Exchangeable Soil Calcium May Not Reliably Predict In-season Calcium Requirements for Enhancing Potato Tuber Calcium Concentration

Previous research has provided evidence that Ca is transported to the tuber along with water via the roots on stolons and tubers. Several studies have documented that in-season Ca application can increase tuber Ca concentration and reduce storage rot and internal defects such as hollow heart, brown center, and internal brown spot. The objective of the present study was to investigate the relationship between preplant soil test Ca levels and the tuber Ca concentration. Recommendation for Ca application in potato production guides are not necessarily geared towards tubers unique nutritional needs. In general, for potato production, Ca applications are recommended only if pre-plant soil exchangeable Ca is below 300 mg kg −1 . Studies were conducted in two soil types, namely loamy sand (Hancock location) and silt loam (Antigo location). The pre-plant soil Ca for the loamy sand tested at 285–563 mg kg −1 and the silt loam tested at 530–1,340 mg kg −1 of exchangeable Ca. Five cultivars were grown with or without in-season Ca applications of 168 kg ha −1 . At Hancock, 30 separate trials were conducted between the years 1999–2006, whereas at Antigo, 15 separate trials were conducted between the years 1995–1998. The tuber Ca concentration increased in 38 of the 45 total trials carried out in both locations. This increase in tuber Ca concentration varied among cultivars and seasons but had no relationship with soil Ca. This increase in tuber CA concentration occurred even when pre-season exchangeable Ca tested at over 1,000 mg kg −1 . These results suggest that testing for exchangeable Ca in these soils is not a good (or reliable) predictor of tuber Ca needs.