共查询到20条相似文献,搜索用时 15 毫秒
1.
Changes in the Above- and Below-ground Biomass and Nutrient Pools of Ground Vegetation After Clear-cutting of a Mixed Boreal Forest 总被引:3,自引:0,他引:3
Marjo Palviainen Leena Finér Hannu Mannerkoski Sirpa Piirainen Michael Starr 《Plant and Soil》2005,275(1-2):157-167
Ground vegetation may act as a sink for nutrients after clear-cutting and thus decrease leaching losses. Biomass and nutrient
(N, P, K, Ca) pools of ground vegetation (mosses, roots and above-ground parts of field layer) were determined one year before
and five years after clear-cutting of a Norway spruce (Picea abies (L.) H. Karst.) dominated boreal mixed forest stand in
eastern Finland (63°51′ N, 28°58′ E). Before clear-cutting the average biomass of ground vegetation was 5307 kg ha−1, with nutrient contents of 46.9 kg N ha−11, 4.1 kg P ha−11, 16.2 kg K ha−11 and 13.9 kg Ca ha−11. The biomass and nutrient pools decreased after clear-cutting being lowest in the second year, the biomass decreasing by
46–65% in the cut plots. The nutrient pools decreased as follows: N 54–72%, P 36–68%, K 51–71% and Ca 57–74%. The decrease
in ground vegetation nutrient uptake, and the observed reduced depth of rooting may decrease nutrient retention after clear-cutting
and decomposing dead ground vegetation is a potential source of leached nutrients. These negative effects of clear-cutting
on the nutrient binding capacity of ground vegetation was short-lived since the total biomass and nutrient pools returned
to pre-cutting levels or were even greater by the end of the 5-year study period. 相似文献
2.
Montás Ramírez L. Claassen N. Amílcar Ubiera A. Werner H. Moawad A.M. 《Plant and Soil》2002,239(2):197-206
During the period January–August 1996, an investigation was carried out in La Mata, Cotuí, Dominican Republic with the objective to study the effect of P, K and Zn fertilizers on Fe toxicity in the rice varieties JUMA-57 (sensitive to Fe toxicity), ISA-40 and PSQ-4 (both tolerant to Fe toxicity). The rate of fertilizer application was 22 and 62 kg P ha–1; 58 and 116 kg K ha–1; 3 and 7 kg Zn ha–1 and a constant dose of 140 kg N ha–1 and 40 kg S ha–1 on all fertilized plots. The control received no fertilizer. JUMA-57 was the only variety that showed symptoms of Fe toxicity. The observed symptoms showed a yellow to orange colour. Symptoms of Fe toxicity appeared first one week after transplanting (WAT), decreased at the fourth WAT, but returned six WAT and continued until the end of the experiment. Fertilizer application reduced symptom intensity and increased grain yield in all varieties, but only JUMA-57 did not reach the maximum yield typical for that variety. Fertilizer application did not completely overcome the toxicity effect, i.e. in symptom intensity and grain yield. The positive effect of fertilizer application could not be attributed to a specific nutrient. Intensity of symptoms was not related to Fe concentration in the leaves. The average Fe concentration of 108 mg kg–1 was not high enough to be considered toxic. Symptoms could not be explained through Mn toxicity (average Mn concentration in the leaves was 733 mg kg–1) nor Zn deficiency (average Zn concentration in the leaves was 20 mg kg–1). There was a clear relationship, though, between soil DTPA extractable Fe and symptom intensity or grain yield. The toxic effect was observed when the DTPA extractable Fe in the flooded soil was above 200 mg kg–1. From these results, we concluded that the Fe toxicity resulted from high Fe in the root zone and not from high Fe concentrations in the leaves. 相似文献
3.
Development of ground vegetation biomass and nutrient pools in a clear-cut disc-plowed boreal forest
Marjo Palviainen Leena Finér Ari Laurén Hannu Mannerkoski Sirpa Piirainen Michael Starr 《Plant and Soil》2007,297(1-2):43-52
Nutrient leaching from forest substrate after clear-cutting and subsequent soil preparation is strongly influenced by the
capacity of ground vegetation to sequester the released nutrients. We studied the rates and patterns of biomass and nutrient
accumulation in ground vegetation growing on ridges, in furrows and on undisturbed surfaces for 2–5 years after disc-plowing
in eastern Finland. The biomass of mosses on ridges remained significantly lower than that in furrows and on undisturbed surfaces.
Field layer biomass on ridges and in furrows was significantly lower than on undisturbed surfaces throughout the study period.
