ISHS Acta Horticulturae 715: VIII International Symposium on Vaccinium Culture
THE UPTAKE AND USE OF 15N-NITROGEN IN YOUNG AND MATURE FIELD-GROWN HIGHBUSH BLUEBERRIES |
| Authors: | M.P. Banados, B. Strik, T. Righetti |
| Keywords: | Vaccinium corymbosum, fertilization, growth, partitioning, yield, berry size, planting |
| Abstract:
The effect of nitrogen (N) fertilization rate on growth, yield and N partitioning in young and mature field-grown Bluecrop was studied. Depleted 15N-(NH4)2SO4 was applied in the first year (2002) and non-labeled fertilized in the second year (2003). Only first-year results are reported here. Three N fertilizer rates (0, 100 and 200 kg N ha 1) and two in-row spacing treatments (0.45m and 1.2m) were studied in the mature planting. Four N fertilizer rates (0, 50, 100 and 150 kg N ha 1) were applied in the establishment year of a new planting, spaced at 1.2m. In both studies, the N fertilizer was applied as a triple split (33%:33%:33%) from April through June. Plants were destructively harvested and divided into parts on six dates from February to October 2002. Plant parts were analyzed for dry weight, N and 15N concentration (%) and nitrogen derived from fertilizer (NDFF) calculated. In the mature planting, N fertilization rate had no effect on plant dry weight, but plants at 1.2m were larger than those at 0.45m. Plants fertilized with 200 kg N ha 1 had a higher total N content in July and September than unfertilized plants. Percent NDFF increased from 3% in April to 23% in September, with no treatment effect. Fertilizer recovery was initially slow (only 1 to 2% recovery two weeks after the first split), but increased to 22% to 43% in September depending on in-row spacing and N rate; plants spaced at 0.45m recovered a higher percentage of the fertilizer. Yield was not affected by N fertilization rate, but was 35% higher at 0.45m than at 1.2m. In the new planting, established using two-year-old plants, N rate affected plant dry weight, total nitrogen content, percent NDFF, and fertilizer recovery. By October, plants fertilized with 50 kg of N ha 1 had the largest dry weight and N accumulation. Ammonium toxicity was observed in plants fertilized with 100 and 150 kg N ha 1. Percent NDFF was 60% and 67% for the 50 and 100 kg N ha 1, respectively. Fertilizer recovery reached its maximum in October (17% and 10% for the 50 and 100 kg of N ha 1). | |
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