Establishing Organic Highbush Blueberry Production Systems – the Effect of Raised Beds, Weed Management, Fertility, and Cultivar

A new research planting was established in Aurora, OR in Oct. 2006 on a silt loam with a soil pH of 4.9 and 3.7% organic matter.  Treatments included: cultivar (Duke or Liberty); planting on flat ground or raised beds; fertilization with either fish emulsion or feather meal (at 25 or 50 kg/ha N); and weed management systems (sawdust mulch and hand weeding; compost plus sawdust mulch and use of flaming or acetic acid; and weed mat).  The planting was certified organic in May 2008.  Data were collected through the first two years of establishment (2007 and 2008).  In general, soil water content was lower through the season on raised beds than on flat ground, especially under weed mat (which increased soil temperature as much as 5 C); this system thus required more irrigation water to maintain adequate soil moisture.  Weed presence was not high in 2007, never exceeding 20% coverage.  Weed mat plots had the fewest weeds whereas compost plus sawdust mulched plots had the most in both years.  Acetic acid, applied every 3 weeks during the warmer months, worked well in 2007; flaming was added in 2008, but hand weeding was still required in both years in all treatments.  In Oct. 2007, total plant dry weight (DW) was higher in Liberty than Duke, raised beds than flat ground, and with fish emulsion than with feather meal but was not affected by weed management system.  Root DW was greater in Duke and lowest in plants receiving 50 kg/ha N as fish emulsion when grown under weed mat.  In Oct. 2008, total plant DW was highest in Liberty and plants grown on raised beds but was not affected by weed management or fertility.  Root DW in Duke was not affected by planting on raised beds but was greater in plants grown with sawdust mulch and fertilized with 25 kg/ha N as fish.  In Liberty, the greatest root DW was in plants with compost plus sawdust mulch and fertilized with 25 kg/ha N as fish, while leaf area was greatest in plants grown on raised beds with sawdust mulch and 50 kg/ha N as fish.  In 2008, yield was greater in Liberty than in Duke and on raised beds compared to flat ground, and fish fertilizer produced more yield than feather meal.  Fruit firmness was affected by cultivar, mulch type, and raised bed production, whereas fruit size was only affected by cultivar.