|COSTELLO, R - OREGON STATE UNIVERSITY|
|SULLIVAN, D - OREGON STATE UNIVERSITY|
|STRIK, B - OREGON STATE UNIVERSITY|
|OWEN, J - VIRGINIA POLYTECHNIC INSTITUTION & STATE UNIVERSITY|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2019
Publication Date: 6/1/2019
Citation: Costello, R.C., Sullivan, D.M., Bryla, D.R., Strik, B.C., Owen, J. 2019. Compost feedstock and compost acidification affect growth and mineral nutrition in northern highbush blueberry. HortScience. 54(6):1067-1076. https://doi.org/10.21273/HORTSCI13599-18.
Interpretive Summary: Northern highbush blueberry is adapted to well-drained, acidic soils with high organic matter content. Acidic organic materials such as pine bark or coniferous sawdust are therefore usually mixed in the soil prior to planting blueberry and are often applied as surface mulch as well. However, due to increasing competition for these products by other industries, bark and sawdust are becoming less available for blueberry production and more expensive for growers to apply. Composts may provide an alternative source of organic matter for blueberry and can be produced from local organic wastes for little or no expense. Municipalities, for example, create and distribute composts created from yard debris, leaf litter, food waste, and wastewater treatment by-product (“biosolids”) feedstocks. The objective of the present study was to determine the effects of sulfur-acidified and non-acidified composts on plant growth and nutrient uptake in highbush blueberry. A wide range of composts were evaluated, including five plant-based composts produced from grass hulls, mint hay, chipped leaves, yard debris, and decomposed bark, two animal-based composts produced from horse manure and separated dairy solids, and three mixed compost products. Among the composts, horse manure and most plant-based composts, including grass:mint, leaves, yard debris, and bark, produced the most plant growth, while mint and those made from dairy manure produced the least. In general, composts with pH < 7.5 produced more shoot growth than those with higher pH. Adding elemental S to the compost prior to planting was also beneficial to blueberry.
Technical Abstract: Ten composts created from local organic waste, including grass hulls, mint hay, chipped leaves, yard debris, decomposed bark, horse manure, separated dairy solids, and three mixed compost products were evaluated in ‘Duke’ blueberry. The objective was to determine the effects of the composts on plant growth and nutrient uptake. Each compost was either acidified or not with elemental sulfur (S) and then mixed with soil before planting. For comparison, plants were also grown in soil mixed with sawdust and in soil only. Separated dairy solids had the highest amount of available nitrogen (N) at planting, with an estimated 0.74 g/pot, while yard debris had the least, with only 0.03 g/pot. Without S, compost pH ranged from 5.4-8.1 while salinity, measured as electrical conductivity (EC), ranged from 0.4-5.0 dS/m. Adding S reduced compost pH by an average of 1.9 units but increased compost EC by an average of 1.3 dS/m. Higher EC in acidified composts was associated with increased availability of soluble nutrients. By and large, plant growth and nutrient uptake, including N, P, K, B, and Mn, were higher in soil with compost than in soil with sawdust or soil only. Among the composts, horse manure and most plant-based composts, including grass:mint, leaves, yard debris, and bark, produced the most total shoot growth, while mint without S and those made from dairy manure produced the least. Grass:mint and leaves also produced the most root growth, whereas mint and dairy manure produced the least. In general, composts with pH < 7.5 produced more shoot growth than those with higher pH, and composts with EC > 2 dS/m produced less root growth. On average, S increased shoot and root growth in the composts as well as uptake of many nutrients, including N, P, K, Ca, Mg, S, Fe, B, Mn, and Zn. Thus, despite the increase in EC, adding elemental S to compost was largely beneficial to blueberry. Plant response to the composts, however, was not affected by compost N.