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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #310839
Title: Response of blackberry cultivars to fertilizer source during establishment in an organic fresh market production system

Author
item FERNANDEZ-SALVADOR, JAVIER - Oregon State University
item STRIK, BERNADINE - Oregon State University
item Bryla, David

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2015
Publication Date: 6/30/2015
Citation: Fernandez-Salvador, J., Strik, B.C., Bryla, D.R. 2015. Response of blackberry cultivars to fertilizer source during establishment in an organic fresh market production system. HortTechnology. 25(3):277-292.

Interpretive Summary: Guidelines for fertilizer and nutrient management in organic blackberry production are presently limited to overarching recommendations and do not address different sources of fertilizers. A two-year study was conducted at a commercial farm in Oregon to evaluate the impact of three organic fertilizer sources, including pelletized, processed poultry litter, pelletized soybean meal, and a fish hydrolysate and emulsion blend with added molasses, on yield and fruit quality of blackberry. Four popular blackberry cultivars were selected for the study, including three trailing types (‘Black Diamond’, ‘Marion’, and ‘Obsidian’) and one semi-erect type (‘Triple Crown’). Each fertilizer was suitable to maintain adequate nutrition in each cultivar, but supplemental applications of boron may be needed in deficient soils. Poultry litter may offer advantages to help mitigate a decline in soil pH that occurs when fertilizing. The fish fertilizer contributed relatively large amounts of sodium to the soil with no adverse effects observed. The cost per lb of N was higher for the liquid fish and molasses blend than for the pelletized soybean meal, and the pelletized, processed poultry litter. All cultivars performed well and would be considered suitable for commercial organic production. ‘Triple Crown’ produced the highest yield and largest fruit weight but was considered soft for a fresh market, shipping cultivar. In contrast, ‘Obsidian’ fruit had the greatest firmness but were more sensitive to botrytis fruit rot. ‘Marion’ and ‘Black Diamond’ had traits that make these cultivars more suitable, as expected, for processing.

Technical Abstract: One semi-erect (‘Triple Crown’) and three trailing (‘Marion’, ‘Black Diamond’, and ‘Obsidian’) blackberry cultivars were studied from 2011-2012 at a certified organic, grower collaborator site located in Jefferson, OR. Plants were fertilized with 56 kg/ha N each spring using three different sources: 1) a liquid fish and molasses blend; 2) pelletized soybean meal; and 3) pelletized, processed poultry litter. ‘Triple Crown’ produced the greatest yield in both years, whereas ‘Black Diamond’ and ‘Marion’ had the lowest yield in 2011 and 2012, respectively. ‘Triple Crown’ fruit had the highest % soluble solids and were the least firm in 2011, while ‘Marion’ fruit were the least firm in 2012. The effect of fertilizer source on yield and fruit quality was relatively small. Soy meal produced the greatest total yield in ‘Triple Crown’ in 2011 and in ‘Obsidian’ in both years. In contrast, poultry and fish produced the greatest total yield in ‘Black Diamond’ in 2011, and fish produced the greatest yield in ‘Black Diamond’ and ‘Marion’ in 2012. Most soil nutrient levels were within the recommended range for all fertilizer treatments, except for B, which declined to deficient levels in the second year. Fertilizer source had no effect on soil nutrient levels other than fertilization with fish increased soil K and Na. Leaf nutrient concentrations were above or within recommended standards for most nutrients, except for Mg, Ca, and B, which, depending on the cultivar, were below standards. Over the 2-year study, the blackberry cultivars responded similarly to the three sources of organic fertilizer. However, the cost per kg N varied from $18.00 ($8.16/lb) for the liquid fish and molasses blend, $11.80 ($5.35/lb) for the pelletized soybean meal, and $5.60 ($2.54/lb) for the pelletized, processed poultry litter. Supplemental fertilization with B, Mg, and Ca would be required with each fertilizer studied to maintain recommended soil fertility levels.