Soil fertility can be evaluated by several methods, such as field or greenhouse tests with plants. In greenhouse studies with untilled soils the sampling of undisturbed soil cores is difficult. The aim of this study was to propose an equipment for undisturbed soil core sampling of untilled soils for greenhouse studies and test its efficiency. A sampler with a diameter of 200 mm and depth of 300 mm was developed. The soil penetration resistance and density of the soil and within the sampler were compared. Soil was sampled at four sites with different clay contents: an Acrisol, at the UFRGS Agronomic Experimental Station (Lat. S 30 º 05 ' 42 " and Long. W 51 º 40 ' 32 "), in Eldorado do Sul; an Oxissol in a crop production area (Lat. S 28 º 44 ' 17 " and Long. W 53 º 41 ' 54 ") in Cruz Alta; an Oxissol in a crop production area (Lat. S 28 º 19 ' 55 " and Long. W 53 º 55 ' 54 ") in Ijuí; and an Oxissol in a crop production area in São Miguel das Missões (Lat. S 28 º 55 ' 53 " and Long. W 54 º 20 ' 47 "). The results did not differ statistically for soil penetration resistance and soil density at each site and sampling depth. The proposed methodology can be used to collect undisturbed soil samples in greenhouse studies with untilled soils.
penetration resistance; compaction; soil bulk density
