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1.
K. Vlassak 《Plant and Soil》1970,32(1-3):27-32
Summary The mineralization capacity of 24 different soils was determined from incubation experiments. Relatively rapid mineralization
and nitrification was found with soils from cultivated land, and pastures, but soils under natural vegetative covers of conifers
and hardwoods were mostly ammonifying. A close relationship could be established between the total nitrogen content of the
soil and the amount of mineral nitrogen formed during incubation. Important connections could also be shown between the available
nitrogen contents at different times during the incubation period; these suggest that the incubation period can be considerably
shortened. 相似文献
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Data from five field experiments using labelled nitrogen fertilizer were used to determine the relative effects of soil nitrogen and fertilizer nitrogen on rice yield. Yield of grain was closely correlated with total aboveground nitrogen uptake (soil+fertilizer), less closely correlated with soil nitrogen uptake and not significantly correlated with fertilizer nitrogen uptake. When yield increase rather than yield was correlated with fertilizer nitrogen uptake, the correlation coefficient was statistically significant.Contribution from the Laboratory for Flooded Soils and Sediments, Agronomy Dept., Louisiana Agri. Exper. Sta., Louisiana State Univ., Baton Rouge, LA 70803, and Univ. of Florida, Agricultural Research and Education Center, Sanford, FL 32771. 相似文献
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为探究氮素亏缺及亏缺后补偿供氮对蕉苗生长及其根系形态特征的影响,该研究以主要栽培品种基因组类型(AAA型和ABB型)的香蕉品种为材料,通过石英砂基质培养结合氮素亏缺与补偿处理,分析其株高、叶长、叶宽、新增绿叶数、地上部和根系的鲜重和干物质质量、根长和根表面积及根体积等指标的变化。结果表明:(1)亏缺30 d,香蕉苗呈现明显的缺氮表型症状,株高、叶长、叶宽及新增绿叶数均显著降低,根系干物质积累增加,品种Ⅰ、Ⅱ根系干物质分别提高64.71%、87.50%,根冠比增加,总根表面积分别增加4.38%、11.85%,体积分别增加71.78%、66.55%。(2)亏缺68 d,干物质积累受到明显抑制,品种Ⅰ、Ⅱ全株干物质质量降低33.74%、42.04%,根系干物质质量与常规处理无显著差异,根系形态参数变化趋势与轻度亏缺一致。(3)亏缺后补偿供氮,缺氮症状消失,植株生长指标恢复正常水平;品种Ⅰ、Ⅱ根系干物质质量显著增加51.22%、52.38%,根冠比显著高于常规处理,根系趋向正常形态生长,并且总根体积分别增加61.80%、45.92%;轻度氮素亏缺后适时补偿供氮,缺氮蕉苗可恢复正常生长,根系干物... 相似文献
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The possibility is examined that carbon (C) released into the soil from a root could enhance the availability of nitrogen (N) to plants by stimulating microbial activity. Two models are described, both of which assume that C released from roots is used by bacteria to mineralise and immobilise soil organic N and that immobilised N released when bacteria are grazed by bacterial-feeding nematodes or protozoa is taken up by the plant. The first model simulates the individual transformations of C and N and indicates that root-induced N mineralisation could supply only up to 10% of the plant's requirement, even if unrealistically ideal conditions are assumed. The other model is based on evidence that about 40% of immobilised N is subsequently taken up by the plant. A small net gain of N by the plant is shown (i.e. the plant takes up more N than it loses through exudation), although with exudate of up to C:N 33:1 less than 6% of the plant's requirement is supplied by root-induced N mineralisation. It is argued, however, that rhizosphere bacteria do not use plant-derived C to mineralise soil organic N to any great extent and that in reality root-induced N mineralisation is even less important than these models indicate. 相似文献
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Responses of morphology and biomass allocation of roots to frequency of nitrogen (N) pulse potentially influence the fitness of plants, but such responses may be determined by root size. We grew 12 plant species of three functional groups (grasses, forbs, and legumes) under two N pulse frequencies (high vs. low supply frequency) and two N amounts (high vs. low supply amount). Compared to low-amount N supply, high-amount N supply stimulated biomass accumulation and root growth by either increasing the thickness and length of roots or decreasing the root mass fraction. Compared to low-frequency N supply, high-frequency N supply improved biomass accumulation and root growth in forbs or grasses, but not in legumes. Furthermore, the magnitude of the response to N frequency was significantly negatively correlated with root size at the species scale, but this was only true when the N amount was high. We conclude that root responses to N frequency are related to plant functional types, and non-legume species is more sensitive to N frequency than legume species. Our results also suggest that root size is a determinant of root responses to N frequency when N supply amount is high. 相似文献
