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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 3 (1987), S. 0 
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The salt regimes in soil under grazed and ungrazed natural grassland were compared on a Natraquoll in the Flooding Pampa of Argentina. The salt concentration in the topsoil of the grazed land increased sharply and episodically after flooding, whereas in the ungrazed land it did not.When the area was flooded groundwater rose and increased the salt content of the deep horizons. Thereafter the topsoil became salinized during drought when the atmospheric water demand was large. The evaporation from the soil surface in the grazed area was faster than in the enclosed field, being probably the cause of the accumulation of salts in the topsoil.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Key words Grasslands ; Mineral nutrition ; Allocation ; Phosphorus ; Adaptations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Waterlogging frequently reduces plant biomass allocation to roots. This response may result in a variety of alterations in mineral nutrition, which range from a proportional lowering of whole-plant nutrient concentration as a result of unchanged uptake per unit of root biomass, to a maintenance of nutrient concentration by means of an increase in uptake per unit of root biomass. The first objective of this paper was to test these two alternative hypothetical responses. In a pot experiment, we evaluated how plant P concentration of Paspalum dilatatum, (a waterlogging-tolerant grass from the Flooding Pampa, Argentina) was affected by waterlogging and P supply and how this related to changes in root-shoot ratio. Under both soil P levels waterlogging reduced root-shoot ratios, but did not reduce P concentration. Thus, uptake of P per unit of root biomass increased under waterlogging. Our second objective was to test three non-exclusive hypotheses about potential mechanisms for this increase in P uptake. We hypothesized that the greater P uptake per unit of root biomass was a consequence of: (1) an increase in soil P availability induced by waterlogging; (2) a change in root morphology, and/or (3) an increase in the intrinsic uptake capacity of each unit of root biomass. To test these hypotheses we evaluated (1) changes in P availability induced by waterlogging; (2) specific root length of waterlogged and control plants, and (3) P uptake kinetics in excised roots from waterlogged and control plants. The results supported the three hypotheses. Soil P avail-ability was higher during waterlogging periods, roots of waterlogged plants showed a morphology more favorable to nutrient uptake (finer roots) and these roots showed a higher physiological capacity to absorb P. The results suggest that both soil and plant mechanisms contributed to compensate, in terms of P nutrition, for the reduction in allocation to root growth. The rapid transformation of the P uptake system is likely an advantage for plants inhabiting frequently flooded environments with low P fertility, like the Flooding Pampa. This advantage would be one of the reasons for the increased relative abundance of P. dilatatum in the community after waterlogging periods.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Zea mays L.) vegetative and reproductive characteristics were measured. Multivariate statistical analyses were applied to the data to determine potential indicators of soil quality. Soil and crop variables explained more than 70% of the variance in soil quality among agricultural histories. The edaphic indicators that showed the greatest change from pristine conditions were organic C, total N, P, Mg, K, B, Ca, and Zn contents and cation exchange capacity. Using crop variables, leaf length, maximum fraction of intercepted photosynthetically active radiation, grain yield, kernel number, prolificacy, and total dry matter at physiological maturity, served to establish a soil quality gradient. Variation of maize growth was associated with edaphic indicators of soil quality and revealed the importance of soil aggregate stability in determining changes in soil quality for crop production.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 175 (1995), S. 251-255 
    ISSN: 1573-5036
    Keywords: Brassica napus ; Ca/Na ratio ; K/Na ratio ; rapeseed yield ; salinity ; sodicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rapeseed (Brassica napus) is a crop relatively tolerant to salt and sodium. Our objective was to study the interactions between Na, K and Ca and their relationship with its yield under the isolated effects of soil salinity or sodicity. Two experiments were carried out using pots filled with the Ah horizon of a Typic Natraquoll. There were three salinity levels (2.3 dS m-1; 6.0 dS m-1 and 10.0 dS m-1) and three sodicity levels, expressed as sodium adsorption ratios (SAR: 12; 27 and 44). The soil was kept near field capacity. As soil salinity increased, the K/Na and Ca/Na ratios in the tissues decreased markedly but yields and aerial biomass production were not affected. As soil SAR value increased, the K/Na and Ca/Na ratios in plants and K-Na and Ca-Na selectivities decreased. Plants could not maintain their Ca concentration in soil with a high SAR. The grain yield and biomass production diminished significantly in the highest SAR treatment. Our results are consistent with those showing detrimental osmotic effects of salts in Brassica napus. Conversely, under sodicity, the K/Na and Ca/Na ratios in plant tissues decreased considerably, in accordance with grain and biomass production. These results show that the effects of sodicity are different from those of salinity.
    Type of Medium: Electronic Resource
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