Influence of staggered sown Spring sunflower (Helianthus Annuus L.) at varying intra–row spacing and applied–N on pre– and post–anthesis N dynamics and dry matter partitioning in Indo–Gangetic Plains Region

In current study, dry-matter accumulation (DMA), pre- and post-anthesis nitrogen (N) accumulation, N translocation (NT) and dry-matter partitioning by sunflower seeds was investigated under three sowing dates (January 20, February 10 & March 2), two intra-row spacings (30 & 24cm) and four nitrogen doses (0, 45, 60 & 75kg ha(-1)) in two alluvial soils. Early sowing resulted in higher DMA and NT; leading to higher nitrogen use efficiency (NUE) that could be associated with higher pre-anthesis N accumulation. The closer intra-row spacing resulted in higher DMA by all plant parts except seed. Each graded N dose improved DMA, but improvement in dry-matter partitioning to seed was significant up to 60 and 75kg N ha(-1) during 2014 and 2015, respectively owing to higher NT under respective treatments. NUE was highest at 60kg N ha(-1) during both years.