Location: Horticultural Crops Research UnitTitle: Weed management, training, and irrigation practices for organic production of trailing blackberry: II. Soil and plant nutrient concentrations
|DIXON, EMILY - Oregon State University|
|STRIK, BERNADINE - Oregon State University|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2015
Publication Date: 2/1/2016
Citation: Dixon, E.K., Strik, B.C., Bryla, D.R. 2016. Weed management, training, and irrigation practices for organic production of trailing blackberry: II. Soil and plant nutrient concentrations. HortScience. 51(1):36–50.
Interpretive Summary: Organic blackberry production is becoming an important niche market in Oregon, where almost 50% of the U.S. acreage is located. Oregon primarily grows trailing types used for the processed market. Although there is an increasing body of knowledge about organic blackberry production, some gaps still remain. The objective of this study was to evaluate several production practices (cultivar, weed management, training time, and irrigation) for their effect on plant and soil nutrients in a mature, organic planting of trailing blackberry. ‘Marion’ and ‘Black Diamond’ were the cultivars used, along with weed mat (geotextile), hand-weeding, and no-weeding management strategies, August and February primocane training dates, and two irrigation strategies (continuous summer irrigation and no irrigation after fruit harvest). Many of the plant and soil nutrients measured were affected in one way or another by these treatments. Withholding irrigation after harvest, for example, affected most soil nutrients, although the effects on plant nutrients were limited. Since the impact of postharvest irrigation on plant growth and yield were also limited after 3 years, deficit irrigation seems to be an effective strategy for water conservation. Organic matter, pH, and most soil nutrients were also higher under weed mat than in hand-weeded plots, as were nutrient concentrations in many plant parts. These results combined with the increased plant growth, yield, and profit gained from using weed mat indicate that it is a very effective management tool for organic blackberries. Training primocanes in August increased the concentration of some nutrients in the aboveground plant, but August training is not recommended in ‘Marion’ due to the greater risk of winter cold damage. Further study is needed to assess treatment effects on blackberry crowns and roots as they comprise a significant portion of the plant, and root and crown storage could impact nutrient concentrations in aboveground plant parts.
Technical Abstract: Organic production of blackberries is increasing, but there is relatively little known about how production practices affect plant and soil nutrient status. The impact of cultivar (‘Black Diamond’ and ‘Marion’), weed management (weed mat, hand weeding, and no weeding), primocane training time (August and February), and irrigation (throughout the summer and none postharvest) on plant nutrient status and soil pH, organic matter, and nutrients was evaluated from Oct. 2012–Dec. 2014 in a mature trailing blackberry (Rubus L. subgenus Rubus Watson) production system. The study site was certified organic and machine-harvested for the processed market. The planting was irrigated by drip and fertigated with fish hydrolysate and fish emulsion fertilizer. Soil pH, organic matter content, and concentrations of soil nutrients, including ammonium-nitrogen (NH4-N), potassium (K), Calcium (Ca), magnesium (Mg), sulfur (S), copper, (Cu), manganese (Mn), and zinc (Zn), were greater under weed mat than in hand-weeded plots. Soil K and boron (B) were below recommended standards during the study, despite a high content of K in the fish fertilizer and supplemental B applications. Primocane leaf nutrient concentrations were below the N, K, Ca, and Mg sufficiency standards in ‘Black Diamond’ and were lower than in ‘Marion’ for N, phosphorus (P), Ca, Mg, S, B, and Zn in at least one year. In contrast, floricane leaves and fruit tended to have higher nutrient concentrations in ‘Black Diamond’ than in ‘Marion’. Weed management strategy affected many nutrients in the soil, leaves, and fruit. Often, use of weed mat led to the highest concentrations. Withholding irrigation postharvest had limited effects on plant nutrient concentrations. The impact of primocane training time varied among years, nutrients, and plant parts.