Analysis of rice sample size variability due to development stage, nitrogen fertilization, sowing technique and variety using visual jacknife
Articolo
Data di Pubblicazione:
2006
Citazione:
Analysis of rice sample size variability due to development stage, nitrogen fertilization, sowing technique and variety using visual jacknife / R. Confalonieri, D. Stroppiana, M. Boschetti, D. Gusberti, S. Bocchi, M. Acutis. - In: FIELD CROPS RESEARCH. - ISSN 0378-4290. - 97:2-3(2006), pp. 135-141. [10.1016/j.fcr.2005.09.008]
Abstract:
The determination of sample size before collecting experimental data is fundamental to obtain reliable estimates of variables describing
agroecosystem development. In order to analyze the influence of experimental factors (artificially-induced variability) on rice sample size, an
experiment was carried out in 2004 in northern Italy. In particular, different sample size determinations were carried out for different
fertilization levels, varieties (Indica and Japonica type), development stages, sowing techniques and typologies of the sampling unit. The
obtained sample sizes were compared to investigate the influence of each factor, keeping the others constant (for example, we have compared
the sample sizes computed for different fertilization levels within the same variety, the same phenological stage and the same sampling unit).
Since original data were often not normally distributed and the variances of the original samples were not homogeneous, a new approach for
sample size determination based on a visual evolution of the jackknife was preferred to classical techniques.
Results (expressed as number of plants) showed that (i) sample sizes computed in an early phenological stage (between 21 and 27) are
higher than those calculated for later stages (15–21); (ii) fertilization hides soil N content variability with the consequence that larger sample
sizes are required for unfertilized plots (21–27) compared to fertilized plots (15–27) and (iii) for the early sampling, the Indica type variety
required larger sample size (always 27) with respect to the Japonica type variety (21–24). For row-seeded rice, the number of plants instead of
linear centimeters as the sampling unit led to lower sample sizes (18–27 versus 30–33). These results highlight the influence of experimental
factors and development stage on within-plot variability, and therefore the importance of preliminary samplings for sample size
determination
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Resampling; Sampling unit; Experimental design; Sample size determination; Sampling technique; Preliminary sampling
Elenco autori:
R. Confalonieri, D. Stroppiana, M. Boschetti, D. Gusberti, S. Bocchi, M. Acutis
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