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THE INFLUENCE OF SAMPLE SIZE AND NUMBER ON THE PRECISION OF ESTIMATES OF HERBAGE PRODUCTION AND CONSUMPTION IN TWO GRAZING EXPERIMENTS
Author(s) -
Waddington J.,
Cooke D. A.
Publication year - 1971
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.1971.tb00642.x
Subject(s) - bromus inermis , elymus , forage , grazing , agronomy , confidence interval , biology , agropyron , zoology , mathematics , medicago sativa , yield (engineering) , poaceae , statistics , materials science , metallurgy
Estimates of forage production and consumption were made, using dry‐weight differences between samples from protected and grazed areas. Two sizes of cage for protecting areas from grazing were compared in four forages: brome grass ( Bromus inermis Leyss.)/Iucerne ( Medicago sativa L.); crested wbeatgrass ( Agropyron crista‐tum L.)/lucerne; intermediate wbeatgrass ( A. intermedium (Host.) Beauv.)/Iucerne; and Russian wild‐rye ( Elymus junceus Fisch.). Production, over a three‐year period, ranged from 1985 to 6286 kg/ha when estimated from 0.84 m 2 cages. Consumption ranged from 1584 to 5878 kg/ha. Yield estimates wben using 2.51 m 2 cages averaged 8% less than estimates from 0.84 m 2 cages. The number of caged sites needed in each plot to estimate a 95% confidence interval for annual production were 14 for four replicates, and over 30 for fewer replicates. Requirements for consumption estimates were similar. To estimate production within a 90% confidence interval 19, 10 and 4 caged sites were required from two, three, and four replicates, respectively. Consumption estimates within tbis confidence interval required 22, 10, and 5 samples from two, tbree, and four replicates, respectively. Caging requirements were tbe same for all combinations of plot size and forage species. Large cages increased precision sligbtly wben used on Russian wild‐rye, probably because the forage was in rows 0.91 m apart.