Spatial complexity of soil plow layer penetrometer resistance as influenced by sugarcane harvesting: A prefractal approach

Sugarcane is one important crop for many Third World countries. Soils dedicated to sugarcane are usually compacted during the harvesting process. The main objective of the present work was to search for prefractal scaling patterns of soil compaction before and after sugarcane harvest. We used descriptive statistics and prefractal analysis with experimental semivariograms for characterizing the spatial patterns of soil penetrometer resistance distributions. The soil is a Vertisol (Typic Hapludert) dedicated to sugarcane production during the last 60 years. Approximately 50% of soil resistance values were over 2.5 MPa after sugarcane harvest. This could restrict sugarcane shoot emergence. A power-law (prefractal) model fitted experimental semivariograms fairly well except for those distributions corresponding to 2.5–5.0 cm soil depth. Those particular distributions could be fitted by any standard geostatistical model. The main findings were (i) scaling exponents larger than 1.5 which indicate anti-persistence and (ii) change of anisotropic directions after sugarcane harvest. The range of prefractal behaviour was approximately 105 m before harvest and 93 m after crop harvest. The spatial structure of some soil physical or mechanical properties connected to soil compaction can resemble those patterns. The combination of Geostatistics and prefractal analysis can assist the mechanized agriculture and scientists through a previous identification of degraded zones within the field and the physical processes involved in the formation of those local areas.