Mulch and Fertilizer Management Practices for Organic Production of Highbush Blueberry. I: Plant Growth and Allocation of Biomass during Establishment

A systems trial was established in Oct. 2006 to evaluate management practices for organic production of northern highbush blueberry (Vaccinium corymbosum L.). The practices included: flat and raised planting beds; feather meal and fish emulsion fertilizer each applied at rates of 29 and 57 kg.ha(-1) nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. Each treatment was irrigated by drip and weeds were controlled as needed. The planting was certified organic in 2008. After one growing season, allocation of biomass to the roots was greater when plants were grown on raised beds than on flat beds, mulched with organic mulch rather than a weed mat, and fertilized with the lower rate of N. Plants also allocated more biomass belowground when fertilized with feather meal than with fish emulsion. Although fish emulsion improved growth relative to feather meal in the establishment year, this was not the case the next year when feather meal was applied earlier. After two seasons, total plant dry weight (DW) was generally greater on raised beds than on flat beds, but the difference varied depending on fertilizer and the type of mulch used. Shoots and leaves accounted for 60% to 77% of total plant biomass, whereas roots accounted for 7% to 19% and fruit accounted for 4% to 18%. Plants produced 33% higher yield when grown on raised beds than on flat beds and had 36% higher yield with weed mat than with sawdust mulch. Yield was also higher when plants were fertilized with the low rate of fish emulsion than with any other fertilizer treatment in 'Duke' but was unaffected by fertilizer source or rate in 'Liberty'. Although raised beds and sawdust or sawdust + compost produced the largest total plant DW, the greatest shoot growth and yield occurred when plants were mulched with weed mat or compost + sawdust on raised beds in both cultivars. The impact of these organic production practices on root development may affect the sustainability of these production systems over time, however, because plants with lower root-to-shoot ratios may be more sensitive to cultural or environmental stresses.