Effect of compaction and trash blanketing on rainfall infiltration in sugarcane soils

Abstract

Efficient use of incident rainfall and irrigation water forms an important feature of sustainable sugarcane farming systems. This study reports the effects of trash management, row spacing and soil compaction on soil hydraulic properties and the infiltration of simulated rainfall in the field at Bundaberg in Queensland, Australia. Trash blanketing has significantly increased concentrations of total and labile C in the surface 30-50 mm of the soil profile, resulting in increased aggregate stability and a reduction in surface crusting under high intensity rain. Infiltration through a developing surface crust was shown to increase more than 3-fold in response to increasing labile C on Red Ferrosols. Despite these advantages being further reinforced by the protection offered by the trash blanket, infiltration capacity of Red and Yellow Podzolics and Red Ferrosols under trash blanketing in the field was either similar or only marginally improved relative to that on bare, low C soils in burnt cane systems. This lack of improvement can be directly linked to soil compaction and the resultant loss of macroporosity, and the high proportion of the ground surface trafficked during harvest under the current farming system. Hydraulic conductivity of the inter-row area fell to less than 10% of that directly under the cane row after harvest of the plant cane crop. Ripping the inter-row area after harvest increased infiltration capacity significantly, but the extent varied with soil type. Closer matching of crop row spacings to harvester wheel spacings (e.g. 1.8 m dual rows) was shown to have a relatively minor impact on infiltration capacity due to the wheel traffic patterns of haulout operators. These results highlight the severe impact of compaction on soil hydraulic properties in the cane industry. They suggest a reduction in efficiency of capture of incident rainfall and irrigation water for crop growth, constraints to irrigation water management and greater risks of runoff and erosion from canelands. Effects on drainage and aeration in wetter environments require investigation.