Using Commercially Available Ion‐Exchange Membranes to Monitor Plant‐Available Nutrients in Cranberry

Abstract

Monitoring in‐season nutrient availability in cranberry (Vaccinium macrocarpon Ait.) is hampered by tissue sampling being limited to a short, late‐summer period, and a low‐pH, high‐iron (Fe) soil environment limits soil‐test result interpretation. To evaluate monitoring available in‐season nitrogen (N), phosphorus (P), and potassium (K), commercially available ion‐exchange membranes (PRS™) were placed in plots where standard fertilizer practices were supplemented with the controlled‐release fertilizer (CRF) Osmocote™ 14–14–14 at 0, 112, 224 or 336 kg/ha rates. PRS™ nitrate (NO₃)‐N was related only to CRF fertilizer, whereas PRS™ ammonium (NH₄)‐N reflected both the CRF and in‐season fertilizer applications. Large increases in PRS™ NH₄‐N with increasing CRF rates suggested a synergistic effect of CRF on fertilizer NH₄‐N availability. PRS™ P was positively correlated with CRF P but negatively to in‐season P applications, whereas PRS™ K was related to in‐season fertilizer applications but not to CRF, suggesting poor plant P availability in the soil environment and relatively little K contribution from CRF, respectively. These results show promise for using PRS™ in cranberry.

Keywords:

• Cranberry
• in‐season monitoring
• ion‐exchange membranes
• nitrogen
• phosphorus
• potassium