共查询到20条相似文献,搜索用时 93 毫秒
1.
Galiana A. Chaumont J. Diem H. G. Dommergues Y. R. 《Biology and Fertility of Soils》1990,9(3):261-267
Summary Two Australian Acacia species, A. mangium and A. auriculiformis were inoculated in vitro with eight strains of Bradyrhizobium spp. and two strains of Rhizobium spp. On the two plant species, only Bradyrhizobium spp. strains formed effective N2-fixing nodules. A. mangium, which nodulates effectively with a restricted range of Bradyrhizobium spp. strains, is a specific host compared to A. auriculiformis. A. auriculiformis is assumed to be a promiscuous host because it nodulates effectively with a wide range of Bradyrhizobium spp. strains. Nodule efficiency as expressed by the ratio of N2 fixed to nodule dry weight appeared to be higher in A. auriculiformis (0.44–0.81) than in A. mangium (0.23–0.55). 相似文献
2.
Inorganic fertilizer enrichment of soil: effect on decomposition of plant litter under subhumid tropical conditions 总被引:7,自引:0,他引:7
A. B. Kwabiah R. P. Voroney C. A. Palm N. C. Stoskopf 《Biology and Fertility of Soils》1999,30(3):224-231
Litter decomposition is controlled by many factors, including the quality of the litter and conditions within the soil environment.
The decomposition and N and P release from prunings of three agroforestry plant species (Sesbania sesban, Croton megalocarpus, and Calliandra calothyrsus) were evaluated on field plots which were amended with: (1) no fertilizer (control), (2) 120 kg N ha–1 applied as urea (urea), and (3) 150 kg P ha–1 applied as triple superphosphate (TSP) over a period of 77 days. For all litters, the percentage of initial mass, N and P
remaining (dry weight basis) over time followed the single exponential model and was strongly influenced by the interaction
of plant species and fertilizer. Decay rate constants (k) of loss of litter mass (k
B), and release of N (k
N), and P (k
P) varied among litters and fertility regimes. The k
B, k
N and k
P of Sesbania and Croton were enhanced more by urea than by TSP and control treatments. For Calliandra, k
B
with TSP was higher (0.016 day–1) than with urea (0.012 day–1) and control (0.012 day–1). Sesbania and Croton showed no differences in k
B, k
N and k
P between control and TSP. For Sesbania and Croton, leaching may have accelerated the release of P to meet the needs of decomposer organisms, resulting in no significant effects
of TSP on their decomposition processes. The low rate of decomposition of Calliandra may be partly due to its high lignin content. In conclusion, the higher the total N or P of litter, the less likely would
be the significant effects of additions of the inorganic form of fertilizer on the decomposition processes.
Received: 1 July 1998 相似文献
3.
Marcos Vinicius Winckler Caldeira Marcilene Favalessa Elzimar de Oliveira Gonçalves Roberto Rorras dos Santos Moura 《Journal of plant nutrition》2018,41(10):1303-1311
This experiment aimed to compare combinations of sewage sludge-based substrates on the growth of Acacia mangium seedlings by principal component analysis (PCA) and orthogonal contrasts (OC). It was conducted in structures of a forest nursery, localized in Southeast of Brazil, in 280 cm3 tubes constituted by 14 treatments and 5 replicates of four plants. When the seedlings reached 100 days after sowing, the treatments containing sewage sludge associated with vermiculite were those that stood out for the growth of A. mangium seedlings, showing the highest averages for the biometric features. The addition of coconut fiber and coffee straw did not produce good growth as well as the evaluated commercial substrate. It can be stated that the use of principal components and OC were efficient in evaluating the best substrate added to the sewage sludge having a limitation in identifying the best ratio between constituents of the substrate. 相似文献
4.
