共查询到20条相似文献，搜索用时 15 毫秒
1.
A study was conducted in an agricultural field to examine the biomass production of three fast-growing short rotation woody
crop (SRWC) species, Populus deltoides, Quercus pagoda, and Platanus occidentalis using fertilization and irrigation (fertigation). The study included a randomized complete block (RCB) with five treatments;
control, irrigated, and irrigated with 56, 112, and 224 kg nitrogen (N) ha−1 year−1. We quantified survival, basal area, standing biomass, aboveground net primary productivity (ANPP), leaf area index (LAI),
and growth efficiency (GE) for each species along the soil nitrogen and water gradient. P. deltoides had low rates of survival (83, 82, and 77% years six, seven, and eight, respectively), but had production values greater
than Q. pagoda and P. occidentalis. Standing biomass reached its peak for P. deltoides and P. occidentalis (17.56 and 10.36 Mg ha1, respectively) in the irrigation treatment, and in the 112 kg N treatment for Q. pagoda (5.42 Mg ha−1). P. deltoides and P. occidentalis ANPP peaked in the irrigation treatment (6.66 and 6.31 Mg ha−1 year−1, respectively) and in the 112 kg N (4.43 Mg ha−1 year−1) for Q. pagoda. ANPP was correlated with LAI; however, the relationship was species specific. Maximum ANPP was reached below the maximum
LAI for Q. pagoda and P. occidentalis. P. deltoides ANPP was highest at the maximum LAI, which was achieved with IRR. These results suggest that species-specific cultural practices
producing optimum LAI and maximum ANPP should be identified before fertigation techniques are adopted widely for SRWC production
on agricultural fields. 相似文献
2.
Four Populus clones were grown for two years at 1×1 m spacing for study of total biomass production and carbon sequestration capacity
on floodplain sites previously in forage grasses under climatic conditions of the lower Midwest, U.S.A. Total biomass (above-and
below-ground) in the first year ranged from 3.9 Mg ha–1 in a Populus deltoides x P. nigra clone (I45/51) to 1.9 Mg ha–1 for a local-source Populus deltoides clone (2059). Second year total biomass production was substantially higher, ranging from 13.9 Mg ha–1 in I45/51 to 7.4 Mg ha–1 in P. deltoides clone 26C6R51. Second-year leaf area index (LAI) values for I45/51 plants reached 4 during mid-season, indicating essentially
complete canopy closure in this clone by the second year after planting. In contrast, maximum mid-season, second-year LAI
was significantly lower in P. deltoides clones ( 2.4). There was some evidence for differential allocation to roots and shoots among Populus clones, with 26C6R51 showing relatively more allocation to root biomass than other clones. Second-year growth in Populus deltoides clone 2059 accelerated substantially, and this genotype exhibited two-year biomass accumulation nearly equal to that of I45/51
despite having less leaf area. This result suggested a higher photosynthetic capacity or assimilation efficiency in the former.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
E. Y. Raddad O. Luukkanen A. A. Salih V. Kaarakka M. A. Elfadl 《Agroforestry Systems》2006,68(3):193-207
Acacia senegal, the gum arabic-producing tree, is the most important component of traditional dryland agroforestry systems in the␣Sudan. The spatial arrangement of trees and the type of agricultural crop used influence the interaction between trees and crops. Tree and crop growth, gum and crop yields and nutrient cycling were investigated over a period of 4 years. Trees were grown at 5 × 5 m and 10 × 10 m spacing alone or in mixtures with sorghum or sesame. No statistically significant differences in sorghum or sesame yields between the intercropping and control treatments were observed (mean values were 1.54 and 1.54 t ha−1 for sorghum grain and 0.36 and 0.42 t ha−1 for sesame seed in the mixed and mono-crop plots, respectively). At an early stage of agroforestry system management, A. senegal had no detrimental effect on crop yield; however, the pattern of resource capture by trees and crops may change as the system matures. A significant positive relationship existed between the second gum picking and the total gum yield. The second gum picking seems to be a decisive factor in gum production and could be used as an indicator for the prediction of the total gum yield. Soil organic carbon, N, P and K contents were not increased by agroforestry as compared to the initial levels. Soil OC was not increased by agroforestry as compared to sole cropping. There was no evidence that P increased in the topsoil as the agroforestry plantations aged. At a stocking density of 400 trees ha−1 (5 × 5 m spacing), A. senegal accumulated in its biomass a total of 18.0, 1.21, 7.8 and 972 kg ha−1 of N, P, K and OC, respectively. Agroforestry contributed ca. 217 and 1500 kg ha−1 of K and OC, respectively, to the top 25-cm of soil during the first four years of intercropping. 相似文献
4.
