Soil Physical Indicators of a Sugarcane Field Subjected to Successive Mechanised Harvests

Abstract

Tillage intensity and successive harvesting before sugarcane replanting are practices that may result in the formation of compacted layers. Compaction alters soil structure and influence soil water retention, soil aeration and soil strength. Thus, this study was designed to assess the soil physical indicators associated with water, air and soil strength functions of a sugarcane field subjected to six successive mechanised harvests. The experiment was performed in 2018 in sugarcane fields from the Carpina sugarcane experimental station, Pernambuco, Brazil. In situ penetrometer measurements were made, and soil cores were sampled at depths of 0–0.20, 0.20–0.40, 0.40–0.60, 0.60–0.80 and 0.80–1.00 m for determination of soil penetration resistance, field capacity and soil bulk density. We calculated the degree of compaction, water capacity and air capacity of cultivated soil and compared the results with indicators of a native forest soil adjacent to the experimental area. The results showed that successive sugarcane cultivation declined the soil physical quality for plant development. Measurements showed that the deterioration of soil physical quality occurs mainly up to 0.40 m depth, which is a layer that undergoes tillage intervention and is susceptible to the formation of plough pan below the tillage depth. An increase in soil compaction, strength and loss of aeration capacity were the main sources of the decline in the soil physical quality. These soil physical factors are known to cause severe restrictions to root development and plant performance. The alleviation of soil compaction with subsequent monitoring of the impact of field traffic (e.g. through machinery and soil conduction controls) could help prevent the decline of soil physical quality in sugarcane areas.