S. K. Tripathi A. Sumida H. Shibata K. Ono S. Uemura Y. Kodama T. Hara 《Biology and Fertility of Soils》2006,43(2):237-246
In many Japanese forests, the forest understory is largely dominated by dwarf bamboo (Sasa) species, which compete with overstory vegetation for soil nutrients. We studied the rate of leaf litterfall, and decomposition and mineralization of carbon (C) and nitrogen (N) from various components (leaf, root, wood, and rhizome) of overstory and understory vegetation in a young Betula ermanii forest from 2002 to 2004. Total litterfall was 377 g m−2 year−1, of which the overstory vegetation contributed about two thirds. A litter decomposition experiment conducted for 770 days indicated that mass loss of different litter components varied significantly, except for Sasa
kurilensis wood and rhizome. Relative decomposition rates were significantly greater in the first growth period (June to October) than the dormant period (November to May) in most cases. Rainfall was the most important abiotic variable, explaining 75–80% of the variability in mass loss rates. Concentrations of ethanol soluble substances and N were significantly positively correlated (r=0.77 to 0.97, P<0.05) with mass loss at an early stage (41 days). The ratios of lignin/N and C/N were found to be negatively correlated with mass loss rates at all stages of litter decomposition. C stock loss was similar to that of mass loss, whereas N stock loss was slower, except for S. kurilensis fine root litter. The evergreen understory species S. kurilensis exhibited greater N use efficiency than B. ermanii, suggesting better competitive ability that might favor the production of a high biomass and invasion under tree species like B. ermanii. 相似文献
5.
M. A. Satter M. M. Hanafi T. M. M. Mahmud H. Azizah 《Biology and Fertility of Soils》2006,42(4):345-349
To investigate the effects of arbuscular mycorrhiza (AM) and phosphorus (P) source on the uptake of major nutrients by Acacia mangium seedlings, three P sources were used: (1) Gafsa phosphate rock (GPR), (2) China phosphate rock (CPR), and (3) triple superphosphate
(TSP). The plant samples were analyzed at 60, 75, 90, 105, 120, and 135 days after planting (DAP) for their N, P, K, Ca, and
Mg contents. The uptake of these nutrients was significantly influenced by AM inoculation. Nutrient use efficiency in the
AM-inoculated seedlings was also significantly higher than that in uninoculated seedlings. The effect of P sources on the
uptake of these nutrients decreased in the order of TSP>GPR>CPR>control. There was a significant (P<0.05) interaction effect of AM and P source on P and K uptake by A. mangium. The uptake of P and K by mycorrhizal seedlings supplemented with TSP was significantly higher than that provided with other
sources of P treatments. As a natural and cheaper P source, GPR might be used in combination with AM for growing A. mangium seedlings on degraded tin tailings. 相似文献
6.
Litterfall, decomposition, and N release in 5-year-old and 8-year-old plantations of Casuarina equisetifolia (Forst.) in the dry tropical region of the Vindhyan plateau were studied during 1989–1990. Maximum litterfall occurred in May. The total litterfall ranged from 7.2 to 9.9t ha-1 year-1 in the 5-year-old stand and from 11.3 to 12.7t ha-1 year-1 in the 8-year-old stand over the 2-year period. Photosynthetic branchlets contributed 87–95% to the total litter. The relative decomposition rates of litter components of the ash-free mass were highest in the rainy months (4.7 to 9.9mg g-1 day-1) followed by winter (2.8 to 3.6 mg g-1 day-1) and lowest in the summer months (1.7 to 3.0 mg g-1 day-1). Similar patterns were observed for N release. The annual decay constant was highest for cone litter and lowest for photosynthetic branchlets. During decomposition, the photosynthetic branchlets showed N immobilization in November and April, the twig litter in March, and the roots in January and February. N release per unit area (g m-2) was maximum from the photosynthetic branchlets (5.3–6.3) followed by cones (4.4) > roots (3.4) > twigs (2.6–3.2). The combination of the litter C:N ratio, moisture, and temperature with the relative decomposition rate in a multiple regression analysis explained 66–84% of the variability in mass loss and 58–66% of the variability in N release. 相似文献
7.
