Strawberry season is quickly approaching and now is the time for strawberry farmers to fertilize plants to give them a healthy boost to produce pretty, large berries. Strawberries grown on black plastic require intensive and precise fertilization, a formula that is best determined by collecting leaf and petiole samples and having them tested for nutrient content. The N.C. Department of Agriculture and Consumer Services’ agronomists recommend collecting the first tissue samples when plants begin to flower and continuing to do so every two weeks throughout flowering and fruiting (approximately March 1 – May 30 in North Carolina).
The NCDA&CS Agronomic Laboratory measures concentrations of essential nutrients within the plant and compares them to established target concentrations for healthy strawberries. By monitoring nutrient levels and adjusting fertilization accordingly, growers can easily optimize crop growth and fruit quality while minimizing unnecessary fertilizer inputs. For strawberry tissue samples, both leaves and petioles are collected and submitted. Analysis of leaflets can reveal nutrient imbalances within the plant. Analysis of petioles indicates the amount of soil nitrogen currently available for crop growth and development, and serves as the basis for the nitrogen rate recommendation.
To collect strawberry tissue samples, select most recently mature, trifoliate leaves (MRMLs). Those leaves are full-sized and green and consist of one petiole (leaf stalk) with three leaflets. MRMLs are usually located three to five leaves back from the growing point. When MRMLs are being collected, it is very important to detach the petiole from the leaflets immediately. This action halts nutrient transfer between the two plant parts, which are analyzed separately.
Each sample should include leaves and petioles from 20 to 25 locations within a uniform area. For example, all of the plant material in a single sample should be the same variety, grown in the same soil type, planted at the same time and having the same management history. The test costs $7 per sample for North Carolina growers and $27 for out-of-state growers and includes both leaf and petiole tests.
When submitting tissue samples, be sure to fill out the information sheet completely, including fertilization history and environmental conditions. It is particularly important to provide the current growth stage (bloom or fruit) and the number of weeks the plants have been in that growth stage. The management recommendations you receive on your report depend on the information you provide with the sample. Turnaround time is about two working days.