Ann anion exchange membrane (AEM) is a solid organic polymer that has a positive electrostatic charge, which is saturated by the addition of a counter ion, such as bicarbonate (HCO3), before use. In the presence of an anion, such as NO3 HCO3 will be exchanged for a stoichiometrically equivalent amount of that anion

Arrobas, Margarida

Rodrigues, M.A.

Biblioteca Digital do IPB

~ I : . j I ' PROCEEDINGS OF Agro201 0 the Xlth ESA Congress ·August 291h - September ard, 2010 Montpellier, France ! '-\• t i Chair • J. Wery, Montpelller SupAgro, France ESA President Scientific Committee • S. Asseng, CSIRO, Australia • J.M. Barbier, INRA Montpelller, UMR Innovation, France • M. Benoit, INRA Mlrecourt, dpt SAD, France • J.E Bergez, INRA Toulouse, UMR Aglr, France J. Boiffin, IN RA Angers, AFA, France • P. Carberry, CSIRO, Australia • J.L. Chotte, lAD Montpelller, UMR EcoSol, France • 0. Christen, Martin Luther University, Halle-Wittenberg, Germany • M. Donatelli, ESA secretary, JRC and CRA, Italy • T. Dare, AgroParisTech-INRNEA, France • C. Gary, INRA Montpellier, UMR System, France • M. Genard, IN RA Avignon, UR PSH, France • P. Gregory, SCRI, United Kingdom • D. Habash, Rothamsted Research, United Kingdom • G. Hammer, APSRU, Australia • P. Hinsinger, INRA Montpelller, UMR EcoSol, France • B.Hubert, Agropolis International, France • J. Jones, University of Florida,USA • J.D. Lebreton, CNRS Montpellier, IFR MEB, France AGRUPOUS £) lNTER~TlONAL agropolis fnndation ' I/ ,. :;@ I I Montpe:U1e.r ···-··! '" • F. Lescouret, IN RA Avignon, UR PSH, France • R. Ufran, iNRA Montpellier, UMR Lameta, France • E. Malezieux, CIRAD Montpellier, France ' F. Maraux, CIRAD Montpellier, France • M. Morison, INRA Grignon, France • N. Munier-Jollain, INRA Dljon-INRNEA, France • M.L. Navas, Montpelller SupAgro, UMR CEFE, France • B. Ney, AgroParisTech & Academle de !'Agriculture, Paris, France • J. Porter, University of Copenhagen, Denmark • F. Tardieu, INRA Montpelller, IFR Daphne, France • M. Van lttersum, WUR and Seamless, The Netherlands ~~~~~~.~~~~. ~.«:>.~~~.~~~ ........ .. ............ .... ... . • I. Bastie, Montpelller SupAgro • B. Cabantous, Agropoiis International • C. Jacquet, CIRAD • F. Lava!, Montpellier SupAgro • E. Mignard, INRA • A. Perrin, Montpellier SupAgro • C. Picard, INRA • P. Prevost, Montpellier SupAgro - AFA • S. Renoir. CIRAD • M. Salas, Agropolis International • I. Shili-Touzi , Montpellier SupAgro • N. Villemejeanne, Agropolis International Agro 2010, the XI ESA Congress, Montpellier Optimising the time of incubation of an anion exchange membrane inserted into the soil to use in studies of monitoring soil nitrate levels Angelo Rodrigues M. ,Arrobas M. Mountain Research Center - ESA, lnstituto Politecnico de Bragan~a Campus de Sta Apol6nia, ap. I I 72, 5301-855 Bragant;:a, Portugal; email: angelor@ipb.pt An anion exchange membrane (AEM) is a solid organic polymer that has a positive electrostatic charge, which is saturated by the addition of a counter ion, such as bicarbonate (HC03-), before use. ln the presence of an anion, such as N03-, HC03- will be exchanged for a stoichiometrically equivalent amount of that anion. By placing the AEM in a concentrated acid solution (hydrochloric acid, for instance), N03- ions are displaced by er and then determined in the extracts by appropriate analytical methods (Pare et al., 1995). Pare et al. (1995) compared the N03-N extracted by AEM buried at 15 cm soil depth for a 2-wk period in a soil cropped with corn subjected to different fertilization treatments with N03-N extracted with 2M KCI. They found a highly significant correlation (r2 = 0.78) between the two N03-N extraction procedures. Qian and Schoenau (1995) used AEM buried in the soil in a Lab incubation experiment to measure the N03-N released from organic matter. They compared the results of the AEM method and those of a chemical extraction technique using 0.001 M CaCh solution with plant N uptake in the field. Rodrigues et al. (2006) compared N03-N adsorbed in AEM with plant N uptake when the AEM were inserted into the soil in a pot experiment with maize subjected to the application of different organic manures permitted in organic farming. Rodrigues et al. (201 0) used AEM in a similar pot experiment with tall cabbage and ryegrass subjected to N fertilisers with different slow-release mechanisms. From all the cited experiments it was clear that there is a great potential for the use of .AEM to provide reliable information on time and rate of N released from organic matter and fertilisers. Despite positive results having been obtained, the technology of placing tb.e membranes directly into the soil can be improved if the most appropriate time could be established for the duration of the incubations. Thus, there is a need to test if the initial soil disturbance influences the flux of nitrates to the AEM and if there is any risk of the saturation of the adsorption capacity of the membrane due to a prolonged exposure in the soil and a high soil nitrate level. This paper relates the effect of the incubation time on the amount of nitrate ion recovered by AEM in