Nitrogen Concentrations of Cotton Leaves, Buds, and Bolls in Relation to Age and Nitrogen Fertilization
1976
Thompson, A. C. | Lane, H. C. | Jones, J. W. | Hesketh, J. D.
Our plant growth models depend on a nitrogen economy in the plant as a limit for the initiation of new organs as well as the slowing of growth or abscission of plant organs. To improve our N-balance model, we needed better information about possible organ age effects for plants growing under different N-levels. Leaf and fruit N and N-effects upon morphology at four preplanting soil nitrogen levels of 0, 67, 134, and 201 kg N/ha were studied in cotton (Gossypium hirsutum) in the field and greenhouse. Three sets of leaves and fruit were monitored for N-content throughout the season. N-concentration in leaves from each N-treatment decreased (6 to 2%) as the season progressed. Regression analysis of these data indicated that the N-concentration dilution was not linear with time. Seventy-nine percent of the variation in N-concentratlon could be accounted for by N-application rate and time in growing season. Regression analysis of fruit data indicated that the dilution of N-concentration (4.5 to 1.5%) was linear with N-application rate. However N-concentration dilution was significant for young fruit from older plants. In plants grown both in the field and greenhouse at the four N-levels, the flowering rule time values (days/flower) increased with lower N-rates. There was a delay in maturity of floral buds in the high N-treatment plants, but no delay in the time required for boll set.
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