March 2014
Production Systems for Organic Blackberries for Processing –
Impact of Cultivar and Weed Management
Authors: Amanda Vance, Faculty Research Assistant and Emily Dixon, M.S. graduate student
Project Leaders: Bernadine C. Strik, Professor of Horticulture, OSU NWREC
& David Bryla, HCRU, USDA-ARS
Data are presented from two M.S. graduate students: Renee Harkins (graduated in 2012); Emily Dixon (in progress)
Objectives:
This project is part of a larger cooperative trial with several different goals. In this study our goal is to
evaluate the effect of weed management, irrigation, and training time on machine-harvested yield and
quality, plant growth, nutrient allocation, and food safety in ‘Marion’ and ‘Black Diamond’
A 1-acre certified organic field was
established at the NWREC in June 2010.
Plants are drip irrigated and fertigated
using fish emulsion. We are also evaluating
the impact of post-harvest irrigation and
training time on plant growth and
production (2012-14).
Treatments:
A) Cultivars: ‘Marion’ and ‘Black
Diamond’
B) Weed management: weed mat,
hand weed, and a non-weeded
control
Results:
Primocane Growth. Weed pressure was not high in the planting year (2010) and there was no effect of
weed management treatment on primocane production. However in the 2011 off (non-fruiting) year,
plants in the weedy control plots produced fewer (6.5/plant) and longer canes (6 m) than those grown in
weed-free (bare soil) or with weed mat (12 canes/plant averaging 4.8 m). In 2013 all treatments had
fewer canes because the planting was recovering from its first on (fruiting) year, but plants in the weedy
March 2014
plots still produced fewer canes than plants with weed mat. Weeds covered the in-row area of weedy
plots in 2011, 2012, and 2013 and weeds were cut to ground height just prior to machine harvest to
prevent interference with the catcher plates.
Tissue Nutrients. Tissue analysis of primocane leaves in early August indicated that leaf nitrogen (%N)
was lower in weedy plots (2.2%N) than in bare soil or weed mat plots (2.9%N) in 2011 and 2012. Also,
plants in weedy plots had lower leaf %P and %K in 2011 than in bare soil or weed mat plots. In 2013 the
%N and %P were the same in the different weed management treatments, but leaf %K and %S were
lower in the weedy plants. The primocane leaf nutrient status of ‘Marion’ and ‘Black Diamond’ differed
in all three years for several nutrients: N, P, Fe, Zn, and Al.
Yield. The machine-harvested yield of ‘Black
Diamond’ was greater (6 tons/acre in 2012
and 4 tons/acre in 2013; averaged over all
weed management treatments) than for
‘Marion’ (5 tons/acre in 2012 and 3 tons/acre
in 2013). The ‘Marion’ harvest season was
more concentrated than that of ‘Black
Diamond’.
On average (over the two cultivars) in 2012,
the weedy plots produced half the yield (3.5
tons/acre) of the weed mat, which was the
highest treatment (7 tons/acre). Bare soil (6
tons/acre) produced less than the weed mat
(Figure 1). In 2013 the total yield was lower
for all treatments, but it followed a similar pattern with weed mat and bare soil plots producing the
most (4 tons/acre) and weedy plots producing significantly less (3 tons/acre). ‘Black Diamond’ produced
larger berries than ‘Marion’ on every harvest date in 2012 and 2013. Plants in the weedy plots produced
smaller fruit with a lower percent moisture content and a higher Brix than plants in the bare soil or
weed mat plots. It is clear that these blackberry cultivars are negatively impacted by competition with
weeds.
The 2012 harvest season extended from July 5 to July 30, whereas the 2013 harvest season began
earlier, on June 24, and ran until July 18. Each year had 8 harvest dates spaced 3-4 days apart.
Figure 1: Effect of weed management on yield (average of ‘Black Diamond’ and ‘Marion’)
8
7
Yield (tons/acre)
6
5
Weedy
4
Bare soil
Weed mat
3
2
1
0
2012
2013
March 2014
Why did weed mat plots have a higher yield than bare soil in 2012? At this point, we are not sure. There
were relatively minor differences in soil temperature, but soil under weed mat was slightly cooler than
bare soil. Soil in weed mat plots had higher soil N, K, Mg, and Ca than bare soil and soil pH was higher
under weed mat. We will investigate treatment differences further.
Nutrient Losses. We measured the nutrient concentration in the
berries in 2012 and calculated the amount of nutrient removed in
the harvested fruit (fresh yield x percent dry weight of fruit x
concentration of nutrient in fruit). For example, about 3 lb N/ton
and 3 lb K/ton or 15 lb/acre each of N and K for a 5 ton/acre yield.
This information coupled with our data on nutrients removed with
pruning (caning out) and what is required for growth, will help us
further develop blackberry nutrient management programs.
When dead floricanes were removed in August (caning out), about
29 lb N/acre was removed in ‘Black Diamond’ and 46 lb N/acre in
‘Marion’. Of course, if these are flailed or chopped in the field, the
nutrients in these canes would ultimately be returned to the soil. We
have not yet analyzed the nutrients required for primocane growth
in 2013.
We imposed our irrigation treatments (with or without post-harvest irrigation) and training time (Aug.
vs. Feb.) in 2012-13 and further results are forthcoming. We are also continuing to evaluate all
treatments and are measuring root growth and soil and plant water status. Fruit quality data (Dr. Zhao)
and microbial content (Dr. Daeschel) were collected but are not presented here.
Acknowledgments:
We would like to thank our many collaborators: Yanyun Zhao & Mark Daeschel (Dept. Food Sci., Oregon
State University); Gil Buller (Senior Faculty Research Assistant, NWREC, OSU); Luis Valenzuela, root
physiology (post-doc); George Cavender, fruit quality (post-doc); Javier Fernandez-Salvador, fertilizer
source in fresh and processed systems & cultivar adaptation (M.S. graduate student); Vaughn Walton
(Dept. Hort., OSU); John McQueen (OSU); Dan Sullivan (Dept. Crop and Soil Sci., OSU)
We also appreciate the contributions of our advisory board: Eric Pond (AgriCare Inc.); Joe Bennett
(Pacifica Organic Advisors); Tom Avinelis (Homegrown Organic Farms, CA); Derek Peacock (Hurst’s Berry
Farms, OR); Anthony Boutard (Ayers Creek
Farm, OR)
Thank you to our funding sources, including
NIFA-OREI (Formula Grant no. OREI 201001940; ORE00409), NCSFR, and Oregon
Organic Cropping Research, and for in-kind
and funding contributions from industry:
Eric Pond (AgriCare Inc.); Riverbend Farms
(Jefferson, Oregon); Littau Harvesters Inc.;
Sakuma Bros. Farms (Burlington, WA);
Oregon Tilth; AgroThrive Inc.