The Rewetting of Partially Dried Grass Swaths by Rain: Part 4, Measurement of Leaching Losses

Abstract

Runoff water collected in laboratory experiments with simulated rainfall on partially dried grass samples was analysed to estimate the extent of leaching losses which occur when rain falls on partially dried swaths in the field. Loss levels varied between grass samples, and between runoff water samples taken at different stages of rewetting on the same grass. Results showed a tendency towards higher losses from initially drier grass swaths, and higher losses from conditioned compared to unconditioned grass, but not in a very consistent manner. The distributed model of the rewetting process was used to attempt to explain variations in losses over time. A leaching loss relationship for use in Operational Research models of forage conservation is suggested; this represents the main trends shown in the results with regard to variation in loss with swath moisture content and conditioning, but not the random variation arising for unknown reasons.