Seasonal and Cropping Effects on Total and Fertilizer Nitrogen Use in June-bearing and Day-neutral Strawberries

Abstract

Total N and fertilizer N (FN) recovery and use by June-bearing `Redchief' strawberry (Fragaria ×ananassa Duch.) and day-neutral `Tribute' grown in matted-row beds were studied over l-year periods. Fertilizer N was field-applied as NH NO at planting in June or September, and all plants were harvested from bed sections in late autumn (November) and at the completion of the spring harvest (June). Distribution patterns of vegetative biomass were similar in both cultivars, with leaf tissue comprising the bulk of the vegetative dry weight per plant at both sampling dates. The fall and spring fruit crops each contributed >40% of the total biomass per plant. Total N accumulation from soil N and FN increased as total biomass increased. Due in part to the additional biomass of the fall fruit crop, `Tribute' recovered 38% more total N per unit bed area than `Redchief'. Over 30% of the fall N total in `Tribute' and the spring N total in both cultivars was partitioned to the fruit. In both cultivars, greater recovery of FN applied in September that at planting time was observed by the postharvest sampling date. However, `Tribute' recovered only 14.2% of the FN applied in September, much less than the amount recovered by `Redchief' during the same interval, implying a diminished ability to absorb FN during fruiting. In all vegetative tissues, soluble reduced N (SRN) was consistently less than insoluble reduced N (IRN) in November and June. Consistent seasonal trends in SRN and IRN values were not evident in any tissue except roots, where SRN content declined from November to June. Allocation of FN to the SRN and IRN pools was related to FN application date, cropping pattern, and total biomass of the component tissue. In both cultivars, the FN content was greater in the IRN than the SRN pool and leaf IRN was the single largest vegetative sink for FN. Fruit N concentration was constant for most of the fall `Tribute' harvest period and declined in both cultivars during spring harvest. The spring `Tribute' fruit crop received more FN from the September than the planting application, while the fall crop exhibited the opposite pattern, suggesting 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 remobilized during spring growth.