Field layer biomass increased more on ridges than in furrows. Root biomass on ridges and undisturbed surfaces was considerably
higher than in furrows. Five years after disc-plowing, total biomass and nutrient pools for ridges (biomass 4,975 kg ha−1, N 40 kg ha−1, P 5 kg ha−1, K 20 kg ha−1 and Ca 18 kg ha−1) and undisturbed surfaces (biomass 5,613 kg ha−1, N 43 kg ha−1, P 5 kg ha−1, K 22 kg ha−1 and Ca 18 kg ha−1) were similar, but considerably lower for furrows (biomass 1,807 kg ha−1, N 16 kg ha−1, P 2 kg ha−1, K 10 kg ha−1 and Ca 6 kg ha−1). Ridges covered 25% of the area, furrows 30 and 45% was undisturbed surfaces. Taking into account the proportion of each
type of surface, values for the whole prepared clear-cut area were 4,312, 34, 4, 18 and 14 kg ha−1 for biomass, N, P, K and Ca, respectively. Biomass and nutrient pools had not returned to uncut forest levels at the end
of the 5-year study period. The results indicate that mosses and field layer vegetation respond differently to soil preparation,
that the development of biomass on ridges, in furrows and on undisturbed surfaces proceeds at different rates, and that the
biomass and nutrient uptake of ground vegetation remains below pre-site preparation levels for several years. However, ridges,
which are known to be the most susceptible to leaching, revegetate rapidly.
Responsible Editor: Tibor Kalapos. 相似文献
4.
Root growth,macro-nutrient uptake dynamics and soil fertility requirements of a high-yielding winter oilseed rape crop 总被引:2,自引:0,他引:2
P. B. Barraclough 《Plant and Soil》1989,119(1):59-70
Shoot growth, root growth and macro-nutrient uptake by a high-yielding (5t/ha grain) winter oilseed rape crop have been measured.
Maximum rooting density in the top 20cm of soil was 9.4 cm cm−3 and roots reached a depth of at least 1.8 m. Maximum nutrient uptakes were 364 kg ha−1 for N, 43 kg ha−1 for P, 308 kg ha−1 for K, 287 kg ha−1 for Ca and 16 kg ha−1 for Mg. A 30-day drought coincided with the flowering period and root and shoot growth, as well as nutrient uptake rates,
were reduced. Nutrient concentrations in the soil solution necessary to sustain the nutrient fluxes into the root system by
diffusive supply have been calculated. Peak values were in the range 10 μM for P to 87 μM for N, lower than the observed concentrations, and it was concluded that nutrient transport to roots was not a limitation
to uptake by this rape crop. 相似文献
5.
Growth and N, P, K uptake of Acala SJ-2 cotton (Gossypium hirsutum) were investigated in an irrigated permanent-plot field (Typic chromoxerert) at Bet Dagan, Israel, under semi-arid conditions
using different nitrogen levels: 0, 60, 120, 180 and 240 kg N ha−1. The total dry matter accumulation at these levels was 9.0, 10.7, 15.1, 17.1 and 15.6 ton ha−1, respectively. The uptake of N, P and K was 110, 144, 267, 322 and 301 kg N ha−1∶31, 34, 46, 44 and 38 kg P ha−1; and 120, 151, 208, 251 and 230 kg K ha−1, respectively.
Dry matter production, as well as N, P, K uptake by the cotton plants were greatly increased by raising the N application
levels to 120 or 180 kg N ha−1, but the pattern of accumulation and relative distribution of dry matter and NPK among plant organs were not considerably
affected.
Joint contribution from the Dept. of Soil Chemistry and Plant Nutrition, ARO, the Volcani Center, Bet Dagan, Israel (No. 1413-E,
1985 series) 相似文献
6.
A study was made over 3 years to find out an optimum rate of Zn application for the maize–mungbean–rice cropping system in
a calcareous soil of Bangladesh. Zinc application was made at 0, 2 and 4 kg ha−1 for maize (cv. Pacific 984, Thai hybrid) and at 0, 1 and 2 kg ha−1 for rice (cv. BRRI dhan33), with no Zn application for mungbean (cv. BARI mung5). Effect of Zn was evaluated in terms of
yield and mineral nutrients contents (N, P, S and Zn). All the three crops responded significantly to Zn application. The
optimum rate of Zn for the maize–mungbean–rice cropping system was found to be 4–0–2 kg ha−1 for the first year and 2–0–2 kg ha−1 for subsequent years particularly when mungbean residue was removed, and such rates for mungbean residue incorporation being
4–0–1 and 2–0–1 kg ha−1, respectively. For all crops, the Zn and N concentrations of grain were significantly increased with Zn application. For
the case of grain-S, the concentration was significantly increased for maize and mungbean, but it remained unchanged for rice.
