1,721,162 research outputs found
Fertilizzanti: commodities e nuove tipologie.
No full textGli elementi che concorrono alla nutrizione vegetale, se si eccetuano il carbonio, idrogeno e ossigeno che sono assunti dall’aria e dall’acqua, vengono assorbiti dal suolo e possono essere chiamati macroelementi o microelementi a seconda della quantità richiesta. I macroelementi vengono distinti in principali, o macroelementi propriamente detti (azoto, fosforo e potassio), e secondari o mesoelementi (zolfo, calcio e magnesio). Tale suddivisione non deve considerarsi rigida. Tal volta il sodio viene aggiunto alla lista degli elementi secondari e il cobalto a quella dei microelementi
The fate of soil organic carbon from compost: a pot test study using labile carbon and 13C natural abundance
Full text linkRecycled organic waste (OW) can be a valuable nutrient source for plant cultivation; however, knowledge is poor regarding its effect on soil carbon conservation, especially in the frame of organic-mineral fertilisation succession. In this study, four composts, green waste (GWC), anaerobically digested bio-waste (DC), sludge (SSC), and bio-waste (BWC), were compared (10 and 20 Mg volatile solids ha−1) in a ryegrass pot test over two growing cycles (112 + 112 days), along with an unamended control (Ctrl) and a chemical reference (Chem), with and without mineral nitrogen (N) fertilisation. At the end of the two growth cycles, the pot soil was analysed for total- (TOC) and labile-carbon (CL) as well as for 13C isotope natural abundance (δ13C and Δ13C vs. Chem). At day 112, the pot test showed that Ctrl and Chem gained poor TOC (8.48 g kg−1), lower than the compost at both 10 and 20 Mg volatile solids ha−1 (10.01 vs. 11.59 g kg−1). At day 224, a deep soil TOC depletion occurred in the pot soil treated with GWC, DC and BWC at both levels (-10 and -20). However, all the compost treatments showed more depleted soil d13C vs. the references, especially Chem, thus revealing relevant compost-derived carbon conservation. Regarding the compost treatments, the carbon management index (CMI) increased over time, indicating high soil functionality, also showing a good relationship with δ13C, suggesting a probable increase in relative lignin which could have been linked to carbon conservation and increased functionality
Determination of free L- and D-alanine in hydrolysed protein fertilisers by capillary electrophoresis
No full textThe objective of this study was to determine the degree of racemisation of hydrolysed protein fertilisers (HPFs) using an inexpensive and easy to handle analytical method for qualitative control of the products. Using a polyacrylamide coated capillary and a run buffer containing 0.1 M Tris-borate+2.5 mM EDTA-Na2+0.1% sodium dodecylsulfate+10 mM β-cyclodextrin a quantitative separation of D- and L-alanine (Ala) was made from an not treated HPF sample derivatised with dansyl chlorine by capillary electrophoresis. The D-Ala:[D-Ala+L-Ala] ratio, called degree of racemisation (RD), was calculated. The analysis of ten commercial HPFs has shown that more than 60% of HPFs have an RD ≥40%, while only one product has shown an RD <5%. These results showed that most of the HPFs on the market are obtained with strong hydrolytic processes and high contents of D-amino acids are probably less effective as plant nutrients or even potentially dangerous to plants. © 2002 Elsevier Science B.V. All rights reserved
Identification of organic matter from peat, leonardite and lignite fertilisers using humification parameters and electrofocusing
No full textThe organic matter extracted from peats (P), leonardites (Le) and lignites (Li) was characterised by humification parameters and electrofocusing (EF). The degree of humification and the humification index might be used to distinguish P from Le and Li, but not Le from Li because they showed overlapped values, while the humification rate could be used only for the identification of Le and EF profiles of P, Le and Li fertilisers revealed different band patterns: P samples did not show bands in the region with isoelectric point, pI>4.4; Le samples showed very intense bands in the region with pI>4.4; Li samples showed a very different band pattern with poorly resolved bands in the region with pI>3.8. P, Le and Li samples can be distinguished by combining humification parameters and EF. © 2002 Elsevier Science Ltd. All rights reserved
Influence of long-term residue and fertilizer applications on soil humic substances: A study by electrofocusing
