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Experimental Design Factors Affecting Error Variation in Orchardgrass
Author(s) -
Casler M. D.,
Tageldin M. H.
Publication year - 1996
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1996.00021962008800050011x
Subject(s) - dactylis glomerata , mathematics , forage , dry matter , randomized block design , statistics , split plot , field experiment , yield (engineering) , neutral detergent fiber , agronomy , standard error , zoology , poaceae , biology , metallurgy , materials science
Several experimental design factors over which the researcher has control may affect the precision of field experiments. The objective of this experiment was to identify the effects of changing plot size, incomplete block size, and incomplete block shape on precision of forage yield and quality estimates in orchardgrass ( Dactylis glomerata L.). Orchardgrass seed was planted uniformly into 288 plots of various sizes. Forage yield, in vitro dry matter digestibility (IVDMD), and neutral‐detergent fiber (NDF) were determined over a 2‐yr period. Error variances ( V w ) were computed for variously sized incomplete blocks (in one or three strips and from 1 to 12 plots strip −1 ) within each plot size and expressed as log( V w ). Values of log( V w ) for IVDMD and NDF concentration were unaffected by experimental design factors. Values of log( V w ) for forage yield increased with increasing number of plots per strip, but these effects varied among plot sizes and for one‐ vs. three‐strip blocks. Three‐strip blocks had a mean log( V w ) 71% greater than one‐strip blocks, an effect that could be offset only by doubling the number of replicates in a field test. To obtain maximum precision in cases where a large number of replicates impossible or impractical, orchardgrass field experiments should employ incomplete block designs, particularly when limited seed stocks or land requires a plot size near 1.4 m 2 . Incomplete block designs with this plot size should not contain multiple strips within incomplete blocks.