《Soil Science and Plant Nutrition》2013,59(5):782-788
Abstract An incubation experiment was conducted to examine the effects of the phosphorus (P) application on nitrous oxide (N2O) and nitric oxide (NO) emissions from soils of an Acacia mangium plantation in Indonesia. The soils were incubated with and without the addition of P (Ca[H2PO4]2; 2 mg P g soil)?1) after adjusting the water-filled pore space (WFPS) to 75% or 100%. The P addition increased N2O emissions under both WFPS conditions and NO emissions at 75% WFPS. Some possible mechanisms are considered. First, the P addition stimulated nitrogen (N) cycling, and N used for nitrification and/or denitrification also increased. Second, the P addition could have relieved the P shortage for nitrifying and/or denitrifying bacteria, producing N2O and NO. Our results suggest that the application of P fertilizer has the potential to stimulate N2O and NO emissions from Acacia mangium plantations, at least when soils are under relatively wet conditions. 相似文献
8.
The fungus Ulocladium botrytis was isolated from Scutia buxifolia leaf litter and its growth was evaluated on both liquid and solid medium with sodium-carboxy-methylcellulose (CMC, 0.5%)
as sole C source at a pH range between 4.0 and 10.0 and the synthesis of cellulose-degrading enzymes on litter. Growth on
CMC-agar medium was maximum at pH 6.0, while in liquid CMC cultures, the highest biomass levels were found at pH 8.0 in both
cases after 7 days of incubation. Cellulose-degrading enzyme activities such as β-glucosidase (2.40 U dry leaf g−1), cellobiohydrolase (3.92 10−3 U dry leaf g−1), and endoglucanase (2.01 U dry leaf g−1) activities were detected in water-soluble fractions of inoculated leaves after 30 days of incubation. Endoglucanase activity
was maximum at pH 6.0 and relatively stable as the pH increase, being 100 and 60% stable at pH 7 and 8, respectively. As a
consequence of these enzyme activities, leaf mass was reduced by 5.8%. Our findings suggest that U. botrytis contains a cellulose-degrading enzyme complex that, unlike other cellulolytic systems, can degrade recalcitrant plant litter
under alkaline conditions. 相似文献
9.
Soil microorganisms and microbial processes are influenced by the quality and quantity of plant waste entering the soil, by its seasonal and spatial distribution, by the ratio of above- to below-ground inputs, and by changes in nutrient inputs. Soil management strategies sometimes promote mixed-species plantations to mitigate the loss of soil nutrients and improve biogeochemical cycling. The objective of this study was to explore changes in microbiological and chemical attributes of soils and litter in the early stages of the second rotation of mixed and pure plantations of Eucalyptus grandis and Acacia mangium, and to look for correlations between attributes. Soil samples at 0–10 cm depth were collected two, seven, 14, and 20 months after planting in the following treatments: monocultures of A. mangium and E. grandis, a monoculture of E. grandis with N-fertilizer, and an intercropped plantation with E. grandis and A. mangium. Microbial soil attributes varied dramatically between treatments 20 months after planting. Total C, N and P contents in litter showed the strongest correlations with microbial biomass C and N (Cmic and Nmic), microbial respiration, and dehydrogenase activity in all sampling periods. Lower C/N and C/P ratios in litter and lower C/N and Cmic/tC ratios in soils after 20 months in the intercropped plantation illustrated the system's capacity for supplying inputs of high-quality organic matter rich in N and P, but this did not result in higher contents of these elements or greater microbial activity in soils. An implication of this finding is that, at least in the initial growth phase of these plantations, chemical attributes of the litter and variation in those attributes govern microbial processes and, consequently, are mostly responsible for plant development. Canonical discriminant analysis revealed changes in the microbiological and chemical attributes of soil in the intercropped plantation due to the plants growth and the leaf litter accumulation. Twenty months after planting, the different plantations could be discriminated by differences in litter chemistry (C, N, and P), total soil C, Nmic, and dehydrogenase activity, which were very similar in intercropped plantations and E. grandis with N-fertilizer. These results from the early stages of plantation development are important for understanding the dynamics of soil attributes in these systems, and especially in intercropped plantations. In intercropped areas the cumulative effect of microbial attributes reflects a more sustainable system. Long-term studies are needed to identify patterns that develop after 20 months, during the growth period of these plantations. 相似文献
10.
