NITROGEN RATE AND TIMING EFFECTS ON COLLARD YIELD AND PLANT NITROGEN CONCENTRATION

As the health benefits of diets high in leafy green vegetables become apparent, there is renewed interest in the production of crops such as collards (Brassica oleracea L. Acephala Group). Although yield increa ses from adding N fertilizer to collards have been demonstrated, the e ffect of split applications of N are not well known. Therefore, the ob jective of this research was to examine the effect of N rate and timin g on yield and N content of fall and spring collard crops. Open pollin ated ('Vates') and hybrid ('Flash') collards were transplanted into 6- in. raised bare planting beds in fall and spring of a 2 yr study. Trea tments consisted of ammonium nitrate (34-0-0) applied at rates of 60, 120, 180, and 240 Ib N/acre either as 100% preplant or in split applic ations. Split applications were applied either half at transplanting a nd half 4 wk after transplanting, or one-third at transplanting, one-t hird 2 wk after transplanting, and one-third 4 wk after transplanting. Yields were increased when N was applied as a split application, and applying N in a three- or two-way split increased yields compared with those obtained when all the N was preplant. There was no further yiel d advantage gained when N was split into three vs. two applications. C ollard yield increased with increasing rates of N. Yields were lower i n fall than spring, and the hybrid Flash usually had a higher yield th an open pollinated Vates in two of four crops. Collard yield response to added N was measured at N rates above the current recommended rate of 120 Ib N/acre.