Rufyikiri, Gervais
[UCL]
Dufey, Joseph
[UCL]
Hennebert, PA.
Solutions collected from lysimeters of acid soils can show pH values close to or even above neutral. Laboratory experiments on an acid soil from Burundi were planned to test if denitrification or CO2 degassing might explain such a paradox. In the first experiment, soil profiles were reconstituted in columns and leached with 55 mu M Ca(NO3)(2) solutions at 30 degrees C and 4 degrees C. Two drainage regimes were applied: intermittent suction or no suction at the bottom of the columns. In the second experiment, pH values were measured in solutions drained from different horizons at 30 degrees C, before and after equilibration with ambient air. Sterilized soil was also tested in the same way. Results from experiment 1 showed that despite the accumulation of water in the bottom of soil profiles when no suction was applied, aeration still existed so that reduction reactions, namely denitrification, are not expected to affect greatly the percolate composition. Indeed nitrate concentration was similar in both drainage regimes and was close to the input value. The pH values in percolates were close to 7 at 30 OC and they dropped to about 5.5 when the columns were at 4 degrees C. In experiment 2, equilibration of percolates with ambient air resulted in pH increase which was greater for the top horizon (C-rich) but negligible when the soil was first sterilized. These convergent results illustrate the very important effect of CO2 degassing on pH of drained solutions when microbial activity is stimulated at high temperatures, in C-rich soil. This is of prime importance when interpreting results from lysimeter experiments. By chance, this study also showed that large quantities of nitrate can be produced in soil at low temperatures.
- Addiscott, Farming, Fertilizers and the nitrate problem. (1991)
- Broadbent, Soil Science Society of America Proceedings, 30, 692 (1965)
- Castelle, Soil Science Society of America Journal, 54, 252 (1990)
- Durand, Science du Sol, 3, 217 (1980)
- Fernandez, Soil Science Society of America Journal, 51, 261 (1987)
- Gupta, Predicting tillage effects on soil physical properties and processes, 151 (1982)
- Gunn, Catena, 9, 81 (1982)
- Hillel, Introduction to soil physics (1982)
- Kissel, Soil Science Society of America Journal, 41, 346 (1977)
- Lindsay, Chemical equilibria in soils (1979)
- Linn, Soil Science Society of America Journal, 48, 1267 (1984)
- Low, Plant and Soil, 33, 393 (1970)
- Marion, Freeze-thaw processes soil chemistry (1995)
- Marion, Soil Science Society of America Journal, 51, 1501 (1987)
- McLaren, Soil Science Society of America Proceedings, 36, 602 (1972)
- Nielsen, Soil Science Society of America Proceedings, 25, 1 (1961)
- Neilson, Soil Science Society of America Journal, 54, 428 (1990)
- Roose, Dynamique actuelle des sols ferrallitiques et ferrugineux tropicaux d'Afrique Occidentale. Etude expérimentale des transferts hydrologiques et biologiques de matières sous végétation naturelles ou cultivées (1981)
- Ross, Journal of Environmental Quality, 19, 108 (1990)
- Rufyikiri, Strategies for the management of upland soils of humid and subhumid tropical Africa (IBSRAM/AFRICALAND), 107 (1994)
- Saad, Biology and Fertility of Soils, 15, 21 (1993)
- Smith, Soil Science Society of America Journal, 58, 1652 (1994)
- Soil Survey Staff, Keys to Soil Taxonomy (1990)
- Suarez, Water Resources Research, 22, 876 (1986)
- Suarez, Soil Science Society of America Journal, 51, 64 (1987)
- Van Breemen, Soil Science Society of America Proceedings, 38, 55 (1974)
- Zabowski, Soil Science Society of America Journal, 55, 1456 (1991)
Bibliographic reference |
Rufyikiri, Gervais ; Dufey, Joseph ; Hennebert, PA.. Interpreting pH and nitrate concentration in solutions drained from acid soils. Possible artefacts of lysimeters. In: Soil Use and Management, Vol. 15, no. 4, p. 208-212 (1999) |
Permanent URL |
http://hdl.handle.net/2078.1/43673 |