Yields under alley cropping might be improved if the most limiting nutrients not adequately supplied or cycled by the leaves
could be added as an inorganic fertilizer supplement. Three historic leaf management strategies had been in effect for 3 years
ina Leucaena leucocephala alley cropping trial on the Lilongwe Plain of central Malawi : 1) leaves returned; 2) leaves removed; and 3) leaves removed,
with 100 kg inorganic N ha−1 added. An initial soil analysis showed P status to be suboptimal under all strategies. A confounded 34 factorial experiment was conducted with the following treatments: leaf management strategy (as above), N fertilizer rate
(0, 30, and 60 kg N ha−1), P fertilizer rate (0, 18, and 35 kg P ha−1), and maize population (14,800, 29,600, and 44,400 plants ha−1). Both N and P were yield limiting, and interacted positively to improve yields. The addition of 30 kg N and 18 kg P ha−1 improved yields similarly under all leaf management strategies by an average of 2440 kg ha−1. Increasing the rates to 60 kg N and 35 kg P ha−1 improved yields an additional 1990 kg ha−1 in the ‘leaves returned’ and leaves removed + N’ strategies, but did not improve yields under the ‘leaves removed’ strategy.
Lower yields were related to lack of P response at the highest P rate in this treatment, which may have induced Zn deficiency.
Plots receiving leaves had higher organic C, total N, pH, exchangeable Ca, Mg, K, and S, and lower C/N ratios in the 0–15
cm soil layer than did plots where leaves had been removed. Leaf removal with N addition was similar to leaf removal alone
for all soil factors measured except for organic C and total N, which were higher where N had been added. The results show
that N and P were the primary yield-limiting nutrients. Historic N application maintained the soil's ability to respond to
N and P on par with leaf additions. 相似文献
5.
Quantity of litter fall, its chemical composition, nutrient addition and changes in chemical constituents of soil were studied
under agroforestry systems involving Populus deltoides and Eucalyptus hybrid tree with intercrops of Cymbopogon martinii Wats and Cymbopogon flexuosus Wats in the tarai tract of Kumaon hills of U.P. India. P. deltoides had significantly more diameter (63%) as compared to E. hybrid. There was decrease in herb (5.4%) and oil yield (15.4%) of grasses due to trees, but both the grasses did not affect the
performance of trees.
On an average, dry litter production of P. deltoides was 5.0 kg tree−1 year−1 where as of E. hybrid 1.5 kg tree−1 year−1. The litter of P. deltoides contained 1.3 times more N and 1.5 times P and K of E. hybrid. Addition of N, P and K through P. deltoides litter was 36.6, 91.6, and 69.9 per cent more than E. hybrid litter, respectively. Under these two canopies soil organic carbon was enhanced by 33.3 to 83.3 per cent, available N by
38.1 to 68.9 per cent, available P by 3.4 to 32.8 per cent and available K by 5.8 to 24.3 per cent over control (no tree canopy)
in 0—15cm layer. P. deltoides plantation was superior to E. hybrib in enriching the soil. 相似文献
6.
