Abstract
ABSTRACT This study aimed to estimate the size of blocks of observations of resistance to penetration, obtained by a motorized digital penetrometer, and the number of blocks with semi-amplitude of the confidence interval between 5 and 20% of the mean penetration resistance, for different soil depth ranges and cone diameters. Data were collected in two contrasting plots of a crop-livestock integration experiment, located in Abelardo Luz, SC, Brazil. Ten blocks were delimited and the resistance to penetration was determined in 20 points spaced by 20 cm, using a motorized digital soil penetrometer. To estimate the mean of resistance to penetration, 12 blocks of four points per experimental plot should be used for a semi-amplitude of the confidence interval equal to 10% of the mean (1 - p = 0.95). Twenty random points may be sampled to estimate mean of penetration resistance for a semiamplitude confidence interval of 10% of the man (1 - p = 0.95). The sample size for the layer of 0-10 cm is larger than in the deeper layers (0-20, 0-30 and 0-40 cm) and smaller for cones with larger diameter.
Highlights
Different grazing pressures may result in different levels of soil degradation, due to animal displacement patterns (Baggio et al, 2009)
The measurement of soil compaction using “penetrometers” allows the assessment of one of the important physical properties for management and evaluation of soil physical quality, since this property is related to various soil attributes (Tavares Filho & Ribon, 2008)
This study aimed to estimate the dimension of blocks of observation obtained by a motorized digital penetrometer and the number of blocks, with semi-amplitude of the confidence interval equal to 5, 10, 15 and 20% of the mean of the soil penetration resistance, in two contrasting environments, at different depths and diameters of the penetration cone
Summary
Different grazing pressures may result in different levels of soil degradation, due to animal displacement patterns (Baggio et al, 2009). Estimates of sample size aiming higher accuracy of research results have been published for different crops (Storck, 2011; Cargnelutti Filho et al, 2011; Storck et al, 2012; Benin et al, 2013). There are cases with less than 10 points (Silveira et al, 2010; Freitas et al, 2012; Moraes et al, 2012; Lima et al, 2013) and cases with 10 to 20 (Ralisch et al, 2008; Tavares Filho & Ribon, 2008), and others, with 16 (Coelho et al, 2012), 570 and 1333 (Mome Filho et al, 2014), 1111 (Roque et al, 2008), 7100 (Iaia et al, 2006) and 11,100 (Molin et al, 2012) points ha-1. The trend is that the standard error shows values between 5 and 15% of the mean without significant decreases in its values from 15 points on (Molin et al, 2012)
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