Counting Fired Leaves: A Potential Method for Evaluating Nitrogen Sufficiency

in Grain SorghumAntonio R. Asebedo and David B. Mengel Department of Agronomy, Kansas State University, Manhattan, KS, USA

Email: ara4747@ksu.edu

•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 10. 2011 Manhattan, KS 134 kg ha-1

Objectives

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.

Results Cont.

0% 10% 20% 30% 40% 50% 60%0%

20%

40%

60%

80%

100%

120%

f(x) = − 1.21359799745021 x² − 1.10561582062322 x + 1.0882639861213R² = 0.620815754417258

2010 Relative Yield vs. Fired Leaf %

2010 High N Re-sponse Locations

Fire leaf %

Rela

tive Y

ield

%

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 %

Figure 9. 2011 Manhattan, KS 0 kg ha-1

• 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.

Results

Conclusions

Acknowledgements

Green Leaf %Salina Ottawa Randolph Belleville

3rd leaf N 0.78 0.81 0.71 0.57Grain Yield 0.91 0.95 0.27 0.12

3rd Leaf NSalina Ottawa Randolph Belleville

Grain Yield 0.72 0.90 0.42 0.62

N RateSalina Ottawa Randolph Belleville

Grain Yield 0.88 0.96 0.65 0.53

Green Leaf %Salina Ottawa Randolph Belleville

% Yield Increase 0.86 0.95 0.31 0.38

3rd Leaf NSalina Ottawa Randolph Belleville

% Yield Increase 0.53 0.90 0.48 0.58

Figure 1. 2010 Salina, KS 0 kg ha-1 Figure 2. 2010 Salina, KS 168 kg ha-1

0 20 40 60 80 100 120 140 1601.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

4.5%

5.0%

0%

5%

10%

15%

20%

25%

30%

35%

40%

f(x) = 4.85759350974081E-06 x² − 0.00185801211749606 x + 0.359522170443198R² = 0.890890956670005

f(x) = − 1.44532812127149E-07 x² + 3.5224600341837E-05 x + 0.0256100064801329R² = 0.953651025813846

2011 Manhattan, KS Fired Leaf % & Flag Leaf N % vs. N Rate

Flag Leaf N %

N Rate (kg ha-1)

Fla

g L

eaf

N (

%)

0 20 40 60 80 100 120 140 160 1800.745000000000001

0.755000000000001

0.765000000000001

0.775000000000001

0.785000000000001

0.795000000000001

0.805000000000001

0.815000000000001

0.825000000000001

f(x) = − 5.02151115079415E-07 x² + 0.000213625982821537 x + 0.780833576352776R² = 0.45536724591257

f(x) = − 7.15646364230644E-07 x² + 0.000250904188160996 x + 0.791280831923267R² = 0.803037015901739

f(x) = 0R² = 0 2011 Manhattan Location Red NDVI vs. N Rate

GS6

Polynomial (GS6)

GS4

N Rate (kg ha-1)

Red

ND

VI

0.8% 1.0% 1.2% 1.4% 1.6% 1.8% 2.0% 2.2% 2.4% 2.6% 2.8%0%

20%

40%

60%

80%

100%

120%

f(x) = − 609.399516516584 x² + 71.2669310984049 x − 0.443901189832239R² = 0.664533833041922

2010 Relative Yield vs 3rd Leaf N %

2010 High N Re-sponse Locations

3rd Leaf N %

Rela

tive Y

ield

%

Figure 3. N deficiency symptoms Figure 4. 2010 Pearson Correlations

• 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.