Skip to main content
ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #281613

Title: Suitability of composts for an acid-loving plant: highbush blueberry

item SULLIVAN, DAN - Oregon State University
item COSTELLO, RYAN - Oregon State University
item Bryla, David
item STRIK, BERNADINE - Oregon State University
item OWENS JR, JIM - Virginia Polytechnic Institution & State University

Submitted to: Western Nutrient Management Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/10/2012
Publication Date: 7/1/2012
Citation: Sullivan, D.M., Costello, R.C., Bryla, D.R., Strik, B.C., Owens Jr, J.S. 2012. Suitability of composts for an acid-loving plant: highbush blueberry. Western Nutrient Management Conference Proceedings. 4:1-2.

Interpretive Summary:

Technical Abstract: Our objectives were to estimate elemental S rate needed to acidify compost to target pH for highbush blueberry and to evaluate diverse composts as soil amendments. The compost feedstocks were animal manures (horse or dairy) or plant materials (yard debris, leaves, mint, or bark). Finished compost pH was 7.5-8.5, except for bark compost, which had a pH of 5.2. Compost acidification to pH 5 required an average of 10 g/kg S across all feedstocks. Dairy and mint composts had the highest S requirements, yard debris compost had a moderate requirement, and bark compost did not require acidification. To evaluate compost suitability, two plant growth trials were conducted in pots in silt loam soil amended with a high rate of compost or sawdust (30% by volume). Plants usually grew better in plant-derived composts (bark, yard debris, or deciduous tree leaf, but not mint) than in manure-derived composts (dairy or horse). Acidification of composts with finely ground S also increased plant growth. At low levels of N fertilizer addition, plants grew better with compost than with sawdust. At a higher N fertilizer rate, plant growth with the best performing composts was equivalent to sawdust. Composts with C:N near 20 produced good growth in both trials. Plant growth response to compost was not related to compost N levels and was good in compost treatments with relatively low levels of nitrate-N. Most composts contained soluble salt (EC) levels considered high for blueberry. Yard, leaf, and bark composts had the lowest EC (< 1 ds/m), while EC in horse, dairy, and mint composts averaged 1.8. 2.5, and 6.1 ds/m, respectively. However, compost EC did not appear to be of primary importance in determining plant response to compost. In fact, plants grew better in composts that had been acidified with S, even though compost EC was elevated by S oxidation to sulphate. Salts were rapidly leached from pots in our trials, limiting the duration of plant exposure to high EC. We conclude woody plant materials acidified with finely ground S are the most promising composts for highbush blueberry.