Methods for determining the presence of slurry on the crop and in the upper soil layer after application to grassland

Slurry injection in grassland may lead to lower ammonia losses and enhance silage quality compared to surface spreading. In order to evaluate the performance of different slurry injectors, there is a need for methods which measure the degree of crop contamination and the position of the slurry in the soil after spreading. The aim of this study was to identify and test possible methods. The amount of cattle slurry present on the grass stubble after spreading was determined by measuring the electrical conductivity of water used for rinsing grass samples. The slurry placement in the soil profile was measured in cross-sections made through the slurry trails. Methods used were analyses of images taken by different cameras, resistance measurements and by measuring the dimensions of the slurry trails. The method for determining the presence of slurry on the crop was practically applicable and is considered to be reliable. The placement of slurry could not be sufficiently resolved from image taken by the different cameras or by measuring resistance. Instead, visual assessment and measurements of width and depth of the slurry trails gave a good description of the slurry placement in the soil profile.