Counting Fired Leaves: A Potential Method for Evaluating Nitrogen Sufficiency in Grain Sorghum

1. Counting Fired Leaves: A Potential Method for Evaluating Nitrogen Sufficiency in Grain Sorghum Antonio R. Asebedo and David B. Mengel Department of Agronomy, Kansas State University, Manhattan, KS, USA Email: ara4747@ksu.edu Results Cont. Objectives • Evaluate the relationship between fired leaf percentage, leaf Nitrogen (N) content, Red Normalized Difference Vegetation Index (NDVI), and grain yield in grain sorghum. • Determine if counting fired leaves could serve as an additional method to evaluate nitrogen status in grain sorghum. Materials and Methods • Plots were established at Salina, Manhattan, Partridge, Randolph, Belleville, and Ottawa, Kansas in 2010 and 2011. • A randomized complete block design with four replications was used. • Six N rates were used in 2010 and five N Rates in 2011; 0, 34, 67, 101, 134, 168 kg N ha-1. • N was broadcast applied as urea or coulter banded as UAN at the 2 leaf stage. • Fired leaf counts were taken at growth stage (GS) 4, GS5 and GS6. • Total number of fired leaves were determined from 10 plants per plot. • Fired leaf percentage = total number of fired leaves/total number of leaves on the plant. • 3rd leaf samples were collected at GS6 during 2010. • 3rd leaf down from the flag leaf was collected from 20 plants per plot. • Flag leaf samples were collected at GS6 during 2011. • Flag leaves were collected from 20 plants per plot. • Flag leaf analysis data is not yet available. • Red NDVI readings were taken using Ntech Industries’ Greenseeker sensor. • Readings taken at GS3 during 2010 and GS3, GS4, and GS6 during 2011. • Yields were hand harvested and adjusted to 130 g kg-1 moisture content. • 2011 locations’ yield data is not yet available. • Statistical differences analyzed with SAS at alpha = 0.05 using proc glm. Figure 5. 2010 Relative Yield vs. Fired Leaf % Figure 6. 2010 Relative Yield vs. 3rd Leaf N % Figure 7. 2011 Red NDVI vs. N Rate by GS Figure 8. 2011 GS6 Red NDVI and Fired Leaf % Results Figure 10. 2011 Manhattan, KS 134 kg ha-1 Figure 9. 2011 Manhattan, KS 0 kg ha-1 Figure 1. 2010 Salina, KS 0 kg ha-1 Figure 2. 2010 Salina, KS 168 kg ha-1 Conclusions • There is a strong correlation between fired leaf percentage, Red NDVI, leaf N content, N rate, and grain yield when N is the limiting factor. (Figures 4-8) • Counting fired leaves could serve as an additional method for evaluating the N status in grain sorghum, however additional site years are needed to make an adequate algorithm for N recommendations. Acknowledgements • We would like to thank the United Sorghum Check-off Program and the Kansas Grain Sorghum Commission for supporting this work. • We would also like to thank fellow graduate students Jason Matz and Matt Wyckoff, and assistant scientist Garry Harter for their assistance in field. Figure 3. N deficiency symptoms Figure 4. 2010 Pearson Correlations