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1.
Soil moisture influence on micronutrient cation availability under aerobic conditions 总被引:1,自引:0,他引:1
Summary The three major soil series comprising the Gezira scheme (Sudan) are Hosh, Suleimi, and Laota. Surface soil samples from each soil series were employed to study the effect of soil moisture on the DTPA-extractable micronutrient cation under aerobic conditions. The study continued for 8 weeks using an incubation technique at two levels of soil moisture (continuously moist and moist/dry cycles). The DTPA-extractable Cu, Fe, Mn and Zn from air-dry soil samples were much higher compared to values from their incubated counterparts. For the three soils the CO2 production (microbial activity) reached the maximum in 5 weeks and then levelled off while the lowest values of micronutrient cation from the incubated soils were obtained between 2 to 8 weeks.Generally, the study suggests that the hot dry months preceding crop growth should increase clay surface acidity and hence availability of mironutrient cations.Contribution from the Texas Agricultural Experiment Station, Texas A&M University, College Station. TX 77843, U.S.A. 相似文献
2.
Summary Phosphorus supply factors (capacity, kinetic, intensity, and diffusivity) and plant growth were the approaches used to assess P supply of flooded rice soils. Increases in the capacity, intensity, and kinetic factors, as measured by E-value, solution P concentration, and soil P release rate to a distilled water sink respectively, were unpronouced and infrequent upon water-saturation of ten soils. However, increases in the diffusitivity factor, as measured by 32P diffusion coefficients, were at least ten-fold as soil moisture increased. The greatest increases in P diffusion occurred as soil moisture increased beyond one-third bar.Using a P fertilized soil or P treated powdered cellulose as the P source and a minus P nutrient solution to nourish a split root system with water and nutrients, data were obtained which suggested that P uptake and rice-shoot growth (indicators of P availability) increased with increasing moisture level. Phosphorus uptake and rice-shoot growth were greatst when the soil or P treated cellulose were water-saturated. These data indicate that increased soil P availability upon flooding can be attributed to an increase in the diffusivity factor.Paper Number 4532 of the Journal Series of the North Carolina Agricultural Experiment Station.Paper Number 4532 of the Journal Series of the North Carolina Agricultural Experiment Station. 相似文献
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Response of different decomposer communities to the manipulation of moisture availability: potential effects of changing precipitation patterns 总被引:1,自引:0,他引:1
Astrid Rita Taylor Dagmar Schröter† Anne Pflug Volkmar Wolters 《Global Change Biology》2004,10(8):1313-1324
The potential impacts of changes in precipitation patterns associated with global climate change on the relationship between soil community diversity and litter decomposition were investigated. For a period of ca. 5 months, two decomposer communities in litterbags (1000 and 45 μm mesh size) containing spruce litter were subjected to two irrigation treatments: constant and fluctuating (drying/rewetting) moisture conditions. The latter were expected to induce moisture stress on the decomposer communities. The two mesh sizes were used to exclude different faunal components from the decomposer communities. The 1000 μm mesh excluded only the macrofauna, whereas the 45 μm mesh excluded both the macro- and mesofauna. In the short-term perspective of the present study, mesofauna abundance showed no response to imposed fluctuating moisture conditions. Irrespective of the presence of mesofauna, mass loss, microbial biomass and the control mechanisms, regulating carbon mineralization appeared unaffected by fluctuating moisture conditions. The reduction in the functional/structural diversity of the decomposer communities in the 45 μm litterbags resulted in strongly increased Nematoda abundance but it did not alter the response of Nematoda to fluctuating moisture conditions. Processes in the nitrogen (N)-cycle and mass loss were sensitive indicators of changes in the structural and functional complexity of decomposer communities. However, a negative effect of fluctuating moisture conditions on extractable N was coupled to the presence of mesofauna. Extremes in rainfall patterns, generated by climate change, may have a negative impact on the availability of nutrients, particularly N, for plants. This effect could be amplified by an additional impoverishment in the structural and functional complexity of the respective decomposer communities. 相似文献
5.
