Slurry Distribution in Soil as influenced by Slurry Application Micro-rate and Injection Tool Type

The study of slurry distribution in soil following slurry injection is important for the design of an efficient injection tool, for the selection of injection tool spacing and for the reduction of slurry nutrient losses. In this research, two types of injection tools (sweep & furrower) were studied in laboratory conditions, and the same furrower and another type of injection tool (disc) were studied in field conditions over 3 years. For each injection tool, experiments were conducted with three slurry application micro-rates: r1 of 1·2×10−3 m3 m−1 tool−1; r2 of 2·4×10−3 m3 m−1 tool−1; and r3 of 3·6×10−3 m3 m−1 tool−1. To quantify slurry distribution in the soil following injection, image analysis technique was used in the laboratory study, while a manual tracing method was used in the field study. Slurry distribution in the soil was characterised by the parameters: lateral spread, vertical thickness and area of the slurry-soil mix zone. The lateral spread for a tool was recommended as the minimum tool spacing. A slurry distribution index was developed as an indicator of injection tool performance. The average values of the area of the slurry-soil mix zone, ranging from 6·5×103 to 18·0×103 mm2 tool−1, increased significantly with an increased micro-rate, as did for the average values of lateral spread and vertical thickness. The laboratory study showed that the sweep and the furrower resulted in similar characteristics of slurry-soil mix zone. The field studies showed the furrowers resulted in greater values of lateral spread, while the discs resulted in greater values of vertical thickness. The slurry distribution index indicated that at the low rate r1, the disc mixed slurry with the soil better, while at the higher rates r2 and r3, the furrower had a better performance.