Nitrogen Affects Seed Production Characteristics in Yellow Mustard

The response of applied N in yellow mustard (Sinapis alba L.) seed production is unknown in the high rainfall environments of the Pacific Northwest. The objective of this study was to determine the effect of applied N on growth, seed yield, and oil production in yellow mustard in this unique environment. Trials were conducted over 3 yr near Corvallis, OR, on cultivar IdaGold yellow mustard with five N rates: 0, 56, 112, 168, and 224 kg N ha–¹. Growth and dry matter partitioning were measured at stem elongation (Biologische Bundesanstalt, Bundessortenamt und CHemische In [BBCH] 30), inflorescence emergence (BBCH 50), and harvest (BBCH 87). Applied N increased height, biomass, leaf area index (LAI), crop growth rate (CGR) and tissue N content. Although rainfall differed among years, N had similar effects on seed yield and yield components. Seed yield increases ranged from 15 to 85% with applied N, primarily as a result of N-induced increases in seed weight and seed number. Yields ranged from 1010 kg ha–¹ with 0 kg N ha–¹ to 2579 kg ha–¹ with 224 kg N ha–¹. Primary racemes plant–¹ was positively associated with increased N. Siliques plant–¹ increased with N rate and resulted from increased siliques production on mainstem and primary racemes. Seed oil content was inconsistently affected by N rate; however, highest oil yield was observed with 224 kg N ha–¹. This study will form the foundation for N recommendations for yellow mustard seed production in the Pacific Northwest.