a pot experiment where different N rates were previously applied. Materials and Methods Pots of 15 kg dried and sieved (6-mm) soil were amended with 0, 2.74, 5.49 and 10.98 g N applied as ammonium nitrate in three replications. The soil was kept bare during the period of the experiment. The pots were incubated under a temperature between 10 to 15 °C for a month. After this period 5 strips of lx2 cm AEM per pot were buried 10 cm in the soil. The AEM were tied with a line allowing for an easy removal from the soil. After 48, 72, 96, 120 and 240 hours the membranes Were recovered, rinsed with distilled water and the nitrate ions eluted in hydrochloric acid as previous described (Rodrigues et al., 201 0). Nitrate concentration in the extracts was determined by UV-vis. spectrophotometrY. The use of an agricultural soil and a common N fertiliser, which was homogenously distributed in the soil, was intended to test the AEM in as similar conditions as possible to those that the AEM would find in a pot or even in a field experiment. Thus, the many aspects that can influence the performance of the AEM, including the saturation of its exchange capacity by anions other than N03-, can then be taken into account Results and discussions ln the higher N rate (I 0.92 g N pof1) the adsorption capacity of the AEM was saturated after 72 h of incubation (figure 1). When 5.49 g N pof1 were used the adsorption capacity of the AEM was saturated after 120 h (5 days) of incubation. In the treatment consisting of the application of 2 .74 g N 239 Agro 2010, the XI ESA Congress, Montpellier port an in the control the soil available nitrate ions were not high enough to saturate the adsorption capacity of the AEM. -120 ~ 100 ?P ~ = .._, 80 = 0 010.98 gN :c 60 c:: loo ~ i + £ 0 5.49 gN ... 40 = Cl.l (,1 ~2.74 gN = 20 0 (,1 OControl . .... 0 0 :z; 0 24 48 72 96 120 144 168 192 216 240 Time of AEM incubation (b) Figure 1. Nitrate concentration in AEM extracts from different N application rates and from different incubation times. Vertical lines represent the mean standard deviations. The application of 1 0.92 g N port lead to soil nitrate levels that will be difficult to find in a soil after the application of a usual N rate. Such a high N rate was precisely used with the expectation that it would saturate the adsorption capacity of the AEM. The experiment also showed that the adsorption capacity of the AEM was reached with the use of 5.49 g N port, a value ofN fertilisation that lead to a soil nitrate level that can easily be found in a cultivated field. This may mean that caution should be taken when using AEM in heavily fertilised crops. From the 5.49 g N port treatment, it was also clear that the saturation of the adsorption capacity of the AEM was a continuous process. In pots which were not irrigated during the incubation period and where the evaporation of water would be minimal, no movement of N03' would occur through mass flow. Diffusion would be the major process leading to the movement of N03' from the soil solution to the AEM. Thus, tllis study also showed that the time of incubation may be an important aspect that must be taken into account in the use of the AEM methodology. In the treatment where 5.49 g N port were applied, the highest N concentration in the AEM extracts never reached the values found in the pots where 10.92 g N port were applied, even after 10 days of incubation. The low soil nitrate levels in the 5.49 g N port treatment would allow that other anions such as er to have increased their position at the exchanging sites of the membrane. A high soil nitrate level may saturate the adsorption capacity ofthe AEM, which could limit the use of AEM in environments with high N03-N levels. Since the saturation of the adsorption capacity of the AEM is a continuous process, the time of incubation must be carefully selected to increase the useful potential of AEM in monitoring nitrate dynamic in the soil. References Pare, T., Gregorich, E.G., Ellert, B.H. 1995. Comparison of soil nitrate extracted by potassium chloride and adsorbed on an Exchange membrane in situ. Commun. Soil Sci. Plant Anal. 26: 883-898. Qian, P., and Schoenau, J.J. 1995. Assessing nitrogen mineralization from soil organic matter using anion exchange membranes. Fert. Res. 40: 143-148. Rodrigues, M.A., Pereira, A., Cabanas, J.E., Dias, L., Pires, J. and Arrobas, M. 2006. Crops use-efficiency of nitrogen from manures allowed for organic farming. Eur. J. Agron. 25: 328-335. Rodrigues, M.A., Santos, H., Ruivo, S., and Arrobas, M. 2010. Slow release N fertilisers are not an alternative to urea for fertilisation of autumn-grown tall cabbage. Eur. J. Agron. 32: 137-143. 240 

Optimizing the time of incubation of an anion exchange membrane inserted into the soil to use in studies of monitoring soil nitrate levels

http://bibliotecadigital.ipb.pt/bitstream/10198/3015/3/Membranas%20teste.pdf

Optimizing the time of incubation of an anion exchange membrane inserted into the soil to use in studies of monitoring soil nitrate levels

Abstract

Similar works

Full text

Available Versions

Biblioteca Digital do IPB