|Authors: ||H. Larco, B. Strik, D.M. Sullivan, D. Bryla|
|Keywords: ||Vaccinium corymbosum, compost, sawdust, mulch, weed mat, landscape fabric, raised beds, nutrient, nitrogen|
A long-term organic blueberry trial was planted in October 2006 in Aurora, Oregon, USA to investigate the effect of mulch on soil and plant nutrient status, plant growth, berry yield, irrigation requirements, and weed control efficacy.
Mulch treatments were applied at planting: 1) weed mat (geotextile), 2) Douglas-fir (Pseudotsuga menziesii) sawdust, and 3) compost + sawdust (compost applied to soil, then covered with sawdust). This paper addresses mulch treatment effects on soil and plant nutrient status during the first two years of the trial, and the first berry harvest in year 2 (2008). Yard-debris compost used in the field experiment had a pH of 7.3 and low soluble salt (EC <1 mS/cm). The yard debris compost + sawdust treatment produced greater berry yields than sawdust alone in the first bearing season.
Relative berry yields were 100% for weedmat, 90% for sawdust + compost, and 70% for sawdust mulch.
The positive effects of compost on berry yield were observed across two cultivars, flat or raised beds, and for two organic fertilizer sources (fish emulsion or feather meal) applied at two rates (29 and 57 kg•ha-1 N). Soil pH underlying the mulch was lowest (most acidic) with weed mat and highest under sawdust + compost mulch.
After two years, compost increased soil organic matter (OM; 0-20 cm) by 9 g•kg-1 vs. weedmat, while sawdust mulch did not increase soil OM. In summary, compost maintained soil pH in the optimum range for blueberry, provided plant-available cations, increased soil organic matter, and increased berry yield (relative to sawdust alone). The mechanism(s) behind the compost benefit deserve further investigation.
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