The Long View: Phenotyping for Enhanced Nitrogen Efficiency in Maize Genotypes without Destructive Sampling.

Maize phenotyping is essential for plant breeding selection or improving field management practices. However, the increasing intensity, complexity and cost of inbred or hybrid trials when the phenotyping trait emphasis goes beyond grain yield alone has become a large obstacle for plant breeding companies. Non-destructive sampling methods are always preferred in the field study to capture phenotype. Many previous studies addressed the possibility of using non-destructive sampling methods to predict grain yield in maize production. However, most of them are focused on using traditional non-destructive methods, such as leaf chlorophyll content (SPAD), leaf photosynthesis, leaf transpiration and respiration, leaf greenness, and leaf area index (LAI). Unfortunately, these measurements require large labor input , and the accuracy of measurements is highly dependent on the skills of the technician. New non-destructive sampling methods, include normalized difference visible index (NDVI), normalized difference water index (NDWI), canopy chlorophyll content (CCCI), thermal infrared (TI). However, those new techniques can be sensitive to the development stage at the time of measurements and to environmental condition, such as temperature, humidity. Hence, this study compared traditional and advanced non-destructive measurements in several fields located in Indiana. Traditional measurements includes SPAD, LAI. Destructive measurements involved periodic measurements of plant biomass and plant nitrogen concentration. Advanced measurements such as NDVI and CCCI will be evaluated for their ability to estimate leaf chlorophyll content (comparable with SPAD) and plant nitrogen concentration, leaf area index (compared with LAI in previous method) and plant biomass in trials with multiple hybrids and N rates.  Preliminary results on the cross validation of using traditional versus advanced measurements for N use efficiency and yield estimation will be discussed.