Effects of liming on phosphate availability in acid soils 总被引:9,自引:0,他引:9
R. J. Haynes 《Plant and Soil》1982,68(3):289-308
Summary The critical factors involved in the plant-soil-phosphorus-lime interaction are outlined and discussed. Conflicting reports suggest that the prior liming of highly weathered acid soils can result in an increase, a decrease, or no change in the availability of applied phosphate. Adsorption of phosphate by amphoteric soil surfaces generally decreases slowly as the pH is raised from 4.0 to 7.0. However, in soils initially high in exchangeable Al3+, liming results in the formation of new, highly active, phosphate adsorbing surfaces as the Al3+ ions precipitate as insoluble polymeric hydroxy-Al cation species. Thus, if an acid soil is reacted with lime and then phosphate, without intervening air drying, liming can increase phosphate adsorption. If the same limed soil is air dried before reaction with phosphate (e.g. adsorption isotherm studies), liming decreases phosphate adsorption. Apparently, air drying alters the surface characteristics of recently limed soils, probably by promoting the crystallization of the hydroxy-Al cation polymers as gibbsite.An important phenomenon, which is often overlooked, is that liming can increase phosphate availability by stimulating mineralization of soil organic phosphorus. However, at high soil pH values, the precipitation of insoluble calcium phosphates can decrease phosphate availability. Since Al toxicity is characterised by the inhibition of the uptake, translocation and utilization of phosphate by plants, liming often increases the utilization of soil phosphate by plants through amelioration of Al toxicity.When making lime recommendations or interpreting the data collected from lime-phosphate experiments, it is important to consider all the complex interacting soil and plant factors involved. 相似文献
6.
The effects of moisture availability on clonal growth and biomass investment in the bamboo Pleioblastus maculata were investigated over a four-year period by transplanting Pleioblastus maculata clones into soils with different levels of moisture availability in the field. The results showed that: (1) The higher the moisture availability, the greater the total biomass of P. maculata clones. Although fewer culms are produced at the higher moisture levels, mean tiller biomass is greater. (2) Under different levels of moisture availability, obvious differences in the total rhizome length (p < 0.01), spacer length (p < 0.05) and the sizes of bamboo culms (height, p < 0.01; diameter, p < 0.01) were observed. Thus, the higher the moisture availability, the shorter the rhizomes and the larger ramets. (3) In microhabitats with low moisture availability, bamboo allocated more biomass to underground organs, which promotes elongation of rhizomes and increases root production, thereby helping to capture underground resources essential to growth. In microhabitats of high moisture availability, the biomass is primarily allocated to the aboveground growth of ramets. (4) We suggest that soil moisture availability effects the foraging strategies of bamboo, that bamboo plants growing with low moisture availability produce longer rhizomes (that is, more, although shorter, spacers) with more biomass allocation than plants in high moisture and have a better ability to forage to increase the probability of locating adequate moisture patches. Also, longer length distance between shoots (that is, longer spacers) in high soil moisture than in low is adapted to avoid intense competition from faster growing aboveground growth in high moisture patches. 相似文献
7.
Konrad Mengel 《Plant and Soil》1994,165(2):275-283
The article describes factors and processes which lead to Fe chlorosis (lime chlorosis) in plants grown on calcareous soils. Such soils may contain high HCO3
- concentrations in their soil solution, they are characterized by a high pH, and they rather tend to accumulate nitrate than ammonium because due to the high pH level ammonium nitrogen is rapidly nitrified and/or even may escape in form of volatile NH3. Hence in these soils plant roots may be exposed to high nitrate and high bicarbonate concentrations. Both anion species are involved in the induction of Fe chlorosis.Physiological processes involved in Fe chlorosis occur in the roots and in the leaves. Even on calcareous soils and even in plants with chlorosis the Fe concentration in the roots is several times higher than the Fe concentration in the leaves. This shows that the Fe availability in the soil is not the critical process leading to chlorosis but rather the Fe uptake from the root apoplast into the cytosol of root cells. This situation applies to dicots as well as to monocots. Iron transport across the plasmamembrane is initiated by FeIII reduction brought about by a plasmalemma located FeIII reductase. Its activity is pH dependent and at alkaline pH supposed to be much depressed. Bicarbonate present in the root apoplast will neutralize the protons pumped out of the cytosol and together with nitrate which is taken up by a H+/nitrate cotransport high pH levels are provided which hamper or even block the FeIII reduction.Frequently chlorotic leaves have higher Fe concentrations than green ones which phenomenon shows that chlorosis on calcareous soils is not only related to Fe uptake by roots and Fe translocation from the roots to the upper plant parts but also dependent on the efficiency of Fe in the leaves. It is hypothesized that also in the leaves FeIII reduction and Fe uptake from the apoplast into the cytosol is affected by nitrate and bicarbonate in an analogous way as this is the case in the roots. This assumption was confirmed by the highly significant negative correlation between the leaf apoplast pH and the degree of iron chlorosis measured as leaf chlorophyll concentration. Depressing leaf apoplast pH by simply spraying chlorotic leaves with an acid led to a regreening of the leaves. 相似文献
8.
