Uniformity of Soil-Plant-Atmosphere-Research Chambers

Abstract

Uniformity of plant responses and gas exchange calculations within and among Soil-Plant-Atmosphere Research (SPAR) chambers was evaluated using 12 SPAR chambers located at Beltsville, Maryland. Periodic non-destructive and destructive measurements were conducted at the same locations within each chamber using wheat (Triticum aestivum L. cv. USU-Apogee) as the crop. Identical experimental protocols were applied to each chamber. Analysis of variance indicated significant location effects within chambers at three different harvest dates. The patterning of variation within the SPAR chambers was primarily south to north and appeared to be a response to wind speed, radiation gradients, and soil media settling. Analysis of canopy radiation interception and photosynthetic responses indicated differences in early leaf area establishment among chambers. This result can be attributed primarily to variations in emergence rate, irrigation delivery, and media settling. However, no significant differences among final chamber means for any plant growth response were found, and most values were within 95% confidence limits of the pooled chamber mean. Overall, this study indicated that although differences in among-chamber and within-chamber variability were present, when appropriate experimental protocols are followed and within-chamber positional effects are taken into account during sampling, effects of inherent differences in chamber performance on plant responses can be reduced.