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21.
Leaching losses of nitrogen from a clay soil under grass and cereal crops in Finland 总被引:1,自引:0,他引:1
Antti Jaakkola 《Plant and Soil》1984,76(1-3):59-66
Summary A 16-plot experimental field was established in 1975 on a clay soil in Jokioinen, Finland. The water discharge through tile drains was measured and its ammonium and nitrate N contents determined for each plot separately. The surface runoff was also measured and analysed. The annual runoff and the N leached from the surface of moderately fertilized (100 kg/ha/y N) cereal plots varied during 1976–1982 from 21 to 301 mm and from 2 to 7 kg/ha, respectively. The discharge of water and leaching of N through subdrains varied from 65 to 225 mm and from 1 to 38 kg/ha, respectively. The highest leaching was probably caused by a previous fallow. The annual N uptake by the crop varied between 41 and 122 kg/ha.Of the fertilizer-N used for cereals, 20% of that applied in the autumn was lost, but only 1 to 4 per cent was lost when applied in the spring. There was much less N leaching from ley than from barley plots, although the former was given twice as much N. The rate of N fertilization had only a very slight effect on N leaching from both ley and barley plots.The results were compared with those obtained in lysimeters filled with clay, silt, sand and peat soils. No definite conclusions can be drawn because the lysimeter experimental data are only for the first year. 相似文献
22.
Alejandro G. Farji-Brener Ernesto Gianoli Marco A. Molina-Montenegro 《Ecological Research》2009,24(1):139-145
Small-scale disturbances caused by animals often modify soil resource availability and may also affect plant attributes. Changes
in the phenotype of plants growing on disturbed, nutrient-enriched microsites may influence the distribution and abundance
of associated insects. We evaluated how the high nutrient availability generated by leaf-cutting ant nests in a Patagonian
desert steppe may spread along the trophic chain, affecting the phenotype of two thistle species, the abundance of a specialist
aphid and the composition of the associated assemblage of tending ants. Plants of the thistle species Carduus nutans and Onopordum acanthium growing in piles of waste material generated by leaf-cutting ant nests (i.e., refuse dumps) had more leaves, inflorescences
and higher foliar nitrogen content than those in non-nest soils. Overall, plants in refuse dumps showed higher abundance of
aphids than plants in non-nest soils, and aphid colonies were of greater size on O. acanthium plants than on C. nutans plants. However, only C. nutans plants showed an increase in aphid abundance when growing on refuse dumps. This resulted in a similar aphid load in both
thistle species when growing on refuse dumps. Accordingly, only C. nutans showed an increase in the number of ant species attending aphids when growing on refuse dumps. The increase of soil fertility
generated by leaf-cutting ant nests can affect aphid abundance and their tending ant assemblage through its effect on plant
size and quality. However, the propagation of small-scale soil disturbances through the trophic chain may depend on the identity
of the species involved. 相似文献
23.
Summary A pot experiment was conducted to study the transformations of organic and inorganic N in soil and its availability to maize plants. Inorganic N was in the form of15N labelled ammonium sulphate (As) and15N labelledSesbania aculeata (Sa), a legume, was used as organic N source. Plants utilized 20% of the N applied as As; presence of Sa reduced the uptake to 14%. Only 5% of the Sa-N was taken up by the plants and As had no effect on the availability of N from Sa. Losses of N from As were found to be 40% which were reduced to 20% in presence of Sa. Losses of N were also observed from Sa which increased in the presence of As. Application of As had no effect on the availability of soil or Sa-N. However, more As-N was transported into microbial biomass and humus components in the presence of Sa.Plants derived almost equal amounts of N from different sourcesi.e., soil, Sa and As. However, more As-N was transported into the shoots whereas the major portion of nitrogen in the roots was derived from Sa. 相似文献
24.
Summary Uniformly14C labelled glucose, cellulose and wheat straw and specifically14C labelled lignin component in corn stalks were aerobically incubated for 12 weeks in a chernozem soil alongwith15N labelled ammonium sulphate. Glucose was most readily decomposed, followed in order by cellulose, wheat straw and corn stalk lignins labelled at methoxyl-, side chain 2-and ring-C. More than 50% of14C applied as glucose, cellulose and wheat straw evolved as CO2 during the first week. Lignin however, decomposed relatively slowly. A higher proportion of14C was transformed into microbial biomass whereas lignins contributed a little to this fraction.After 12 weeks of incubation nearly 60% of the lignin14C was found in humic compounds of which more than 70% was resistant to hydrolysis with 6N HCl. Maximum incorporation of15N in humic compounds was observed in cellulose amended soil. However, in this case more than 80% of the15N was in hydrolysable forms.Immobilization-remineralization of applied15N was most rapid in glucose treated soil and a complete immobilization followed by remineralization was observed after 3 days. The process was much slow in soil treated with cellulose, wheat straw or corn stalks. More than 70% of the newly immobilized N was in hydrolysable forms mainly reepresenting the microbial component.Serial hydrolysis of soil at different incubation intervals showed a greater proportion of 6N HCl hydrolysable14C and15N in fractions representing microbial material.14C from lignin carbons was relatively more uniformly distributed in different fractions as compared to glucose, cellulose and wheat straw where a major portion of14C was in easily hydrolysable fractions. 相似文献
25.
对草原土壤N2O释放及其受全球变暖土壤养分变化的影响研究表明,以沼泽泥炭土N2O释放量最大,生长季节为1.3~12.2kgN·hm-2·a-1,其次灰壤土,为1.5~2.4kgN·hm-2·a-1,酸性棕壤最小,为0~3.2kgN·hm-2·a-1;N2O的释放层灰壤土在0~5cm,其它2种土壤为0~10cm;施肥试验表明,N、P肥在生长季节对土壤N2O释放量影响不显着,但在生长季末期,N肥对酸性棕壤及灰壤土N2O影响显着,施肥后第3天酸性棕壤由对照的1.3提高到44.2kgN·hm-2·a-1,灰壤土则由对照的1.9提高到31.1kgN·hm-2·a-1,说明全球变暖对土壤有机质分解的影响不会诱发N2O释放量的大幅度增加. 相似文献
26.
