerant forage species for forested grazing lands of the Southeastern United States has been recognized for some time. Introduced grasses and temperate legumes have been evaluated for this use with some success. Sparse stands of native legumes occur throughout these woodlands. The potential value of these native legumes has received little attention. Seedlings of Galactia elliottii Nuttall, a widely occurring native legume in the pine flatwoods (Spodosols), were established in pots and subsequently evaluated for growth response to shade levels of 0, 25, 55, 75, and 92% under vinyl shade cloth. Maximum herbage yield and maximum nitrogen yield after a 60-day growth period were obtained under 25% shade. Responses of herbage yield, percent nitrogen, and nitrogen yield to shade were described by quadratic equations with initial increases followed by decreases as shade increased. A second experiment involving small plots of G. elliottii in dense bahiagrass (Paspalum notatum Flugge) sod produced negative linear relationships between shade and yield of each forage species. However, G. elliottii yield declined at a slower rate than bahiagrass. These results indicate that G. elliottii is adapted to shaded flatwoods environments and suggest that further efforts to evaluate local woodland legumes for forage potential could provide productive species for reseeding shaded woodland sites in the Southeastern United States.This article is Florida Agricultural Experiment Station paper number 7831. 相似文献
18.
Although only Leucaena leucocephala is widely used, most members of the Leucaena genus have potential as multipurpose species for tropical agroforestry systems. To investigate the wood and biomass production
potential of the Leucaena genus, 116 accessions covering the 22 species were evaluated over a two-year period at Brisbane, southeast Queensland, Australia.
Trees were planted into replicated line plots 5 m long, with rows spaced 3 m apart. Trees were initially planted at 0.5 m
spacings within the plots, but were thinned to 1 m spacings prior to the evaluation period. The hybrid accessions, KX2 (L. pallida × L. leucocephala) and KX3 (L. diversifolia × L. leucocephala), were the most productive, yielding over 50 kg dry matter (DM)/tree. L. trichandra OFI53/88 and L. diversifolia CPI33820 were the most productive non-hybrid accessions producing total yields of 41 and 37 kg DM/tree, respectively. Cultivar
Tarramba (26 kg DM/tree) was the most productive of the 26 L. leucocephala accessions assessed in the trial but all these accessions suffered from psyllid (Heteropsylla cubana) attack at this site. A series of non-destructive growth measurements was recorded every three months over the two-year evaluation
period. Root collar diameter (RCD), stem number and plant height were found to be the most useful of the measurements for
non-destructive assessment of accession agronomic characteristics. A relationship between yield and a growth index (calculated
as RCD2 × Height/1000), was derived from data from all accessions and could be used as a reliable predictor of yield (r
2 = 0.94). The widespread use of the F1 hybrid leucaenas is currently limited by a lack of seed. Technologies to economically
produce F1 hybrid seed on a commercial scale are required before the potential of these accessions in agroforestry systems
can be fully realized.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
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
20.
A. P.G. Schönau 《Southern Forests》2013,75(1):72-81
The results of six fertilizer experiments with Eucalyptus grandis are discussed and the development of various tree parameters with age are studied. It is shown that in the initial years of growth mean height and breast height diameter are increased as a result of fertilizing at the time of planting, but the absolute differences between fertilized and unfertilized trees remain more or less constant with increasing age. Fertilizing increases total basal area also, and consequently timber yield, but this increase becomes greater up to at least nine years of age or final felling. These increases in timber yield economically justify fertilizing at planting. Brief recommendations are given of how best to conduct field experiments designed to study fertilizer application. 相似文献