[ Évaluation de la volatilisation ammoniacale et de la transformation de l’azote uréique dans un Arénoferralsol et un Ferralsol de la RD Congo ]
Volume 64, Issue 1, December 2022, Pages 14–24
Jared MATABA MPONGATE1 and Christophe LUMPUNGU KABAMBA2
1 Département de Gestion des Ressources Naturelles, Université de Kinshasa, BP 117 Kinshasa XI, RD Congo
2 Département de Gestion des Ressources Naturelles, Université de Kinshasa, BP 117 Kinshasa XI, RD Congo
Original language: French
Copyright © 2022 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
By this study, we evaluate, by incubation in the laboratory, the hydrolysis and the kinetics of mineralization of the urea used in Arenoferralsol and Ferralsol, as well as to appreciate, at the same time, the activity of microorganisms by the quantity of CO2 released over 15 days. In Arenoferralsol, the sharp rise in pH observed during the first 7 days of incubation denotes a strong hydrolysis of urea inhibiting the activity of microorganisms with, as a consequence, a low mineralization of nitrogen. The sharp rise in pH correlates with the massive volatilization of NH3 recorded during this time span. Beyond the 7th day, the decrease in volatile NH3 began, the resumption of microbial activity and the gradual increase in nitrification. On the other hand, in Ferralsol, it was recorded, in the same space of time, a weak rise in pH indicating a weak release of NH3, but, at the same time also a weak microbial respiration and a weak transformation of urea nitrogen. The pH, although raised to an average of 5.5, nevertheless remained strongly acidic. The drop in pH observed from the 11th day of incubation did not, however, stimulate the formation of NH4+-N and CO2, which still remained low. Thus, the NO3--N content experienced some increase. Hence, the conclusion that nitrification in this type of soil is very slow due to its high acidity. Taking into account the results observed in the two soils, nitrification as well as volatilization seem to be more active in Arenoferralsol compared to Ferralsol. Because, the acid state of Ferralsol as well as the quality of the organic matter combine to inhibit nitrification by destroying microbial life, especially those responsible for nitrification while progressive nitrification is noticeable in Arenoferralsol.
Author Keywords: Urea, Mineralization, Nitrification, Volatilization, Soil Respiration, Soils of Congo (DRC).
Volume 64, Issue 1, December 2022, Pages 14–24
Jared MATABA MPONGATE1 and Christophe LUMPUNGU KABAMBA2
1 Département de Gestion des Ressources Naturelles, Université de Kinshasa, BP 117 Kinshasa XI, RD Congo
2 Département de Gestion des Ressources Naturelles, Université de Kinshasa, BP 117 Kinshasa XI, RD Congo
Original language: French
Copyright © 2022 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
By this study, we evaluate, by incubation in the laboratory, the hydrolysis and the kinetics of mineralization of the urea used in Arenoferralsol and Ferralsol, as well as to appreciate, at the same time, the activity of microorganisms by the quantity of CO2 released over 15 days. In Arenoferralsol, the sharp rise in pH observed during the first 7 days of incubation denotes a strong hydrolysis of urea inhibiting the activity of microorganisms with, as a consequence, a low mineralization of nitrogen. The sharp rise in pH correlates with the massive volatilization of NH3 recorded during this time span. Beyond the 7th day, the decrease in volatile NH3 began, the resumption of microbial activity and the gradual increase in nitrification. On the other hand, in Ferralsol, it was recorded, in the same space of time, a weak rise in pH indicating a weak release of NH3, but, at the same time also a weak microbial respiration and a weak transformation of urea nitrogen. The pH, although raised to an average of 5.5, nevertheless remained strongly acidic. The drop in pH observed from the 11th day of incubation did not, however, stimulate the formation of NH4+-N and CO2, which still remained low. Thus, the NO3--N content experienced some increase. Hence, the conclusion that nitrification in this type of soil is very slow due to its high acidity. Taking into account the results observed in the two soils, nitrification as well as volatilization seem to be more active in Arenoferralsol compared to Ferralsol. Because, the acid state of Ferralsol as well as the quality of the organic matter combine to inhibit nitrification by destroying microbial life, especially those responsible for nitrification while progressive nitrification is noticeable in Arenoferralsol.
Author Keywords: Urea, Mineralization, Nitrification, Volatilization, Soil Respiration, Soils of Congo (DRC).
Abstract: (french)
Par cette étude, nous avons évalués, par incubation au laboratoire, l’hydrolyse et la cinétique de minéralisation de l’urée utilisée dans un Arénoferralsol et Ferralsol, ainsi qu’apprécier, par la même occasion, l’activité de microorganismes par la quantité de CO2 libéré pendant 15 jours. Dans l’Arénoferralsol, sableux (85,5%) à pH moyen de 5,38 et 6-17% d’argile, la forte montée de pH constatée les 7 premiers jours d’incubation dénote une forte hydrolyse de l’urée inhibant l’activité microbienne avec comme conséquence une faible minéralisation de l’azote. La forte montée du pH est en corrélation avec la massive volatilisation de NH3 dans ce sol sableux. Au-delà du 7ème jour, s’amorçaient la diminution de NH3 volatil, la reprise de l’activité microbienne et l’accroissement progressive de la nitrification. Par contre, dans le Ferralsol, à pH ± 4,5 et 76-84% d’argile, il a été enregistré, à 7 jour d’incubation, une faible montée de pH indiquant une faible libération de NH3 mais, en même temps aussi une faible respiration microbienne et une faible transformation de l’azote uréique. Le pH, quoique monté à une moyenne de 5,5 est, néanmoins, resté fortement acides, susceptible de neutraliser l’ammoniac. La chute du pH observée à partir du 11ème jour d’incubation n’a pourtant pas stimulé la formation de NH4+-N et CO2 demeurant toujours faible. Ainsi, la teneur en NO3--N a connu une certaine augmentation. Il découle de nos résultats que l’état acide du Ferralsol ainsi que la qualité de la matière organique se conjuguent pour inhiber la nitrification en détruisant la vie microbienne, surtout ceux responsables de la nitrification alors qu’une nitrification progressive est remarquée chez l’Arénoferralsol.
Author Keywords: Urée, Minéralisation, Nitrification, Volatilisation, Respiration du sol, Sols du Congo (RDC).
How to Cite this Article
Jared MATABA MPONGATE and Christophe LUMPUNGU KABAMBA, “Evaluation of ammoniacal volatilization and transformation of urea nitrogen in Arenoferralsol and Ferralsol from the DR Congo,” International Journal of Innovation and Scientific Research, vol. 64, no. 1, pp. 14–24, December 2022.