A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste
disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization,
(2) milk sewage sludge at 40 kg N ha−1 target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two
pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha−1. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1); (2) Lolium perenne L. var. Tove (25 kg ha−1) + Trifolium repens L. group Ladino (4 kg ha−1) + Trifolium pratense L. var. Marino (1 kg ha−1). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea
(Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m2, with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect
on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage
sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but
affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
Pastures store over 90% of their carbon and nitrogen below-ground as soil organic matter. In contrast, temperate conifer forests
often store large amounts of organic matter above-ground in woody plant tissue and fibrous litter. Silvopastures, which combine
managed pastures with forest trees, should accrete more carbon and nitrogen than pastures or timber plantations because they
may produce more total annual biomass and have both forest and grassland nutrient cycling patterns active. This hypothesis
was investigated by conducting carbon and nitrogen inventories on three replications of 11 year-old Douglas-fir (Pseudotsuga menziesii)/perennial ryegrass (Lolium perenne)/subclover (Trifolium subterraneum) agroforests, ryegrasss/subclover pastures, and Douglas-fir timber plantations near Corvallis, Oregon in August 2000. Over
the 11 years since planting, agroforests accumulated approximately 740 kg ha–1 year –1 more C than forests and 520 kg ha–1 year–1 more C than pastures. Agroforests stored approximately 12% of C and 2% of N aboveground compared to 9% of C and 1% of N above
ground in plantations and less than 1% of N and C aboveground in pastures. Total N content of agroforests and pastures, both
of which included a nitrogen-fixing legume, were approximately 530 and 1200 kg ha–1 greater than plantations, respectively. These results support the proposition that agroforests, such as silvopastures, may
be more efficient at accreting C than plantations or pasture monocultures. However, pastures may accrete more N than agroforests
or plantations. This apparent separation of response in obviously interrelated agroecosystem processes, points out the difficulty
in using forest plantation or pasture research results to predict outcomes for mixed systems such as agroforests.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Veiko Uri Krista Lõhmus Ivika Ostonen Hardi Tullus Renal Lastik Merit Vildo 《European Journal of Forest Research》2007,126(4):495-506
The above-ground biomass and production, below-ground biomass, nutrient (NPK) accumulation, fine roots and foliar characteristics
of a 8-year-old silver birch (Betula pendula) natural stand, growing on abandoned agricultural land in Estonia, were investigated. Total above-ground biomass and current
annual production after eight growing seasons was 31.2 and 11.9 t DM ha−1, respectively. The production of stems accounted for 62.4% and below-ground biomass accounted for 19.2% of the total biomass
of the stand. Carbon sequestration in tree biomass reaches roughly 17.5 t C ha−1 during the first 8 years. The biomass of the fine roots (d < 2 mm) was 1.7 ± 0.2 t DM ha−1 and 76.2% of it was located in the 20 cm topsoil layer. The leaf area index (LAI) of the birch stand was estimated as 3.7 m2 m−2 and specific leaf area (SLA) 15.0 ± 0.1 m2 kg−1. The impact of the crown layer on SLA was significant as the leaves are markedly thicker in the upper part of the crown compared
with the lower part. The short-root specific area (SRA) in the 30 cm topsoil was 182.9 ± 9.5 m2 kg−1, specific root length (SRL), root tissue density (RTD) and the number of short-root tips (>95% ectomycorrhizal) per dry mass
unit of short roots were 145.3 ± 8.6 m g−1, 58.6 ± 3.0 kg m−3 and 103.7 ± 5.5 tips mg−1, respectively. In August the amount of nitrogen, phosphorus and potassium, accumulated in above ground biomass, was 192.6,
25.0 and 56.6 kg ha−1, respectively. The annual flux of N and P retranslocation from the leaves to the other tree parts was 57.2 and 3.7 kg ha−1 yr−1 (55 and 27%), respectively, of which 29.1 kg ha−1 N and 2.8 kg ha−1 P were accumulated in the above-ground part of the stand. 相似文献
9.