No full textSoil samples were taken from the plots of an experimental field that had been treated continuously for 22 years with different residue and fertilizer applications (cereal residues, cattle manure, NH4NO3). The electrofocusing (EF) technique was used to characterize the humic substances extracted from these soils with 0.5 M NaOH. The EF patterns of the organic matter extracted from the soil which had received applications of cattle manure showed many bands focused in the typical pH gradient region of the most humified compounds. The EF patterns of the organic matter extracted from both unfertilized soil and from soils amended with straw appeared to be much less complex. The addition of NH4NO3 did not affect the soil organic matter characteristics investigated with the EF technique. The results obtained show that electrofocusing is a promising technique for the characterization of humic substances and may well be particularly useful in the evaluation of differences that occur in the humic substances in soil due to residue and organic fertilizer applications. © 1992 Williams and Wilkins
Activity and stability of jack bean urease in the presence of peat humic acids obtained using different extractants
No full textThe effects of two humic acid extractants, 0.1 M Na4P2O7 plus 0.1 M NaOH (NaPP) and 0.1 M NaOH (NaOH), on the activity and stability of a humic-urease complex were studied. The two humic acids isolated (HANaPP and HANaOH) exhibited different elemental compositions, metal concentrations and structural modifications in the FT-IR spectra. Depending on the pH, HANaPP and HANaOH influenced both the urease activity and urease kinetic parameters (Vmax and Km) in the same way. They inhibited urease activity between pH 6 and 7 and reduced the Vmax of the reaction at pH 6 and 7. The presence of humic acids improved the affinity of the enzyme for the substrate (Km). The stability of the urease with time, and in the presence of pronase, was improved by HANaPP and HANaOH with respect to free enzyme. These results confirm the importance of the interaction of urease with humic acids as a fundamental gateway for extracellular urease stabilisation. Since no difference in the extent of urease inhibition and urease stabilisation was observed for the two humic acids, it may be concluded that neither urease activity nor stability are influenced by the humic acid extractant used
Extraction of humic acids from a natural matrix by alkaline pyrophosphate. Evaluation of the molecular weight of fractions obtained by ultrafiltration
No full textFractions of humic acids, resolved by ultrafiltration of extracts from a sample of peat treated with alkaline pyrophosphate solution, have been submitted to high-performance size-exclusion chromatography, with the aim of determining the molecular weight distributions. Anomalous peaks, located at retention volumes higher than those corresponding to the main signal, are present in the elution profiles relative to the lightest fractions. These peaks are more intense when using a refractive index detector rather than a UV detector. Elemental analysis data for the lightest fractions suggested that the spurious peaks are due to the presence of inorganic material. The hypothesis that pyrophosphate interacts with humic acids in the course of the extraction has been confirmed by colorimetric determination of the phosphorus content in the different fractions. As a consequence, the extraction procedure has been modified by using 0.1 mol/L NaOH as extractant.The average molecular weights of the various fractions, following NaOH extraction, result in substantial agreement with those obtained following pyrophosphate solution extraction (if the ‘pyrophosphate peaks’ present in the chromatographic profile are discarded in the calculations)
Thermal analysis (TG-DTA) and isotopic characterization ( 13C-15N) of humic acids from different origins
No full textThermal analyses (TG-DTA), elemental composition and isotope analyses (13C and 15N) were performed on humic acids (HA) from peats, leonardites and lignites, in order to investigate their structure and the changes taking place during the humification process. Thermal analyses showed structural differences between HA samples in relation to their coalification rank. In particular the lignite HA were characterized by a more stable chemical composition at high temperatures. The δ13C and δ15N values can provide information on the biogeochemical processes involved in HA formation. In particular, peat HA were linked to anoxic environments that enable plant residues to persist in their structure. In contrast, leonardite and lignite HA formation seems to be governed by different biogeochemical processes from those responsible for peat diagenesis. However, the isotopic analyses did not provide any distinction between leonardite and lignite HA. On the basis of the data presented in this study, it may be concluded that TG-DTA and isotope ratio measurements are powerful tools for investigating the formation pathway of humic substances from coals. © 2004 Elsevier Ltd. All rights reserved
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