Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2003
Publication Date: 10/1/2003
Citation: Zhao, D., Reddy, K.R., Kakani, V.G., Read, J.J., Carter, G.A. 2003. Corn (Zea mays L.) growth, leaf pigment concentration, photosynthesis and leaf hyperspectral reflectance properties as affected by nitrogen supply. Plant and Soil Journal. 257:205-217. Interpretive Summary: Experiments were conducted in ten sunlit, temperature- and humidity- controlled growth chambers to determine the effects of nitrogen (N) nutrition on corn (Zea mays L.) growth and changes in leaf optical properties in the visible (350-700 nm) and near infrared (750-2500 nm) wavebands at 1-nm intervals. The supply of N was decreased in the irrigation water at different days after plant emergence (DAE); otherwise, environmental conditions were favorable for plant growth. The four N treatments were 1) half-strength nutrient solution throughout the experiment (control); 2) 20% of the control N at 15 DAE (20% N); 3) N withheld starting 15 DAE (0% N); and 4) N withheld from the nutrient solution starting 23 DAE (0% NL). Under these treatments, the concentration of N in fully expanded uppermost leaves ranged between 1.1% and 4.8% across all sampling dates. Nitrogen deficiency significantly decreased plant growth rate and leaf photosynthesis except in 0% NL treatment. As compared to controls, final plant height, leaf area and shoot biomass at end of experiment were reduced 34-35% in 20% N treatment and about 44-54% in 0% N treatment. These two treatments of 20% and 0% of control N could be readily distinguished using leaf reflectance in the wavelengths of 552 and 710 nm at about 7 days following treatment. Relationships between changes in leaf reflectance and the concentrations of chlorophyll and N in mature leaves of corn are also discussed.
Technical Abstract: Because nitrogen (N) often limits crop productivity, detecting N status early in the season may improve fertilizer use efficiency and crop yield. An experiment was conducted in sunlit controlled environment chambers to determine effects of N stress on corn (Zea mays L. cv. 33A14) growth and leaf hyperspectral reflectance (350-2500 nm, 1-nm resolution). Four N treatments were: (1) half strength Hoagland's nutrient solution throughout the experiment (control); (2) 20% of control N at 15 days after emergence (DAE) (20% N); (3) 0% N at 15 DAE (0% N); and (4) 0% N at 23 DAE (0% NL). Data for plant height, number of nodes, leaf area and leaf length were recorded every 3-4 days. Uppermost fully expanded leaves were also sampled periodically for leaf hyperspectral reflectance, total chlorophyll (a + b), carotenoids, leaf N, and photosynthetic gas exchange. Leaf N ranged from about 11 to 48 g kg-1 DW across N treatments and sampling dates. At final harvest (42 DAE), plant height, leaf area and shoot biomass were about 64-66% of the control for 20% N treatment, and 46-56% of the control for 0% N treatment. At 22 DAE, the 20% N and 0% N treatments differed in leaf reflectance at 552 and 710 nm, and reflectance values at these two wavebands were negatively correlated with either leaf N (r = -0.72 to -75**) or chlorophyll (r = -0.60 to -0.72**). In addition, larger correlation was obtained between leaf N and simple ratios of leaf reflectance. These N-specific spectral algorithms may be used for remote assessment of corn N status in precision agriculture.