Diammonium Phosphate Application Date Affects Vaccinium angustifolium Ait. Nutrient Uptake and Yield

摘要

A commercial lowbush blueberry field with a Colton sandy soil characteristic of the blueberry barrens of Washington County, Maine was the site for this study. Diammonium phosphate (DAP, 18-46-0) was applied at 448 kg/ha on 17 May (preemergent), 31 May, 14 June, 28 June, or 12 July 2000 for comparison with an unfertilized control plot. Stem height was measured on 20 tagged stems in each control plot of blocks 1,2, and 3 at the time of fertilizer application. Composite leaf tissue samples taken for nutrient analysis indicated that there was a positive linear and quadratic relationship between leaf N concentration and fertilizer application date. Leaf P concentration had a quadratic relationship with application date. Applying fertilizer on 14 June resulted in the greatest uptake of N and P as indicated by leaf nutrient concentrations. Soil samples taken at the time of leaf sampling indicated no effect of any fertilizer application on soil P concentration. Fertilizer application did not affect stem density, stem height, or number of branches. Branch length was increased only by the 17 May preemergent application of DAP. Flower bud density was increased by fertilization on 17 May, 31 May, 14 June, or 28 June, compared to the control. Yield was increased by fertilizing with DAP applied preemergent (May 17) or on May 31 but not at the later dates. This quadratic relationship was significant at the 0.1% level. Apparently, N and P from DAP accumulated to high levels in leaf tissue when applied on 14 Junebut there was inadequate time to influence flower formation in flower buds.