The grain-P concentration on the other hand tended to decrease with Zn application. For maize, the grain-Zn concentration
increased to 27.0 μg g−1 due to 2 kg Zn ha−1 treatment from 16.5 μg g−1 for Zn control and at higher Zn rate (4 kg Zn ha−1) the increment was very minimum. Another field experiment was performed over 3 years on the same soil to screen out maize
varieties for Zn efficiency. Of the eight varieties tested, the BARI maize 6 and BARI hybrid maize 3 were found Zn in-responsive
(Zn efficient) and the others Zn responsive (Zn-inefficient). 相似文献
7.
Increasing phosphorus supply in subsurface soil in northern Australia: Rationale for deep placement and the effects with various crops 总被引:6,自引:0,他引:6
Three field experiments involving wheat, lucerne or cotton were established at different sites in the semiarid cropping regions
of northern Australia, to test whether the deep placement of P fertiliser improved P availability, compared to the conventional
practice of placing the fertiliser beside or adjacent to the seed. At Mulga View, near St George in southern Queensland on
a red Kandosol soil with a Colwell soil test value of 19 mg P kg soil−1 in the top 10 cm, there was no response to 10 kg P ha−1 applied in the 5–7 cm layer. However, increasing the depth of placement of 10 kg P ha−1 from 5–7 to 10–15 cm resulted in increased shoot growth and grain yield of spring wheat (Triticum aestivum) by 43 and 30%, respectively. A further grain yield increase of 43% to 3.2 t ha−1 resulted when the deep P rate was increased from 10 to 40 kg P ha−1. At Roma, in southern Queensland, on a grey/brown Vertosol with a Colwell soil test value of 15 mg P kg soil−1, there was no difference in the winter growth of lucerne (Medicago sativa) when P fertiliser had been applied at 5–7 cm depth at rates of 10 and 40 kg P ha−1. Shoot dry matter yields were around 2 t ha−1. However dry matter yields increased significantly to 2.6 and 3.7 t ha−1 when 10 and 40 kg P ha−1, respectively were applied at the 10–15 cm depth. The third experiment was carried out on a grey Vertosol at Kununurra in
Western Australia. Significant increases in the yield of seed cotton (Gossypium hirsutum) occurred when 50 kg P ha−1 was applied at depth (10–15 and 25–30 cm), compared with the conventional placement at 7–10 cm, with maximum yield response
to deep placement occurring with DAP, and the minimal response with MAP. The cotton was grown on raised beds and the crop
was irrigated according to district practice. The response to deep P at all sites was attributed to the rapid drying of the
soil surface layers, reducing the availability of soil or fertiliser P in these layers. The deep fertiliser P remained available
during the growing season and alleviated the P deficiency that appears to be a feature of these soils when the surface layers
become dry. 相似文献
8.
Fire in the Brazilian Amazon 2. Biomass, nutrient pools and losses in cattle pastures 总被引:3,自引:0,他引:3
Conversion to cattle pasture is the most common fate of the ≈426,000 km2 of tropical forest that has been deforested in the Brazilian Amazon. Yet little is known about the biomass, C, nutrient pools,
or their responses to the frequent fires occurring in these pastures. We sampled biomass, nutrient pools and their losses
or transformation during fire in three Amazonian cattle pastures with typical, but different, land-use histories. Total aboveground
biomass (TAGB) ranged from to 53 to 119 Mg ha−1. Residual wood debris from the forests that formally occupied the sites composed the majority of TAGB (47–87%). Biomass of
fine fuels, principally pasture grasses, was ≈16–29 Mg ha−1. Grasses contained as much as 52% of the aboveground K pool and the grass and litter components combined composed as much
as 88% of the aboveground P pool. Fires consumed 21–84% of the TAGB. Losses of C to the atmosphere ranged from 11 to 21 Mg ha−1 and N losses ranged from 205 to 261 kg ha−1. Losses of S, P, Ca, and K were <33 kg ha−1. There were no changes in surface soil (0–10 cm) nutrient concentration in pastures compared to adjacent primary forests.