Plant canopy effects on litter accumulation and soil microbial biomass in two temperate forests 总被引:2,自引:0,他引:2
The objective of this study was to determine whether differences in canopy structure and litter composition affect soil characteristics
and microbial activity in oak versus mixed fir-beech stands. Mean litter biomass was greater in mixed fir-beech stands (51.9t
ha−1) compared to oak stands (15.7t ha−1). Canopy leaf area was also significantly larger in mixed stands (1.96m2 m−2) than in oak stands (1.73m2 m−2). Soil organic carbon (C
org) and moisture were greater in mixed fir-beech stands, probably as a result of increased cover. Soil microbial biomass carbon
(C
mic), nitrogen (N
mic), and total soil nitrogen (N
tot) increased slightly in the mixed stand, although this difference was not significant. Overall, mixed stands showed a higher
mean C
org/N
tot ratio (22.73) compared to oak stands (16.39), indicating relatively low rate of carbon mineralization. In addition, the percentage
of organic C present as C
mic in the surface soil decreased from 3.17% in the oak stand to 2.26% in the mixed stand, suggesting that fir-beech litter may
be less suitable as a microbial substrate than oak litter. 相似文献
11.
R. K. Kasongo E. Van Ranst A. Verdoodt P. Kanyankagote G. Baert 《Soil Use and Management》2009,25(1):21-27
A 17‐year chronosequence of Acacia auriculiformis fallows on Arenosols of the Batéké Plateau (D.R. Congo) was surveyed and compared with virgin savannah soils to assess chemical soil fertility changes induced by these N‐fixing trees. Significant increases in organic carbon content, total nitrogen content, cation exchange capacity and sum of base cations were found after relatively short fallow periods of only 4 years and did not only affect the forest floor, but extended to at least 50 cm depth. The Acacia act as a major source of organic matter (OM), hence increasing organic carbon and nitrogen content and decreasing the C/N ratio. The increased OM content suggests that humification processes are the main cause of the significant decrease in pH. Total exchangeable cations initially increased slowly but doubled (topsoil 0–25 cm) and tripled (subsoil 25–50 cm) after 10 years. The point of zero net proton charge was systematically lower than soil pH and decreased with increasing OM content, thereby increasing the cation exchange capacity, although concurrent acidification retarded a significant beneficial impact at field pH on Acacia fallows of 10 years and older. Although the chemical soil fertility improves steadily with time, after 8 years of Acacia fallow the absolute amounts of available nutrients are still small and slash and burn practices are required to liberate the nutrients stored in the remaining biomass and litter before each new cropping period. 相似文献
12.
Jacqui Horswell Hedda J. Weitz Harry J. Percival Tom W. Speir 《Biology and Fertility of Soils》2006,42(6):569-576
Bacterial and fungal bioluminescence-based biosensors were used as indicators of potential heavy metal toxicity to microorganisms in the needle litter of a mature Pinus radiata forest under heavy metal contaminated sewage sludge. Sewage sludge was amended with increasing concentrations of Cu, Ni and Zn and applied to the surface of a mature P. radiata forest. The response of the bacterial and fungal biosensors to soluble Cu, Ni and Zn in needle litter extracts was investigated. The bioluminescence response of the bacterial biosensor Escherichia coli HB101 pUCD607 declined as water-soluble Zn concentrations increased. The effective concentrations that gave a 50% reduction in bioluminescence (EC50 values) for water-soluble Zn and total litter Zn were 1.3 mg l−1 and 3700 mg kg−1, respectively. The bioluminescence response of the fungal biosensor Armillaria mellea declined as soluble Cu concentrations increased. The EC50 values for water-soluble Cu and total litter Cu were 0.12 mg l−1 and 540 mg kg−1, respectively. No decline in bioluminescence was noted for either the bacterial or fungal biosensor on exposure to increasing concentrations of water-soluble Ni. The use of a combination of bacterial and fungal biosensors offers a rapid and sensitive tool for assessing toxicity of heavy metals to microorganisms and, thus, elucidating the environmental impact of contaminants in sewage sludge on litter dwelling microorganisms. 相似文献
13.
