Environmental parameters influencing phenological development of mustard in relation to yield

Experiments were conducted during rabi 1993–94, 94–95 and 96–97 to ascertain the effect of environmental parameters and their derivatives viz., mean temperature, growing degree days (GDD), sunshine hours and heliothermal units (HTU) on phenological development, growth and yield of mustard (Brassica juncea (L) Czern). Two genotypes of mustard, viz. Kranti and Vaibhav were sown at intervals of ten days starting from October 1 to December 10 (total 8 sowings). Daily maximum and minimum temperatures and sunshine hours were used to calculate GDD and HTU. Optimum sowing dates for mustard were between October 31 to November 20 for achieving maximum yield. The latter was positively correlated with total dry matter production. Multiple regression analysis between duration of growth as dependent variable and sunshine hours, HTU, GDD, and mean temperature during that phase as independent variables yielded correlation coefficient (R²) values ranging from 0.966 to 0.989. Partial correlation revealed negative correlation between duration of growth and HTU or mean temperature. However, GDD and HTU were found to be positively associated with the duration between successive phenophases. It has been inferred that phenological developmental pattern of mustard regulates its yield and the former is regulated by environmental variables, which could be explained on the basis of GDD. Late sowing of mustard retarded yield by adversely altering reproductive growth.