The effects of nitrogen supply and stem density on leaf attributes and stem branching in potato (Solanum tuberosum L.)

Summary The interaction between nitrogen supply and stem density on leaf attributes and branching was studied in two field experiments. Stem densities included 8, 16, 24, 32 and 40 stems m⁻². The low-N treatments received 5 or 10 g m⁻² nitrogen, and the high-N treatments 20 or 25 g m⁻². The sizes of mature individual leaves on the main stem declined with increase in stem density and were larger for greater N supply, with additive effects of nitrogen and stem density. The specific leaf area was not affected by nitrogen supply and increased with stem density (range of values: 210 to 310 cm² g⁻¹). The leaf weight ratio was not affected by the treatments. At 8 and 16 stems m⁻² basal branches contributed substantially to the total leaf area per stem: at 24 stems m⁻² and higher densities the development of basal branches was negligible. Leaf area on apical branches was always smaller for higher plant densities and lower rates of N supply.