MECHANISTIC PROCESS-LEVEL CROP SIMULATION MODELS FOR RESEARCH AND ON-FARM DECISION SUPPORT
Title: Uniformity of soil-plant-atmosphere-research chambers
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 8, 2009
Publication Date: October 1, 2009
Citation: Fleisher, D.H., Timlin, D.J., Yang, Y., Reddy, V., Reddy, K.R. 2009. Uniformity of soil-plant-atmosphere-research chambers. Transactions of the ASABE. 52(5):1721-1731.
Interpretive Summary: Soil-Plant-Atmosphere-Research (SPAR) chambers are a unique type of growth chamber technology that provides precise control over most aspects of plant growth and development. Due to their outdoor location and transparency to natural sunlight, such chambers are well-suited to global climate change and crop modeling research. However, this transparency to sunlight also makes it difficult to replicate experimental results. To ensure the highest quality plant research, it is critical to detect and characterize differences in SPAR chamber performance when multiple chambers are used. As an example, determining if plant growth responds the same exact way in all chambers. A study was conducted with wheat crop using 12 chambers with identical experimental conditions. The results of this study showed the necessity for using appropriate protocols and ways to improve sampling techniques within the SPAR chambers. These findings will benefit SPAR chamber researchers in the design and analysis of their experiments. Scientists can have additional confidence in the statistical conclusions obtained from experiments in these chambers.
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, MD. 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 locational effects within chambers at three different harvest dates. The patterning of variation within the SPAR chambers was primarily South to North and largely a response to radiation gradients, wind speed, and soil media settling. No significant differences among final chamber means for any plant response were found, and most values were within 95% confidence limits of the pooled chamber mean. Analysis of canopy radiation interception and photosynthetic responses indicated that differences among chambers were due to variation in establishment of leaf area. This variation was attributed primarily to differences in emergence rate, irrigation delivery, and media settling. Overall, this study indicated that, when appropriate, experimental protocols are followed and within-chamber positional effects are taken into account during sampling. Differences among chambers for plant responses are due to experimental treatment and not inherent differences in chamber performance.