CHEMICAL AND MINERALOGICAL PROPERTIES OF AGRICULTURAL LOESS SOILS IN VITRO ACIDIFIED

LAURA ANTONELA ITURRI; DANIEL EDUARDO BUSCHIAZZO

Nueva York

Conferencia; 9th Acid Rain Conference; 2015

University of Illinois

Agricultural loess soils of the Pampas show some evidences of an incipient acidification process, linked with both climatic conditions and N-fertilization. An in vitro study was developed to know how will be the future trends of soils if N-fertilization continues. An equivalent amount of H+ to those produced by a constant application of 84 kg N ha-1 year-1, the most frequent N dose applied in these soils, during 1, 10, 30 and 50 years were performed over samples from the topsoil of four Mollisols placed in a climosequence. Mostly H+ additions did not modify CEC nor the contents of both amorphous- and crystalline Al-, Mn- and Fe oxides. However, the most acidified treatments of soils placed in the transition zone of the climosequence (Hapludolls) showed decreases in phyllosilicates crystallinity. This effect was not so pronounced in soils placed in both the moist- and the driest extreme of the sequence, due to the abundance of buffer substances. Soils of the driest extreme (Haplustolls) will be the less affected soils by acidification because the presence of high amounts of both free lime- and soil organic matter as well as by the smectitic mineralogy of the soil-size fractions. Soils of the moist extreme of the climosequence (Argiudolls) are the soils with better neutralizing mechanisms, due to the high contents of both soil organic matter and soil-size fractions, though illitic. Hapludolls would be the soils with the highest risk to acidification if N-fertilization continues at similar doses as those was used in this study, because both the quantity- and the quality of the buffer substances prevailing.