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A penetrometer has been designed for field use to simulate the stresses exerted on the ground by the hoof of a walking cow, and to measure the resulting deformation of the soil. The extent of deformation produced by the penetrometer in two intact topsoils under pasture was found to be small and independent of water content, whilst significant correlations between soil strength and water content were obtained using a cone penetrometer and a hand-held shear vane. The results imply that the deep hoofprints associated with poached pasture are not produced immediately upon treading wet soil, but only after a progressive loss of soil strength due to repeated treading. Thus the rate of loss, which is deduced to be a measure of the susceptibility of pasture to poaching, cannot be estimated directly from a single measure of soil strength.

Abstract. A new method of measuring susceptibility to poaching is described, based on the concept that poaching is caused by a progressive loss of soil strength during repeated treading in wet weather. Susceptibility was measured by the rate of loss of strength in response to concurrent treading and irrigation at standard rates. The pressures exerted on the ground by a walking dairy cow were simulated by a purpose‐built penetrometer, whilst water was applied via a network of plastic pipes fitted with syringe needles. Measurements were performed on four pasture soils having a range of clay contents and compared in relation to a mechanism proposed for the process. The results show susceptibility to be a property not wholly determined by the clay content of the soil, but suggest that it is influenced by bulk density and the strength of the sward, which will van, according to weather and pasture management.

Pimaricin was added to samples from each of five crop species to give the following nominal rates of application: 0, 0.01 I , 0.022, 0.034, 0.045, 0.09 and 0.27 kg t fresh weight and the materials were ensiled in 100 g and 10 kg fresh weight quantities.Pimaricin applied at ensiling at 0.01 1 or 0.022 kg t 1 reduced aerobic deterioration in three of the five crops-ryegrass, lucerne and tall fescue; a much higher rate of 0.27 kg t was required with silages made from red clover and maize. This beneficial effect occurred even though only from 1-66?; of the pimaricin initially applied was recovered after the period of anaerobic storage in the silos. Pimaricin had no apparent effect on the course of fermentation nor on the composition of the silages, all of which were well preserved.

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