Fires occur frequently in cattle pastures (i.e., about every 2 years) and pastures are now likely the most common type of
land burned in Amazonia. The first 6 years of a pastures existence would likely include the primary forest slash fire and
three pasture fires. Based upon our results, the cumulative losses of N from these fires would be 1935 kg ha−1 (equivalent to 94% of the aboveground pool of primary forest). Postfire aboveground C pools in old pastures are as low as
3% of those in adjacent primary forest. The initial primary forest slash fire and the repeated fires occurring in the pastures
result in the majority of aboveground C and nutrient pools being released via combustion processes rather than decomposition
processes.
Received: 6 January 1997 / Accepted: 2 September 1997 相似文献
9.
Peanut growth as affected by liming,Ca-Mn interactions,and Cu plus Zn applications to oxidic samoan soils 总被引:1,自引:0,他引:1
Effects of coralline lime, in combination with 3 kg Cu ha−1 plus 3 kg Zn ha−1, on yield and nutrient uptake by peanut (Arachis hypogea) were studied at three locations in Western Samoa. Coarse (0–10 mm) coralline lime material containing 31.1% Ca and 1.7%
Mg was used as lime at 0, 555, 2222 and 5000 kg ha−1. In the Togitogiga soil, which had the lowest level of exchangeable Ca, peanut yield increased by 6 fold after liming with
555 kg ha−1, relative to the unamended control. This yield increase was associated with reduced Mn toxicity as well as reduced Ca deficiency.
The alleviation of Mn toxicity was not likely due to decreased Mn solubility because the lime application (555 kg ha−1) increased soil pH by <0.1 unit. Rather it was the increased Ca availability which reduced the Mn toxicity through a Ca/Mn
antagonism. The critical range of exchangeable Ca for peanut growth was found to be about 1.5–1.6 cmol 1/2Ca2+ kg−1. A Ca/Mn-ratio >80 was required for a desirable Ca/Mn balance in peanut tissue. On the other two locations (with exchangeable
Ca levels of 1.5–1.6 cmol 1/2Ca2+ kg−1), liming increased peanut yields by 15–20%. Additions of Cu plus Zn also increased the yields, although the increases were
small (7%) and not significant at the 95% probability level.
This research was made possible by Grant No. 936-5542-G-SS-9092 from the Program in Science and Technology Cooperation, AID/ST/AGR,
U.S. Agency for International Development. 相似文献
10.
Mingsheng Fan Xuejun Liu Rongfeng Jiang Fusuo Zhang Shihua Lu Xiangzhong Zeng Peter Christie 《Plant and Soil》2005,277(1-2):265-276
A field experiment was conducted for 5 years to examine the effects of non-flooded mulching cultivation on crop yield, internal
nutrient efficiency and soil properties in rice–wheat (R–W) rotations of the Chengdu Plain, southwest China. Compared with
traditional flooding (TF), non-flooded plastic film mulching (PM) resulted in 12 and 11% higher average rice (Oryza sativa L.) yield and system productivity (combined rice and wheat yields), and the trends in rice and wheat (Triticum aestivum L.) yields under PM were stable over time. However, non-flooded wheat straw mulching (SM) decreased average rice yield by
11% compared with TF, although no significant difference in system productivity was found between SM and TF. Uptakes of N
and K by rice under PM were higher than those under TF and SM, but internal nutrient efficiency was significantly lower (N)
or similar (K) under PM compared to SM and TF. This implies that more N and K accumulated in rice straw under PM. After 5-year
rice–wheat rotation, apparent P balances (112–160 kg ha−1) were positive under all three cultivation systems. However, the K balances were negative under PM (−419 kg ha−1) and TF (−90 kg ha−1) compared with SM (45 kg ha−1). This suggests that higher K inputs from fertilizer, straw or manure may be necessary, especially under PM. After five rice
seasons and four wheat seasons, non-flooded mulching cultivation led to similar (PM) or higher (SM) soil organic carbon (SOC),
total N (TN) and alkali hydrolyzable N (AH-N) in the top 0–5 and 5–12 cm layers compared with TF. SOC, TN, AH-N and Olsen-P
(OP) in the sub-surface layer (12–24 cm) were significantly higher under PM or SM than under TF, indicating that rice under
non-flooded mulching conditions may fail to make use of nutrients from the subsoil. Thus, the risk of decline in soil fertility
under non-flooded mulching cultivation could be very low if input levels match crop requirements. Our data indicate that PM
and SM may be alternative options for farmers using R–W rotations for enhancement or maintenance of system productivity and
soil fertility. 相似文献
11.