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Although nutrient stress is known to alter partitioning between shoots and roots, the physiological basis for the phenomenon is unresolved. Experiments were conducted to examine assimilation of 15NO3 by N-stressed plants and to determine whether apparent changes in assimilation in the root contributed to alterations in whole-plant partitioning of reduced-N. Tobacco plants (Nicotiana tabacum L. cv. NC 2326) were exposed to a low concentration of NO3? in solution (80 μM) for 9 days to effect a N-stress response. Exposure of plants to 1000 μM15NO3? for 12 h on selected days revealed that roots of N-stressed plants developed an increased capacity to absorb NO3?, and accumulation of reduced-15N in the root increased to an even greater extent. When plants were exposed to 80 or 1000 μM15NO3? in steady-state, 15NO3? uptake over a 12 h period was noticeably restricted at the lower concentration, but a larger proportion of the absorbed 15N still accumulated as reduced-15N in the root. The alteration in reduced-15N partitioning was maintained in N-stressed plants during the subsequent 3-day “chase” period when formation of insoluble reduced-15N in the root was quantitatively related to the disappearance of 15NO3? and soluble reduced-15N. The results indicate that increased assimilation of absorbed NO3?, in the root may contribute significantly to the altered reduced-N partitioning which occurs in N-stressed plants. 相似文献
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Dodds WK Martí E Tank JL Pontius J Hamilton SK Grimm NB Bowden WB McDowell WH Peterson BJ Valett HM Webster JR Gregory S 《Oecologia》2004,140(3):458-467
Stoichiometric analyses can be used to investigate the linkages between N and C cycles and how these linkages influence biogeochemistry at many scales, from components of individual ecosystems up to the biosphere. N-specific NH4+ uptake rates were measured in eight streams using short-term 15N tracer additions, and C to N ratios (C:N) were determined from living and non-living organic matter collected from ten streams. These data were also compared to previously published data compiled from studies of lakes, ponds, wetlands, forests, and tundra. There was a significant negative relationship between C:N and N-specific uptake rate; C:N could account for 41% of the variance in N-specific uptake rate across all streams, and the relationship held in five of eight streams. Most of the variation in N-specific uptake rate was contributed by detrital and primary producer compartments with large values of C:N and small values for N-specific uptake rate. In streams, particulate materials are not as likely to move downstream as dissolved N, so if N is cycling in a particulate compartment, N retention is likely to be greater. Together, these data suggest that N retention may depend in part on C:N of living and non-living organic matter in streams. Factors that alter C:N of stream ecosystem compartments, such as removal of riparian vegetation or N fertilization, may influence the amount of retention attributed to these ecosystem compartments by causing shifts in stoichiometry. Our analysis suggests that C:N of ecosystem compartments can be used to link N-cycling models across streams. 相似文献
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《Journal of biological education》2012,46(1):24-30
And he gave it for his opinion, that whoever could make two ears of corn or two blades of grass to grow upon a spot of ground where only one grew before, would deserve better of mankind, and do more essential service to his country than the whole race of politicians put together. {Jonathan Swift, ‘Gulliver's Travels’, Voyage to Brobdingnag, Ch. 7.) 相似文献
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Summary The effect of fertilizer nitrogen on the available amount of soil nitrogen was investigated in a greenhouse experiment. To 9 different soils, 0, 50, 100 and 200 kg N/ha were applied, resp., as (N15H4)2SO4 with an atom excess N-15 of 1%.No priming effect could be found for any of the treatments. The available amount of soil N, expressed as AN value, was not affected by rate of N-fertilizer application. 相似文献
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M. Sharifi B. J. Zebarth G. A. Porter D. L. Burton C. A. Grant 《Plant and Soil》2009,320(1-2):267-279
Two-year potato rotations were evaluated for their effects on soil mineralizable N and soil N supply. Pre-plant soil samples (0–15 cm) collected from the potato year after seven rotation cycles were used to estimate soil mineralizable N using a 24 week aerobic incubation. Potentially mineralizable N (N 0 ) ranged from 102 to 149 kg N ha?1, and was greater after pea/white clover and oats/Italian ryegrass than after oats by an average of 35 and 22%, respectively. Labile, intermediate and stable mineralizable N pools were increased after pea/white clover compared with oats, whereas only the stable mineralizable N pool was increased after oats/Italian ryegrass. Potato plant N uptake with no fertilizer applied was greater in potato-pea/white clover compared with the three other rotations (126 vs. average of 67 kg N ha?1). Choice of rotation crop in potato production influences both the quantity and quality of soil mineralizable N. 相似文献
