Relationship Between Plant Nitrogen and NDVI of Cotton on the Texas High Plains

A. Bumguardner1, K. Lewis1, G. Ritchie2, K. Bronson3, M. Maeda4
1Texas A&M AgriLife Research, 2Texas Tech University, 3USDA-ARS, 4Texas A&M AgriLife Extension
Introduction
  • Nitrogen (N) is a limiting factor for plant growth due to its involvement in both vegetative and reproductive growth (Li et al., 2001)
  • Plant available N in the soil is very limited and can be lost easily due to environmental conditions (IPNI, 2012)
  • Normalized difference vegetation index (NDVI) is a tool used to manage water use, N status, crop development and to predict yield at peak bloom (Li et al., 2001; Zhou and Yin 2014)
  • According to Zhao et al. (2010) it is uncertain if in-season N uptake by cotton corresponds with canopy reflectance
Objective
  • Evaluate the interaction of N rates with irrigation level and cultivar on plant health and cotton productivity to increase nitrogen use efficiency (NUE)
Results- Lint Yield
Figure 1. Cotton lint yield in 2019 with the 70% ET (A) and 30% ET (B) irrigation levels. Uppercase letters within DP 1820 and lowercase letters within DP 1823 are not different at α<0.05 by Fisher’s protected LSD. The vertical bars represent standard error of the mean
 
 
Figure 2. Cotton lint yield in 2020 with the 70% ET (A) and 30% ET (B) irrigation levels. Uppercase letters within DP 1820 and lowercase letters within DP 1823 are not different at α<0.05 by Fisher’s protected LSD. The vertical bars represent standard error of the mean
 
Figure 3. Nitrogen uptake in 2020 with the 70% ET (A) and 30% ET (B) irrigation levels. Uppercase letters within DP 1820 and lowercase letters within DP 1823 are not different at α<0.05 by Fisher’s protected LSD. The vertical bars represent standard error of the mean
Results- NDVI
Table 2. Nitrogen use efficiencies in 2019 and 2020 with the DP 1820 and DP 1823 cultivars. Letters within irrigation levels are not different at α<0.05 by Fisher’s protected LSD
 
Table 3. Regression R2 and p-values for normalized difference vegetation index (NDVI) vs lint yield in 2019
 
Table 4. Regression R2 and p-values for normalized difference vegetation index (NDVI) vs lint yield in 2020
† Highlighted boxes indicate greatest R2 values within irrigation level and cultivar
Materials and Methods
•Location: Texas A&M AgriLife Research Center- Lubbock, Tx (2019 & 2020)
•Soil type: Acuff loam
•Cotton cultivars: DP 1820 B3XF & DP 1823 NR B2XF
•Irrigation levels: 70% ET & 30% ET
•Fertilizer source: Urea ammonium nitrate (UAN; 32-0-0)
•Measurements:
•Soil sampled at three depths prior to N application
•0-6”, 6-12”, 12-24”
•N uptake: Plant N x biomass
•Internal NUE (iNUE): Lint yield/total N uptake (Bronson, 2021)
•Agronomic N use efficiency (ANUE): (Y-Y0)/F
•NDVI
•Holland Scientific GeoScoutX data logger
•Holland Scientific Crop Circle Sensors ACS-211 & ACS-435
•Lint yield
•Treatments:
1)15 lb acre-1 N pre (15-0-0)
2)15 lb acre-1 N pre + 60 lb acre-1 N  (75-0-0)
3)15 lb acre-1 N pre + 120 lb acre-1 N (135-0-0)
•Analysis:
•ArcGIS 10.5.1
•SAS 9.4- GLIMMIX, Proc REG
Soil Characterization
Table 1. Characteristics of soil samples collected at three depths (0-6”, 6-12” and 12-24”) prior to fertilizer application for all four years
Discussion
•ANUE
•DP 1820 within the 70% ET irrigation level was greater with the 75-0-0 treatment in 2019
•DP 1823 within the 70% ET irrigation level was greater with the 75-0-0 treatment in 2020
•DP 1820 and 1823 within the 30% ET irrigation level was greater with the 135-0-0 treatment in 2020
•iNUE
•DP 1823 in 2019 had an iNUE of 13.96 lb lint lb N-1 with the 135-0-0 treatment, which was considered deficient in N (Bronson, 2021)
•In 2020, treatment 15-0-0 had the greatest iNUE of 13.61 lb lint lb N-1 which was considered deficient in N, however N was mostly taken up in excess according to Bronson, 2021
•Lint Yield
•70% ET Irrigation- DP 1820 had the lowest lint yield with the 135-0-0 treatment for both years, while DP 1823 had the lowest lint yield with the 15-0-0 treatment in 2019 and 2020 had the lowest lint yield with the 15-0-0 and 135-0-0 treatments
•30% ET Irrigation- DP 1820 in 2019 had the lowest lint yield with the 15-0-0 treatment, while in 2020 the 75-0-0 treatment had the lowest lint yield.
•NDVI- DP 1820 had a better relationship with lint yield during flowering, while DP 1823 had a better relationship during squaring in 2019 and in 2020 had a better relationship during boll development
•70% ET
•In 2019 NDVI had a greater relationship with lint yield 56 DAP (R2=0.616) with the cultivar DP 1820 and 42 DAP (R2=0.606) with the cultivar DP 1823
•In 2020 NDVI had a greater relationship with lint yield 92 DAP (R2=0.389) with the cultivar DP 1820
•30% ET
•In 2019 NDVI had a greater relationship with lint yield 69 DAP (R2=0.569) with the cultivar DP 1820
•In 2020 NDVI had a greater relationship with lint yield 69 DAP (R2=0.578) with the cultivar DP 1820
Summary
•The lack of yield response to the greatest N rate (135-0-0) when compared to the 75-0-0 treatment may be due to high levels of N in irrigation water
•The lack of a strong relationship between NDVI and lint yield may be due to the limited range in lint yield across N treatments. Hail damage to the test plots in 2019 is also acknowledged here as a possible confounding effect
•Similar results to Bronson et al. (2003 & 2005) were determined in which NDVI had a moderate to poor correlation to lint yield
•When N uptake was the greatest, iNUE was the lowest, which resulted in excess N uptake (Rochester, 2011; Bronson, 2021)
 
Acknowledgements
Contact  
Amee Bumguardner, Research Associate 
Department of Plant and Soil Science |Texas Tech University 
Texas A&M AgriLife Research – Lubbock
979.422.9474 |  amee.bumguardner@ag.tamu.edu

Video conference

Resources

Abstract

Contact author