A field experiment conducted at Central Rice Research Institute, Cuttack, during three successive seasons showed that with
the 120-day-duration variety Ratna two dual crops ofAzolla pinnata R. Brown (Bangkok isolate) could be achieved 25 and 50 days after transplanting (DAT) by inoculating 2.0 t ha−1 of fresh Azolla 10 and 30 DAT respectively. One basal crop of Azolla could also be grown using the same inoculum 20 days
before transplanting (DBT) in fallow rice fields. The three crops of Azolla grown—once before transplanting and twice after
transplanting—gave an average total biomass of 38–63 and 43–64 t ha−1 fresh Azolla containing 64–90 and 76–94 kg N ha−1 respectively in the square and rectangular spacings. Two crops of Azolla grown only as a dual crop, on the other hand, gave
26–39 and 29–41 t ha−1 fresh Azolla which contained 44–61 and 43–59 kg N ha−1 respectively.
Growth and yield of rice were significantly higher in Azolla basal plus Azolla dual twice incorporated treatments than in
the Azolla dual twice incorporation, Azolla basal plus 30 kg N ha−1 urea and 60 kg N ha−1 urea treatments. Azolla basal plus 30 kg N ha−1 urea and 60 kg N ha−1 urea showed similar yields but Azolla dual twice incorporation was significantly lower than those. The different spacing
with same plant populations did not affect growth and yield significantly, whereas Azolla growth during dual cropping was
8.3 and 64% more in the rectangular spacing than in the square spacing in Azolla basal plus Azolla dual twice incorporation
and Azolla dual twice incorporation treatments. 相似文献
12.
Intercropping cotton (Gossypium hirsutum L.) and cowpea (Vigna unguiculata (L.) Walp) is one of the ways to improve food security and soil fertility whilst generating cash income of the rural poor. A study was carried out to find out the effect of cotton–cowpea intercropping on cowpea N2-fixation capacity, nitrogen balance and yield of a subsequent maize crop. Results showed that cowpea suppressed cotton yields but the reduction in yield was compensated for by cowpea grain yield. Cowpea grain yield was significantly different across treatments and the yields were as follows: sole cowpea (1.6 Mg ha−1), 1:1 intercrop (1.1 Mg ha−1), and 2:1 intercrop (0.7 Mg ha−1). Cotton lint yield was also significantly different across treatments and was sole cotton (2.5 Mg ha−1), 1:1 intercrop (0.9 Mg ha−1) and 2:1 intercrop (1.5 Mg ha−1). Intercropping cotton and cowpea increased the productivity with land equivalence ratios (LER) of 1.4 and 1.3 for 1:1 and 2:1 intercrop treatments, respectively. There was an increase in percentage of N fixation (%Ndfa) by cowpea in intercrops as compared to sole crops though the absolute amount fixed (Ndfa) was lower due to reduced plant population. Sole cowpea had %Ndfa of 73%, 1:1 intercrop had 85% and 2:1 intercrop had 77% while Ndfa was 138 kg ha−1 for sole cowpea, 128 kg ha−1 for 1:1 intercrop and 68 kg ha−1 for 2:1 intercrop and these were significantly different. Sole cowpea and the intercrops all showed positive N balances of 92 kg ha−1 for sole cowpea and 1:1 intercrop, and 48 kg ha−1 for 2:1 intercrop. Cowpea fixed N transferred to the companion cotton crop was very low with 1:1 intercrop recording 3.5 kg N ha−1 and 2:1 intercrop recording 0.5 kg N ha−1. Crop residues from intercrops and sole cowpea increased maize yields more than residues from sole cotton. Maize grain yield was, after sole cotton (1.4 Mg ha−1), sole cowpea (4.6 Mg ha−1), 1:1 intercrops (4.4 Mg ha−1) and 2:1 intercrops (3.9 Mg ha−1) and these were significantly different from each other. The LER, crop yields, %N fixation and, N balance and residual fertility showed that cotton–cowpea intercropping could be a potentially productive system that can easily fit into the current smallholder farming systems under rain-fed conditions. The fertilizer equivalency values show that substantial benefits do accrue and effort should be directed at maximizing the dry matter yield of the legume in the intercrop system while maintaining or improving the economic yield of the companion cash crop. 相似文献
13.
