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  • Author or Editor: Mark Bolda x
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In strawberry (Fragaria ×ananassa), initial bare-root crown diameter and early-season flower cluster removal have been two factors suspected of influencing fruit yield and size. This study evaluated the effect of these two factors on the day-neutral strawberry varieties Monterey and Cabrillo. Bare-root crowns with three different diameters were categorized into small (< 0.5 cm), medium (> 0.5 to 1 cm), and large (> 1 cm) at planting. Each of the crown diameter treatments was split into two plots for flower removal or no flower removal in the early season and data on canopy diameter, fruit yield, and fruit size collected in the subsequent months of production. The study was conducted over two growing seasons (2019–20 and 2020–21). No difference was found in plant canopy diameters measured in February, ∼3 months after planting, between any of the treatments in either year. Although early-season flower removal and some crown sizes resulted in lower fruit yield in March and April, none of these treatments resulted in any fruit yield or size differences in subsequent months nor in season end totals.

Open Access

Diagnosis and recommendation integrated system (DRIS) leaf blade and petiole optimum nutrient ranges were developed through tissue sampling in 53 commercial strawberry (Fragaria ×ananassa) fields in the coastal valleys of central California in 2010 and 2011. All fields were in an annual production system using the day-neutral cultivar Albion. Leaf blades and petioles were sampled five times from early flowering through the fruit harvest period. Data on soil nutrient availability and grower fertilization practices were also collected. DRIS analysis was used to develop nutrient optimum ranges based on nutrient concentrations observed in nutritionally balanced, high-yield fields. Blade nitrogen (N), phosphorus (P), and potassium (K) concentrations declined from the vegetative stage until the main harvest period, and stabilized thereafter. Blade calcium (Ca), boron (B), and iron (Fe) increased over time while magnesium (Mg), sulfur (S), manganese (Mn), zinc (Zn), and copper (Cu) decreased. The blade N optimum range was lower than previously published sufficiency ranges during the fruit harvest period, and the Zn optimum range was lower throughout the season. Other nutrients were in general agreement with previously established sufficiency ranges with the exception of Ca, Mn, and Fe, which were higher. Petiole nitrate-nitrogen (NO3-N) was highly variable among high-yield fields, was not correlated with soil NO3-N at any growth stage, and was therefore of limited value as an indicator of crop N status. Comparison of soil nutrient availability with grower fertilization practices suggested that significant improvement in fertilizer management was possible.

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The use of polyethylene (PE) mulch causes environmental pollution where incomplete removal leaves fragments susceptible to escape to ecosystems, such as the ocean, where they can cause ecological harm. PE mulch is generally nonrecyclable due to contamination with soil and crop debris after use, leaving growers with few end-of-life options for used PE mulch. Research studies have shown that soil-biodegradable plastic mulch (BDM) is comparable to PE mulch in terms of performance, soil health, and overall economics and is preferred from an environmental perspective, but the adoption of BDM by producers is still low. Previous research has shown that the primary barriers to BDM adoption are insufficient knowledge about BDM, high purchase cost, and unpredictable breakdown of BDM in the soil. The high purchase cost of BDM compared with PE mulch is offset by the costs for PE mulch removal, transport, and disposal fees. This project was conducted to develop BDM training materials, to educate and assess BDM knowledge gained by extension personnel and other agricultural professionals through trainings and webinars, and to educate producers about BDM through hands-on experience. Thirty-six research and extension publication outputs from two previous US Department of Agriculture Specialty Crop Research Initiative BDM projects were reviewed and transcribed into 45 new extension publications that included 11 slide presentations, 5 lecture slides, 10 fact sheets, and 3 videos. All the training materials are posted on a public university website. Professional development trainings were conducted at local, regional, national, and international levels to provide agricultural professionals the current, science-based information on BDM and resources for information. Survey results showed that at a local level, the greatest change of knowledge among participants was observed for “BDM use in organic production” (60%), and the lowest reported change of knowledge was observed for “limitations to PE mulch disposal” (19%). At a regional level, out of 58 participants, 23% to 35% of participants learned “a lot” and 35% to 51% learned “some new information” regarding BDM from the webinar. At the national level, out of 30 participants, 48% responded that they learned “a lot” and another 48% learned “some new information” on BDM from the training. Growers were trained about BDM via field days and on-farm demonstrations where five strawberry (Fragaria ×ananassa) growers volunteered to participate in BDM trials. The participant growers observed no difference in weed control and fruit yield between the PE mulch and the BDM. Growers expressed concerns about slow biodegradation of BDM after soil incorporation, potential impacts on soil biological activity, food safety concerns with BDM fragments and that BDM is not currently permitted for use in organic production.

Open Access

Strawberry anthracnose caused by Colletotrichum acutatum is often asymptomatic on plants in sprinkler-irrigated nurseries but destructive after transplantation into fruiting fields. This study evaluated the impact of strawberry nursery sprinkler and drip irrigation in the presence or absence of C. acutatum on post-transplantation plant growth, mortality, and fruit yield in fruiting fields in California. In a 2005 nursery at Tulelake, CA, dip infestation of mother plants with C. acutatum reduced early-season mother plant canopy size by 21% and delayed runner production in mother plants but otherwise had no obvious disease symptoms. In comparison with sprinkler-irrigated treatments in the nursery, drip irrigation of infested nursery plots reduced plant losses in fruit production fields by 86% at Watsonville, CA, in 2005 and 50% and 75% at Oxnard, CA, in 2005 and 2008. Transplants from infested nursery treatments had a 33% to 60% smaller canopy and 11% to 42% lower yield than transplants from uninfested nursery treatments. However, transplant canopy size and yield from the infested and then drip-irrigated nursery treatment were similar to the sprinkler-irrigated, non-infested nursery treatment. Quantitative polymerase chain reaction measurements of C. acutatum in crown tissue of fruiting field plants seven weeks after transplanting showed significantly more C. acutatum (≈11×) in their crowns in sprinkler-irrigated than drip-irrigated, infested nursery transplant treatments. During the course of fruit production, the amount of C. acutatum in crown tissue increased in all treatments. However, at the end of the fruit season, there was still significantly more (≈8×) C. acutatum in the crowns of the plants produced by sprinkler irrigation than by drip irrigation in the nursery. These data suggest that if C. acutatum is present in the nursery, drip irrigation can reduce subsequent plant stunting and yield losses in strawberry production fields.

Free access