Evaluating cotton response to free‐air carbon dioxide enrichment with canopy reflectance observations

Abstract

Most approaches for monitoring plant growth and development have serious drawbacks which limit their use in agricultural research programs. First of all, traditional methods for measuring above-ground green leaf area index (LAI) and biomass are very labor intensive, tedious and time consuming to execute. The size, number and frequency of samples required to characterize the plant canopy and detect statistically significant differences between treatments are usually large and often not practicable because of constraints on labor and space for cold storage and oven drying. Destructive sampling techniques are usually not appropriate in small research plots because the removal of some individuals from the population alters the response of remaining plants. Furthermore, the time required for physically separating leaves from stems and measuring them with a leaf area meter or waiting for tissues to dry in an oven precludes the use of these data in real-time decision making processes. Thus, important information that has immediate utility for assessing the efficacy of different treatments, identifying incipient problems, or guiding future sampling efforts is typically not available until several days or weeks after the samples have been collected. Non-invasive, remote sensing techniques which use plant canopy reflectance to monitor changes in canopy conditionmore » avoid these problems while providing scientists with an efficient tool for research and management of their projects. 19 refs., 9 figs., 10 tabs.« less