Luis Cáceres Alfonso F. Davila Alvaro Soliz Jessica Saldivia 《Antonie van Leeuwenhoek》2018,111(8):1293-1299
Here we consider that the corrosion of polished bared metal coupons can be used as a passive sensor to detect or identify the lower limit of water availability suitable for biological activity in Atacama Desert soils or solid substrates. For this purpose, carbon steel coupons were deposited at selected sites along a west–east transect and removed at predetermined times for morphological inspection. The advantage of this procedure is that the attributes of the oxide layer (corrosion extent, morphology and oxide phases) can be considered as a fingerprint of the atmospheric moisture history at a given time interval. Two types of coupons were used, long rectangular shaped ones that were half-buried in a vertical position, and square shaped ones that were deposited on the soil surface. The morphological attributes observed by SEM inspection were found to correlate to the so-called humectation time which is determined from local meteorological parameters. The main finding was that the decreasing trend of atmospheric moisture along the transect was closely related to corrosion behaviour and water soil penetration. For instance, at the coastal site oxide phases formed on the coupon surface rapidly evolve into well-crystallized species, while at the driest inland site Lomas Bayas only amorphous oxide was observed on the coupons. 相似文献
9.
Summary Three indices of available P were evaluated with 20 mainly calcareous Lebanese soils using wheat (Triticum aestivum L.) and tomato (Lycopersicum esculentum L.) in the greenhouse. Both the NaHCO3-and anion exchange resin-extractable P were significantly correlated with P uptake. The relationship for NaOH–Na2C2O4 was not significant. Langmuir isotherm and actual sorption parameters were also poorly related to uptake. In general, soil properties were not significantly related to extractable P or crop uptake. Sequential inclusion of selected soil properties with test values only slightly improved the multiple correlation coefficients.Contribution from the Department of Soils, Irrigation and Mechanization, American University of Beirut, Beirut, Lebanon. Journal No. 523B. Sci. Paper Series No.297. 相似文献
10.
Benjamin McClosky Steven D. Tanksley 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2013,126(9):2299-2312
Recombination is a requirement for response to selection, but researchers still debate whether increasing recombination beyond normal levels will result in significant gains in short-term selection. We tested this hypothesis, in the context of plant breeding, through a series of simulation experiments comparing short-term selection response (≤20 cycles) between populations with normal levels of recombination and similar populations with unconstrained recombination (i.e., free recombination). We considered additive and epistatic models and examined a wide range of values for key design variables: selection cycles, QTL number, heritability, linkage phase, selection intensity and population size. With few exceptions, going from normal to unconstrained levels of recombination produced only modest gains in response to selection (≈11 % on average). We then asked how breeders might capture some of this theoretical gain by increasing recombination through either (1) extra rounds of mating or (2) selection of highly recombinant individuals via use of molecular markers/maps. All methods tested captured less than half of the potential gain, but our analysis indicates that the most effective method is to select for increased recombination and the trait simultaneously. This recommendation is based on evidence of a favorable interaction between trait selection and the impact of recombination on selection gains. Finally, we examined the relative contributions of the two components of meiotic recombination, chromosome assortment and crossing over, to short-term selection gain. Depending primarily on the presence of trait selection pressure, chromosome assortment alone accounted for 40–75 % of gain in response to short-term selection. 相似文献
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Summary Alfalfa plants,Medicago sativa L., were selected from the Florida 66 cultivar for vigor in an acid (pH 4.4, Al≥.4 meq/100 g) and a limed, fertilized (pH 6.5, Al=0 meq/100 g, P and K added) Cecil topsoil. The selected plants were intermated by selection condition to achieve two germplasms, acid selected (A-1) and limed, fertile selected (L-1). ARhizobium meliloti strain (79-4s) was isolated from a high acetylene reducing nodule from a plant in a similar acid soil. The germplasms and the Rhizobium strain were then tested in greenhouse pots for agronomic performance under a variety of soil pH and fertility conditions. The 79-4s inoculum, as well as commercially prepared inoculum, gave better plant yield and acetylene reduction (N2-fixation) at all harvests when compared to a sterile peat control, but the commercial inoculum was the best inoculum treatment. The A-1 germplasm produced higher shoot dry weight at the final harvest than did the L-1 germplasm at all soil pH’s when P and K were applied at the highest rates. The A-1 germplasm also had better root weight (mainly fibrous roots) and acetylene reduction in these soil conditions. The two germplasms appear to be genetically distinct and respond differently depending on soil pH and fertility conditions. 相似文献
13.
