Doing whatever it takes to give yourself a competitive edge as a grower may mean the difference between a successful crop or the loss of time, money and produce. As horticulture advances, that means (possibly) trying out new tests and technologies.
Fortunately, Extension agents and land grant universities can do some of those tests for you before you invest in them. Discussing sap testing in berry crops at the most recent Great Lakes Expo was Zilfina Rubio Ames, assistant professor and small fruit Extension specialist with the University of Georgia.
Rubio Ames said some of the potential benefits of sap analysis include the rapid diagnosis of deficiencies or excesses of nutrients; a reduction in production costs; an increase in fertilizer use efficiency; more sustainable production systems; reduction in soil acidification; and the reduction of nutrient leaching.
She focused on that last one, since fertilizer and nutrient amendments can be expensive. Specifically, Rubio Ames noted:
Nitrogen is mobile in berry plants and in the soil. Deficient plants are commonly stunted, with low vigor and pale green to chlorotic leaves.
Phosphorus is mobile in the plant with low mobility in the soil. Deficient plants are stunted and often dark green; leaves may have red tinge due to accumulation of anthocyanins.
Potassium is mobile in the plant with low to medium mobility in the soil. Deficient plants have older leaves with necrotic lesions.
Calcium has low mobility in the plant and the soil.
Boron has low mobility in the plant and high mobility in the soil.
She wanted to identify the best methodology for testing for these elements in berry plants, believing she’d find similarities between soil, sap, leaf and fruit nutrient levels.
Testing berry plant tissue to check nutrient levels is a good idea to see what your plants may need. Photo by Courtney Llewellyn
Rubio Ames tested both blueberries and blackberries planted at two different sites over two years. Sap was sampled from the plants at different times of the day as well, to see if that affected nutrient levels.
She noted that petiole testing could be a good way to look for nitrogen levels/deficiencies, but otherwise, her two-year trial results were unsurprising.
Rubio Ames’s team summarized that sampling time does not influence nutrient concentration in sap. Samples can be taken any time during the day.
They found older plant tissue had higher nutrient concentrations, which could be linked to nutrient mobility, which is similar to leaf tissue sampling. Sap nutrient concentration does change throughout the year and follows a similar trend to leaf nutrient concentration.
A lot of the results that came from sap sampling were very close to those that came from leaf sampling.
“Do we even need sap analysis when leaf testing is so similar?” Rubio Ames wondered, implying the answer might be no.
If you grow berries, take this into consideration before investing in sap sampling and analysis.
by Courtney Llewellyn
