Understanding the Physiological Response of Perennial Strawberry to Nitrogen Limitations and Developing Nutrient Management Practices to Improve Plant Growth and Productivity

Strawberry plants have many physiological characteristics in common with perennial trees and shrubs, despite their small size. Over the last 50 years, strawberries increasingly have been grown as annuals in warmer climates where cold weather does not interrupt the growth cycle. However, in many temperate regions of the world, strawberries are still grown as perennials. So while the basic physiology between annual and perennial strawberries is the same, the nutritional management is quite different. With perennial strawberries, the plant establishes a vegetative structure, initiates flower primordia, prepares for winter, regrows the vegetative structure quite rapidly after winter, produces flowers and fruits, produces stolons, and then repeats the process for another year. To understand the management of key nutrients in perennial systems, growth, carbon acquisition and metabolism must be understood, because these influence the demand for essential nutrients, particularly nitrogen. As with most other perennial crops, soil tests are used to determine macronutrient needs. If the recommendations are correct, then adequate nutrients (e.g. Ca, Mg, K) are applied to ensure that the plant can meet demand for most nutrients for several years after planting, without supplemental additions or further pH adjustment. Nitrogen is the exception in that most soils do not provide adequate amounts to optimize growth and fruiting, so periodic additions are required. Several principles apply to the application of N in perennial strawberries: 1) during establishment, excessive N fertilizer in spring can damage root systems and create too much vegetative growth and runnering, 2) excessive N in the fall can reduce C reserves and potentially reduce yield the following spring, 3) if C reserves are adequate, supplemental fall N can increase yields, 4) spring N applications have only a small effect on subsequent yield, but stimulate vegetative growth and may cause increased Botrytis on fruit. Many soil testing labs routinely recommend P incorporation during strawberry plant establishment, yet there is little evidence that additional P is helpful when levels are above a minimum level. In fact, excessive P can suppress availability of some micronutrients (e.g. Zn) and cause deficiency symptoms under certain circumstances. Perennial strawberry roots are active during colder times of the year, so are able to acquire and accumulate nutrients like P when the plant is not actively growing above ground. Inadequate B can trigger deficiencies in K and P, despite adequate levels in soil.