Impact of long-term nitrogen addition on carbon stocks in trees and soils in northern Europe 总被引:4,自引:2,他引:2
The aim of this study was to quantify the effects of fertiliser N on C stocks in trees (stems, stumps, branches, needles,
and coarse roots) and soils (organic layer +0–10 cm mineral soil) by analysing data from 15 long-term (14–30 years) experiments
in Picea abies and Pinus sylvestris stands in Sweden and Finland. Low application rates (30–50 kg N ha−1 year−1) were always more efficient per unit of N than high application rates (50–200 kg N ha−1 year−1). Addition of a cumulative amount of N of 600–1800 kg N ha−1 resulted in a mean increase in tree and soil C stock of 25 and 11 kg (C sequestered) kg−1 (N added) (“N-use efficiency”), respectively. The corresponding estimates for NPK addition were 38 and 11 kg (C) kg−1 (N). N-use efficiency for C sequestration in trees strongly depended on soil N status and increased from close to zero at
C/N 25 in the humus layer up to 40 kg (C) kg−1 (N) at C/N 35 and decreased again to about 20 kg (C) kg−1 (N) at C/N 50 when N only was added. In contrast, addition of NPK resulted in high (40–50 kg (C) kg−1 (N)) N-use efficiency also at N-rich (C/N 25) sites. The great difference in N-use efficiency between addition of NPK and
N at N-rich sites reflects a limitation of P and K for tree growth at these sites. N-use efficiency for soil organic carbon
(SOC) sequestration was, on average, 3–4 times lower than for tree C sequestration. However, SOC sequestration was about twice
as high at P. abies as at P. sylvestris sites and averaged 13 and 7 kg (C) kg−1 (N), respectively. The strong relation between N-use efficiency and humus C/N ratio was used to evaluate the impact of N
deposition on C sequestration. The data imply that the 10 kg N ha−1 year−1 higher deposition in southern Sweden than in northern Sweden for a whole century should have resulted in 2.0 ± 1.0 (95% confidence
interval) kg m−2 more tree C and 1.3 ± 0.5 kg m−2 more SOC at P. abies sites in the south than in the north for a 100-year period. These estimates are consistent with differences between south
and north in tree C and SOC found by other studies, and 70–80% of the difference in SOC can be explained by different N deposition. 相似文献
14.
Selenium accumulation by sequentially grown wheat and rice as influenced by gypsum application in a seleniferous soil 总被引:2,自引:0,他引:2
A field experiment was conducted for 2 years on an alkaline calcareous seleniferous soil to study the effect of different
levels of gypsum (0.2 – 3.2 t ha−1) applied to wheat only in the first year on Se accumulation by wheat (Triticum aestivum L.) – rice (Oryza sativa L.) cropping sequence. With gypsum application, grain yield of both rice and wheat crops increased by 0.4 – 0.5 t ha−1; the increase in straw yield was 0.4 – 1.1 t ha−1. Significant reduction in Se accumulation by wheat was observed with gypsum application up to 0.8 t ha−1 and its residual effect was evident on the following crops for 2 years. Reduction in Se accumulation varied from 53 to 64%
in wheat grain, 46 to 49% in wheat straw, 35 to 63% in rice grain and 36 to 51% in rice straw with an application of gypsum
at 0.8 t ha−1. A corresponding increase in S concentration was observed. In the gypsum-treated plots, the ratio of S:Se increased by 6
– 8 times in wheat and 3 – 6 times in rice. Reduction in Se accumulation by crop plants through gypsum application may help
in lowering the risk of Se over-exposure of animals and humans that depend on diet materials grown on high selenium soils.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
Phosphorus cycling in rainfed lowland rice ecosystems is poorly understood. Soil drying and grazing of rice straw during the
long dry season, the growth of volunteer pastures during the early wet season, and intermittent loss of soil-water saturation
while the rice crop is growing are important distinguishing characteristics of the rainfed lowlands in relation to P cycling.
We studied P cycling in an acid sandy rainfed lowland soil that covers about 30% of the rice growing area of Cambodia. Soils
with similar properties in comparable rainfed sub- ecosystems occur in Laos and northeast Thailand. We developed a general
schema of P pools and fluxes in the crop and soil for rice-based cropping systems in the rainfed lowlands of Cambodia. The
schema was derived from a number of field experiments carried out over five consecutive cropping seasons to quantify the residual
value of P fertiliser, P mass balances, soil P fractions, the effect on subsequent rice crops of crop residues and volunteer
pastures incorporated into the soils, and the dynamics of P turnover in the soil. With a single rice crop yielding 2.5–3 t
ha−1, application of 8–10 kg P ha−1 maintained yields and a small positive P balance in the soil. However, the soil P balance was sensitive to the proportion
of rice straw returned to the soil. Volunteer pastures growing during the early wet season accumulated significant amounts
of P, and increased their P uptake when soils were previously fertilised with P. These pastures recycled 3–10 kg P ha−1 for the succeeding rice crops. While inorganic soil P pools extractable with ion exchange resins and 0.1 M NaOH appeared
to be the main source of P absorbed by rice, microbial and organically-bound P pools responded dynamically to variation in
soil water regimes of the main wet, dry and early wet seasons. The schema needs to be developed further to incorporate site-specific
conditions and management factors that directly or indirectly affect P cycling, especially loss of soil-water saturation during
the rice cropping cycle. The paper discusses the application of results for acid sandy soils to other significant rice soils
in the rainfed lowlands of southeast Asia. 相似文献
16.
