Using Hemispherical Radiation Measurements to Predict Weight-Related Growth Traits in Oilseed Rape (Brassica napus L.) and Barley (Hordeum vulgare L.) Canopies

Methods for determining growth traits in the field are mostly work-intensive and/or often erroneous. Further development of multi-temporal techniques of growth analyses provided by fast and non-destructive tools for monitoring canopy properties may result in a substantial gain for practical use. Among them, the LAI-2000 Canopy Analyzer can be used to determine the canopy area index (CAI) resulting from radiation measurements. In plant breeding, single-date measurements were usually made across a wide number of genoptypes. In contrast, multi-temporal information on canopy status is needed in agronomy. In our study, data of the CAI based on hemispherical radiation measurements with the LAI-2000 were used to estimate developmental courses of weight-related growth traits. For this purpose, seasonal courses of shoot fresh matter, shoot dry matter, shoot N and water content and CAI of winter oilseed rape (Brassica napus L.) and spring barley (Hordeum vulgare L.) were investigated simultaneously in field experiments from 2002 to 2006 in northern Germany with and without nitrogen (N) fertilization. Courses of 2003 and 2004 were used to calculate relationships between CAI and growth traits. Results show that each of the weight-related growth trait is related to the CAI. In this mechanistic approach relationships were found gathered across 2 years, two N-treatments and several growth stages being unaffected by N-fertilization, cultivar and experimental year. These relationships were verified using independent data sets of the years 2005 (winter oilseed rape and spring barley) and 2006 (winter oilseed rape). The results of the current study show that the use of LAI-2000 and its rapid and non-destructive determination of weight-related growth traits over the entire growth period will substantially improve the determination of weight-related growth traits in agriculture.