Submitted to: Acta Agriculturae Scandinavica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 28, 2009
Publication Date: October 14, 2010
Repository URL: http://hdl.handle.net/10113/45030
Citation: Zhao, D., Reddy, R., Kakani, G.V., Read, J.J. 2010. Remote sensing algorithms for estimating nitrogen uptake and nitrogen use efficiency in cotton. Acta Agriculturae Scandinavica, Section B-Plant Soil Science. 60:500-509. Interpretive Summary: Better understanding cotton (Gossypium hirsutum L.) plant nitrogen (N) uptake and portioning can help growers manage N application and improve N use efficiency (NUE) in high-yielding cotton production systems. We conducted a 2-year field experiment at the Mississippi State University’s Plant Science Research Center to investigate cotton growth and lint yield responses to N fertilizer rate and to determine plant N uptake, N partitioning and NUE in Mississippi Delta. Treatments included four N rates of 0, 56, 112, and 168 kg N ha-1 with one time (for the 56-N) or equal split (for the 112- and 168-N) applications at the 2nd true leaf and squaring stages. During plant growth, leaf photosynthetic rates (Pn), aboveground biomass (ABM), canopy reflectance, tissue N contents, and plant N uptake were measured. Lint yield, fertilizer N uptake and recovery, and NUE were determined. Nitrogen rate significantly affected leaf Pn, leaf N concentration, plant N uptake and NUE, however, the effects on N partitioning in plant tissues was less compared to other measured variables. Lint yield response to N rate depended upon soil N level and year. Plant tissue N concentration and N uptake linearly correlated with the ratios of canopy reflectance at 715 and 405 nm (R715/R405; r2 = 0.65***) and R795/R755 (r2 = 0.70***), respectively. Results of this study indicate that proper management of N application in cotton could improve lint yield and NUE. Canopy reflectance measurements may be a useful tool to monitor cotton plant N status and to assess N uptake.
Technical Abstract: Nitrogen management is a major concern in high-yielding cotton (Gossypium hirsutum L.) production systems. Objectives of this study were to investigate cotton leaf photosynthesis, plant growth, canopy spectral reflectance, and lint yield responses to N application rate and to determine plant N uptake, partitioning and use efficiency in Mississippi Delta, USA. Treatments included four N rates of 0, 56, 112, and 168 kg N ha-1. Increased N rate significantly affected cotton leaf photosynthetic rate, leaf area index, N concentrations of leaves and fruit, plant N uptake and N use efficiency, but has less effect on N partitioning among the plant tissues. Lint yield response to N rate depended on soil N level and experimental year. Cotton plant shoot N concentration and N uptake significantly and linearly correlated with the selected ratios (R715/R405, r2 = 0.65*** and R795/R755, r2 = 0.70***, respectively) of canopy reflectance measured during the squaring and fruiting of plant development. Proper management of N application in cotton based on soil N analysis and plant N status could improve cotton N use efficiency and lint yield. Remote sensing algorisms, developed from canopy reflectance ratios in this study, may be used to estimate N concentration in cotton shoots and plant N uptake and help producers make cotton N management decisions during the growing season.