Abstract
Leaf Area Index (LAI) is an important plant parameter for both farmers and plant scientists to monitor and/or model the growth and the well-being of plants. Since direct LAI measurement techniques are relatively laborious and time-consuming, various indirect methods have been developed and widely used since the early 1990s. The LP-80 ceptometer uses a linear array of PAR (photosynthetically active radiation) sensors for non-destructive LAI measurements that is backed by 15 years of research. Despite this, considerable discrepancy can be found between the expert opinions regarding the optimal illumination conditions recommended for the measurement. The sensitivity of ceptometer-based LAI values to PAR was investigated, and a simple method was devised to correct raw ceptometer data collected under non-ideal light conditions. Inadequate light conditions (PAR < 1700 µmol m−2 s−1) could cause an underestimation of LAI. Using the corrected LAI values, the ceptometer data showed a significantly better fit (higher R2, smaller mean average error and closer to zero mean signed error values) to the destructive LAI data for both wheat and maize. With the help of the correction equations, the use of the LP-80 ceptometer could be extended to days when light conditions are not ideal.
Highlights
Leaves represent the largest portion of the canopy surface of field crops and are the primary interface for energy and mass exchange between the atmosphere and plants
Values to photosynthetically active radiation (PAR) was investigated, and a simple method was devised to correct raw ceptometer data collected under non-ideal light conditions
With the help of the correction equations, the use of the LP-80 ceptometer could be extended to days when light conditions are not ideal
Summary
Leaves represent the largest portion of the canopy surface of field crops and are the primary interface for energy and mass exchange between the atmosphere and plants. Significant processes, such as canopy light interception, element deposition, transpiration, respiration and assimilation, are directly proportional to the surface of leaves. LAI is the ratio of the total, one-sided leaf surface area of the canopy and the ground area below the canopy These parameters are important for both farmers and plant scientists to monitor the growth and well-being of plants [1] and are especially important for crop modelers for scaling up the leaf and plant level processes to canopy level [2,3]. The direct measurement methods are considered to be the most accurate, and usually serve as a standard for validating the indirect methods [5], though in some cases newly developed instruments are compared to well-performing and thoroughly tested indirect methods [6,7]
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