Girma Abera Endalkachew Wolde-meskel Lars R. Bakken 《Biology and Fertility of Soils》2012,48(1):51-66
Seasonal drought in tropical agroecosystems may affect C and N mineralization of organic residues. To understand this effect,
C and N mineralization dynamics in three tropical soils (Af, An1, and An2) amended with haricot bean (HB; Phaseolus vulgaris L.) and pigeon pea (PP; Cajanus cajan L.) residues (each at 5 mg g−1 dry soil) at two contrasting soil moisture contents (pF2.5 and pF3.9) were investigated under laboratory incubation for 100–135 days.
The legume residues markedly enhanced the net cumulative CO2–C flux and its rate throughout the incubation period. The cumulative CO2–C fluxes and their rates were lower at pF3.9 than at pF2.5 with control soils and also relatively lower with HB-treated than
PP-treated soil samples. After 100 days of incubation, 32–42% of the amended C of residues was recovered as CO2–C. In one of the three soils (An1), the results revealed that the decomposition of the recalcitrant fraction was more inhibited by drought stress than easily
degradable fraction, suggesting further studies of moisture stress and litter quality interactions. Significantly (p < 0.05) greater NH4+–N and NO3−–N were produced with PP-treated (C/N ratio, 20.4) than HB-treated (C/N ratio, 40.6) soil samples. Greater net N mineralization
or lower immobilization was displayed at pF2.5 than at pF3.9 with all soil samples. Strikingly, N was immobilized equivocally
in both NH4+–N and NO3−–N forms, challenging the paradigm that ammonium is the preferred N source for microorganisms. The results strongly exhibited
altered C/N stoichiometry due to drought stress substantially affecting the active microbial functional groups, fungi being
dominant over bacteria. Interestingly, the results showed that legume residues can be potential fertilizer sources for nutrient-depleted
tropical soils. In addition, application of plant residue can help to counter the N loss caused by leaching. It can also synchronize
crop N uptake and N release from soil by utilizing microbes as an ephemeral nutrient pool during the early crop growth period. 相似文献
14.
Jean Weber Marc Ducousso Foong Yee Tham Sophie Nourissier-Mountou Antoine Galiana Yves Prin Sing Kong Lee 《Biology and Fertility of Soils》2005,41(4):233-239
Acacia mangium grown in aeroponic culture was co-inoculated with selected strains of Bradyrhizobium sp. and Glomus intraradices. A single-step technique using alginate as an embedding and sticking agent for an inoculum composed of arbuscular mycorrhiza (AM)-infected sheared roots was used to infect plants. This method resulted in the successful establishment of AM in 100% of the inoculated plants after 7 weeks. The results indicated that dual microbial inoculation with Glomus intraradices strain S-043 and Bradyrhizobium strain AUST 13C stimulated the growth of A. mangium in aeroponic culture. The effects of single and dual microbial inoculations were also evaluated at two levels of P in the nutrient medium. A concentration of 5 mg P kg–1 stimulated the development of AM without affecting plant development or establishment of Bradyrhizobium symbiosis. In contrast, saplings supplemented with a higher concentration of P (25 mg kg–1) alone or co-inoculated with Bradyrhizobium had lower AM frequencies. 相似文献
15.
Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol 总被引:2,自引:0,他引:2
Wisal Muhammad Sarah M. Vaughan Ram C. Dalal Neal W. Menzies 《Biology and Fertility of Soils》2011,47(1):15-23
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N2O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content
55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral
N addition, on N mineralization–immobilization and N2O emission. Residues were added at the rate of 3 t C ha−1 to soil with, and without, 150 kg urea N ha−1. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of
soil N. Amended soil had significantly (P < 0.05) lower NO3−–N, which reached minimum values of 2.8 mg N kg−1 for sugarcane (at day 28), 10.3 mg N kg−1 for maize (day 7), and 5.9 mg N kg−1 for sorghum (day 7), compared to 22.7 mg N kg−1 for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased
by 45 mg N kg−1 in sugarcane, 34 mg kg−1 in maize, 29 mg kg−1 in sorghum, and 16 mg kg−1 in cotton amended soil compared to soil + N fertilizer, although soil NO3−–N increased by 7 mg kg−1 in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum
emissions of N2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N2O emission was significantly and positively correlated with NO3−–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO2 in the first 3 and 5 days of incubation (r = 0.59, P < 0.05). 相似文献
16.
A. A. Larionova I. N. Kurganova V. O. Lopes de Gerenyu B. N. Zolotareva I. V. Yevdokimov V. N. Kudeyarov 《Eurasian Soil Science》2010,43(2):168-176
The effect of droughts and drying-wetting cycles on the respiration activity of agrogray soils was studied in field and laboratory
experiments. The alternation of drought periods and rains during the vegetation season did not increase the annual emission
of CO2 from the soils under a sown meadow and an agrocenosis. In laboratory experiments, the wetting of dried soil released 1–1.5%
of Corg with a high decomposition constant n × 10−1 day−1 and a very short renewal time (2.1–2.4 days); therefore, an abrupt change in the wetting conditions did not intensify the
loss of soil carbon under field conditions. 相似文献
17.
Role of organic fractions on C decomposition and N mineralization of animal wastes in soil 总被引:1,自引:0,他引:1
The relative contributions of water-soluble, water-non-soluble, Van Soest-soluble, and neutral detergent fiber (NDF) fractions
of pig slurry (PS), cattle slurry (CS), cattle farmyard manure (FYM), and composted cattle farmyard manure (CFYM) to the overall
C and N mineralization of the raw wastes were studied by incubating treated soil for 107 days at 15°C under non-limiting N
conditions. The C or N mineralization of soluble fractions was calculated from the difference between C or N mineralization
of the raw and non-soluble fractions. The organic N content of raw wastes ranged from 15 to 32 mg N g−1 dry matter and organic C to organic N ratio from 13 to 29. The water-soluble fraction (SOLW) was close to 100 mg C g−1 raw waste C for CS, FYM, and CFYM but reached 200 mg C g−1 for PS. The Van Soest-soluble fraction (SOLVS) was the main fraction for PS, CS, and CFYM (>500 mg C g−1 raw waste C) but only 303 mg C g−1 raw waste C for FYM. Both soluble and non-soluble fractions contributed to C decomposition of slurries, with half to more
than half of the decomposed C derived from the degradation of soluble compounds. Most of the C decomposed from FYM was derived
from the large NDF fraction, but the contribution from the water-soluble C to the decomposition was also significant. Carbon
mineralization of CFYM was due to the degradation of the NDF fraction, whereas soluble C did not contribute. Amounts of N
mineralized or immobilized by raw wastes and non-soluble fractions at the end of incubation were significantly correlated
(P < 0.01) with their organic C to organic N ratio. The contribution of the Van Soest-soluble fraction to N mineralization varied
greatly between the four wastes. Finally, large differences in the C degradability and N availability of the water and Van
Soest-soluble fractions were demonstrated. 相似文献
18.
