Tissue concentration of nitrogen and phosphorus in grain sorghum

• Published in: Field crops research 1987-12, Vol.17 (3), p.289-303
• Main Authors: Myers, R.J.K., Foale, M.A., Smith, F.W., Ratcliff, D.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Genetics and breeding of economic plants; Varietal selection. Specialized plant breeding, plant breeding aims; Yield, quality, earliness, varia
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/0378-4290(87)90041-4

Changes in tissue concentration of nitrogen (N) and phosphorus (P) with time were examined for seven sorghum cultivars and three times of sowing on a fertile soil in south-east Queensland, and for four other northern Australian sites each with a single cultivar. Tissue concentrations of N and P were closely related to accumulated degree days ( add; base temperature=0°C) from emergence, irrespective of cultivar or time of sowing, but were less closely related to days from emergence, because of differences in rates of development with different sowing dates. Concentrations were poorly related to stage of growth, because of differences between cultivars. Nitrogen concentration of shoot, green leaf, and stem underwent a rapid decline until 2000 degree days had accumulated, after which %N of green leaf remained almost constant, while that of shoot and stem continued to decline slowly. Percent-N in the inflorescence declined linearly from its first observation at 1000 add. Comparisons with other field data known to be just non-limiting for N allow the conclusion that luxury consumption of N had not occurred to a measurable extent. Green leaf %P declined rapidly until 2000 add and was then almost constant. Shoot and stem %P declined rapidly until 1300 add and then continued with a slower decline. Percent-P in the inflorescence exhibited a slow linear decline. From comparison with the field data known to be just non-limiting for P, it was obvious that considerable luxury consumption for P had occurred in the highly fertile soil and two separate sets of curves, for adequate and for maximum P levels, are presented. Close linear relationships occurred between shoot and grain N concentration and between shoot and grain P concentration. The only outliers were for N, where two very low-yielding photoperiod-sensitive cultivars had comparatively low shoot-N concentration. Harvest indices for N and P were closely, and linearly, related to harvest index for dry matter.