Nitrogen Fertilization Rate, Sawdust Mulch, and Pre-Plant Incorporation of Sawdust—Long-Term Impact on Yield, Fruit Quality, and Soil and Plant Nutrition in ‘Elliott' Blueberry, Poster Board #287

A planting of ‘Elliott’ northern highbush blueberry was established in Oct. 2003. Treatments were: 1) raised beds constructed with or without the incorporation of sawdust; 2) with or without application of a sawdust mulch after planting; and 3) nitrogen (N) fertilizer rate (low: 22–56 kg/ha; medium: 67–168 kg/ha; and high: 112–269 kg/ha, depending on planting age). There was no significant effect of N rate on machine-harvested yield which increased from 10.8 t/ha in 2006 to 21.1 t/ha in 2011. While cumulative yield has not been affected by incorporation of sawdust or mulch, plots in which sawdust was incorporated before planting had a higher cumulative yield if no mulch was used (103.3 t/ha vs. 93.6 t/ha for mulched) whereas the opposite was true for plots in which no sawdust was incorporated (89.1 t/ha and 94.6 t/ha, for bare soil or with sawdust mulch, respectively). While leaf N concentration has been lower than recommended standards in some years, this has had no negative impact on yield. Nitrogen fertilization with the high rate decreased average berry weight in all years. Plots in which no sawdust was incorporated before planting had greater berry weight when sawdust mulch was used (2.13 g) compared to unmulched plots (2.09 g). To date, there has been no treatment effect on the firmness of berries picked by hand, just prior to machine harvest. Plants fertilized with the low rate of N had a lower fruit N concentration at harvest in 2010, but not in 2011. Fertilization rate and use of sawdust before or after planting has affected soil organic matter and nutrient content. Soil pH of plots fertilized with the high rate of N was lower than in plots fertilized with the medium or low rate of N in 2010. Implications of planting management on long-term sustainability will be presented.