Summary The effect of lime and P application on yield (top and root weigh), nodulation, intervally collected acetylene reduction (N2-fixation), and N and Al uptake of young alfalfa (46 days growth) were investigated in greenhouse pots containing acid Bladen or Bradson topsoils. The effect on seed germination and seedling persistence under these greenhouse conditions was also recorded.Alfalfa yield and acetylene reduction increased with lime and P additions in both soils, but, predominately, with P. There was no advantage of increasing these two parameters with liming past pH 6.0 provided P was adequate. Positive relationships (R2) existed between yield and acetylene reduction, and with both factors and root weight, nodule weight, and N uptake. Increased uptake of Al by alfalfa seedlings depressed yield, but data indicate P may block Al uptake at high soil pH. There were no treatment effects on seed germination, but P application increased plant persistence in the Bladen soil. 相似文献
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15.
Phosphorus availability to maize as influenced by organic manures and fertilizer P associated phosphatase activity in soils 总被引:2,自引:0,他引:2
Laboratory incubation and green house studies were conducted to compare the P availability of organic manures and P uptake from organic manures by maize. Various organic manures viz. Poultry manure (PM), Farmyard manure (FYM), Green manure (GM) and Crop residue (CR) and graded levels of fertilizer P were applied in Samana sandy loam and Ladhowal silt loam soils and incubated for 7, 15, 30, 60 and 90 days. Samples were analyzed for P availability, P uptake and alkaline phosphatase activity. The overall, phosphatase activity, Paranitrophenyl phosphate (PNP h−1 g−1), in the Ladhowal silt loam soil was higher than in the Samana sandy loam soil. As the level of inorganic P increased, the release of PNP h−1 g−1 soil also increased. Among different organic manures, PM registered the highest enzyme activity followed by FYM, GM and CR. Compared to 7 days incubation a slightly higher increase in PNP was noticed in samples from 90 days incubation in both soils. The differential phosphatase activity in the organic manures was further reflected in dynamic P availability. The highest amount of Olsen extractable P was in PM-treated soil followed by FYM, GM and field pea crop residue. Organic manure addition along with inorganic P, irrespective of the source, increased the Olsen extractable P throughout the incubation period. Total P uptake by maize increased with the increasing level of inorganic P in both soils. The highest uptake was obtained in PM-treated soil and lowest in the CR-amended soil. We conclude that PM more readily supplies P to plants than other organic manure sources. 相似文献
16.
Historical data from the 1930s were compared with new data gathered during the 2000s to evaluate the effects of increased numbers of larger stature submersed species (both elodeids and characeans) on resident isoetid communities. The cover and species richness of submersed species were assessed in 23 seepage lakes in northwestern Wisconsin, USA, using randomly located 1 m × 1 m plots. Water clarity, conductivity and residential land use were determined on a whole-lake basis and the sediment type and water depth were recorded at each plot. The probability of elodeids or characeans occurring in isoetid plots increased with the number of elodeids and characeans gained by a lake since the 1930s, with additions ranging from two to 15 species per lake. However, not all species were equally likely to co-occur with isoetids. Six elodeid species (Najas flexilis, Najas gracillima, Potamogeton gramineus, Potamogeton pusillus, Potamogeton spirillus and Vallisneria americana) along with Chara spp. were the most frequent isoetid associates, while other species that were common in the lakes, such as Elodea canadensis and Potamogeton robbinsii, were less frequent in isoetid plots. The lake-wide proportion of isoetid plots colonized by elodeids or characeans ranged from 5% to 100%, with increasing conductivity and total elodeids (plus Chara spp. and Nitella spp.) the strongest predictors of this colonization. Approximately half (49.6%) of all isoetid plots sampled had elodeids or characeans present (39.2% elodeids, 7.4% elodeids and characeans, 3.0% characeans), and isoetid cover and species richness were lower when these larger stature species were present. The risks this colonization poses for the long-term viability of isoetid species appeared to depend on multiple factors, including whole-lake characteristics, opportunities for refuge, and connections among regional isoetid populations. There was evidence of a time lag between the introduction of elodeid or characean species to a lake and invasion of isoetid plots within the lake, a process that deserves further study. 相似文献
17.
