The effect of plant population and growth regulators on the growth and yield of lentil (Lens culinaris Medik.) cv. Olympic

Two field experiments were conducted, one in spring 1987/88, and one in autumn 1988/89, to investigate the effect of plant population and growth regulators on the growth and yield of lentil (Lens culinaris Medik.) cv. Olympic. In 1987/88, a relatively wet season, with a total rainfall of 227 mm, increasing the plant population from 100 to 300 plants m⁻² significantly increased dry matte)" production, from 457 to 515 g m⁻² (equivalent to 4,568 and 5,146 kg ha⁻¹), seed yield from 225 to 239 g m⁻², mean ,seed weight from 67 to 69 mg, plant height from 347 to 370 mm, mean internode length from 14.2 to 16.7 mm, and first flowering node from 10.7 to 13.8. However, increased plant population reduced harvest index from 48.7 to 47.2%: branch number from 24.4 to 9.6, pod number plant⁻¹ from 46.4 to 17.1, number of nodes from 24.4 to 22.2, and individual leaf area from 5.25 to 4.56 cm²; but population did nor affect the number of seeds pod⁻¹. Pac1obutrazol significantly increased seed yield from 215 to 253 g m⁻², harvest index from 44.8 to 49.8%, and mean seed weight from 65 to 70 mg, but reduced plant height from 381 to 319 mm, and mean internode length from 16.4 to 13.9 mm. Dry matter production, branch number, pod number, number of nodes plant⁻¹, seed number pod⁻¹, first flowering node, and individual leaf area were not affected by paclobutrazol. Triapenthenol significantly increased seed yield from 214 to 241 g m⁻², harvest index from 44.7 to 48.6%, mean seed weight from 68 to 70 mg, and branch number from 12.3 to 17.1; but reduced mean internode length from 16.5 to 15.1 mm. Dry matter production, pods plant⁻¹, seeds pod⁻¹, plant height, number of nodes plane1, first flowering node, and individual leaf area were not affected. Increasing plant population from 100 to 300 plants m⁻² significantly increased length of internodes 10 to 16. Paclobutrazol significantly reduced length of internodes 10 to 16, Triapenthenol reduced length of internodes 10 to 14. In 1988/89, a very dry season, with a total rainfall of 157 mm, increasing plant populations from 100 to 300 plants m⁻² significantly increased dry matter production from 396 to 468 g m⁻², seed yield from 146 to 188 g m⁻², harvest index from 34.9 to 39.0 %, mean seed weight from 56 to 63 mg, mean internode length from 11.6 to 16.6 mm, first flowering node from 12.6 to 13.3, green area index from 0.81 to 2.03, and green area duration from 103.1 to 163.0 days, but significantly reduced branch number from 14.8 to 8.0, pods plant⁻¹ from 28.0 to 12.2, seeds pod⁻¹ from 1.11 to 1.07, number of nodes from 17.5 to 16.6; and the mean net assimilation rate from 2.329 to 1.771 g m⁻² d⁻¹. Neither paclobutrazol and triapenthenol nor timing of PGR application had a significant effect on dry matter production, seed yield, harvest index, mean seed weight, branch number, or first flowering node. Increasing plant population increased both crop growth rate and relative growth rate during early crop growth stage but the rates gradually declined with increased crop age. Neither PGRs nor timing of PGR application affected crop growth rate and relative growth rate. The effect of plant population on individual internode length was inconsistent, while PGRs and time of their application only affected internode number 12.