Slow nitrogen release from humic substances modified with aminoorganosilanesстатья
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Дата последнего поиска статьи во внешних источниках: 10 августа 2018 г.
Аннотация:Abstract
Purpose. To evaluate slow release nitrogen capabilities of soil amendments obtained by modification of humic materials from peat and lignite with alkoxyorganosilanes carrying different amine-substituents.
Materials and methods. The humates from lignite and peat were modified using (3-aminopropyl¬triethoxy)-silane (APTES) and (1-aminohexamethylenene, 6-aminomethylene)-triethoxysilane (AHATES). The obtained derivatives were characterized using elemental analysis and Fourier transform infrared spectroscopy. Nitrogen release in the form of ammonium and nitrate was evaluated using dissolution tests under sterile aqueous conditions as well as long-term soil experiments. Ammonium and nitrate were determined using ion-selective electrodes. Activity index (AI) was calculated from the dissolution tests. For soil trials, arable Retisol was sampled from 0–5 cm layer in Yaroslavl region (Russia). The soil experiments were conducted over 78 days using (NH4)2SO4 as an activator of nitrification, and 3-amino-1,2,4-triazole - as an inhibitor of autotrophic nitrifying bacteria.
Results and discussion. Modification of lignite and peat humates lead to an increase in nitrogen content up to 2 and 4.3 %, respectively, in case of APTES, and up to 3 and 6 %, respectively, in case of AHATES. All humic derivatives gradually released N upon dissolution in water over 6 d up to 51% of the total N. The AI values ranged from 4 to 13%. Amendment of soil with the modified humic materials induced an increase in nitrate content resulting from nitrification of released ammonia by soil microflora. This was confirmed by aminotriasole experiments. The nitrogen release occurred slowly: over first week of incubation it did not exceed 36-69 % of the total N content. The higher release rate of ammonium nitrogen was observed for CHS-AHATES versus CHS-APTES derivative, whereas no difference was seen between the two peat derivatives, which showed release rate on the level of CHS-AHATES derivative. Positive effect of all modified humic materials lasted over 78 days.
Conclusions. Modification of lignite and peat humates with two aminoorganosilanes brought about two to three fold enrichment of the parent humic materials with nitrogen, which was capable of slow release upon incubation in soils. It was released in the form of ammonia and nitrified by autotrophic microflora. There was no clear relationship established between structure of amine substituent and slow release properties of the corresponding humic derivatives. The conclusion was met that nitrogen fertilizing capabilities might be considered as beneficial added-value feature of these humic products.
Keywords Aminoorganosilanes • Modification • Humic substances • Slow nitrogen release fertilizers •Soil amendments