SEASONAL AND CROPPING EFFECTS ON TOTAL AND FERTILIZER NITROGEN USE INJUNE-BEARING AND DAY-NEUTRAL STRAWBERRIES

Total N and fertilizer N (FN) recovery and use by June-bearing 'Redchi ef' strawberry (Fragaria xananassa Duch.) and day-neutral 'Tribute' gr own in matted-row beds were studied over 1-year periods, Fertilizer N was field-applied as (NH4NO3)-N-15-N-15 at planting in June or Septemb er, and all plants were harvested from bed sections in late autumn (No vember) and at the completion of the spring harvest (June), Distributi on patterns of vegetative biomass were similar in both cultivars, with leaf tissue comprising the bulk of the vegetative dry weight per plan t at both sampling dates, The fall and spring fruit crops each contrib uted >40% of the total biomass per plant, Total N accumulation from so il N and FN increased as total biomass increased, Due in part to the a dditional biomass of the fall fruit crop,'Tribute' recovered 38% more total N per unit bed area than 'Redchief'. Over 30% of the fall N tota l in 'Tribute' and the spring N total in both cultivars was partitione d to the fruit. In both cultivars, greater recovery of FN applied in S eptember that at planting time was observed by the postharvest samplin g date. However,'Tribute' recovered only 14.2% of the FN applied in Se ptember, much less than the amount recovered by 'Redchief' during the same interval, implying a diminished ability to absorb FN during fruit ing, In all vegetative tissues, soluble reduced N (SRN) was consistent ly less than insoluble reduced N (IRN) in November and June, Consisten t seasonal trends in SRN and IRN values were not evident in any tissue except roots, where SRN content declined from November to June, Alloc ation of FN to the SRN and IRN pools was related to FN application dat e, cropping pattern, and total biomass of the component tissue, In bot h cultivars, the FN content was greater in the IRN than the SRN pool a nd leaf IRN was the single largest vegetative sink for FN, Fruit N con centration was constant for most of the fall 'Tribute' harvest period and declined in both cultivars during spring harvest, The spring 'Trib ute' fruit crop received more FN from the September than the planting application, while the fall crop exhibited the opposite pattern, sugge sting the fruit crop receives more storage than newly absorbed FN, The accumulation of FN in the root SRN pool in November and its depletion through the spring harvest reveals that root SRN plays a significant role in the temporary seasonal storage and internal cycling of N remob ilized during spring growth.