Ecosystem restoration by rewetting of degraded fens led to the new formation of large-scale shallow lakes in the catchment
of the River Peene in NE Germany. We analyzed the biomass and the nutrient stock of the submersed (Ceratophyllum demersum) and the floating macrophytes (Lemna minor and Spirodela polyrhiza) in order to assess their influence on temporal nutrient storage in water bodies compared to other freshwater systems. Ceratophyllum demersum displayed a significantly higher biomass production (0.86–1.19 t DM = dry matter ha−1) than the Lemnaceae (0.64–0.71 t DM ha−1). The nutrient stock of submersed macrophytes ranged between 28–44 kg N ha−1 and 8–12 kg P ha−1 and that of floating macrophytes between 14–19 kg N ha−1 and 4–5 kg P ha−1 which is in the range of waste water treatment plants. We found the N and P stock in the biomass of aquatic macrophytes being
20–900 times and up to eight times higher compared to the nutrient amount of the open water body in the shallow lakes of rewetted
fens (average depth: 0.5 m). Thereafter, submersed and floating macrophytes accumulate substantial amounts of dissolved nutrients
released from highly decomposed surface peat layers, moderating the nutrient load of the shallow lakes during the growing
season from April to October. In addition, the risk of nutrient loss to adjacent surface waters becomes reduced during this
period. The removal of submersed macrophytes in rewetted fens to accelerate the restoration of the low nutrient status is
discussed. 相似文献
17.
Grass fallow shifting cultivation is an important land use practice in the highlands of Bhutan. Part of the nutrient pool
contained in soil organic matter is made available for the traditional buckwheat (Fagopyrum tataricum) crop through a highly labor intensive system exposing 250–500 MT soil ha−1 to temperatures of 500°C and above. Dry topsoil is collected in mounds and burned using plant biomass or manure and soil
organic matter as fuel. Labor input ranged from 150–401 days ha−1 with land preparation accounting for 65–85% of the total requirement. The burning increased soil pH from 6.0 to 6.9 and available
K from 34 to 69 mg kg−1. Soil organic C and total N were reduced from 3.3 and 0.17% to 0.8 and 0.08%, respectively. Release of P from soil organic
matter and plant material and reduction in C/N ratio resulting in increased N availability are considered the most essential
effects required for good crop yields. Through the burning about 16 MT of C and 470 kg N ha−1 are released into the atmosphere. Fallow periods of 15–20 years are required for the system to be sustainable.
The research was supported by the Department of Agriculture. Royal Government of Bhuttan and the Swiss Association for Technical
Assistance
The research was supported by the Department of Agriculture. Royal Government of Bhuttan and the Swiss Association for Technical
Assistance 相似文献
18.
Eva Ritter 《Plant and Soil》2007,295(1-2):239-251
Afforestation has become an important tool for soil protection and land reclamation in Iceland. Nevertheless, the harsh climate
and degraded soils are growth-limiting for trees, and little is know about changes in soil nutrients in maturing forests planted
on the volcanic soils. In the present chronosequence study, changes in C, N and total P in soil (0–10 and 10–20 cm depth)
and C and N in foliar tissue were investigated in stands of native Downy birch (Betula pubescens Enrh.) and the in Iceland introduced Siberian larch (Larix sibirica Ledeb.). The forest stands were between 14 and 97 years old and were established on heath land that had been treeless for
centuries. Soils were Andosols derived from basaltic material and rhyolitic volcanic ash. A significant effect of tree species
was only found for the N content in foliar tissue. Foliar N concentrations were significantly higher and foliar C/N ratios
significantly lower in larch needles than in birch leaves. There was no effect of stand age. Changes in soil C and the soil
nutrient status with time after afforestation were little significant. Soil C concentrations in 0–10 cm depth in forest stands
older than 30 years were significantly higher than in heath land and forest stands younger than 30 years. This was attributed
to a slow accumulation of organic matter. Soil N concentrations and soil Ptot were not affected by stand age. Nutrient pools in the two soil layers were calculated for an average weight of soil material
(400 Mg soil ha−1 in 0–10 cm depth and 600 Mg soil ha−1 in 10–20 cm depth, respectively). Soil nutrient pools did not change significantly with time. Soil C pools were in average
23.6 Mg ha−1 in the upper soil layer and 16.9 Mg ha−1 in the lower soil layer. The highest annual increase in soil C under forest compared to heath land was 0.23 Mg C ha−1 year−1 in 0–10 cm depth calculated for the 53-year-old larch stand. Soil N pools were in average 1.0 Mg N ha−1 in both soil layers and did not decrease with time despite a low N deposition and the uptake and accumulation of N in biomass
of the growing trees. Soil Ptot pools were in average 220 and 320 kg P ha−1 in the upper and lower soil layer, respectively. It was assumed that mycorrhizal fungi present in the stands had an influence
on the availability of N and P to the trees.
