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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.

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.