The response of faba bean to the application of four rates of gypsum (0, 2.5, 5.0, 10.0 t ha−1) to a non-saline, alkaline sodic soil was measured in terms of grain yield, dry matter (DM) production, N accumulation and
the proportional dependence of the legume on symbiotic N2 fixation (P
atm). A yield-independent, time-integrated 15N-dilution model was used to estimate symbiotic dependence. A significant decrease in the exchangeable sodium percentage and
significant increases in exchangeable Ca++ and the Ca++:Mg++ ratio in the 0–10-cm soil layer were measured 30 months after application of 10 t ha−1 gypsum. Despite low and erratic rainfall during crop growth, faba bean DM and N uptake responded positively to gypsum application.
The symbiotic dependence of the legume at physiological maturity was little affected by sodicity (P
atm = 0.74 at zero gypsum and 0.81–0.82 at 2.5–10 t ha−1 gypsum). The increase in fixed N due to gypsum application was mainly due to increases in legume DM and total N uptake. At
10 t ha−1 of gypsum, faba bean fixed more than 200 kg N ha−1 in above-ground biomass. 相似文献
19.
Nicola M. Hall Bocary Kaya Jan Dick Ute Skiba Amadou Niang Ramadjita Tabo 《Biology and Fertility of Soils》2006,42(3):224-230
The impacts of fallow on soil fertility, crop production and climate-forcing gas emissions were determined in two contrasting
legumes, Gliricidia sepium and Acacia colei, in comparison with traditional unamended fallow and continuous cultivation systems. After 2 years, the amount of foliar
material produced did not differ between the two improved fallow species; however, grain yield was significantly elevated
by 55% in the first and second cropping season after G. sepium compared with traditional fallow. By contrast, relative to the unamended fallow, a drop in grain yield was observed in the
first cropping season after A. colei, followed by no improvement in the second. G. sepium had higher foliar N, K and Mg, while A. colei had lower foliar N but higher lignin and polyphenols. In the third year after fallow improvement, a simulated rainfall experiment
was performed on soils to compare efflux of N2O and CO2. Improved fallow effects on soil nutrient composition and microbial activity were demonstrated through elevated N2O and CO2 efflux from soils in G. sepium fallows compared with other treatments. N2O emissions were around six times higher from this nitrogen-fixing soil treatment, evolving 69.9 ngN2O–N g−1soil h−1 after a simulated rainfall event, compared with only 8.5 and 4.8 ngN2O–N g−1soil h−1 from soil under traditional fallow and continuous cultivation, respectively. The findings indicate that selection of improved
fallows for short-term fertility enhancement has implications for regional N2O emissions for dry land regions. 相似文献
20.
The effect of potassium (K) supply on dry matter accumulation and partitioning of biomass between different among parts of
cotton (Gossypium hirsutum L.) was determined under irrigated conditions. The treatments were four cotton cultivars (CIM-448, CIM-1100, Karishma, and
S-12), four K rates (0, 62.5, 125, and 250 kg K ha−1), and two K-fertilizer sources (K2SO4, KCl). Sequential harvests were collected at four stages of growth, viz first flower, peak flowering, first boll split, and
maturity. The dry weights (DW) of vegetative and reproductive organs were determined. Maximum total DW was obtained at 125 days
after planting, and then it declined because of leaf senescence at maturity. Cultivars differed significantly among themselves
in the production of total DW and its partitioning between different organs. The addition of K fertilizer increased DW substantially
at various stages of growth. Potassium fertilizer stimulated cotton plant to translocate resources towards reproductive organs
rather than vegetative organs. Crop receiving 250 kg K ha−1 allocated 77% more dry matter into reproductive organs. The K-sources produced a little effect on the allocation of DW in
various parts of the plant. Maximum reproductive–vegetative ratio (RVR) was maintained by cv CIM-448 and minimum in cv CIM-1100.
Data showed that a shift in DW allocation into reproductive organs was dependent upon sustained supply of K+ throughout the season. There were positive significant correlations (0.86, 0.71, and 0.90) between seed cotton yield and
total DW, vegetative DW, and reproductive DW, respectively. 相似文献