27.
The role of nitrification-denitrification in the loss of nitrogen from urea applied to puddled soils planted to rice and subjected
to continuous and intermittent flooding was evaluated in three greenhouse pot studies. The loss of N via denitrification was
estimated indirectly using the15N balance, after either first accounting for NH3 volatilization or by analyzing the15N balance immediately before and after the soil was dried and reflooded.
When urea was broadcast and incorporated the loss of15N from the soil-plant systems depended on the soil, being about 20%–25% for the silt loams and only 10%–12% for the clay.
Ammonia volatilization accounted for an average 20% of the N applied in the silt loam. Denitrification losses could not account
for more than 10% of the applied N in any of the continuously flooded soil-plant systems under study and were most likely
less than 5%. Intermittent flooding of soil planted to rice did not increase the loss of N.
Denitrification appeared to be an important loss mechanism in continuously flooded fallow soils, accounting for the loss of
approximately 40% of the applied15N. Loss of15N was not appreciably enhanced in fallow soils undergoing intermittent flooding. Apparently, nitrate formed in oxidized zones
in the soil was readily denitrified in the absence of plant roots.
Extensive loss (66%) of15N-labeled nitrate was obtained when 100 mg/pot of nitrate-N was applied to the surface of nonflooded soil prior to reflooding.
This result suggests that rice plants may not compete effectively with denitrifiers if large quantities of nitrate were to
accumulate during intermittent dry periods. 相似文献
28.
L. Wiklicky 《Plant and Soil》1982,64(1):115-127
Summary The relationship between the EUF-nutrient fractions in the soil on the one hand and the nutrient uptake of sugar beet as well
as root yield and quality (polarization, α-amino N etc.) on the other is described on the basis of results obtained over several
years in surveys conducted in farmers' fields (5000–6000 fields under sugar beet per year) and in field experiments (25–35
sites per year).
Statistically significant close correlations with the respective parameters were found for the following EUF nutrient fractions:
EUF-NO3, EUF-P, EUF-K, EUF-Na, EUF-B and EUF-Mn.
Within five years it was possible to determine the EUF-nutrient values which are required for the production of 9 t sugar/ha.
These EUF values are the following: Ca: 65–70 mg/100 g at 20°C K: 11–15 mg/100 g at 20°C (depending on the clay content) Mg:
3–5 mg/100 g at 20°C Na: 2–3 mg/100 g at 20°C P: 1.4–1.6 mg/100 g at 20°C
For calculation of the N fertilizer requirements of sugar beet it is suggested to use the sum of the EUF-extractable N amounts.
It was found in Austria, Yugoslavia and Denmark over a period of 3 years that the EUF-N value of 1 mg/100 g soil determined
between June and September was equivalent to 40 kg N/ha. If, for example, the analysed soil contains 3 mg EUF-N/100 g, 3×40=120
kg N/ha will be available to the sugar beet crop in the following year. 相似文献
29.
The biological nitrogen fixation carried out by some Bacteria and Archaea is one of the most attractive alternatives to synthetic nitrogen fertilizers. In this study we compared the effect of controlling the maximum activation state of the Azotobacter vinelandii glutamine synthase by a point mutation at the active site (D49S mutation) and impairing the ammonium-dependent homeostatic control of nitrogen-fixation genes expression by the ΔnifL mutation on ammonium release by the cells. Strains bearing the single D49S mutation were more efficient ammonium producers under carbon/energy limiting conditions and sustained microalgae growth at the expense of atmospheric N2 in synthetic microalgae–bacteria consortia. Ammonium delivery by the different strains had implications for the microalga׳s cell-size distribution. It was uncovered an extensive cross regulation between nitrogen fixation and assimilation that extends current knowledge on this key metabolic pathway and might represent valuable hints for further improvements of versatile N2-fixing microbial-cell factories. 相似文献
30.
If phenotypic plasticity is under genetic control, it may vary in amount and pattern on a geographical scale, e.g. among different regions of a species distribution. It may also differ between large and small or between less and more isolated populations, due to differences in genetic diversity. In a 2-year common garden study, the responses of several traits to drought and fertilizer treatments were studied in the grassland herb Carlina vulgaris. Individuals originating from populations of different size and degree of isolation in six European countries, representing central and marginal regions, were compared. Fertilizing had a negative effect on early plant survival, as well as on flowering probability in surviving plants. However, in those plants that flowered, fertilizing strongly increased mean number of flowerheads, flowerhead area (a correlate of seed number), and seed mass. Drought had generally weaker effects but enhanced survivorship, indicating that this treatment was closer to optimal conditions than were non-drought conditions. For some traits there were significant interactions of region × fertilizer, but the geographical pattern of reaction norms was inconsistent and lent no support to the hypothesis that central and marginal populations differ in overall plasticity. Population size and isolation had hardly any influence on treatment responses, but populations within regions differed in their mean response to fertilizing with regard to survival and flowering probabilities, as well as in their response to drought with regard to survival and total flowerhead area. It is concluded that response to raised nutrient levels is highly variable within populations, ranging from death to strongly increased reproductive output, but also among populations irrespective of size or isolation. This also goes for the response to water supply, though this variation shows a more unclear pattern. There is no evidence that small or isolated/marginal populations are less plastic than large or non-isolated/central populations, and the explanation for differences in treatment responses among plant populations should be sought in other population characteristics. 相似文献