DELAYED ANTHESIS IN SORGHUM UNDER LOW NITROGEN AVAILABILITY

Sorghum (Sorghum bicolor L. Moench) is a major crop in many regions of the world, especially where rainfall may limit the length of the grow ing season. Therefore, matching the length of plant development of sor ghum with precipitation patterns is an important consideration. This s tudy was undertaken to determine the extent to which soil N applicatio ns might influence sorghum development patterns, and particularly anth esis date. Three sets of field experiments were undertaken to examine changes in anthesis date in response to differing levels of N applicat ion under well-watered conditions. In most tests, treatments without t he application of N had anthesis dates that were delayed up to 20 d re lative to the well-fertilized treatments. In a study of vegetative dev elopment, it was found that a delay in leaf development and panicle ex ersion also occurred under low levels of N application. In a few cases , however, low levels of N applications resulted in delayed anthesis o f only 2 to 4 d. In these latter cases, it was hypothesized that mean daily temperature was an over-riding factor that prevented an expressi on of the delay in anthesis as a result of low soil N availability.