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Aggregation studied by laser diffraction in relation to plowing and liming in the Cerrado region in Brazil |
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| Authors: | R Westerhof P Buurman C van Griethuysen M Ayarza L Vilela and W Zech |
| Institution: | a Institute of Soil Science and Geography, University of Bayreuth, 95440 Bayreuth, Germany b Department of Soil Science and Geology, Agricultural University, PO Box 37, 6700 AA Wageningen, the Netherlands c Centro Internacional de Agricultura Tropical (CIAT), Apartedo Aereo 6713, Cali, Colombia d Centro de Pesquisa Agropecuária dos Cerrados (EMBRAPA-CPAC), CxP 08223 Br20 Km18 73301-970 Planaltina (DF) Brazil |
| Abstract: | In the Cerrado savanna region in Brazil, the effects of different land use on Oxisol aggregation were studied using laser diffraction grain size analyses. The topsoil of plowed systems had significantly lower amount of macroaggregates (2000–194 μm) and a significantly higher amount of soil in the microaggregate size and primary particle fraction (<76 μm) compared to pastures and the native Cerrado. In plowed systems low in soil organic carbon (SOC), lime had a negative effect on aggregate stability. Lime addition had no effect on topsoil aggregation in land use systems that were not plowed regularly and generally had a higher SOC content. For all the studied topsoils, pHKCl was positively correlated with the amount of clay dispersed after 3 h of shaking in water. SOC did not influence clay dispersion in the range of soils studied. In continuous cropping systems in the Cerrado region, with a combination of mechanical stress and low SOC, liming will cause an increase in small aggregates and primary particles and hence contribute to a destabilization of the soil structure. |
| Keywords: | aggregates laser diffraction grain size analyses lime Oxisol water dispersible clay |
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