Responsible Editor: Hans Lambers. 相似文献
19.
Mark S. Castro Keith N. Eshleman Louis F. Pitelka Geoff Frech Molly Ramsey William S. Currie Karen Kuers Jeffrey A. Simmons Bob R. Pohlad Carolyn L. Thomas David M. Johnson 《Biogeochemistry》2007,84(3):333-348
The objective of this study was to evaluate the nitrogen (N) biogeochemistry of an 18–22 year old forested watershed in western
Maryland. We hypothesized that this watershed should not exhibit symptoms of N saturation. This watershed was a strong source
of nitrate (NO3
−) to the stream in all years, with a mean annual export of 9.5 kg N ha−1 year−1 and a range of 4.4–18.4 kg N ha−1 year−1. During the 2001 and 2002 water years, wet deposition of inorganic N was 9.0 kg N ha−1 year−1 and 6.3 kg N ha−1 year−1, respectively. Watershed N export rates in 2001 and 2002 water years were 4.2 kg N ha−1 year−1 and 5.3 kg N ha−1 year−1, respectively. During the wetter water years of 2003 and 2004, the watershed exported 15.0 kg N ha−1 year−1 and 18.4 kg N ha−1 year−1, rates that exceeded annual wet deposition of N by a factor of two (7.5 kg N ha−1 year−1 in 2003) and three (5.5 kg N ha−1 year−1 in 2004). Consistent with the high rates of N export, were high concentrations (2.1–3.3%) of N in foliage, wood (0.3%) and
fine roots, low C:N ratios in the forest floor (17–24) and mineral soil (14), high percentages (83–96%) of the amount of mineralized
N that was nitrified and elevated N concentrations (up to 3 mg N l−1) in soil solution. Although this watershed contained a young aggrading forest, it exhibited several symptoms of N saturation
commonly observed in more mature forests. 相似文献
20.
The effects on growth, quality and N uptake by turfgrass (Cynodon dactylon L.) during sod production of four fertiliser types applied at three application rates (100, 200 or 300 kg N ha−1 per ‘crop’) under two irrigation treatments (70% and 140% daily replacement of pan evaporation) were investigated. The fertiliser
types were: water-soluble (predominately NH4NO3), control-release, pelletised poultry manure, and pelletised biosolids; and the experiment was conducted on a sandy soil
in a Mediterranean-type climate. Plots were established from rhizomes, with the turfgrass harvested as sod every 16–28 weeks
depending upon the time of the year. Four crops were produced during the study. Applying water-soluble and control-release
fertilisers doubled shoot growth and improved turfgrass greenness by up to 10% in comparison with plots receiving pelletised
poultry manure and pelletised biosolids. Nitrogen uptake into the shoots after four crops (averaged across irrigation treatments
and N rates) was 497 kg N ha−1 for the water-soluble fertiliser, 402 kg N ha−1 for the control-release, 188 kg N ha−1 for the pelletised poultry manure and 237 kg N ha−1 for the pelletised biosolids. Consequently, the agronomic nitrogen-use efficiency (NAE, kg DM kg−1 N applied) of the inorganic fertilisers was approximately twice that of the organic fertilisers. Increasing irrigation from
70% to 140% replacement of pan evaporation was detrimental to turfgrass growth and N uptake for the first crop when supplied
with the water-soluble fertiliser. Under the low irrigation treatment, inorganic N fertilisers applied at 200–300 kg N ha−1 were adequate for production of turfgrass sod.
Section Editor: P. J. Randall 相似文献