Evaluation of Cattle Excreta on Pasture Fertility : I. The excretal dispersion models and their applicable conditions

Abstract

The dispersion characteristics of heifer excreta on pasture were investigated and described quantitatively. Dispersion patterns were examined by fitting the theoretical distributions to the observed excretal frequency distributions and by MORISITA's I_δ-index. The results obtained were as follows: 1) Most of the excretal clumps of 2-8a were formed by the effect of grazing equipments, e.g., watering place and salt racks. Excretal dispersion including these clumps were more aggregated, and when these clumps were removed they became less aggregated. 2) Frequency distributions of excreta per quadrat were described by the Poisson or the negative binomial models after the significant clumps caused by grazing equipments were removed. 3) When significant clumps caused by grazing equipments were removed, applicable conditions of the two kinds of models were divided into three parts by the relationship between the quadrat size and the mean density of dung and urine as shown in Fig.4, and the 'common k' of the negative binomial model estimated on dung was 4.40 (confidence limits: 4.00-4.88).