Productivity of spring sunflower (Helianthus annuus) in response to sowing dates and foliar application of boron and TIBA

A field experiment was conducted during 2014 and 2015 at Ludhiana, to study growth attributes, physiological parameters, pre-and post-anthesis dry-matter accumulation (DMA), dry-matter translocation (DMT), contribution of pre-anthesis dry-matter assimilates to seed (CDMS), yield-contributing traits and seed yield of sunflower (Helianthus annuus L.). The experiment was laid out in a split-plot design by keeping 3 sowing dates (20 January, 10 February and 2 March) in main plots and 8 treatments of foliar applications (control, water spray, boron at 110, 220, 440 ppm, and TIBA at 100, 200, 400 ppm) in subplots in 3 replications. Early-sown crop gave better yield-contributing characters (head diameter, seed weight/head, thalamus weight, number of seeds/head, seed filling percentage, 1, 000-seed weight) and higher seed yield (2.01 t/ha) owing to higher post-anthesis DMA (1, 908 kg/ha) coupled with better photosynthetic parameters (chlorophyll fluorescence and chlorophyll-content index), growth attributes and root-mass density. Foliar application of boron at 220 and 440 ppm as well as TIBA at 100, 200 and 400 ppm also significantly improved yield-contributing characters and seed yield (by 10.7 to 21.5%) over the control and water spray probably owing to higher post-anthesis DMA (147 to 267 kg/ha higher than the control), DMT (29 to 80 kg/ha higher than the control), DMTE, CDMS and better photosynthetic parameters. Economic analysis indicated that foliar application of B at 110, 220 and 440 ppm and TIBA at 100 ppm can be used to obtain higher profitability from sunflower crop.