Effect of nitrogen fertilization on ‘Arapaho’ Thornless blackberry

Abstract

A three year‐old ‘Arapaho’ blackberry planting at the University of Arkansas Fruit Substation was used for a nitrogen (N) study. Treatments, which began in 1994 and continued through 1996, were: 1) control—no N applied, 2) 56 kg ha^‐1 N applied in a single application in early spring, 3) 112 kg ha^‐1 N applied in a single application in early spring, and 4) 112 kg ha^‐1 N applied in a split application with one‐half applied in the early spring and one‐half applied immediately after harvest. Fruit was harvested from the plots in June and total yield and average berry mass were determined. Foliar samples were collected in August and elemental analysis conducted. Primocanes in each plot were counted at the end of the growing season. Over the three years, there was no significant treatment effect on yield, berry mass, or primocane number. A trend toward higher primocane number with N application was seen, however. Foliar elemental content of N, phosphorus (P), potassium (K), calcium (Ca), sulfur (S), and manganese (Mn) were affected by either N dose or time of application. Foliar N content was highest for the split application but no other benefit was found from that practice. Calcium was higher when no N was applied, Mn was greater at higher N rates, and the control had the lowest foliar N level each year. No effect from N treatment was found for leaf chlorophyll content or stem and bud cold hardiness.