Abstract

The objective was to estimate the sample size (number of points by experimental plot) to estimate soil resistance to penetration in different depth ranges and for different animal stocking density rates. The data was obtained from a factorial experiment in a randomized block design, three replicates, consisting of two grazing intensity levels (canopy heights: 10 and 20 cm) and two levels of nitrogen fertilization applied on the coverage (0 and 200 kg N ha^-1) in the form of urea. The penetration resistance (PR) of the soil was achieved in 20 points randomly determined inside each experimental unit (paddock). A "Motorized soil penetrometer" was used (DLG, Model PNT-2000-M). The PR average values were determined for the depth range of the soil (characters): 00-40, 00-10, 10-20, 20-30 and 30-40 cm. For the same estimation error of the soil's penetration resistance, the sample size (number of points) depends on the depth range of soil and animal stocking density. In experiments with varying animal stocking density rate on pasture in winter, 15 points per experimental unit are sufficient to estimate the average with an estimation error of 15% of the average soil penetration resistance.

Key words: Sample size, grazing pressure, crop-livestock integration, soil depth.