Soil compaction is a major factor affecting soil quality and crop growth. The objective of this study was to determine the degree of compaction that restricts soybean growth in a Latossolo Bruno alumínico típico (Oxisol). The experiment was conducted in a greenhouse, and the soil used was collected in Guarapuava, PR, Brazil, from the 0-20 cm layer. The soil consisted of 570 g kg-1 of clay, 370 g kg-1 of silt, and 60 g kg-1 of sand. The soil was artificially compacted to obtain bulk densities of 0.90, 0.96, 1.02, 1.08, 1.14, 1.20, and 1.27 kg dm-3, corresponding to degrees of compaction between 75 and 105 %, which was determined from the ratio between the current bulk density and maximum bulk density obtained from the Normal Proctor test. Root and shoot growth were determined during soybean cropping, as well as daily evapotranspiration. The dry matter of roots and shoots was determined at 60 days after emergence. Any increase in the degree of compaction above 75 % reduces root growth in the compacted layer, and roots do not grow when the degree of compaction is 105 % or more. Plant height decreases when the degree of compaction is greater than 82 %, and shoot dry matter and evapotranspiration reduce when the degree of compaction is over 87 and 93 %, respectively. Thus, the degree of compaction restrictive to the soybean crop depends on plant characteristic being measured.
soil compaction; plant dry matter; root development; evapotranspiration