Actinomycete growth in conditions of low moisture 总被引:1,自引:0,他引:1
D. G. Zvyagintsev G. M. Zenova E. A. Doroshenko A. A. Gryadunova T. A. Gracheva I. I. Sudnitsyn 《Biology Bulletin》2007,34(3):242-247
Actinomycete communities demonstrated a replacement of the generic composition in time as a function of soil moisture. Representatives of the genera Streptomyces, Micromonospora, Actinomadura, Saccharopolyspora, and Microbispora were repeatedly isolated from soil under different moisture conditions (field capacity, maximum molecular capacity, and maximum adsorption capacity). Representatives of some rare genera (Thermomonospora and Kibdelosporangium) were isolated from soil with low moisture levels inhibiting growth of more hydrophilic actinomycetes and bacteria. Spores of some actinomycetes could grow at low relative air humidity (RH) (50 and 67%). The complete growth cycle of all actinomycetes starting from spore germination to sporulation was observed only at RH of 98%. 相似文献
18.
Summary Rooting into acid subsoils would be a desirable trait for alfalfa which should result in better water extraction and yield. In this study, the rooting depth into acid subsoils and top yield of alfalfa plants selected for acid tolerance were investigated in a repacked profile with a limed, fertile topsoil, but unamended, acid subsoil. The effects of subsoil modification by CaCO3 and CaSO4·2H2O addition on alfalfa rooting, top growth, and water extraction were also studied. Plants from acid selections rooted deeper into acid subsoil when compared to control plants (selected under limed conditions). However, the reverse response was found in the CaSO4·2H2O treated subsoil. There were no differences among selections for total top yield for any subsoil treatment. Water extraction from the lower subsoil and top growth yield (data pooled by selections) were improved mainly in the subsoil treatment containing the highest addition of CaCO3. 相似文献
19.
Summary Seedlings of a broad based population of alfalfa, (Medicago sativa L.), were visually selected for 2 generations (cycles) in an acid Cecil soil (pH=4.8). Simultaneously, 2 generations of selections
were made in a limed Cecil soil (pH=6.2) amended with phosphorus.
When tested in acid soil (pH=4.8) with added P, the cycle 2 acid selections yielded significantly more top yield than either
the limed selections or the original seed. When grown in the limed soil (pH=6.2) without added P, the acid selections yielded
significantly less. There were no significant differences among selections in other soil conditions (pH=4.8, no P added and
pH=6.2, P added). Root weight and length and nodule fresh weight correlated well with top yield in all treatments.
The yield of the 10 parent varieties and polycrossed seed of their cycle 1 acid and cycle 1 limed selections were compared
under two soil conditions (acid and limed). The results of this test indicate that some varieties were more responsive to
acid soil selection than other. Overall, none of the 10 varieties showed any decreases in total top yield due to one cycle
of selection in either the acid or limed soil conditions. 相似文献
20.
Standing crop and species composition in semiarid grassland are linked to long-term patterns of water availability, but grasslands
are characterized by large single-season variability in rainfall. We tested whether a single season of altered water availability
influenced the proportions of grasses and shrubs in a semiarid grassland near the northern edge of the North American Great
Plains. We studied stands of the clonal shrub snowberry (Symphoricarpos occidentalis) and adjacent grassland dominated by the native grasses Stipa spartea and Bouteloua gracilis. Rain was excluded and water supplied in amounts corresponding to years of low, medium, and high rainfall, producing a 2
− 4-fold range in monthly precipitation among water supply treatments. There were ten replicate plots of each water treatment
in both snowberry stands and grassland. Grass standing crop increased significantly with water availability in grassland but
not inside snowberry stands. Total standing crop and shrub stem density increased significantly with water supply, averaged
across both communities. In contrast, water had no effect on shrub standing crop or light penetration. In summary, our finding
that water has significant effects on a subset of components of grassland vegetation is consistent with long-term, correlational
studies, but we also found that a single season of altered water supply had no effect on other important aspects of the ecosystem.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献