Tree based land use systems make a valuable contribution to sequester carbon and improve productivity and nutrient cycling
within the systems. This study was conducted to determine biomass production, C-sequestration and nitrogen allocation in Gmelina arborea planted as sole and agrisilviculture system on abandoned agricultural land. At 5 years, total stand biomass in agrisilviculture
system was 14.1 Mg ha−1. Plantations had 35% higher biomass than agrisilviculture system. At 5 years, leaves, stem, branches and roots contributed
4.1, 65.2, 10.0 and 20.7%, respectively to total standing biomass (17.9 Mg ha−1). Over the 5 years of study, trees had 3.5 Mg ha−1 more C and 36 kg ha−1 more N in plantation than agrisilviculture system. Biomass and C storage followed differential allocation. Relatively more
C was allocated in above ground components in plantations compared to agrisilviculture system. C:N ratios for tree components
were higher in stem wood (135–142) followed by roots (134–139), branches (123–128) and leaves (20–21). In agrisilviculture
system crops recommended are: soybean and cowpea in rainy season; wheat and mustard in winter season. After 5 years, soil
organic C increased by 51.2 and 15.1% and N by 38.4 and 9.3% in plantation and agrisilviculture system, respectively. Total
C storage in abandoned agricultural land before planting was 26.3 Mg ha−1, which increased to 33.7 and 45.8 Mg ha−1 after 5 years in plantation and agrisilviculture system, respectively. Net C storage (soil + tree) was 7.4 Mg ha−1 in agrisilviculture system compared to 19.5 Mg ha−1 in G. arborea monoculture stands. The studies suggest that competitive interactions played a significant role in agrisilviculture system.
Plantations were more efficient in accreting C than agrisilviculture system on abandoned agricultural land. 相似文献
10.
Agroforestry systems based on poplar (Populus deltoides) are becoming popular in eastern and northern parts of India. Therefore studies on the structure and function of the systems
are important. The investigations included allometric equations for above- and belowground tree components, crop and plantation
floor biomass and litter fall estimation at Pusa, Bihar, India. Biomass, floor litter mass, litter fall and net primary productivity
(NPP) of plantations increased with an increase in age of trees whereas, crop biomass for any specific crop interplanted with
poplar decreased with the age of the plantation. The total plantation biomass increased from 12.08 to 90.59 Mg ha−1 and NPP varied from 5.69 to 27.9 Mg ha−1 year−1. The biomass accumulation ratio ranged from 2.1 to 3.2. Total annual litter fall was in between 1.95 and 10.00 Mg ha−1 year−1, of which 92–94% was contributed by leaf litter. Compartmental models were developed for dry matter distribution in agroforestry
systems involving young (3-year-old) and mature (9-year-old) poplar trees interplanted with various crops, the crops being
grown in two rotations maize (Zea mays) – wheat (Triticum aestivum) – turmeric (Curcuma domestica) and pigeonpea (Cajanus cajan) – turmeric. This study substantiates the potential of Populus deltoides G3 under agroforestry combinations. 相似文献
11.
Fertilizing plantations of fast-growing tree crops, in manners which supply nutrients at rates that match plant demand and
maintain stable internal plant nutrient ratios, can maximize biomass production and carbon sequestration while reducing fertilizer
wastage and pollution. Our objectives were to determine nutrient ratios of common hybrid poplar (Populus trichocarpa Torr. and Gray × Populus deltoides Marsh.) (T × D) clones under steady-state nutrition, and to determine if incremental additions of fertilizer were more successful
than conventional (evenly-split) fertilizer additions in maximizing biomass production and inducing stable nutrient ratios.
