Soil penetration resistance mapping quality: effect of the number of subsamples

• Published in: Acta scientiarum. Agronomy Vol. 40; no. 1; pp. 34989 - e34989
• Main Authors: Pias, Osmar Henrique de Castro, Cherubin, Maurício Roberto, Basso, Claudir José, Santi, Antônio Luis, Molin, José Paulo, Bayer, Cimélio
• Format: Journal Article
• Language: English
• Published: Maringa Editora da Universidade Estadual de Maringá - EDUEM 01-01-2018; Eduem (Editora da Universidade Estadual de Maringá)
• Subjects: AGRONOMY; Deviation; Mapping; microvariability; Penetration; Penetration resistance; precision agriculture; Sampling; sampling protocol; soil compaction; Soil mapping; Soil resistance; precision agriculture; microvariabilidade; sampling protocol; agricultura de precisão; microvariability; compactação do solo; soil compaction; protocolo amostral
• ISSN: 1679-9275; 1807-8621; 1807-8621
• DOI: 10.4025/actasciagron.v40i1.34989

There is no consensus in the literature regarding how many subsamples are needed to perform accurate on-farm soil penetration resistance (SPR) mapping. Therefore, the objective of this study was to define the number of subsamples per sampling point needed to quantify the SPR. The experiment was performed in a 4.7 ha area and employed a 50 × 50 m grid system (18 sampling points). The SPR was evaluated using a digital penetrometer in two different years with 1, 2, 3, 4, 5, 6, 9, 12, and 15 subsamples per sampling point. The SPR maps produced with increasing numbers of subsamples were compared to the reference maps (15 subsamples) using the relative deviation coefficient and Pearson´s linear correlation. A reduction in the number of subsamples promoted an increase in the variability of the SPR data. Generally, the results from this study suggest the use of at least four subsamples per sampling point to achieve SPR maps with a coefficient of relative deviation less than 10% (30% maximum error per point around the mean) and significant correlation with the reference maps (15 subsamples).