1,721,076 research outputs found
Microcarenze: la sostanzza organica ha un ruolo chiave
No full textLa sostanza organica influenza assorbimento e disponibilità dei micronutrienti, conoscere i meccanismi di tale interazione è fondamentale per evitare carenze nutrizionali. Ad esempio un eccessivo contenuto di sostanza organica può causare rame-carenza, di contro una buona dotazione di humus favorisce l'assorbimento del boro
Nitrogen availability from organo-mineral fertilizers
No full textA field experiment was conducted during two years to determine N availability to corn (Zea Mays L.) and NO3- leaching risk from a peat-based organo-mineral fertilizer (OMF) in comparison to conventional mineral N fertilizers (MF). Randomized blocks with four replicates and an unfertilized control were performed during 2003 and 2004. The rate of N application was set at 300 N, 120 P2O5 and 120 K2O kg ha-1.
The two growing seasons differed widely for main climatic parameters (air temperature and rainfall) that produced remarkable effects on soil mineral N dynamics. Generally, the higher temperatures that characterized 2003 reduced the differences between MF and OMF. The MF produced a peak in extractable NH4+-N few days after spreading (6-10 d) whereas this peak shifted for the OMF from 5 to 30 days during 2003 and 2004 respectively. The OMF left an higher amount of mineral N during the whole growing season, especially in 2004. At the end of the growing season, the amount of total soil N and their mineral forms (NO3- plus NH4+) in plots fertilized with the OMF were similar to the plots manured with MF and only slightly higher than unfertilized control plot, suggesting that the delay in N availability of OMF was of limited duration and that nearly all NO3- not absorbed by plants was lost by leaching
COMPARISON OF TWO METHODS FOR EXTRACTION OF ATP FROM SOIL
No full textThe main aim of this work was to investigate previously published reports that an acidic mixture
of 0.67 M phosphoric acid, 20% dimethyl sulphoxide, 2 M urea, 20 mM EDTA, 0.75 mM adenosine and
32.5 mM Zwittergent (termed the PA reagent) extracted up to 7 times more adenosine S-triphosphate (ATP)
from soil than a reagent consisting of 0.5 M trichloroacetic acid (TCA), 0.25 M phosphate and 0.10 M
paraquat (termed the TCA reagent). Several extraction tests were performed using both fresh and air-dried
soils at different soil-to-extractant ratios. The ATP concentrations in the soil extracts were determined by
the fire-fly hlciferin-luciferase system. In 5 fresh U.K. arable soils the amounts of ATP extracted, corrected
for incomplete extraction by measurement of the recovery of an internal standard of added ATP (the spike),
ranged from 1.29 to 7.80 and from 1.01 to 5.24 nmol ATP g-’ soil, for the TCA and PA reagent,
respectively. In air-dried soils the range was from 0.35 to 1.11 and from 0.35 to 1.24 nmol ATP g-’ soil,
respectively, for the TCA and PA reagent. Except for an acid soil, the amount of native ATP extracted from
the soils by the two reagents and uncorrected for incomplete extraction was not significantly different within
soils when a 1:5 soil-to-extractant ratio was used. However, the percentage recovery of added ATP as a spike
was larger at higher soil-to-solution ratios with the TCA reagent but not with the PA reagent. The recoveries
of the spike with the TCA reagent were always lower than with PA reagent. However, soil ATP, corrected
for incomplete extraction, was always greater with the TCA reagent than with PA. The use of [14C]ATP as
a spike showed that no appreciable dephosphorylation of ATP added as the spike occurred with either
reagents. The main difference between PA and TCA reagents was that with PA a constant and high recovery
of spike ATP (ca. 90%) was obtained at all soil-to-solution ratios tested, while TCA gave higher recoveries
of spike ATP at higher soil-to-solution ratios. Paradoxically, the amounts of native ATP extracted at each
soil-to-solution ratio were generally similar between PA and TCA, although increasing with increasing
soil-to-solufon ratio. Correction for incomplete extraction of the spike with the TCA reagent gave very
similar soil ATP concentrations while this was not the case with the PA reagent. We suggest that this is the
main difference between the two reagents. We can find no evidence to support other work which suggested
that the PA reagent extracts more ATP from soil than the TCA reagent
Applicazioni ICP-AES-SEC nello studio della complessazione di Pb e Zn in suoli contaminati
No full textInvestigation of the intereactions between humic substances and a cationic detergent
No full textVisible spectrophotometric measurements were used to study binding of cetltrimethylammonium to humic molecules. Detergent molecules appeared to bind to ionized carboxyl and phenolic groups. Complete neutralization of negative charges caused quantitative precipitation of humic substances at low ionic strength. Detergent amounts higher than the stoichiometric ratio caused salting in of precipitate. The influence of organic carbon concentration, ionic strength and pH of the solution on the complex composition at minimum solubility was investigated
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