Un-rooted cuttings of three T × D clones (49–177, DTAC-7, 15–29) were grown under a conventional regime and a modified-exponential
fertilization regime at three application rates (1.8, 3.7 or 7.4 g N plant−1). Above- and below-ground biomass and nutrient concentrations were measured after one growing season. There were few differences
in total plant biomass between conventional and modified-exponential fertilization regimes, but for one clone, biomass accumulation
equivalent to the highest rate under the conventional regime was achieved with the medium rate of the modified-exponential
regime. Stable nutrient ratios (at conditions consistent with steady-state nutrition) were: 100N:14P:50K (49–177), 100N:13P:49K
(DTAC-7) and 100N:12P:60K (15–29). 相似文献
12.
Kevin Lombard Mick O’Neill Robert Heyduck Blake Onken April Ulery John Mexal Adrian Unc 《Agroforestry Systems》2011,81(1):45-56
Composted sewage sludge (biosolids) supply plant available Fe and may represent a sustainable alternative to more costly chelated
Fe fertilizers currently used to supplement nutrition in hybrid poplar test plots of elevated soil pH. To test the response
of poplars, field plots were amended with composted biosolids at two agricultural rates: 22.75 and 44.5 Mg ha−1. Iron EDDHA served as a fertilizer check and control plots received no amendment. The hybrid poplar OP-367 (Populus deltoides × P. nigra) was planted on a 3.6 m grid spacing. Significant amounts of P and Fe originating from the sewage treatment process were
detected in soils 13 months after amending. Chlorosis evaluated with a SPAD-502 meter, showed that poplars amended with biosolids
remained the least chlorotic and had greater tree growth when compared to Fe EDDHA and control plots during two growing seasons.
Biosolids show promise as a cost effective alternative for the remediation of Fe chlorosis in hybrid poplar agroforestry plantations
and present new opportunities in northwestern New Mexico for municipalities seeking solid waste land disposal options. 相似文献
13.
Efforts to overcome declining soil fertility on small holder farms in western Kenya must be consistent with the reality of
low utilization of inorganic fertilizers. Likewise organic inputs alone cannot supply adequate nutrients. The use of two organic
resources, Tithonia diversifolia (tithonia) and Senna spectabilis (senna) leaves, and their combination with inorganic P for
improving soil fertility and maize yields was investigated on a P limiting soil in Western Kenya. Treatments included: 1)
control, no inputs; 2) 5 t ha−1 (dry matter) tithonia leaves; 3) 5 t ha−1 senna leaves; 4) 5 t ha−1 tithonia leaves + 25 kg P ha−1 as triple superphosphate (TSP); 5) 5 t ha−1 senna leaves + 25 kg P ha−1 (as TSP); and 6) 25 kg P ha−1 of TSP. Maize was used as a test crop. Decomposition and P and N release of tithonia and senna leaves were determined in
a litterbag study. Tithonia + TSP applications tripled maize yields compared to the control, senna + TSP and tithonia sole
application doubled yields, while senna sole applications did not increase yields substantially. A large residual yield was
produced in the tithonia treatments in a subsequent crop. These yield results were consistent with the higher quality and
faster release of N and P from the tithonia leaves compared to senna. The tithonia biomass transfer system can improve yields
in the short term but has limitations because of the large amount of biomass and the associated labor requirements.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
The ability of Tithonia diversifolia, fertilizers and their combination to improve maize production in a P-deficient Ferralsol was studied in western Kenya. Tithonia and fertilizers were applied separately or combined in different proportions to give equal rates of165 kg N ha−1, 15.5 kg P ha−1 and 155 kg K ha−1 in two consecutive maize growing seasons, followed by two residual maize crops. Maize grain yields and P recovered in the
above-ground biomass were higher in the pure Tithonia than the pure fertilizer treatments. Maize yields increased with increasing proportions ofTithonia in the mixed treatments. When less than 36% of theP applied in the mixture was supplied by Tithonia, there was no additional yield benefit in the combined treatments compared to the pure fertilizer treatments. However an
added value ranging from 18 to 24% in yield was observed at greater Tithonia proportions. Economic returns were greater when Tithonia was applied alone than when fertilizers were used, with a larger profit whenTithonia was collected from existing niches than when produced on site. Collecting Tithonia from current niches resulted also in larger net returns for all the combined treatments compared to the fertilizer treatments.
