Remote-sensing algorithms for estimating nitrogen uptake and nitrogen-use efficiency in cotton
2010
Zhao, Duli | Reddy, K Raja | Kakani, V Gopal | Read, John J.
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 had 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 (R (715)/R (405), r 2=0.65*** and R (795)/R (755), r 2=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 algorithms, 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.
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