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Abstract

This study evaluated compaction level of a 15-year old no-till vertisol field crop (40.91% clay, 44.16% loam and 14.93% sand) having organic matter contents of 2.23% and 2.91% in 0-10 cm and 10-20 cm profiles, respectively. The bulk density ranged from 1.30 g/cm 3 to 1.80 g/cm 3 in the field boundaries, and from 1.01 g/cm 3 to 1.40 g/cm 3 in its center. The field showed a gradient of limestone from 3% to 13%. Measurements were done to evaluate soil strength (cone index) and soil plasticity (Atterberg limits). The soil strength showed different levels of compaction from 4.5 MPa to 16 MPa to distinct five spatial clusters in the field. The soil compactness was related to limestone gradient according the correlation found between the soil strength and limestone levels. The soil plasticity test showed occurrence of plastic limits when the moisture content decreased from 26% to 15% within 5 d interval. The Atterberg limits showed the importance of respecting intervention delays to avoid soil compaction due to its plasticity. A pedotransfer function was developed using soil parameters of texture, organic matter, bulk density, cohesion, internal friction angle and moisture content to compute its precompression stress. Results showed importance of compaction in the field extremities due to importance of machines/tools traffic without avoiding cropping interventions during soil plasticity state. The soil strength (as measured value) was correlated to precompression stress (as estimated values) to show the importance of using pedotransfer function as significant method to evaluate indirectly compactness or susceptibility to compaction of the studied vertisol.