The results of this study indicate that a high quality organic residue such as Tithonia can increase maize production to a greater extent than fertilizers. In low input systems, the combination of Tithonia and fertilizers is a valuable alternative when resources are scarce and an added benefit can be obtained by maximizing the
proportion of Tithonia in the mixture.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
M. K. O’Neill C. C. Shock K. A. Lombard R. F. Heyduck E. B. G. Feibert D. Smeal R. N. Arnold 《Agroforestry Systems》2010,79(3):409-418
The rapid growth rates of hybrid poplar (Populus spp.) enable rotations of 3–6 years for biofuels or 10–15 years to obtain merchantable timber, but many clones are susceptible
to nutrient deficiencies when grown in alkaline soils. A 1995 Oregon study demonstrated that clone OP-367 (P. deltoides × P. nigra) was the only clone tested that performed well on alkaline soils. Tests in Colorado and New Mexico confirmed the adaptation
of this clone. A multi-clonal trial was established in 2003 at Farmington, New Mexico and Ontario, Oregon in order to screen
a larger number of clones for adaptability to alkaline soils. Trees were planted at 1.5 × 1.5 m spacing and irrigated by surface
drip irrigation. Diameter at breast height (DBH) and tree height were recorded annually (2003–2006); wood volumes (WVol) and
total aboveground biomass (TAB) were calculated from these measurements. Of the 25 clones tested, 19 were common to both sites.
Mean height was greater at the Ontario site through the first 3 years (2003–2005). By the end of four seasons, the tallest
Farmington entry was OP-367 at 9.4 m with 177 Mg ha−1 TAB while the tallest Ontario entry was Malheur-3 at 8.9 m with 195 Mg ha−1 TAB and several other clones had statistically similar production. Given the growth and productivity range at these two sites,
it is difficult to make generalizations across wide areas, but it appears feasible to identify clones suited to alkaline soils
in arid and semi-arid regions. 相似文献
16.
Nutrient concentrations in plant and soil and their rates of cycling in poplar (Populus deltoides)-based agroforestry systems were studied at Pusa, Bihar, India. The nutrient concentrations in the standing biomass of the
crop were more than those in tree, whereas the nutrient contents showed the reverse trend. Soil, litter and vegetation accounted
for 80.3–99.5, 0.1–5.0 and 0.4–14.7%, respectively, of the total nutrients in the system. Considerable reduction (40–54%)
in concentration of nutrients in leaves occurred during senescence. The uptake of nutrients by vegetation, and also by different
components with and without adjustment for internal recycling, were calculated separately. Annual transfer of litter nutrient
to the soil by vegetation was 37.3–146.2 N, 5.6–17.9 P and 25.0–66.3 K kg ha−1 year−1 in young (3-year-old) and mature (9-year-old) plantations. Turnover rate and time for different nutrients ranged between
0.86–0.99 year−1 and 1.01–1.16 years, respectively. Compartmental models for nutrient dynamics have been developed to represent the distribution
of nutrient contents and net annual fluxes within the system. This study shows that the poplar-based agroforestry system can
be sustainable in terms of soil nutrient status. 相似文献
17.
This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system
to increase soil fertility and insure sustainability. We analyzed the N2 fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted
in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning
residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied.
Dinitrogen fixation, as estimated by the 15N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average,
76% of the N exports from the plot in tree pruning (194 kg [N] ha–1 yr–1) originated from N2 fixation. Grass production averaged 13 Mg ha–1 yr–1 and N export in cut grass was 195 kg [N] ha–1 yr–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha–1 yr–1. Carbon sequestration averaged 1.9 Mg [C] ha–1 yr–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha–1 yr–1, corresponding to 30% of N2 fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha–1 yr–1) and litter decomposition (40 kg [N] ha–1 yr–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground
tree biomass than nodules.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
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
19.
