Impacts of compaction relief treatments on soil physical properties and performance of sugarcane (Saccharum spp.) under zonal tillage system

An on-farm experiment was conducted at Ramu sugarcane plantation of Papua New Guinea to assess implications of alleviating soil compaction in wheel tracks under the zonal tillage production system. Under zonal tillage system only the row area is cultivated in preparation for planting the sugarcane sett and the inter-row area remains undisturbed and much compacted. Three soil tillage treatments were imposed to wheel tracks formed after planting sugarcane genotype Q198 in 2004. Treatments involved, ripping the soils in the compacted wheel track zones (with a pair of rippers), ripping and hilling the compacted soil to cane rows (with the hilling boards attached to the rippers) and a control. Millable cane and sugar yields were monitored for the plant-cane (2005) and subsequent 3 ratoonsʹ (2006, 2007 and 2008). Millable cane yield and sugar yields were found to be consistently (in four crop cycles) and significantly (P < 0.05) higher in ripping and hilling treatment than the ripping and control. Millable cane yield production of plant-cane and three ratoonsʹ (cumulative) in ripping and hilling treatment was 21% greater than the control plots and sugar yields were greater by almost 6.75 t ha− 1, which was 24.5% higher than the control. Soil physical investigations revealed that cane rows in ripping and hilling treatment had significantly (P < 0.05) lower soil bulk density of 1.21 g cm− 3 in the first 30 cm soil depth compared to the 1.37 g cm− 3 in ripped and 1.39 g cm− 3 in control plots. Ripping and hilling the wheel tracks significantly (P < 0.05) decreased the penetration resistance in cane rows by 29%. Beneficial effects of ripping and hilling of compacted wheel tracks was attributed to the appreciable improvement in the water infiltration rates in cane rows and consequent enhanced sub-surface (10–30 cm) moisture storage.