Efficiency of Glasshouse Pot Experiments Rotating versus Stationary Benches

Abstract

Pot cultures of rice (Oryza sativa L., var. Colusa) in flooded soil were used to measure comparative uniformity of growth where mutual shading was the primary source of variation. Data were analyzed according to various divisions of each layout into blocks, sections, and replicate pots to compare statistical effi-ciencies. Experiments on stationary benches were subject to large border effects that were not suitably compensated for by any of the systems of replication tested. On the turntable, which carried 24 pots in single file, all plans of analysis tested were acceptable and resulted in coefficients of variability ranging from 2.5 to 4.5%. Consideration of these results, along with the cost of increased replication and the fact that use of a turntable minimizes the effects of environmental variability inherent in greenhouses , leads to the conclusion that the turntable provides more efficient use of greenhouse space for precision experiments than do stationary benches. Rotating circular benches (turntables) have been used for growing plants but have never become common, partly because of the space they occupy. Their efficiency appears not to have been evaluated statistically. Efficiency is involved in two ways: (a) On stationary benches, border effects and uncontrolled variables inherent in glasshouses necessitate a large number of replicates, whereas on turntables replication may be minimized , thereby limiting space requirements. (b) Some costs vary with the number of cultures, particularly labor and the investment in culture equipment. A technique suggested by Cox and Cochran (1) is to leave "sufficient space between pots to mitigate the effects of inter-pot competition." This procedure may reduce environmental variability due to mutual shading, but it increases space requirement .