Patrick Chesney 《Agroforestry Systems》2008,72(2):149-159
The effect of pruning all branches (complete pruning) or retaining one branch (partial pruning) on the dynamics of nitrogen
cycling in aboveground biomass, nitrogen supplying power of an amended Eutric Cambisol, and fine root length, was studied
in an Erythrina poeppigiana (Walp.) O.F. Cook—tomato (Lycopersicon esculentum Mill.) alley cropping practice in Turrialba, Costa Rica during 1999–2000. Over the 1 year pruning cycle, in which trees were
completely or partially pruned four times, respective aboveground biomass production was 4.4 Mg or 7 Mg ha−1 (2-year-old trees) and 5.5 Mg or 9 Mg ha−1 (8-year-old trees); N cycled in aboveground biomass was 123 kg or 187 kg ha−1 (2-year-old trees) and 160 kg or 256 kg N ha−1 (8-year-old trees); mean fine root length was 489 or 821 m (2-year-old-trees), 184 or 364 m per tree (8-year-old-trees).
Pruning intensity did not significantly affect net N mineralisation and net nitrification rates during the tomato-cropping
season. For the tomato crop, pre-plant mean net N mineralisation rate of 2.5 mg N kg−1 soil day−1 was significantly lower than 16.7 or 11.6 mg N kg−1 soil day−1 at the end of vegetative development and flowering, respectively. Mean net nitrification rates of 3.5, and 4.3 mg N kg−1 soil day−1, at pre-plant and end of vegetative development, respectively, were significantly higher than 0.3 mg N kg−1 soil day−1 at end of flowering. In humid tropical low-input agroforestry practices that depend on organic inputs from trees for crop
nutrition, retention of a branch on the pruned tree stump appears to be a good alternative to removal of all branches for
reducing N losses through higher N cycling in aboveground biomass, and for conserving fine root length for higher N uptake,
although it might enhance competition for associated crops. 相似文献
20.
Shaoxiong Chen Roger Arnold Zhihui Li Tianhui Li Guofu Zhou Zhihua Wu Qunying Zhou 《New Forests》2011,41(1):95-112
A large initial stocking × fertilizer factorial field trial established in 1993 with a Eucalyptus urophylla × grandis hybrid clone in southern Guangxi province, China, included 6 initial stocking treatments ranging from 667 to 2,222 trees ha−1 and 6 fertilizer treatments. Growth data was collected at various intervals up to age 192 months and also data on outer-wood
pilodyn penetration (as an indicator of wood density) and acoustic velocity through the outer-wood (as an indicator of modulus
of elasticity) at the last assessment. This report examines the results for the main effect of initial stocking treatments
and stocking × fertilizer interactions across ages. There were significant differences between initial stockings for both
average individual tree volume and standing volume ha−1 at all ages up to 144 months, but just average individual tree volume at 192 months. At ages up to 75 months total standing
volume decreased as initial stocking decreased—maximum volume being obtained at 2,222 trees ha−1. From 88 to 110 months the highest standing volume was obtained at 1,667 trees ha−1 and then at ages 144 and 192 months, 833 trees ha−1 provided the highest standing volume. Average individual tree volume at all ages generally increased as initial stocking
decreased—the largest trees were obtained at 667 trees ha−1. As age increased the proportional differences between tree volumes at higher and lower stockings increased—at age 27 months
average individual tree volume at 667 trees ha−1 was 72% greater than that at 2,222 trees ha−1 and differences increased steadily with age up to 190% at 192 months. There were no significant differences between initial
stockings for the properties of the outer-wood assessed by pilodyn penetration and acoustic velocity. Also, no significant
interactions were found between initial stocking and fertilizer treatments for any traits at any ages implying that effects
of initial stocking and fertilizer are additive for the traits assessed. 相似文献