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Soil nitrogen mineralization potential (N min) has to be spatially quantified to enable farmers to vary N fertilizer rates, optimize crop yields, and minimize N transfer from soils to the environment. The study objectives were to assess the spatial variability in soil N min potential based on clay and organic matter (OM) contents and the impact of grouping soils using these criteria on corn grain (Zea mays L.) yield, N uptake response curves to N fertilizer, and soil residual N. Four indicators were used: OM content and three equations involving OM and clay content. The study was conducted on a 15-ha field near Montreal, Quebec, Canada. In the spring 2000, soil samples (n = 150) were collected on a 30- x 30-m grid and six rates of N fertilizer (0 to 250 kg N ha(-1)) were applied. Kriged maps of particle size showed areas of clay, clay loam, and fine sandy loam soils. The N min indicators were spatially structured but soil nitrate (NO3-) was not. The N fertilizer rate to reach maximum grain yield (N max), as estimated by a quadratic model, varied among textural classes and Nmin indicators, and ranged from 159 to 250 kg N ha(-1). The proportion of variability (R2) and the standard error of the estimate (SE) varied among textural groups and N min indicators. The R2 ranged from 0.53 to 0.91 and the SE from 0.13 to 1.62. Corn grain N uptake was significantly affected by N fertilizer and the pattern of response differed with soil texture. For the 50 kg N ha(-1) rate, the apparent N min potential (ANM) was significantly larger in the clay loam (122 kg ha(-1)) than in the fine sandy loam (80 kg ha(-1)) or clay (64 kg ha(-1)) soils. The fall soil residual N was not affected by N fertlizer inputs. Textural classes can be used to predict N max. The N min indicators may also assist the variable rate N fertilizer inputs for corn production. 相似文献
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添加氮素对沙质草地土壤氮素有效性的影响 总被引:4,自引:1,他引:3
通过氮素添加(20g.m-2.a-1)试验,研究了科尔沁沙地东南部沙质草地生态系统土壤氮矿化及有效氮的季节变化。对2006年生长季的观测发现,添加氮素显著提高了沙质草地生长季土壤铵态氮、硝态氮、矿质氮的含量以及9月1日至10月15日的净氮矿化速率与硝化速率;添加氮素导致土壤有效氮的季节变异增大,净氮矿化(1.29~11.60mg.kg-1.30d-1)与硝化(-4.15~11.20mg.kg-1.30d-1)速率随时间呈上升趋势,铵态氮含量逐渐降低,硝态氮与矿质氮(6.49~20.66mg.kg-1)含量的变化呈"V"型,最小值出现在生物量生长高峰期的7月中旬。该沙质草地土壤氮的有效性较低,施氮肥可明显提高土壤供氮能力。 相似文献
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Monitored and modeled data provided the basis for the establishment of two nitrogen (N) budgets covering the Kattegat-Belt Sea area in the period 2000–2009: one for total nitrogen (TN) and one for bioavailable nitrogen (Nbio). Our results show a significant difference between the two budgets, and we argue that Nbio is more important than TN for our understanding of the sources causing marine eutrophication. Consequently, an optimal strategy for abatement of eutrophication aims at minimizing Nbio rather than TN. The TN budget shows that advection from the adjacent seas is the dominant source of N to the Kattegat-Belt Sea area. The loadings from land and atmosphere only account for 14 and 9 % of the TN loadings, respectively. However, when the bioavailability of the different N sources is taken into account, the supply from land and atmosphere becomes relatively more important, now accounting for 21 and 16 %, respectively (37 % in total). The ecological relevance of land and atmosphere loadings is most likely even larger since a fraction of the input from the Skagerrak is exported again before it can support primary production. Water action plans have reduced the direct loadings of TN from land and atmosphere by about 35 % since the 1980s. The contributions from land and atmosphere accounted for 47 % of the Nbio loadings in the 1980s. Hence, loadings from land and atmosphere have only decreased by 10 % points since the 1980s: from 47 to 37 %. The largest sink of TN in the study areas is advection to the adjacent seas (71 %) whereas denitrification and burial only accounts for 17 and 11 %, respectively. 相似文献
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模拟氮沉降对杂草生长和氮吸收的影响 总被引:6,自引:3,他引:6
以杂草早熟禾、黑麦草、野燕麦、天蓝苜蓿、白车轴草、北美车前、婆婆纳、无芒稗、牛筋草和刺苋为试验材料,以4.0g·m-2·yr-1的N输入为模拟氮沉降浓度,研究了不同杂草功能类群对模拟氮沉降的响应.结果表明,模拟氮沉降处理下,杂草的生物量(总生物量、地上部分生物量、根生物量)呈增加趋势,但不同功能类群对氮增加的响应明显不同,C4禾本科、C3豆科及C3禾本科植物的生物量受到氮沉降的显著促进,但C3非禾本科和C4非禾本科植物的生物量则受氮沉降的影响不显著;不同功能类群的根冠比、植株含氮及植株吸收氮的总量对模拟氮沉降的响应无明显规律,但物种间差异显著.氮沉降提高野燕麦和北美车前的生物量的根冠比,但对其他生物种类没有显著影响.没有发现氮沉降对植物体内的含氮量有显著的影响,但氮沉降却显著地提高了除刺苋、早熟禾及婆婆纳之外的所有杂草物种对N的摄收.由于物种对氮沉降的响应不同,未来氮沉降的增加将加速杂草群落组成的变化. 相似文献